xref: /openbmc/linux/mm/mmap.c (revision b9ddb2500e7e544410f38476ab928fc2fe01e381)
1  // SPDX-License-Identifier: GPL-2.0-only
2  /*
3   * mm/mmap.c
4   *
5   * Written by obz.
6   *
7   * Address space accounting code	<alan@lxorguk.ukuu.org.uk>
8   */
9  
10  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11  
12  #include <linux/kernel.h>
13  #include <linux/slab.h>
14  #include <linux/backing-dev.h>
15  #include <linux/mm.h>
16  #include <linux/vmacache.h>
17  #include <linux/shm.h>
18  #include <linux/mman.h>
19  #include <linux/pagemap.h>
20  #include <linux/swap.h>
21  #include <linux/syscalls.h>
22  #include <linux/capability.h>
23  #include <linux/init.h>
24  #include <linux/file.h>
25  #include <linux/fs.h>
26  #include <linux/personality.h>
27  #include <linux/security.h>
28  #include <linux/hugetlb.h>
29  #include <linux/shmem_fs.h>
30  #include <linux/profile.h>
31  #include <linux/export.h>
32  #include <linux/mount.h>
33  #include <linux/mempolicy.h>
34  #include <linux/rmap.h>
35  #include <linux/mmu_notifier.h>
36  #include <linux/mmdebug.h>
37  #include <linux/perf_event.h>
38  #include <linux/audit.h>
39  #include <linux/khugepaged.h>
40  #include <linux/uprobes.h>
41  #include <linux/rbtree_augmented.h>
42  #include <linux/notifier.h>
43  #include <linux/memory.h>
44  #include <linux/printk.h>
45  #include <linux/userfaultfd_k.h>
46  #include <linux/moduleparam.h>
47  #include <linux/pkeys.h>
48  #include <linux/oom.h>
49  #include <linux/sched/mm.h>
50  
51  #include <linux/uaccess.h>
52  #include <asm/cacheflush.h>
53  #include <asm/tlb.h>
54  #include <asm/mmu_context.h>
55  
56  #define CREATE_TRACE_POINTS
57  #include <trace/events/mmap.h>
58  
59  #include "internal.h"
60  
61  #ifndef arch_mmap_check
62  #define arch_mmap_check(addr, len, flags)	(0)
63  #endif
64  
65  #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
66  const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
67  const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
68  int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS;
69  #endif
70  #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
71  const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN;
72  const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
73  int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
74  #endif
75  
76  static bool ignore_rlimit_data;
77  core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
78  
79  static void unmap_region(struct mm_struct *mm,
80  		struct vm_area_struct *vma, struct vm_area_struct *prev,
81  		unsigned long start, unsigned long end);
82  
83  /* description of effects of mapping type and prot in current implementation.
84   * this is due to the limited x86 page protection hardware.  The expected
85   * behavior is in parens:
86   *
87   * map_type	prot
88   *		PROT_NONE	PROT_READ	PROT_WRITE	PROT_EXEC
89   * MAP_SHARED	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
90   *		w: (no) no	w: (no) no	w: (yes) yes	w: (no) no
91   *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
92   *
93   * MAP_PRIVATE	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
94   *		w: (no) no	w: (no) no	w: (copy) copy	w: (no) no
95   *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
96   */
97  pgprot_t protection_map[16] __ro_after_init = {
98  	__P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
99  	__S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
100  };
101  
102  #ifndef CONFIG_ARCH_HAS_FILTER_PGPROT
103  static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
104  {
105  	return prot;
106  }
107  #endif
108  
109  pgprot_t vm_get_page_prot(unsigned long vm_flags)
110  {
111  	pgprot_t ret = __pgprot(pgprot_val(protection_map[vm_flags &
112  				(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
113  			pgprot_val(arch_vm_get_page_prot(vm_flags)));
114  
115  	return arch_filter_pgprot(ret);
116  }
117  EXPORT_SYMBOL(vm_get_page_prot);
118  
119  static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
120  {
121  	return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
122  }
123  
124  /* Update vma->vm_page_prot to reflect vma->vm_flags. */
125  void vma_set_page_prot(struct vm_area_struct *vma)
126  {
127  	unsigned long vm_flags = vma->vm_flags;
128  	pgprot_t vm_page_prot;
129  
130  	vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
131  	if (vma_wants_writenotify(vma, vm_page_prot)) {
132  		vm_flags &= ~VM_SHARED;
133  		vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags);
134  	}
135  	/* remove_protection_ptes reads vma->vm_page_prot without mmap_lock */
136  	WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
137  }
138  
139  /*
140   * Requires inode->i_mapping->i_mmap_rwsem
141   */
142  static void __remove_shared_vm_struct(struct vm_area_struct *vma,
143  		struct file *file, struct address_space *mapping)
144  {
145  	if (vma->vm_flags & VM_DENYWRITE)
146  		allow_write_access(file);
147  	if (vma->vm_flags & VM_SHARED)
148  		mapping_unmap_writable(mapping);
149  
150  	flush_dcache_mmap_lock(mapping);
151  	vma_interval_tree_remove(vma, &mapping->i_mmap);
152  	flush_dcache_mmap_unlock(mapping);
153  }
154  
155  /*
156   * Unlink a file-based vm structure from its interval tree, to hide
157   * vma from rmap and vmtruncate before freeing its page tables.
158   */
159  void unlink_file_vma(struct vm_area_struct *vma)
160  {
161  	struct file *file = vma->vm_file;
162  
163  	if (file) {
164  		struct address_space *mapping = file->f_mapping;
165  		i_mmap_lock_write(mapping);
166  		__remove_shared_vm_struct(vma, file, mapping);
167  		i_mmap_unlock_write(mapping);
168  	}
169  }
170  
171  /*
172   * Close a vm structure and free it, returning the next.
173   */
174  static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
175  {
176  	struct vm_area_struct *next = vma->vm_next;
177  
178  	might_sleep();
179  	if (vma->vm_ops && vma->vm_ops->close)
180  		vma->vm_ops->close(vma);
181  	if (vma->vm_file)
182  		fput(vma->vm_file);
183  	mpol_put(vma_policy(vma));
184  	vm_area_free(vma);
185  	return next;
186  }
187  
188  static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags,
189  		struct list_head *uf);
190  SYSCALL_DEFINE1(brk, unsigned long, brk)
191  {
192  	unsigned long retval;
193  	unsigned long newbrk, oldbrk, origbrk;
194  	struct mm_struct *mm = current->mm;
195  	struct vm_area_struct *next;
196  	unsigned long min_brk;
197  	bool populate;
198  	bool downgraded = false;
199  	LIST_HEAD(uf);
200  
201  	if (mmap_write_lock_killable(mm))
202  		return -EINTR;
203  
204  	origbrk = mm->brk;
205  
206  #ifdef CONFIG_COMPAT_BRK
207  	/*
208  	 * CONFIG_COMPAT_BRK can still be overridden by setting
209  	 * randomize_va_space to 2, which will still cause mm->start_brk
210  	 * to be arbitrarily shifted
211  	 */
212  	if (current->brk_randomized)
213  		min_brk = mm->start_brk;
214  	else
215  		min_brk = mm->end_data;
216  #else
217  	min_brk = mm->start_brk;
218  #endif
219  	if (brk < min_brk)
220  		goto out;
221  
222  	/*
223  	 * Check against rlimit here. If this check is done later after the test
224  	 * of oldbrk with newbrk then it can escape the test and let the data
225  	 * segment grow beyond its set limit the in case where the limit is
226  	 * not page aligned -Ram Gupta
227  	 */
228  	if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
229  			      mm->end_data, mm->start_data))
230  		goto out;
231  
232  	newbrk = PAGE_ALIGN(brk);
233  	oldbrk = PAGE_ALIGN(mm->brk);
234  	if (oldbrk == newbrk) {
235  		mm->brk = brk;
236  		goto success;
237  	}
238  
239  	/*
240  	 * Always allow shrinking brk.
241  	 * __do_munmap() may downgrade mmap_lock to read.
242  	 */
243  	if (brk <= mm->brk) {
244  		int ret;
245  
246  		/*
247  		 * mm->brk must to be protected by write mmap_lock so update it
248  		 * before downgrading mmap_lock. When __do_munmap() fails,
249  		 * mm->brk will be restored from origbrk.
250  		 */
251  		mm->brk = brk;
252  		ret = __do_munmap(mm, newbrk, oldbrk-newbrk, &uf, true);
253  		if (ret < 0) {
254  			mm->brk = origbrk;
255  			goto out;
256  		} else if (ret == 1) {
257  			downgraded = true;
258  		}
259  		goto success;
260  	}
261  
262  	/* Check against existing mmap mappings. */
263  	next = find_vma(mm, oldbrk);
264  	if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
265  		goto out;
266  
267  	/* Ok, looks good - let it rip. */
268  	if (do_brk_flags(oldbrk, newbrk-oldbrk, 0, &uf) < 0)
269  		goto out;
270  	mm->brk = brk;
271  
272  success:
273  	populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
274  	if (downgraded)
275  		mmap_read_unlock(mm);
276  	else
277  		mmap_write_unlock(mm);
278  	userfaultfd_unmap_complete(mm, &uf);
279  	if (populate)
280  		mm_populate(oldbrk, newbrk - oldbrk);
281  	return brk;
282  
283  out:
284  	retval = origbrk;
285  	mmap_write_unlock(mm);
286  	return retval;
287  }
288  
289  static inline unsigned long vma_compute_gap(struct vm_area_struct *vma)
290  {
291  	unsigned long gap, prev_end;
292  
293  	/*
294  	 * Note: in the rare case of a VM_GROWSDOWN above a VM_GROWSUP, we
295  	 * allow two stack_guard_gaps between them here, and when choosing
296  	 * an unmapped area; whereas when expanding we only require one.
297  	 * That's a little inconsistent, but keeps the code here simpler.
298  	 */
299  	gap = vm_start_gap(vma);
300  	if (vma->vm_prev) {
301  		prev_end = vm_end_gap(vma->vm_prev);
302  		if (gap > prev_end)
303  			gap -= prev_end;
304  		else
305  			gap = 0;
306  	}
307  	return gap;
308  }
309  
310  #ifdef CONFIG_DEBUG_VM_RB
311  static unsigned long vma_compute_subtree_gap(struct vm_area_struct *vma)
312  {
313  	unsigned long max = vma_compute_gap(vma), subtree_gap;
314  	if (vma->vm_rb.rb_left) {
315  		subtree_gap = rb_entry(vma->vm_rb.rb_left,
316  				struct vm_area_struct, vm_rb)->rb_subtree_gap;
317  		if (subtree_gap > max)
318  			max = subtree_gap;
319  	}
320  	if (vma->vm_rb.rb_right) {
321  		subtree_gap = rb_entry(vma->vm_rb.rb_right,
322  				struct vm_area_struct, vm_rb)->rb_subtree_gap;
323  		if (subtree_gap > max)
324  			max = subtree_gap;
325  	}
326  	return max;
327  }
328  
329  static int browse_rb(struct mm_struct *mm)
330  {
331  	struct rb_root *root = &mm->mm_rb;
332  	int i = 0, j, bug = 0;
333  	struct rb_node *nd, *pn = NULL;
334  	unsigned long prev = 0, pend = 0;
335  
336  	for (nd = rb_first(root); nd; nd = rb_next(nd)) {
337  		struct vm_area_struct *vma;
338  		vma = rb_entry(nd, struct vm_area_struct, vm_rb);
339  		if (vma->vm_start < prev) {
340  			pr_emerg("vm_start %lx < prev %lx\n",
341  				  vma->vm_start, prev);
342  			bug = 1;
343  		}
344  		if (vma->vm_start < pend) {
345  			pr_emerg("vm_start %lx < pend %lx\n",
346  				  vma->vm_start, pend);
347  			bug = 1;
348  		}
349  		if (vma->vm_start > vma->vm_end) {
350  			pr_emerg("vm_start %lx > vm_end %lx\n",
351  				  vma->vm_start, vma->vm_end);
352  			bug = 1;
353  		}
354  		spin_lock(&mm->page_table_lock);
355  		if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
356  			pr_emerg("free gap %lx, correct %lx\n",
357  			       vma->rb_subtree_gap,
358  			       vma_compute_subtree_gap(vma));
359  			bug = 1;
360  		}
361  		spin_unlock(&mm->page_table_lock);
362  		i++;
363  		pn = nd;
364  		prev = vma->vm_start;
365  		pend = vma->vm_end;
366  	}
367  	j = 0;
368  	for (nd = pn; nd; nd = rb_prev(nd))
369  		j++;
370  	if (i != j) {
371  		pr_emerg("backwards %d, forwards %d\n", j, i);
372  		bug = 1;
373  	}
374  	return bug ? -1 : i;
375  }
376  
377  static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
378  {
379  	struct rb_node *nd;
380  
381  	for (nd = rb_first(root); nd; nd = rb_next(nd)) {
382  		struct vm_area_struct *vma;
383  		vma = rb_entry(nd, struct vm_area_struct, vm_rb);
384  		VM_BUG_ON_VMA(vma != ignore &&
385  			vma->rb_subtree_gap != vma_compute_subtree_gap(vma),
386  			vma);
387  	}
388  }
389  
390  static void validate_mm(struct mm_struct *mm)
391  {
392  	int bug = 0;
393  	int i = 0;
394  	unsigned long highest_address = 0;
395  	struct vm_area_struct *vma = mm->mmap;
396  
397  	while (vma) {
398  		struct anon_vma *anon_vma = vma->anon_vma;
399  		struct anon_vma_chain *avc;
400  
401  		if (anon_vma) {
402  			anon_vma_lock_read(anon_vma);
403  			list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
404  				anon_vma_interval_tree_verify(avc);
405  			anon_vma_unlock_read(anon_vma);
406  		}
407  
408  		highest_address = vm_end_gap(vma);
409  		vma = vma->vm_next;
410  		i++;
411  	}
412  	if (i != mm->map_count) {
413  		pr_emerg("map_count %d vm_next %d\n", mm->map_count, i);
414  		bug = 1;
415  	}
416  	if (highest_address != mm->highest_vm_end) {
417  		pr_emerg("mm->highest_vm_end %lx, found %lx\n",
418  			  mm->highest_vm_end, highest_address);
419  		bug = 1;
420  	}
421  	i = browse_rb(mm);
422  	if (i != mm->map_count) {
423  		if (i != -1)
424  			pr_emerg("map_count %d rb %d\n", mm->map_count, i);
425  		bug = 1;
426  	}
427  	VM_BUG_ON_MM(bug, mm);
428  }
429  #else
430  #define validate_mm_rb(root, ignore) do { } while (0)
431  #define validate_mm(mm) do { } while (0)
432  #endif
433  
434  RB_DECLARE_CALLBACKS_MAX(static, vma_gap_callbacks,
435  			 struct vm_area_struct, vm_rb,
436  			 unsigned long, rb_subtree_gap, vma_compute_gap)
437  
438  /*
439   * Update augmented rbtree rb_subtree_gap values after vma->vm_start or
440   * vma->vm_prev->vm_end values changed, without modifying the vma's position
441   * in the rbtree.
442   */
443  static void vma_gap_update(struct vm_area_struct *vma)
444  {
445  	/*
446  	 * As it turns out, RB_DECLARE_CALLBACKS_MAX() already created
447  	 * a callback function that does exactly what we want.
448  	 */
449  	vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
450  }
451  
452  static inline void vma_rb_insert(struct vm_area_struct *vma,
453  				 struct rb_root *root)
454  {
455  	/* All rb_subtree_gap values must be consistent prior to insertion */
456  	validate_mm_rb(root, NULL);
457  
458  	rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
459  }
460  
461  static void __vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
462  {
463  	/*
464  	 * Note rb_erase_augmented is a fairly large inline function,
465  	 * so make sure we instantiate it only once with our desired
466  	 * augmented rbtree callbacks.
467  	 */
468  	rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
469  }
470  
471  static __always_inline void vma_rb_erase_ignore(struct vm_area_struct *vma,
472  						struct rb_root *root,
473  						struct vm_area_struct *ignore)
474  {
475  	/*
476  	 * All rb_subtree_gap values must be consistent prior to erase,
477  	 * with the possible exception of
478  	 *
479  	 * a. the "next" vma being erased if next->vm_start was reduced in
480  	 *    __vma_adjust() -> __vma_unlink()
481  	 * b. the vma being erased in detach_vmas_to_be_unmapped() ->
482  	 *    vma_rb_erase()
483  	 */
484  	validate_mm_rb(root, ignore);
485  
486  	__vma_rb_erase(vma, root);
487  }
488  
489  static __always_inline void vma_rb_erase(struct vm_area_struct *vma,
490  					 struct rb_root *root)
491  {
492  	vma_rb_erase_ignore(vma, root, vma);
493  }
494  
495  /*
496   * vma has some anon_vma assigned, and is already inserted on that
497   * anon_vma's interval trees.
498   *
499   * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
500   * vma must be removed from the anon_vma's interval trees using
501   * anon_vma_interval_tree_pre_update_vma().
502   *
503   * After the update, the vma will be reinserted using
504   * anon_vma_interval_tree_post_update_vma().
505   *
506   * The entire update must be protected by exclusive mmap_lock and by
507   * the root anon_vma's mutex.
508   */
509  static inline void
510  anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
511  {
512  	struct anon_vma_chain *avc;
513  
514  	list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
515  		anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
516  }
517  
518  static inline void
519  anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
520  {
521  	struct anon_vma_chain *avc;
522  
523  	list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
524  		anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
525  }
526  
527  static int find_vma_links(struct mm_struct *mm, unsigned long addr,
528  		unsigned long end, struct vm_area_struct **pprev,
529  		struct rb_node ***rb_link, struct rb_node **rb_parent)
530  {
531  	struct rb_node **__rb_link, *__rb_parent, *rb_prev;
532  
533  	__rb_link = &mm->mm_rb.rb_node;
534  	rb_prev = __rb_parent = NULL;
535  
536  	while (*__rb_link) {
537  		struct vm_area_struct *vma_tmp;
538  
539  		__rb_parent = *__rb_link;
540  		vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
541  
542  		if (vma_tmp->vm_end > addr) {
543  			/* Fail if an existing vma overlaps the area */
544  			if (vma_tmp->vm_start < end)
545  				return -ENOMEM;
546  			__rb_link = &__rb_parent->rb_left;
547  		} else {
548  			rb_prev = __rb_parent;
549  			__rb_link = &__rb_parent->rb_right;
550  		}
551  	}
552  
553  	*pprev = NULL;
554  	if (rb_prev)
555  		*pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
556  	*rb_link = __rb_link;
557  	*rb_parent = __rb_parent;
558  	return 0;
559  }
560  
561  /*
562   * vma_next() - Get the next VMA.
563   * @mm: The mm_struct.
564   * @vma: The current vma.
565   *
566   * If @vma is NULL, return the first vma in the mm.
567   *
568   * Returns: The next VMA after @vma.
569   */
570  static inline struct vm_area_struct *vma_next(struct mm_struct *mm,
571  					 struct vm_area_struct *vma)
572  {
573  	if (!vma)
574  		return mm->mmap;
575  
576  	return vma->vm_next;
577  }
578  
579  /*
580   * munmap_vma_range() - munmap VMAs that overlap a range.
581   * @mm: The mm struct
582   * @start: The start of the range.
583   * @len: The length of the range.
584   * @pprev: pointer to the pointer that will be set to previous vm_area_struct
585   * @rb_link: the rb_node
586   * @rb_parent: the parent rb_node
587   *
588   * Find all the vm_area_struct that overlap from @start to
589   * @end and munmap them.  Set @pprev to the previous vm_area_struct.
590   *
591   * Returns: -ENOMEM on munmap failure or 0 on success.
592   */
593  static inline int
594  munmap_vma_range(struct mm_struct *mm, unsigned long start, unsigned long len,
595  		 struct vm_area_struct **pprev, struct rb_node ***link,
596  		 struct rb_node **parent, struct list_head *uf)
597  {
598  
599  	while (find_vma_links(mm, start, start + len, pprev, link, parent))
600  		if (do_munmap(mm, start, len, uf))
601  			return -ENOMEM;
602  
603  	return 0;
604  }
605  static unsigned long count_vma_pages_range(struct mm_struct *mm,
606  		unsigned long addr, unsigned long end)
607  {
608  	unsigned long nr_pages = 0;
609  	struct vm_area_struct *vma;
610  
611  	/* Find first overlaping mapping */
612  	vma = find_vma_intersection(mm, addr, end);
613  	if (!vma)
614  		return 0;
615  
616  	nr_pages = (min(end, vma->vm_end) -
617  		max(addr, vma->vm_start)) >> PAGE_SHIFT;
618  
619  	/* Iterate over the rest of the overlaps */
620  	for (vma = vma->vm_next; vma; vma = vma->vm_next) {
621  		unsigned long overlap_len;
622  
623  		if (vma->vm_start > end)
624  			break;
625  
626  		overlap_len = min(end, vma->vm_end) - vma->vm_start;
627  		nr_pages += overlap_len >> PAGE_SHIFT;
628  	}
629  
630  	return nr_pages;
631  }
632  
633  void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
634  		struct rb_node **rb_link, struct rb_node *rb_parent)
635  {
636  	/* Update tracking information for the gap following the new vma. */
637  	if (vma->vm_next)
638  		vma_gap_update(vma->vm_next);
639  	else
640  		mm->highest_vm_end = vm_end_gap(vma);
641  
642  	/*
643  	 * vma->vm_prev wasn't known when we followed the rbtree to find the
644  	 * correct insertion point for that vma. As a result, we could not
645  	 * update the vma vm_rb parents rb_subtree_gap values on the way down.
646  	 * So, we first insert the vma with a zero rb_subtree_gap value
647  	 * (to be consistent with what we did on the way down), and then
648  	 * immediately update the gap to the correct value. Finally we
649  	 * rebalance the rbtree after all augmented values have been set.
650  	 */
651  	rb_link_node(&vma->vm_rb, rb_parent, rb_link);
652  	vma->rb_subtree_gap = 0;
653  	vma_gap_update(vma);
654  	vma_rb_insert(vma, &mm->mm_rb);
655  }
656  
657  static void __vma_link_file(struct vm_area_struct *vma)
658  {
659  	struct file *file;
660  
661  	file = vma->vm_file;
662  	if (file) {
663  		struct address_space *mapping = file->f_mapping;
664  
665  		if (vma->vm_flags & VM_DENYWRITE)
666  			put_write_access(file_inode(file));
667  		if (vma->vm_flags & VM_SHARED)
668  			mapping_allow_writable(mapping);
669  
670  		flush_dcache_mmap_lock(mapping);
671  		vma_interval_tree_insert(vma, &mapping->i_mmap);
672  		flush_dcache_mmap_unlock(mapping);
673  	}
674  }
675  
676  static void
677  __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
678  	struct vm_area_struct *prev, struct rb_node **rb_link,
679  	struct rb_node *rb_parent)
680  {
681  	__vma_link_list(mm, vma, prev);
682  	__vma_link_rb(mm, vma, rb_link, rb_parent);
683  }
684  
685  static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
686  			struct vm_area_struct *prev, struct rb_node **rb_link,
687  			struct rb_node *rb_parent)
688  {
689  	struct address_space *mapping = NULL;
690  
691  	if (vma->vm_file) {
692  		mapping = vma->vm_file->f_mapping;
693  		i_mmap_lock_write(mapping);
694  	}
695  
696  	__vma_link(mm, vma, prev, rb_link, rb_parent);
697  	__vma_link_file(vma);
698  
699  	if (mapping)
700  		i_mmap_unlock_write(mapping);
701  
702  	mm->map_count++;
703  	validate_mm(mm);
704  }
705  
706  /*
707   * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
708   * mm's list and rbtree.  It has already been inserted into the interval tree.
709   */
710  static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
711  {
712  	struct vm_area_struct *prev;
713  	struct rb_node **rb_link, *rb_parent;
714  
715  	if (find_vma_links(mm, vma->vm_start, vma->vm_end,
716  			   &prev, &rb_link, &rb_parent))
717  		BUG();
718  	__vma_link(mm, vma, prev, rb_link, rb_parent);
719  	mm->map_count++;
720  }
721  
722  static __always_inline void __vma_unlink(struct mm_struct *mm,
723  						struct vm_area_struct *vma,
724  						struct vm_area_struct *ignore)
725  {
726  	vma_rb_erase_ignore(vma, &mm->mm_rb, ignore);
727  	__vma_unlink_list(mm, vma);
728  	/* Kill the cache */
729  	vmacache_invalidate(mm);
730  }
731  
732  /*
733   * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
734   * is already present in an i_mmap tree without adjusting the tree.
735   * The following helper function should be used when such adjustments
736   * are necessary.  The "insert" vma (if any) is to be inserted
737   * before we drop the necessary locks.
738   */
739  int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
740  	unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert,
741  	struct vm_area_struct *expand)
742  {
743  	struct mm_struct *mm = vma->vm_mm;
744  	struct vm_area_struct *next = vma->vm_next, *orig_vma = vma;
745  	struct address_space *mapping = NULL;
746  	struct rb_root_cached *root = NULL;
747  	struct anon_vma *anon_vma = NULL;
748  	struct file *file = vma->vm_file;
749  	bool start_changed = false, end_changed = false;
750  	long adjust_next = 0;
751  	int remove_next = 0;
752  
753  	if (next && !insert) {
754  		struct vm_area_struct *exporter = NULL, *importer = NULL;
755  
756  		if (end >= next->vm_end) {
757  			/*
758  			 * vma expands, overlapping all the next, and
759  			 * perhaps the one after too (mprotect case 6).
760  			 * The only other cases that gets here are
761  			 * case 1, case 7 and case 8.
762  			 */
763  			if (next == expand) {
764  				/*
765  				 * The only case where we don't expand "vma"
766  				 * and we expand "next" instead is case 8.
767  				 */
768  				VM_WARN_ON(end != next->vm_end);
769  				/*
770  				 * remove_next == 3 means we're
771  				 * removing "vma" and that to do so we
772  				 * swapped "vma" and "next".
773  				 */
774  				remove_next = 3;
775  				VM_WARN_ON(file != next->vm_file);
776  				swap(vma, next);
777  			} else {
778  				VM_WARN_ON(expand != vma);
779  				/*
780  				 * case 1, 6, 7, remove_next == 2 is case 6,
781  				 * remove_next == 1 is case 1 or 7.
782  				 */
783  				remove_next = 1 + (end > next->vm_end);
784  				VM_WARN_ON(remove_next == 2 &&
785  					   end != next->vm_next->vm_end);
786  				/* trim end to next, for case 6 first pass */
787  				end = next->vm_end;
788  			}
789  
790  			exporter = next;
791  			importer = vma;
792  
793  			/*
794  			 * If next doesn't have anon_vma, import from vma after
795  			 * next, if the vma overlaps with it.
796  			 */
797  			if (remove_next == 2 && !next->anon_vma)
798  				exporter = next->vm_next;
799  
800  		} else if (end > next->vm_start) {
801  			/*
802  			 * vma expands, overlapping part of the next:
803  			 * mprotect case 5 shifting the boundary up.
804  			 */
805  			adjust_next = (end - next->vm_start);
806  			exporter = next;
807  			importer = vma;
808  			VM_WARN_ON(expand != importer);
809  		} else if (end < vma->vm_end) {
810  			/*
811  			 * vma shrinks, and !insert tells it's not
812  			 * split_vma inserting another: so it must be
813  			 * mprotect case 4 shifting the boundary down.
814  			 */
815  			adjust_next = -(vma->vm_end - end);
816  			exporter = vma;
817  			importer = next;
818  			VM_WARN_ON(expand != importer);
819  		}
820  
821  		/*
822  		 * Easily overlooked: when mprotect shifts the boundary,
823  		 * make sure the expanding vma has anon_vma set if the
824  		 * shrinking vma had, to cover any anon pages imported.
825  		 */
826  		if (exporter && exporter->anon_vma && !importer->anon_vma) {
827  			int error;
828  
829  			importer->anon_vma = exporter->anon_vma;
830  			error = anon_vma_clone(importer, exporter);
831  			if (error)
832  				return error;
833  		}
834  	}
835  again:
836  	vma_adjust_trans_huge(orig_vma, start, end, adjust_next);
837  
838  	if (file) {
839  		mapping = file->f_mapping;
840  		root = &mapping->i_mmap;
841  		uprobe_munmap(vma, vma->vm_start, vma->vm_end);
842  
843  		if (adjust_next)
844  			uprobe_munmap(next, next->vm_start, next->vm_end);
845  
846  		i_mmap_lock_write(mapping);
847  		if (insert) {
848  			/*
849  			 * Put into interval tree now, so instantiated pages
850  			 * are visible to arm/parisc __flush_dcache_page
851  			 * throughout; but we cannot insert into address
852  			 * space until vma start or end is updated.
853  			 */
854  			__vma_link_file(insert);
855  		}
856  	}
857  
858  	anon_vma = vma->anon_vma;
859  	if (!anon_vma && adjust_next)
860  		anon_vma = next->anon_vma;
861  	if (anon_vma) {
862  		VM_WARN_ON(adjust_next && next->anon_vma &&
863  			   anon_vma != next->anon_vma);
864  		anon_vma_lock_write(anon_vma);
865  		anon_vma_interval_tree_pre_update_vma(vma);
866  		if (adjust_next)
867  			anon_vma_interval_tree_pre_update_vma(next);
868  	}
869  
870  	if (file) {
871  		flush_dcache_mmap_lock(mapping);
872  		vma_interval_tree_remove(vma, root);
873  		if (adjust_next)
874  			vma_interval_tree_remove(next, root);
875  	}
876  
877  	if (start != vma->vm_start) {
878  		vma->vm_start = start;
879  		start_changed = true;
880  	}
881  	if (end != vma->vm_end) {
882  		vma->vm_end = end;
883  		end_changed = true;
884  	}
885  	vma->vm_pgoff = pgoff;
886  	if (adjust_next) {
887  		next->vm_start += adjust_next;
888  		next->vm_pgoff += adjust_next >> PAGE_SHIFT;
889  	}
890  
891  	if (file) {
892  		if (adjust_next)
893  			vma_interval_tree_insert(next, root);
894  		vma_interval_tree_insert(vma, root);
895  		flush_dcache_mmap_unlock(mapping);
896  	}
897  
898  	if (remove_next) {
899  		/*
900  		 * vma_merge has merged next into vma, and needs
901  		 * us to remove next before dropping the locks.
902  		 */
903  		if (remove_next != 3)
904  			__vma_unlink(mm, next, next);
905  		else
906  			/*
907  			 * vma is not before next if they've been
908  			 * swapped.
909  			 *
910  			 * pre-swap() next->vm_start was reduced so
911  			 * tell validate_mm_rb to ignore pre-swap()
912  			 * "next" (which is stored in post-swap()
913  			 * "vma").
914  			 */
915  			__vma_unlink(mm, next, vma);
916  		if (file)
917  			__remove_shared_vm_struct(next, file, mapping);
918  	} else if (insert) {
919  		/*
920  		 * split_vma has split insert from vma, and needs
921  		 * us to insert it before dropping the locks
922  		 * (it may either follow vma or precede it).
923  		 */
924  		__insert_vm_struct(mm, insert);
925  	} else {
926  		if (start_changed)
927  			vma_gap_update(vma);
928  		if (end_changed) {
929  			if (!next)
930  				mm->highest_vm_end = vm_end_gap(vma);
931  			else if (!adjust_next)
932  				vma_gap_update(next);
933  		}
934  	}
935  
936  	if (anon_vma) {
937  		anon_vma_interval_tree_post_update_vma(vma);
938  		if (adjust_next)
939  			anon_vma_interval_tree_post_update_vma(next);
940  		anon_vma_unlock_write(anon_vma);
941  	}
942  
943  	if (file) {
944  		i_mmap_unlock_write(mapping);
945  		uprobe_mmap(vma);
946  
947  		if (adjust_next)
948  			uprobe_mmap(next);
949  	}
950  
951  	if (remove_next) {
952  		if (file) {
953  			uprobe_munmap(next, next->vm_start, next->vm_end);
954  			fput(file);
955  		}
956  		if (next->anon_vma)
957  			anon_vma_merge(vma, next);
958  		mm->map_count--;
959  		mpol_put(vma_policy(next));
960  		vm_area_free(next);
961  		/*
962  		 * In mprotect's case 6 (see comments on vma_merge),
963  		 * we must remove another next too. It would clutter
964  		 * up the code too much to do both in one go.
965  		 */
966  		if (remove_next != 3) {
967  			/*
968  			 * If "next" was removed and vma->vm_end was
969  			 * expanded (up) over it, in turn
970  			 * "next->vm_prev->vm_end" changed and the
971  			 * "vma->vm_next" gap must be updated.
972  			 */
973  			next = vma->vm_next;
974  		} else {
975  			/*
976  			 * For the scope of the comment "next" and
977  			 * "vma" considered pre-swap(): if "vma" was
978  			 * removed, next->vm_start was expanded (down)
979  			 * over it and the "next" gap must be updated.
980  			 * Because of the swap() the post-swap() "vma"
981  			 * actually points to pre-swap() "next"
982  			 * (post-swap() "next" as opposed is now a
983  			 * dangling pointer).
984  			 */
985  			next = vma;
986  		}
987  		if (remove_next == 2) {
988  			remove_next = 1;
989  			end = next->vm_end;
990  			goto again;
991  		}
992  		else if (next)
993  			vma_gap_update(next);
994  		else {
995  			/*
996  			 * If remove_next == 2 we obviously can't
997  			 * reach this path.
998  			 *
999  			 * If remove_next == 3 we can't reach this
1000  			 * path because pre-swap() next is always not
1001  			 * NULL. pre-swap() "next" is not being
1002  			 * removed and its next->vm_end is not altered
1003  			 * (and furthermore "end" already matches
1004  			 * next->vm_end in remove_next == 3).
1005  			 *
1006  			 * We reach this only in the remove_next == 1
1007  			 * case if the "next" vma that was removed was
1008  			 * the highest vma of the mm. However in such
1009  			 * case next->vm_end == "end" and the extended
1010  			 * "vma" has vma->vm_end == next->vm_end so
1011  			 * mm->highest_vm_end doesn't need any update
1012  			 * in remove_next == 1 case.
1013  			 */
1014  			VM_WARN_ON(mm->highest_vm_end != vm_end_gap(vma));
1015  		}
1016  	}
1017  	if (insert && file)
1018  		uprobe_mmap(insert);
1019  
1020  	validate_mm(mm);
1021  
1022  	return 0;
1023  }
1024  
1025  /*
1026   * If the vma has a ->close operation then the driver probably needs to release
1027   * per-vma resources, so we don't attempt to merge those.
1028   */
1029  static inline int is_mergeable_vma(struct vm_area_struct *vma,
1030  				struct file *file, unsigned long vm_flags,
1031  				struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1032  {
1033  	/*
1034  	 * VM_SOFTDIRTY should not prevent from VMA merging, if we
1035  	 * match the flags but dirty bit -- the caller should mark
1036  	 * merged VMA as dirty. If dirty bit won't be excluded from
1037  	 * comparison, we increase pressure on the memory system forcing
1038  	 * the kernel to generate new VMAs when old one could be
1039  	 * extended instead.
1040  	 */
1041  	if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
1042  		return 0;
1043  	if (vma->vm_file != file)
1044  		return 0;
1045  	if (vma->vm_ops && vma->vm_ops->close)
1046  		return 0;
1047  	if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
1048  		return 0;
1049  	return 1;
1050  }
1051  
1052  static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
1053  					struct anon_vma *anon_vma2,
1054  					struct vm_area_struct *vma)
1055  {
1056  	/*
1057  	 * The list_is_singular() test is to avoid merging VMA cloned from
1058  	 * parents. This can improve scalability caused by anon_vma lock.
1059  	 */
1060  	if ((!anon_vma1 || !anon_vma2) && (!vma ||
1061  		list_is_singular(&vma->anon_vma_chain)))
1062  		return 1;
1063  	return anon_vma1 == anon_vma2;
1064  }
1065  
1066  /*
1067   * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1068   * in front of (at a lower virtual address and file offset than) the vma.
1069   *
1070   * We cannot merge two vmas if they have differently assigned (non-NULL)
1071   * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1072   *
1073   * We don't check here for the merged mmap wrapping around the end of pagecache
1074   * indices (16TB on ia32) because do_mmap() does not permit mmap's which
1075   * wrap, nor mmaps which cover the final page at index -1UL.
1076   */
1077  static int
1078  can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
1079  		     struct anon_vma *anon_vma, struct file *file,
1080  		     pgoff_t vm_pgoff,
1081  		     struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1082  {
1083  	if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1084  	    is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1085  		if (vma->vm_pgoff == vm_pgoff)
1086  			return 1;
1087  	}
1088  	return 0;
1089  }
1090  
1091  /*
1092   * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1093   * beyond (at a higher virtual address and file offset than) the vma.
1094   *
1095   * We cannot merge two vmas if they have differently assigned (non-NULL)
1096   * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1097   */
1098  static int
1099  can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
1100  		    struct anon_vma *anon_vma, struct file *file,
1101  		    pgoff_t vm_pgoff,
1102  		    struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1103  {
1104  	if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1105  	    is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1106  		pgoff_t vm_pglen;
1107  		vm_pglen = vma_pages(vma);
1108  		if (vma->vm_pgoff + vm_pglen == vm_pgoff)
1109  			return 1;
1110  	}
1111  	return 0;
1112  }
1113  
1114  /*
1115   * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
1116   * whether that can be merged with its predecessor or its successor.
1117   * Or both (it neatly fills a hole).
1118   *
1119   * In most cases - when called for mmap, brk or mremap - [addr,end) is
1120   * certain not to be mapped by the time vma_merge is called; but when
1121   * called for mprotect, it is certain to be already mapped (either at
1122   * an offset within prev, or at the start of next), and the flags of
1123   * this area are about to be changed to vm_flags - and the no-change
1124   * case has already been eliminated.
1125   *
1126   * The following mprotect cases have to be considered, where AAAA is
1127   * the area passed down from mprotect_fixup, never extending beyond one
1128   * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
1129   *
1130   *     AAAA             AAAA                   AAAA
1131   *    PPPPPPNNNNNN    PPPPPPNNNNNN       PPPPPPNNNNNN
1132   *    cannot merge    might become       might become
1133   *                    PPNNNNNNNNNN       PPPPPPPPPPNN
1134   *    mmap, brk or    case 4 below       case 5 below
1135   *    mremap move:
1136   *                        AAAA               AAAA
1137   *                    PPPP    NNNN       PPPPNNNNXXXX
1138   *                    might become       might become
1139   *                    PPPPPPPPPPPP 1 or  PPPPPPPPPPPP 6 or
1140   *                    PPPPPPPPNNNN 2 or  PPPPPPPPXXXX 7 or
1141   *                    PPPPNNNNNNNN 3     PPPPXXXXXXXX 8
1142   *
1143   * It is important for case 8 that the vma NNNN overlapping the
1144   * region AAAA is never going to extended over XXXX. Instead XXXX must
1145   * be extended in region AAAA and NNNN must be removed. This way in
1146   * all cases where vma_merge succeeds, the moment vma_adjust drops the
1147   * rmap_locks, the properties of the merged vma will be already
1148   * correct for the whole merged range. Some of those properties like
1149   * vm_page_prot/vm_flags may be accessed by rmap_walks and they must
1150   * be correct for the whole merged range immediately after the
1151   * rmap_locks are released. Otherwise if XXXX would be removed and
1152   * NNNN would be extended over the XXXX range, remove_migration_ptes
1153   * or other rmap walkers (if working on addresses beyond the "end"
1154   * parameter) may establish ptes with the wrong permissions of NNNN
1155   * instead of the right permissions of XXXX.
1156   */
1157  struct vm_area_struct *vma_merge(struct mm_struct *mm,
1158  			struct vm_area_struct *prev, unsigned long addr,
1159  			unsigned long end, unsigned long vm_flags,
1160  			struct anon_vma *anon_vma, struct file *file,
1161  			pgoff_t pgoff, struct mempolicy *policy,
1162  			struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1163  {
1164  	pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
1165  	struct vm_area_struct *area, *next;
1166  	int err;
1167  
1168  	/*
1169  	 * We later require that vma->vm_flags == vm_flags,
1170  	 * so this tests vma->vm_flags & VM_SPECIAL, too.
1171  	 */
1172  	if (vm_flags & VM_SPECIAL)
1173  		return NULL;
1174  
1175  	next = vma_next(mm, prev);
1176  	area = next;
1177  	if (area && area->vm_end == end)		/* cases 6, 7, 8 */
1178  		next = next->vm_next;
1179  
1180  	/* verify some invariant that must be enforced by the caller */
1181  	VM_WARN_ON(prev && addr <= prev->vm_start);
1182  	VM_WARN_ON(area && end > area->vm_end);
1183  	VM_WARN_ON(addr >= end);
1184  
1185  	/*
1186  	 * Can it merge with the predecessor?
1187  	 */
1188  	if (prev && prev->vm_end == addr &&
1189  			mpol_equal(vma_policy(prev), policy) &&
1190  			can_vma_merge_after(prev, vm_flags,
1191  					    anon_vma, file, pgoff,
1192  					    vm_userfaultfd_ctx)) {
1193  		/*
1194  		 * OK, it can.  Can we now merge in the successor as well?
1195  		 */
1196  		if (next && end == next->vm_start &&
1197  				mpol_equal(policy, vma_policy(next)) &&
1198  				can_vma_merge_before(next, vm_flags,
1199  						     anon_vma, file,
1200  						     pgoff+pglen,
1201  						     vm_userfaultfd_ctx) &&
1202  				is_mergeable_anon_vma(prev->anon_vma,
1203  						      next->anon_vma, NULL)) {
1204  							/* cases 1, 6 */
1205  			err = __vma_adjust(prev, prev->vm_start,
1206  					 next->vm_end, prev->vm_pgoff, NULL,
1207  					 prev);
1208  		} else					/* cases 2, 5, 7 */
1209  			err = __vma_adjust(prev, prev->vm_start,
1210  					 end, prev->vm_pgoff, NULL, prev);
1211  		if (err)
1212  			return NULL;
1213  		khugepaged_enter_vma_merge(prev, vm_flags);
1214  		return prev;
1215  	}
1216  
1217  	/*
1218  	 * Can this new request be merged in front of next?
1219  	 */
1220  	if (next && end == next->vm_start &&
1221  			mpol_equal(policy, vma_policy(next)) &&
1222  			can_vma_merge_before(next, vm_flags,
1223  					     anon_vma, file, pgoff+pglen,
1224  					     vm_userfaultfd_ctx)) {
1225  		if (prev && addr < prev->vm_end)	/* case 4 */
1226  			err = __vma_adjust(prev, prev->vm_start,
1227  					 addr, prev->vm_pgoff, NULL, next);
1228  		else {					/* cases 3, 8 */
1229  			err = __vma_adjust(area, addr, next->vm_end,
1230  					 next->vm_pgoff - pglen, NULL, next);
1231  			/*
1232  			 * In case 3 area is already equal to next and
1233  			 * this is a noop, but in case 8 "area" has
1234  			 * been removed and next was expanded over it.
1235  			 */
1236  			area = next;
1237  		}
1238  		if (err)
1239  			return NULL;
1240  		khugepaged_enter_vma_merge(area, vm_flags);
1241  		return area;
1242  	}
1243  
1244  	return NULL;
1245  }
1246  
1247  /*
1248   * Rough compatibility check to quickly see if it's even worth looking
1249   * at sharing an anon_vma.
1250   *
1251   * They need to have the same vm_file, and the flags can only differ
1252   * in things that mprotect may change.
1253   *
1254   * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
1255   * we can merge the two vma's. For example, we refuse to merge a vma if
1256   * there is a vm_ops->close() function, because that indicates that the
1257   * driver is doing some kind of reference counting. But that doesn't
1258   * really matter for the anon_vma sharing case.
1259   */
1260  static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
1261  {
1262  	return a->vm_end == b->vm_start &&
1263  		mpol_equal(vma_policy(a), vma_policy(b)) &&
1264  		a->vm_file == b->vm_file &&
1265  		!((a->vm_flags ^ b->vm_flags) & ~(VM_ACCESS_FLAGS | VM_SOFTDIRTY)) &&
1266  		b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
1267  }
1268  
1269  /*
1270   * Do some basic sanity checking to see if we can re-use the anon_vma
1271   * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
1272   * the same as 'old', the other will be the new one that is trying
1273   * to share the anon_vma.
1274   *
1275   * NOTE! This runs with mm_sem held for reading, so it is possible that
1276   * the anon_vma of 'old' is concurrently in the process of being set up
1277   * by another page fault trying to merge _that_. But that's ok: if it
1278   * is being set up, that automatically means that it will be a singleton
1279   * acceptable for merging, so we can do all of this optimistically. But
1280   * we do that READ_ONCE() to make sure that we never re-load the pointer.
1281   *
1282   * IOW: that the "list_is_singular()" test on the anon_vma_chain only
1283   * matters for the 'stable anon_vma' case (ie the thing we want to avoid
1284   * is to return an anon_vma that is "complex" due to having gone through
1285   * a fork).
1286   *
1287   * We also make sure that the two vma's are compatible (adjacent,
1288   * and with the same memory policies). That's all stable, even with just
1289   * a read lock on the mm_sem.
1290   */
1291  static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
1292  {
1293  	if (anon_vma_compatible(a, b)) {
1294  		struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
1295  
1296  		if (anon_vma && list_is_singular(&old->anon_vma_chain))
1297  			return anon_vma;
1298  	}
1299  	return NULL;
1300  }
1301  
1302  /*
1303   * find_mergeable_anon_vma is used by anon_vma_prepare, to check
1304   * neighbouring vmas for a suitable anon_vma, before it goes off
1305   * to allocate a new anon_vma.  It checks because a repetitive
1306   * sequence of mprotects and faults may otherwise lead to distinct
1307   * anon_vmas being allocated, preventing vma merge in subsequent
1308   * mprotect.
1309   */
1310  struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
1311  {
1312  	struct anon_vma *anon_vma = NULL;
1313  
1314  	/* Try next first. */
1315  	if (vma->vm_next) {
1316  		anon_vma = reusable_anon_vma(vma->vm_next, vma, vma->vm_next);
1317  		if (anon_vma)
1318  			return anon_vma;
1319  	}
1320  
1321  	/* Try prev next. */
1322  	if (vma->vm_prev)
1323  		anon_vma = reusable_anon_vma(vma->vm_prev, vma->vm_prev, vma);
1324  
1325  	/*
1326  	 * We might reach here with anon_vma == NULL if we can't find
1327  	 * any reusable anon_vma.
1328  	 * There's no absolute need to look only at touching neighbours:
1329  	 * we could search further afield for "compatible" anon_vmas.
1330  	 * But it would probably just be a waste of time searching,
1331  	 * or lead to too many vmas hanging off the same anon_vma.
1332  	 * We're trying to allow mprotect remerging later on,
1333  	 * not trying to minimize memory used for anon_vmas.
1334  	 */
1335  	return anon_vma;
1336  }
1337  
1338  /*
1339   * If a hint addr is less than mmap_min_addr change hint to be as
1340   * low as possible but still greater than mmap_min_addr
1341   */
1342  static inline unsigned long round_hint_to_min(unsigned long hint)
1343  {
1344  	hint &= PAGE_MASK;
1345  	if (((void *)hint != NULL) &&
1346  	    (hint < mmap_min_addr))
1347  		return PAGE_ALIGN(mmap_min_addr);
1348  	return hint;
1349  }
1350  
1351  static inline int mlock_future_check(struct mm_struct *mm,
1352  				     unsigned long flags,
1353  				     unsigned long len)
1354  {
1355  	unsigned long locked, lock_limit;
1356  
1357  	/*  mlock MCL_FUTURE? */
1358  	if (flags & VM_LOCKED) {
1359  		locked = len >> PAGE_SHIFT;
1360  		locked += mm->locked_vm;
1361  		lock_limit = rlimit(RLIMIT_MEMLOCK);
1362  		lock_limit >>= PAGE_SHIFT;
1363  		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1364  			return -EAGAIN;
1365  	}
1366  	return 0;
1367  }
1368  
1369  static inline u64 file_mmap_size_max(struct file *file, struct inode *inode)
1370  {
1371  	if (S_ISREG(inode->i_mode))
1372  		return MAX_LFS_FILESIZE;
1373  
1374  	if (S_ISBLK(inode->i_mode))
1375  		return MAX_LFS_FILESIZE;
1376  
1377  	if (S_ISSOCK(inode->i_mode))
1378  		return MAX_LFS_FILESIZE;
1379  
1380  	/* Special "we do even unsigned file positions" case */
1381  	if (file->f_mode & FMODE_UNSIGNED_OFFSET)
1382  		return 0;
1383  
1384  	/* Yes, random drivers might want more. But I'm tired of buggy drivers */
1385  	return ULONG_MAX;
1386  }
1387  
1388  static inline bool file_mmap_ok(struct file *file, struct inode *inode,
1389  				unsigned long pgoff, unsigned long len)
1390  {
1391  	u64 maxsize = file_mmap_size_max(file, inode);
1392  
1393  	if (maxsize && len > maxsize)
1394  		return false;
1395  	maxsize -= len;
1396  	if (pgoff > maxsize >> PAGE_SHIFT)
1397  		return false;
1398  	return true;
1399  }
1400  
1401  /*
1402   * The caller must write-lock current->mm->mmap_lock.
1403   */
1404  unsigned long do_mmap(struct file *file, unsigned long addr,
1405  			unsigned long len, unsigned long prot,
1406  			unsigned long flags, unsigned long pgoff,
1407  			unsigned long *populate, struct list_head *uf)
1408  {
1409  	struct mm_struct *mm = current->mm;
1410  	vm_flags_t vm_flags;
1411  	int pkey = 0;
1412  
1413  	*populate = 0;
1414  
1415  	if (!len)
1416  		return -EINVAL;
1417  
1418  	/*
1419  	 * Does the application expect PROT_READ to imply PROT_EXEC?
1420  	 *
1421  	 * (the exception is when the underlying filesystem is noexec
1422  	 *  mounted, in which case we dont add PROT_EXEC.)
1423  	 */
1424  	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
1425  		if (!(file && path_noexec(&file->f_path)))
1426  			prot |= PROT_EXEC;
1427  
1428  	/* force arch specific MAP_FIXED handling in get_unmapped_area */
1429  	if (flags & MAP_FIXED_NOREPLACE)
1430  		flags |= MAP_FIXED;
1431  
1432  	if (!(flags & MAP_FIXED))
1433  		addr = round_hint_to_min(addr);
1434  
1435  	/* Careful about overflows.. */
1436  	len = PAGE_ALIGN(len);
1437  	if (!len)
1438  		return -ENOMEM;
1439  
1440  	/* offset overflow? */
1441  	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
1442  		return -EOVERFLOW;
1443  
1444  	/* Too many mappings? */
1445  	if (mm->map_count > sysctl_max_map_count)
1446  		return -ENOMEM;
1447  
1448  	/* Obtain the address to map to. we verify (or select) it and ensure
1449  	 * that it represents a valid section of the address space.
1450  	 */
1451  	addr = get_unmapped_area(file, addr, len, pgoff, flags);
1452  	if (IS_ERR_VALUE(addr))
1453  		return addr;
1454  
1455  	if (flags & MAP_FIXED_NOREPLACE) {
1456  		struct vm_area_struct *vma = find_vma(mm, addr);
1457  
1458  		if (vma && vma->vm_start < addr + len)
1459  			return -EEXIST;
1460  	}
1461  
1462  	if (prot == PROT_EXEC) {
1463  		pkey = execute_only_pkey(mm);
1464  		if (pkey < 0)
1465  			pkey = 0;
1466  	}
1467  
1468  	/* Do simple checking here so the lower-level routines won't have
1469  	 * to. we assume access permissions have been handled by the open
1470  	 * of the memory object, so we don't do any here.
1471  	 */
1472  	vm_flags = calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
1473  			mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1474  
1475  	if (flags & MAP_LOCKED)
1476  		if (!can_do_mlock())
1477  			return -EPERM;
1478  
1479  	if (mlock_future_check(mm, vm_flags, len))
1480  		return -EAGAIN;
1481  
1482  	if (file) {
1483  		struct inode *inode = file_inode(file);
1484  		unsigned long flags_mask;
1485  
1486  		if (!file_mmap_ok(file, inode, pgoff, len))
1487  			return -EOVERFLOW;
1488  
1489  		flags_mask = LEGACY_MAP_MASK | file->f_op->mmap_supported_flags;
1490  
1491  		switch (flags & MAP_TYPE) {
1492  		case MAP_SHARED:
1493  			/*
1494  			 * Force use of MAP_SHARED_VALIDATE with non-legacy
1495  			 * flags. E.g. MAP_SYNC is dangerous to use with
1496  			 * MAP_SHARED as you don't know which consistency model
1497  			 * you will get. We silently ignore unsupported flags
1498  			 * with MAP_SHARED to preserve backward compatibility.
1499  			 */
1500  			flags &= LEGACY_MAP_MASK;
1501  			fallthrough;
1502  		case MAP_SHARED_VALIDATE:
1503  			if (flags & ~flags_mask)
1504  				return -EOPNOTSUPP;
1505  			if (prot & PROT_WRITE) {
1506  				if (!(file->f_mode & FMODE_WRITE))
1507  					return -EACCES;
1508  				if (IS_SWAPFILE(file->f_mapping->host))
1509  					return -ETXTBSY;
1510  			}
1511  
1512  			/*
1513  			 * Make sure we don't allow writing to an append-only
1514  			 * file..
1515  			 */
1516  			if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1517  				return -EACCES;
1518  
1519  			/*
1520  			 * Make sure there are no mandatory locks on the file.
1521  			 */
1522  			if (locks_verify_locked(file))
1523  				return -EAGAIN;
1524  
1525  			vm_flags |= VM_SHARED | VM_MAYSHARE;
1526  			if (!(file->f_mode & FMODE_WRITE))
1527  				vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1528  			fallthrough;
1529  		case MAP_PRIVATE:
1530  			if (!(file->f_mode & FMODE_READ))
1531  				return -EACCES;
1532  			if (path_noexec(&file->f_path)) {
1533  				if (vm_flags & VM_EXEC)
1534  					return -EPERM;
1535  				vm_flags &= ~VM_MAYEXEC;
1536  			}
1537  
1538  			if (!file->f_op->mmap)
1539  				return -ENODEV;
1540  			if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1541  				return -EINVAL;
1542  			break;
1543  
1544  		default:
1545  			return -EINVAL;
1546  		}
1547  	} else {
1548  		switch (flags & MAP_TYPE) {
1549  		case MAP_SHARED:
1550  			if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1551  				return -EINVAL;
1552  			/*
1553  			 * Ignore pgoff.
1554  			 */
1555  			pgoff = 0;
1556  			vm_flags |= VM_SHARED | VM_MAYSHARE;
1557  			break;
1558  		case MAP_PRIVATE:
1559  			/*
1560  			 * Set pgoff according to addr for anon_vma.
1561  			 */
1562  			pgoff = addr >> PAGE_SHIFT;
1563  			break;
1564  		default:
1565  			return -EINVAL;
1566  		}
1567  	}
1568  
1569  	/*
1570  	 * Set 'VM_NORESERVE' if we should not account for the
1571  	 * memory use of this mapping.
1572  	 */
1573  	if (flags & MAP_NORESERVE) {
1574  		/* We honor MAP_NORESERVE if allowed to overcommit */
1575  		if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1576  			vm_flags |= VM_NORESERVE;
1577  
1578  		/* hugetlb applies strict overcommit unless MAP_NORESERVE */
1579  		if (file && is_file_hugepages(file))
1580  			vm_flags |= VM_NORESERVE;
1581  	}
1582  
1583  	addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
1584  	if (!IS_ERR_VALUE(addr) &&
1585  	    ((vm_flags & VM_LOCKED) ||
1586  	     (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
1587  		*populate = len;
1588  	return addr;
1589  }
1590  
1591  unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
1592  			      unsigned long prot, unsigned long flags,
1593  			      unsigned long fd, unsigned long pgoff)
1594  {
1595  	struct file *file = NULL;
1596  	unsigned long retval;
1597  
1598  	if (!(flags & MAP_ANONYMOUS)) {
1599  		audit_mmap_fd(fd, flags);
1600  		file = fget(fd);
1601  		if (!file)
1602  			return -EBADF;
1603  		if (is_file_hugepages(file)) {
1604  			len = ALIGN(len, huge_page_size(hstate_file(file)));
1605  		} else if (unlikely(flags & MAP_HUGETLB)) {
1606  			retval = -EINVAL;
1607  			goto out_fput;
1608  		}
1609  	} else if (flags & MAP_HUGETLB) {
1610  		struct user_struct *user = NULL;
1611  		struct hstate *hs;
1612  
1613  		hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1614  		if (!hs)
1615  			return -EINVAL;
1616  
1617  		len = ALIGN(len, huge_page_size(hs));
1618  		/*
1619  		 * VM_NORESERVE is used because the reservations will be
1620  		 * taken when vm_ops->mmap() is called
1621  		 * A dummy user value is used because we are not locking
1622  		 * memory so no accounting is necessary
1623  		 */
1624  		file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
1625  				VM_NORESERVE,
1626  				&user, HUGETLB_ANONHUGE_INODE,
1627  				(flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1628  		if (IS_ERR(file))
1629  			return PTR_ERR(file);
1630  	}
1631  
1632  	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1633  
1634  	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1635  out_fput:
1636  	if (file)
1637  		fput(file);
1638  	return retval;
1639  }
1640  
1641  SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1642  		unsigned long, prot, unsigned long, flags,
1643  		unsigned long, fd, unsigned long, pgoff)
1644  {
1645  	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
1646  }
1647  
1648  #ifdef __ARCH_WANT_SYS_OLD_MMAP
1649  struct mmap_arg_struct {
1650  	unsigned long addr;
1651  	unsigned long len;
1652  	unsigned long prot;
1653  	unsigned long flags;
1654  	unsigned long fd;
1655  	unsigned long offset;
1656  };
1657  
1658  SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1659  {
1660  	struct mmap_arg_struct a;
1661  
1662  	if (copy_from_user(&a, arg, sizeof(a)))
1663  		return -EFAULT;
1664  	if (offset_in_page(a.offset))
1665  		return -EINVAL;
1666  
1667  	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1668  			       a.offset >> PAGE_SHIFT);
1669  }
1670  #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1671  
1672  /*
1673   * Some shared mappings will want the pages marked read-only
1674   * to track write events. If so, we'll downgrade vm_page_prot
1675   * to the private version (using protection_map[] without the
1676   * VM_SHARED bit).
1677   */
1678  int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
1679  {
1680  	vm_flags_t vm_flags = vma->vm_flags;
1681  	const struct vm_operations_struct *vm_ops = vma->vm_ops;
1682  
1683  	/* If it was private or non-writable, the write bit is already clear */
1684  	if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1685  		return 0;
1686  
1687  	/* The backer wishes to know when pages are first written to? */
1688  	if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite))
1689  		return 1;
1690  
1691  	/* The open routine did something to the protections that pgprot_modify
1692  	 * won't preserve? */
1693  	if (pgprot_val(vm_page_prot) !=
1694  	    pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags)))
1695  		return 0;
1696  
1697  	/* Do we need to track softdirty? */
1698  	if (IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) && !(vm_flags & VM_SOFTDIRTY))
1699  		return 1;
1700  
1701  	/* Specialty mapping? */
1702  	if (vm_flags & VM_PFNMAP)
1703  		return 0;
1704  
1705  	/* Can the mapping track the dirty pages? */
1706  	return vma->vm_file && vma->vm_file->f_mapping &&
1707  		mapping_can_writeback(vma->vm_file->f_mapping);
1708  }
1709  
1710  /*
1711   * We account for memory if it's a private writeable mapping,
1712   * not hugepages and VM_NORESERVE wasn't set.
1713   */
1714  static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1715  {
1716  	/*
1717  	 * hugetlb has its own accounting separate from the core VM
1718  	 * VM_HUGETLB may not be set yet so we cannot check for that flag.
1719  	 */
1720  	if (file && is_file_hugepages(file))
1721  		return 0;
1722  
1723  	return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1724  }
1725  
1726  unsigned long mmap_region(struct file *file, unsigned long addr,
1727  		unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
1728  		struct list_head *uf)
1729  {
1730  	struct mm_struct *mm = current->mm;
1731  	struct vm_area_struct *vma, *prev, *merge;
1732  	int error;
1733  	struct rb_node **rb_link, *rb_parent;
1734  	unsigned long charged = 0;
1735  
1736  	/* Check against address space limit. */
1737  	if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
1738  		unsigned long nr_pages;
1739  
1740  		/*
1741  		 * MAP_FIXED may remove pages of mappings that intersects with
1742  		 * requested mapping. Account for the pages it would unmap.
1743  		 */
1744  		nr_pages = count_vma_pages_range(mm, addr, addr + len);
1745  
1746  		if (!may_expand_vm(mm, vm_flags,
1747  					(len >> PAGE_SHIFT) - nr_pages))
1748  			return -ENOMEM;
1749  	}
1750  
1751  	/* Clear old maps, set up prev, rb_link, rb_parent, and uf */
1752  	if (munmap_vma_range(mm, addr, len, &prev, &rb_link, &rb_parent, uf))
1753  		return -ENOMEM;
1754  	/*
1755  	 * Private writable mapping: check memory availability
1756  	 */
1757  	if (accountable_mapping(file, vm_flags)) {
1758  		charged = len >> PAGE_SHIFT;
1759  		if (security_vm_enough_memory_mm(mm, charged))
1760  			return -ENOMEM;
1761  		vm_flags |= VM_ACCOUNT;
1762  	}
1763  
1764  	/*
1765  	 * Can we just expand an old mapping?
1766  	 */
1767  	vma = vma_merge(mm, prev, addr, addr + len, vm_flags,
1768  			NULL, file, pgoff, NULL, NULL_VM_UFFD_CTX);
1769  	if (vma)
1770  		goto out;
1771  
1772  	/*
1773  	 * Determine the object being mapped and call the appropriate
1774  	 * specific mapper. the address has already been validated, but
1775  	 * not unmapped, but the maps are removed from the list.
1776  	 */
1777  	vma = vm_area_alloc(mm);
1778  	if (!vma) {
1779  		error = -ENOMEM;
1780  		goto unacct_error;
1781  	}
1782  
1783  	vma->vm_start = addr;
1784  	vma->vm_end = addr + len;
1785  	vma->vm_flags = vm_flags;
1786  	vma->vm_page_prot = vm_get_page_prot(vm_flags);
1787  	vma->vm_pgoff = pgoff;
1788  
1789  	if (file) {
1790  		if (vm_flags & VM_DENYWRITE) {
1791  			error = deny_write_access(file);
1792  			if (error)
1793  				goto free_vma;
1794  		}
1795  		if (vm_flags & VM_SHARED) {
1796  			error = mapping_map_writable(file->f_mapping);
1797  			if (error)
1798  				goto allow_write_and_free_vma;
1799  		}
1800  
1801  		/* ->mmap() can change vma->vm_file, but must guarantee that
1802  		 * vma_link() below can deny write-access if VM_DENYWRITE is set
1803  		 * and map writably if VM_SHARED is set. This usually means the
1804  		 * new file must not have been exposed to user-space, yet.
1805  		 */
1806  		vma->vm_file = get_file(file);
1807  		error = call_mmap(file, vma);
1808  		if (error)
1809  			goto unmap_and_free_vma;
1810  
1811  		/* Can addr have changed??
1812  		 *
1813  		 * Answer: Yes, several device drivers can do it in their
1814  		 *         f_op->mmap method. -DaveM
1815  		 * Bug: If addr is changed, prev, rb_link, rb_parent should
1816  		 *      be updated for vma_link()
1817  		 */
1818  		WARN_ON_ONCE(addr != vma->vm_start);
1819  
1820  		addr = vma->vm_start;
1821  
1822  		/* If vm_flags changed after call_mmap(), we should try merge vma again
1823  		 * as we may succeed this time.
1824  		 */
1825  		if (unlikely(vm_flags != vma->vm_flags && prev)) {
1826  			merge = vma_merge(mm, prev, vma->vm_start, vma->vm_end, vma->vm_flags,
1827  				NULL, vma->vm_file, vma->vm_pgoff, NULL, NULL_VM_UFFD_CTX);
1828  			if (merge) {
1829  				/* ->mmap() can change vma->vm_file and fput the original file. So
1830  				 * fput the vma->vm_file here or we would add an extra fput for file
1831  				 * and cause general protection fault ultimately.
1832  				 */
1833  				fput(vma->vm_file);
1834  				vm_area_free(vma);
1835  				vma = merge;
1836  				/* Update vm_flags to pick up the change. */
1837  				vm_flags = vma->vm_flags;
1838  				goto unmap_writable;
1839  			}
1840  		}
1841  
1842  		vm_flags = vma->vm_flags;
1843  	} else if (vm_flags & VM_SHARED) {
1844  		error = shmem_zero_setup(vma);
1845  		if (error)
1846  			goto free_vma;
1847  	} else {
1848  		vma_set_anonymous(vma);
1849  	}
1850  
1851  	/* Allow architectures to sanity-check the vm_flags */
1852  	if (!arch_validate_flags(vma->vm_flags)) {
1853  		error = -EINVAL;
1854  		if (file)
1855  			goto unmap_and_free_vma;
1856  		else
1857  			goto free_vma;
1858  	}
1859  
1860  	vma_link(mm, vma, prev, rb_link, rb_parent);
1861  	/* Once vma denies write, undo our temporary denial count */
1862  	if (file) {
1863  unmap_writable:
1864  		if (vm_flags & VM_SHARED)
1865  			mapping_unmap_writable(file->f_mapping);
1866  		if (vm_flags & VM_DENYWRITE)
1867  			allow_write_access(file);
1868  	}
1869  	file = vma->vm_file;
1870  out:
1871  	perf_event_mmap(vma);
1872  
1873  	vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
1874  	if (vm_flags & VM_LOCKED) {
1875  		if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) ||
1876  					is_vm_hugetlb_page(vma) ||
1877  					vma == get_gate_vma(current->mm))
1878  			vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
1879  		else
1880  			mm->locked_vm += (len >> PAGE_SHIFT);
1881  	}
1882  
1883  	if (file)
1884  		uprobe_mmap(vma);
1885  
1886  	/*
1887  	 * New (or expanded) vma always get soft dirty status.
1888  	 * Otherwise user-space soft-dirty page tracker won't
1889  	 * be able to distinguish situation when vma area unmapped,
1890  	 * then new mapped in-place (which must be aimed as
1891  	 * a completely new data area).
1892  	 */
1893  	vma->vm_flags |= VM_SOFTDIRTY;
1894  
1895  	vma_set_page_prot(vma);
1896  
1897  	return addr;
1898  
1899  unmap_and_free_vma:
1900  	fput(vma->vm_file);
1901  	vma->vm_file = NULL;
1902  
1903  	/* Undo any partial mapping done by a device driver. */
1904  	unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1905  	charged = 0;
1906  	if (vm_flags & VM_SHARED)
1907  		mapping_unmap_writable(file->f_mapping);
1908  allow_write_and_free_vma:
1909  	if (vm_flags & VM_DENYWRITE)
1910  		allow_write_access(file);
1911  free_vma:
1912  	vm_area_free(vma);
1913  unacct_error:
1914  	if (charged)
1915  		vm_unacct_memory(charged);
1916  	return error;
1917  }
1918  
1919  static unsigned long unmapped_area(struct vm_unmapped_area_info *info)
1920  {
1921  	/*
1922  	 * We implement the search by looking for an rbtree node that
1923  	 * immediately follows a suitable gap. That is,
1924  	 * - gap_start = vma->vm_prev->vm_end <= info->high_limit - length;
1925  	 * - gap_end   = vma->vm_start        >= info->low_limit  + length;
1926  	 * - gap_end - gap_start >= length
1927  	 */
1928  
1929  	struct mm_struct *mm = current->mm;
1930  	struct vm_area_struct *vma;
1931  	unsigned long length, low_limit, high_limit, gap_start, gap_end;
1932  
1933  	/* Adjust search length to account for worst case alignment overhead */
1934  	length = info->length + info->align_mask;
1935  	if (length < info->length)
1936  		return -ENOMEM;
1937  
1938  	/* Adjust search limits by the desired length */
1939  	if (info->high_limit < length)
1940  		return -ENOMEM;
1941  	high_limit = info->high_limit - length;
1942  
1943  	if (info->low_limit > high_limit)
1944  		return -ENOMEM;
1945  	low_limit = info->low_limit + length;
1946  
1947  	/* Check if rbtree root looks promising */
1948  	if (RB_EMPTY_ROOT(&mm->mm_rb))
1949  		goto check_highest;
1950  	vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
1951  	if (vma->rb_subtree_gap < length)
1952  		goto check_highest;
1953  
1954  	while (true) {
1955  		/* Visit left subtree if it looks promising */
1956  		gap_end = vm_start_gap(vma);
1957  		if (gap_end >= low_limit && vma->vm_rb.rb_left) {
1958  			struct vm_area_struct *left =
1959  				rb_entry(vma->vm_rb.rb_left,
1960  					 struct vm_area_struct, vm_rb);
1961  			if (left->rb_subtree_gap >= length) {
1962  				vma = left;
1963  				continue;
1964  			}
1965  		}
1966  
1967  		gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
1968  check_current:
1969  		/* Check if current node has a suitable gap */
1970  		if (gap_start > high_limit)
1971  			return -ENOMEM;
1972  		if (gap_end >= low_limit &&
1973  		    gap_end > gap_start && gap_end - gap_start >= length)
1974  			goto found;
1975  
1976  		/* Visit right subtree if it looks promising */
1977  		if (vma->vm_rb.rb_right) {
1978  			struct vm_area_struct *right =
1979  				rb_entry(vma->vm_rb.rb_right,
1980  					 struct vm_area_struct, vm_rb);
1981  			if (right->rb_subtree_gap >= length) {
1982  				vma = right;
1983  				continue;
1984  			}
1985  		}
1986  
1987  		/* Go back up the rbtree to find next candidate node */
1988  		while (true) {
1989  			struct rb_node *prev = &vma->vm_rb;
1990  			if (!rb_parent(prev))
1991  				goto check_highest;
1992  			vma = rb_entry(rb_parent(prev),
1993  				       struct vm_area_struct, vm_rb);
1994  			if (prev == vma->vm_rb.rb_left) {
1995  				gap_start = vm_end_gap(vma->vm_prev);
1996  				gap_end = vm_start_gap(vma);
1997  				goto check_current;
1998  			}
1999  		}
2000  	}
2001  
2002  check_highest:
2003  	/* Check highest gap, which does not precede any rbtree node */
2004  	gap_start = mm->highest_vm_end;
2005  	gap_end = ULONG_MAX;  /* Only for VM_BUG_ON below */
2006  	if (gap_start > high_limit)
2007  		return -ENOMEM;
2008  
2009  found:
2010  	/* We found a suitable gap. Clip it with the original low_limit. */
2011  	if (gap_start < info->low_limit)
2012  		gap_start = info->low_limit;
2013  
2014  	/* Adjust gap address to the desired alignment */
2015  	gap_start += (info->align_offset - gap_start) & info->align_mask;
2016  
2017  	VM_BUG_ON(gap_start + info->length > info->high_limit);
2018  	VM_BUG_ON(gap_start + info->length > gap_end);
2019  	return gap_start;
2020  }
2021  
2022  static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
2023  {
2024  	struct mm_struct *mm = current->mm;
2025  	struct vm_area_struct *vma;
2026  	unsigned long length, low_limit, high_limit, gap_start, gap_end;
2027  
2028  	/* Adjust search length to account for worst case alignment overhead */
2029  	length = info->length + info->align_mask;
2030  	if (length < info->length)
2031  		return -ENOMEM;
2032  
2033  	/*
2034  	 * Adjust search limits by the desired length.
2035  	 * See implementation comment at top of unmapped_area().
2036  	 */
2037  	gap_end = info->high_limit;
2038  	if (gap_end < length)
2039  		return -ENOMEM;
2040  	high_limit = gap_end - length;
2041  
2042  	if (info->low_limit > high_limit)
2043  		return -ENOMEM;
2044  	low_limit = info->low_limit + length;
2045  
2046  	/* Check highest gap, which does not precede any rbtree node */
2047  	gap_start = mm->highest_vm_end;
2048  	if (gap_start <= high_limit)
2049  		goto found_highest;
2050  
2051  	/* Check if rbtree root looks promising */
2052  	if (RB_EMPTY_ROOT(&mm->mm_rb))
2053  		return -ENOMEM;
2054  	vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
2055  	if (vma->rb_subtree_gap < length)
2056  		return -ENOMEM;
2057  
2058  	while (true) {
2059  		/* Visit right subtree if it looks promising */
2060  		gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
2061  		if (gap_start <= high_limit && vma->vm_rb.rb_right) {
2062  			struct vm_area_struct *right =
2063  				rb_entry(vma->vm_rb.rb_right,
2064  					 struct vm_area_struct, vm_rb);
2065  			if (right->rb_subtree_gap >= length) {
2066  				vma = right;
2067  				continue;
2068  			}
2069  		}
2070  
2071  check_current:
2072  		/* Check if current node has a suitable gap */
2073  		gap_end = vm_start_gap(vma);
2074  		if (gap_end < low_limit)
2075  			return -ENOMEM;
2076  		if (gap_start <= high_limit &&
2077  		    gap_end > gap_start && gap_end - gap_start >= length)
2078  			goto found;
2079  
2080  		/* Visit left subtree if it looks promising */
2081  		if (vma->vm_rb.rb_left) {
2082  			struct vm_area_struct *left =
2083  				rb_entry(vma->vm_rb.rb_left,
2084  					 struct vm_area_struct, vm_rb);
2085  			if (left->rb_subtree_gap >= length) {
2086  				vma = left;
2087  				continue;
2088  			}
2089  		}
2090  
2091  		/* Go back up the rbtree to find next candidate node */
2092  		while (true) {
2093  			struct rb_node *prev = &vma->vm_rb;
2094  			if (!rb_parent(prev))
2095  				return -ENOMEM;
2096  			vma = rb_entry(rb_parent(prev),
2097  				       struct vm_area_struct, vm_rb);
2098  			if (prev == vma->vm_rb.rb_right) {
2099  				gap_start = vma->vm_prev ?
2100  					vm_end_gap(vma->vm_prev) : 0;
2101  				goto check_current;
2102  			}
2103  		}
2104  	}
2105  
2106  found:
2107  	/* We found a suitable gap. Clip it with the original high_limit. */
2108  	if (gap_end > info->high_limit)
2109  		gap_end = info->high_limit;
2110  
2111  found_highest:
2112  	/* Compute highest gap address at the desired alignment */
2113  	gap_end -= info->length;
2114  	gap_end -= (gap_end - info->align_offset) & info->align_mask;
2115  
2116  	VM_BUG_ON(gap_end < info->low_limit);
2117  	VM_BUG_ON(gap_end < gap_start);
2118  	return gap_end;
2119  }
2120  
2121  /*
2122   * Search for an unmapped address range.
2123   *
2124   * We are looking for a range that:
2125   * - does not intersect with any VMA;
2126   * - is contained within the [low_limit, high_limit) interval;
2127   * - is at least the desired size.
2128   * - satisfies (begin_addr & align_mask) == (align_offset & align_mask)
2129   */
2130  unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
2131  {
2132  	unsigned long addr;
2133  
2134  	if (info->flags & VM_UNMAPPED_AREA_TOPDOWN)
2135  		addr = unmapped_area_topdown(info);
2136  	else
2137  		addr = unmapped_area(info);
2138  
2139  	trace_vm_unmapped_area(addr, info);
2140  	return addr;
2141  }
2142  
2143  #ifndef arch_get_mmap_end
2144  #define arch_get_mmap_end(addr)	(TASK_SIZE)
2145  #endif
2146  
2147  #ifndef arch_get_mmap_base
2148  #define arch_get_mmap_base(addr, base) (base)
2149  #endif
2150  
2151  /* Get an address range which is currently unmapped.
2152   * For shmat() with addr=0.
2153   *
2154   * Ugly calling convention alert:
2155   * Return value with the low bits set means error value,
2156   * ie
2157   *	if (ret & ~PAGE_MASK)
2158   *		error = ret;
2159   *
2160   * This function "knows" that -ENOMEM has the bits set.
2161   */
2162  #ifndef HAVE_ARCH_UNMAPPED_AREA
2163  unsigned long
2164  arch_get_unmapped_area(struct file *filp, unsigned long addr,
2165  		unsigned long len, unsigned long pgoff, unsigned long flags)
2166  {
2167  	struct mm_struct *mm = current->mm;
2168  	struct vm_area_struct *vma, *prev;
2169  	struct vm_unmapped_area_info info;
2170  	const unsigned long mmap_end = arch_get_mmap_end(addr);
2171  
2172  	if (len > mmap_end - mmap_min_addr)
2173  		return -ENOMEM;
2174  
2175  	if (flags & MAP_FIXED)
2176  		return addr;
2177  
2178  	if (addr) {
2179  		addr = PAGE_ALIGN(addr);
2180  		vma = find_vma_prev(mm, addr, &prev);
2181  		if (mmap_end - len >= addr && addr >= mmap_min_addr &&
2182  		    (!vma || addr + len <= vm_start_gap(vma)) &&
2183  		    (!prev || addr >= vm_end_gap(prev)))
2184  			return addr;
2185  	}
2186  
2187  	info.flags = 0;
2188  	info.length = len;
2189  	info.low_limit = mm->mmap_base;
2190  	info.high_limit = mmap_end;
2191  	info.align_mask = 0;
2192  	info.align_offset = 0;
2193  	return vm_unmapped_area(&info);
2194  }
2195  #endif
2196  
2197  /*
2198   * This mmap-allocator allocates new areas top-down from below the
2199   * stack's low limit (the base):
2200   */
2201  #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
2202  unsigned long
2203  arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
2204  			  unsigned long len, unsigned long pgoff,
2205  			  unsigned long flags)
2206  {
2207  	struct vm_area_struct *vma, *prev;
2208  	struct mm_struct *mm = current->mm;
2209  	struct vm_unmapped_area_info info;
2210  	const unsigned long mmap_end = arch_get_mmap_end(addr);
2211  
2212  	/* requested length too big for entire address space */
2213  	if (len > mmap_end - mmap_min_addr)
2214  		return -ENOMEM;
2215  
2216  	if (flags & MAP_FIXED)
2217  		return addr;
2218  
2219  	/* requesting a specific address */
2220  	if (addr) {
2221  		addr = PAGE_ALIGN(addr);
2222  		vma = find_vma_prev(mm, addr, &prev);
2223  		if (mmap_end - len >= addr && addr >= mmap_min_addr &&
2224  				(!vma || addr + len <= vm_start_gap(vma)) &&
2225  				(!prev || addr >= vm_end_gap(prev)))
2226  			return addr;
2227  	}
2228  
2229  	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
2230  	info.length = len;
2231  	info.low_limit = max(PAGE_SIZE, mmap_min_addr);
2232  	info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
2233  	info.align_mask = 0;
2234  	info.align_offset = 0;
2235  	addr = vm_unmapped_area(&info);
2236  
2237  	/*
2238  	 * A failed mmap() very likely causes application failure,
2239  	 * so fall back to the bottom-up function here. This scenario
2240  	 * can happen with large stack limits and large mmap()
2241  	 * allocations.
2242  	 */
2243  	if (offset_in_page(addr)) {
2244  		VM_BUG_ON(addr != -ENOMEM);
2245  		info.flags = 0;
2246  		info.low_limit = TASK_UNMAPPED_BASE;
2247  		info.high_limit = mmap_end;
2248  		addr = vm_unmapped_area(&info);
2249  	}
2250  
2251  	return addr;
2252  }
2253  #endif
2254  
2255  unsigned long
2256  get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
2257  		unsigned long pgoff, unsigned long flags)
2258  {
2259  	unsigned long (*get_area)(struct file *, unsigned long,
2260  				  unsigned long, unsigned long, unsigned long);
2261  
2262  	unsigned long error = arch_mmap_check(addr, len, flags);
2263  	if (error)
2264  		return error;
2265  
2266  	/* Careful about overflows.. */
2267  	if (len > TASK_SIZE)
2268  		return -ENOMEM;
2269  
2270  	get_area = current->mm->get_unmapped_area;
2271  	if (file) {
2272  		if (file->f_op->get_unmapped_area)
2273  			get_area = file->f_op->get_unmapped_area;
2274  	} else if (flags & MAP_SHARED) {
2275  		/*
2276  		 * mmap_region() will call shmem_zero_setup() to create a file,
2277  		 * so use shmem's get_unmapped_area in case it can be huge.
2278  		 * do_mmap() will clear pgoff, so match alignment.
2279  		 */
2280  		pgoff = 0;
2281  		get_area = shmem_get_unmapped_area;
2282  	}
2283  
2284  	addr = get_area(file, addr, len, pgoff, flags);
2285  	if (IS_ERR_VALUE(addr))
2286  		return addr;
2287  
2288  	if (addr > TASK_SIZE - len)
2289  		return -ENOMEM;
2290  	if (offset_in_page(addr))
2291  		return -EINVAL;
2292  
2293  	error = security_mmap_addr(addr);
2294  	return error ? error : addr;
2295  }
2296  
2297  EXPORT_SYMBOL(get_unmapped_area);
2298  
2299  /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
2300  struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
2301  {
2302  	struct rb_node *rb_node;
2303  	struct vm_area_struct *vma;
2304  
2305  	/* Check the cache first. */
2306  	vma = vmacache_find(mm, addr);
2307  	if (likely(vma))
2308  		return vma;
2309  
2310  	rb_node = mm->mm_rb.rb_node;
2311  
2312  	while (rb_node) {
2313  		struct vm_area_struct *tmp;
2314  
2315  		tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
2316  
2317  		if (tmp->vm_end > addr) {
2318  			vma = tmp;
2319  			if (tmp->vm_start <= addr)
2320  				break;
2321  			rb_node = rb_node->rb_left;
2322  		} else
2323  			rb_node = rb_node->rb_right;
2324  	}
2325  
2326  	if (vma)
2327  		vmacache_update(addr, vma);
2328  	return vma;
2329  }
2330  
2331  EXPORT_SYMBOL(find_vma);
2332  
2333  /*
2334   * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
2335   */
2336  struct vm_area_struct *
2337  find_vma_prev(struct mm_struct *mm, unsigned long addr,
2338  			struct vm_area_struct **pprev)
2339  {
2340  	struct vm_area_struct *vma;
2341  
2342  	vma = find_vma(mm, addr);
2343  	if (vma) {
2344  		*pprev = vma->vm_prev;
2345  	} else {
2346  		struct rb_node *rb_node = rb_last(&mm->mm_rb);
2347  
2348  		*pprev = rb_node ? rb_entry(rb_node, struct vm_area_struct, vm_rb) : NULL;
2349  	}
2350  	return vma;
2351  }
2352  
2353  /*
2354   * Verify that the stack growth is acceptable and
2355   * update accounting. This is shared with both the
2356   * grow-up and grow-down cases.
2357   */
2358  static int acct_stack_growth(struct vm_area_struct *vma,
2359  			     unsigned long size, unsigned long grow)
2360  {
2361  	struct mm_struct *mm = vma->vm_mm;
2362  	unsigned long new_start;
2363  
2364  	/* address space limit tests */
2365  	if (!may_expand_vm(mm, vma->vm_flags, grow))
2366  		return -ENOMEM;
2367  
2368  	/* Stack limit test */
2369  	if (size > rlimit(RLIMIT_STACK))
2370  		return -ENOMEM;
2371  
2372  	/* mlock limit tests */
2373  	if (vma->vm_flags & VM_LOCKED) {
2374  		unsigned long locked;
2375  		unsigned long limit;
2376  		locked = mm->locked_vm + grow;
2377  		limit = rlimit(RLIMIT_MEMLOCK);
2378  		limit >>= PAGE_SHIFT;
2379  		if (locked > limit && !capable(CAP_IPC_LOCK))
2380  			return -ENOMEM;
2381  	}
2382  
2383  	/* Check to ensure the stack will not grow into a hugetlb-only region */
2384  	new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
2385  			vma->vm_end - size;
2386  	if (is_hugepage_only_range(vma->vm_mm, new_start, size))
2387  		return -EFAULT;
2388  
2389  	/*
2390  	 * Overcommit..  This must be the final test, as it will
2391  	 * update security statistics.
2392  	 */
2393  	if (security_vm_enough_memory_mm(mm, grow))
2394  		return -ENOMEM;
2395  
2396  	return 0;
2397  }
2398  
2399  #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
2400  /*
2401   * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
2402   * vma is the last one with address > vma->vm_end.  Have to extend vma.
2403   */
2404  int expand_upwards(struct vm_area_struct *vma, unsigned long address)
2405  {
2406  	struct mm_struct *mm = vma->vm_mm;
2407  	struct vm_area_struct *next;
2408  	unsigned long gap_addr;
2409  	int error = 0;
2410  
2411  	if (!(vma->vm_flags & VM_GROWSUP))
2412  		return -EFAULT;
2413  
2414  	/* Guard against exceeding limits of the address space. */
2415  	address &= PAGE_MASK;
2416  	if (address >= (TASK_SIZE & PAGE_MASK))
2417  		return -ENOMEM;
2418  	address += PAGE_SIZE;
2419  
2420  	/* Enforce stack_guard_gap */
2421  	gap_addr = address + stack_guard_gap;
2422  
2423  	/* Guard against overflow */
2424  	if (gap_addr < address || gap_addr > TASK_SIZE)
2425  		gap_addr = TASK_SIZE;
2426  
2427  	next = vma->vm_next;
2428  	if (next && next->vm_start < gap_addr && vma_is_accessible(next)) {
2429  		if (!(next->vm_flags & VM_GROWSUP))
2430  			return -ENOMEM;
2431  		/* Check that both stack segments have the same anon_vma? */
2432  	}
2433  
2434  	/* We must make sure the anon_vma is allocated. */
2435  	if (unlikely(anon_vma_prepare(vma)))
2436  		return -ENOMEM;
2437  
2438  	/*
2439  	 * vma->vm_start/vm_end cannot change under us because the caller
2440  	 * is required to hold the mmap_lock in read mode.  We need the
2441  	 * anon_vma lock to serialize against concurrent expand_stacks.
2442  	 */
2443  	anon_vma_lock_write(vma->anon_vma);
2444  
2445  	/* Somebody else might have raced and expanded it already */
2446  	if (address > vma->vm_end) {
2447  		unsigned long size, grow;
2448  
2449  		size = address - vma->vm_start;
2450  		grow = (address - vma->vm_end) >> PAGE_SHIFT;
2451  
2452  		error = -ENOMEM;
2453  		if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
2454  			error = acct_stack_growth(vma, size, grow);
2455  			if (!error) {
2456  				/*
2457  				 * vma_gap_update() doesn't support concurrent
2458  				 * updates, but we only hold a shared mmap_lock
2459  				 * lock here, so we need to protect against
2460  				 * concurrent vma expansions.
2461  				 * anon_vma_lock_write() doesn't help here, as
2462  				 * we don't guarantee that all growable vmas
2463  				 * in a mm share the same root anon vma.
2464  				 * So, we reuse mm->page_table_lock to guard
2465  				 * against concurrent vma expansions.
2466  				 */
2467  				spin_lock(&mm->page_table_lock);
2468  				if (vma->vm_flags & VM_LOCKED)
2469  					mm->locked_vm += grow;
2470  				vm_stat_account(mm, vma->vm_flags, grow);
2471  				anon_vma_interval_tree_pre_update_vma(vma);
2472  				vma->vm_end = address;
2473  				anon_vma_interval_tree_post_update_vma(vma);
2474  				if (vma->vm_next)
2475  					vma_gap_update(vma->vm_next);
2476  				else
2477  					mm->highest_vm_end = vm_end_gap(vma);
2478  				spin_unlock(&mm->page_table_lock);
2479  
2480  				perf_event_mmap(vma);
2481  			}
2482  		}
2483  	}
2484  	anon_vma_unlock_write(vma->anon_vma);
2485  	khugepaged_enter_vma_merge(vma, vma->vm_flags);
2486  	validate_mm(mm);
2487  	return error;
2488  }
2489  #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
2490  
2491  /*
2492   * vma is the first one with address < vma->vm_start.  Have to extend vma.
2493   */
2494  int expand_downwards(struct vm_area_struct *vma,
2495  				   unsigned long address)
2496  {
2497  	struct mm_struct *mm = vma->vm_mm;
2498  	struct vm_area_struct *prev;
2499  	int error = 0;
2500  
2501  	address &= PAGE_MASK;
2502  	if (address < mmap_min_addr)
2503  		return -EPERM;
2504  
2505  	/* Enforce stack_guard_gap */
2506  	prev = vma->vm_prev;
2507  	/* Check that both stack segments have the same anon_vma? */
2508  	if (prev && !(prev->vm_flags & VM_GROWSDOWN) &&
2509  			vma_is_accessible(prev)) {
2510  		if (address - prev->vm_end < stack_guard_gap)
2511  			return -ENOMEM;
2512  	}
2513  
2514  	/* We must make sure the anon_vma is allocated. */
2515  	if (unlikely(anon_vma_prepare(vma)))
2516  		return -ENOMEM;
2517  
2518  	/*
2519  	 * vma->vm_start/vm_end cannot change under us because the caller
2520  	 * is required to hold the mmap_lock in read mode.  We need the
2521  	 * anon_vma lock to serialize against concurrent expand_stacks.
2522  	 */
2523  	anon_vma_lock_write(vma->anon_vma);
2524  
2525  	/* Somebody else might have raced and expanded it already */
2526  	if (address < vma->vm_start) {
2527  		unsigned long size, grow;
2528  
2529  		size = vma->vm_end - address;
2530  		grow = (vma->vm_start - address) >> PAGE_SHIFT;
2531  
2532  		error = -ENOMEM;
2533  		if (grow <= vma->vm_pgoff) {
2534  			error = acct_stack_growth(vma, size, grow);
2535  			if (!error) {
2536  				/*
2537  				 * vma_gap_update() doesn't support concurrent
2538  				 * updates, but we only hold a shared mmap_lock
2539  				 * lock here, so we need to protect against
2540  				 * concurrent vma expansions.
2541  				 * anon_vma_lock_write() doesn't help here, as
2542  				 * we don't guarantee that all growable vmas
2543  				 * in a mm share the same root anon vma.
2544  				 * So, we reuse mm->page_table_lock to guard
2545  				 * against concurrent vma expansions.
2546  				 */
2547  				spin_lock(&mm->page_table_lock);
2548  				if (vma->vm_flags & VM_LOCKED)
2549  					mm->locked_vm += grow;
2550  				vm_stat_account(mm, vma->vm_flags, grow);
2551  				anon_vma_interval_tree_pre_update_vma(vma);
2552  				vma->vm_start = address;
2553  				vma->vm_pgoff -= grow;
2554  				anon_vma_interval_tree_post_update_vma(vma);
2555  				vma_gap_update(vma);
2556  				spin_unlock(&mm->page_table_lock);
2557  
2558  				perf_event_mmap(vma);
2559  			}
2560  		}
2561  	}
2562  	anon_vma_unlock_write(vma->anon_vma);
2563  	khugepaged_enter_vma_merge(vma, vma->vm_flags);
2564  	validate_mm(mm);
2565  	return error;
2566  }
2567  
2568  /* enforced gap between the expanding stack and other mappings. */
2569  unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT;
2570  
2571  static int __init cmdline_parse_stack_guard_gap(char *p)
2572  {
2573  	unsigned long val;
2574  	char *endptr;
2575  
2576  	val = simple_strtoul(p, &endptr, 10);
2577  	if (!*endptr)
2578  		stack_guard_gap = val << PAGE_SHIFT;
2579  
2580  	return 0;
2581  }
2582  __setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);
2583  
2584  #ifdef CONFIG_STACK_GROWSUP
2585  int expand_stack(struct vm_area_struct *vma, unsigned long address)
2586  {
2587  	return expand_upwards(vma, address);
2588  }
2589  
2590  struct vm_area_struct *
2591  find_extend_vma(struct mm_struct *mm, unsigned long addr)
2592  {
2593  	struct vm_area_struct *vma, *prev;
2594  
2595  	addr &= PAGE_MASK;
2596  	vma = find_vma_prev(mm, addr, &prev);
2597  	if (vma && (vma->vm_start <= addr))
2598  		return vma;
2599  	/* don't alter vm_end if the coredump is running */
2600  	if (!prev || expand_stack(prev, addr))
2601  		return NULL;
2602  	if (prev->vm_flags & VM_LOCKED)
2603  		populate_vma_page_range(prev, addr, prev->vm_end, NULL);
2604  	return prev;
2605  }
2606  #else
2607  int expand_stack(struct vm_area_struct *vma, unsigned long address)
2608  {
2609  	return expand_downwards(vma, address);
2610  }
2611  
2612  struct vm_area_struct *
2613  find_extend_vma(struct mm_struct *mm, unsigned long addr)
2614  {
2615  	struct vm_area_struct *vma;
2616  	unsigned long start;
2617  
2618  	addr &= PAGE_MASK;
2619  	vma = find_vma(mm, addr);
2620  	if (!vma)
2621  		return NULL;
2622  	if (vma->vm_start <= addr)
2623  		return vma;
2624  	if (!(vma->vm_flags & VM_GROWSDOWN))
2625  		return NULL;
2626  	start = vma->vm_start;
2627  	if (expand_stack(vma, addr))
2628  		return NULL;
2629  	if (vma->vm_flags & VM_LOCKED)
2630  		populate_vma_page_range(vma, addr, start, NULL);
2631  	return vma;
2632  }
2633  #endif
2634  
2635  EXPORT_SYMBOL_GPL(find_extend_vma);
2636  
2637  /*
2638   * Ok - we have the memory areas we should free on the vma list,
2639   * so release them, and do the vma updates.
2640   *
2641   * Called with the mm semaphore held.
2642   */
2643  static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
2644  {
2645  	unsigned long nr_accounted = 0;
2646  
2647  	/* Update high watermark before we lower total_vm */
2648  	update_hiwater_vm(mm);
2649  	do {
2650  		long nrpages = vma_pages(vma);
2651  
2652  		if (vma->vm_flags & VM_ACCOUNT)
2653  			nr_accounted += nrpages;
2654  		vm_stat_account(mm, vma->vm_flags, -nrpages);
2655  		vma = remove_vma(vma);
2656  	} while (vma);
2657  	vm_unacct_memory(nr_accounted);
2658  	validate_mm(mm);
2659  }
2660  
2661  /*
2662   * Get rid of page table information in the indicated region.
2663   *
2664   * Called with the mm semaphore held.
2665   */
2666  static void unmap_region(struct mm_struct *mm,
2667  		struct vm_area_struct *vma, struct vm_area_struct *prev,
2668  		unsigned long start, unsigned long end)
2669  {
2670  	struct vm_area_struct *next = vma_next(mm, prev);
2671  	struct mmu_gather tlb;
2672  
2673  	lru_add_drain();
2674  	tlb_gather_mmu(&tlb, mm, start, end);
2675  	update_hiwater_rss(mm);
2676  	unmap_vmas(&tlb, vma, start, end);
2677  	free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
2678  				 next ? next->vm_start : USER_PGTABLES_CEILING);
2679  	tlb_finish_mmu(&tlb, start, end);
2680  }
2681  
2682  /*
2683   * Create a list of vma's touched by the unmap, removing them from the mm's
2684   * vma list as we go..
2685   */
2686  static bool
2687  detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
2688  	struct vm_area_struct *prev, unsigned long end)
2689  {
2690  	struct vm_area_struct **insertion_point;
2691  	struct vm_area_struct *tail_vma = NULL;
2692  
2693  	insertion_point = (prev ? &prev->vm_next : &mm->mmap);
2694  	vma->vm_prev = NULL;
2695  	do {
2696  		vma_rb_erase(vma, &mm->mm_rb);
2697  		mm->map_count--;
2698  		tail_vma = vma;
2699  		vma = vma->vm_next;
2700  	} while (vma && vma->vm_start < end);
2701  	*insertion_point = vma;
2702  	if (vma) {
2703  		vma->vm_prev = prev;
2704  		vma_gap_update(vma);
2705  	} else
2706  		mm->highest_vm_end = prev ? vm_end_gap(prev) : 0;
2707  	tail_vma->vm_next = NULL;
2708  
2709  	/* Kill the cache */
2710  	vmacache_invalidate(mm);
2711  
2712  	/*
2713  	 * Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
2714  	 * VM_GROWSUP VMA. Such VMAs can change their size under
2715  	 * down_read(mmap_lock) and collide with the VMA we are about to unmap.
2716  	 */
2717  	if (vma && (vma->vm_flags & VM_GROWSDOWN))
2718  		return false;
2719  	if (prev && (prev->vm_flags & VM_GROWSUP))
2720  		return false;
2721  	return true;
2722  }
2723  
2724  /*
2725   * __split_vma() bypasses sysctl_max_map_count checking.  We use this where it
2726   * has already been checked or doesn't make sense to fail.
2727   */
2728  int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2729  		unsigned long addr, int new_below)
2730  {
2731  	struct vm_area_struct *new;
2732  	int err;
2733  
2734  	if (vma->vm_ops && vma->vm_ops->may_split) {
2735  		err = vma->vm_ops->may_split(vma, addr);
2736  		if (err)
2737  			return err;
2738  	}
2739  
2740  	new = vm_area_dup(vma);
2741  	if (!new)
2742  		return -ENOMEM;
2743  
2744  	if (new_below)
2745  		new->vm_end = addr;
2746  	else {
2747  		new->vm_start = addr;
2748  		new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
2749  	}
2750  
2751  	err = vma_dup_policy(vma, new);
2752  	if (err)
2753  		goto out_free_vma;
2754  
2755  	err = anon_vma_clone(new, vma);
2756  	if (err)
2757  		goto out_free_mpol;
2758  
2759  	if (new->vm_file)
2760  		get_file(new->vm_file);
2761  
2762  	if (new->vm_ops && new->vm_ops->open)
2763  		new->vm_ops->open(new);
2764  
2765  	if (new_below)
2766  		err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
2767  			((addr - new->vm_start) >> PAGE_SHIFT), new);
2768  	else
2769  		err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
2770  
2771  	/* Success. */
2772  	if (!err)
2773  		return 0;
2774  
2775  	/* Clean everything up if vma_adjust failed. */
2776  	if (new->vm_ops && new->vm_ops->close)
2777  		new->vm_ops->close(new);
2778  	if (new->vm_file)
2779  		fput(new->vm_file);
2780  	unlink_anon_vmas(new);
2781   out_free_mpol:
2782  	mpol_put(vma_policy(new));
2783   out_free_vma:
2784  	vm_area_free(new);
2785  	return err;
2786  }
2787  
2788  /*
2789   * Split a vma into two pieces at address 'addr', a new vma is allocated
2790   * either for the first part or the tail.
2791   */
2792  int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2793  	      unsigned long addr, int new_below)
2794  {
2795  	if (mm->map_count >= sysctl_max_map_count)
2796  		return -ENOMEM;
2797  
2798  	return __split_vma(mm, vma, addr, new_below);
2799  }
2800  
2801  /* Munmap is split into 2 main parts -- this part which finds
2802   * what needs doing, and the areas themselves, which do the
2803   * work.  This now handles partial unmappings.
2804   * Jeremy Fitzhardinge <jeremy@goop.org>
2805   */
2806  int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
2807  		struct list_head *uf, bool downgrade)
2808  {
2809  	unsigned long end;
2810  	struct vm_area_struct *vma, *prev, *last;
2811  
2812  	if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
2813  		return -EINVAL;
2814  
2815  	len = PAGE_ALIGN(len);
2816  	end = start + len;
2817  	if (len == 0)
2818  		return -EINVAL;
2819  
2820  	/*
2821  	 * arch_unmap() might do unmaps itself.  It must be called
2822  	 * and finish any rbtree manipulation before this code
2823  	 * runs and also starts to manipulate the rbtree.
2824  	 */
2825  	arch_unmap(mm, start, end);
2826  
2827  	/* Find the first overlapping VMA */
2828  	vma = find_vma(mm, start);
2829  	if (!vma)
2830  		return 0;
2831  	prev = vma->vm_prev;
2832  	/* we have  start < vma->vm_end  */
2833  
2834  	/* if it doesn't overlap, we have nothing.. */
2835  	if (vma->vm_start >= end)
2836  		return 0;
2837  
2838  	/*
2839  	 * If we need to split any vma, do it now to save pain later.
2840  	 *
2841  	 * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2842  	 * unmapped vm_area_struct will remain in use: so lower split_vma
2843  	 * places tmp vma above, and higher split_vma places tmp vma below.
2844  	 */
2845  	if (start > vma->vm_start) {
2846  		int error;
2847  
2848  		/*
2849  		 * Make sure that map_count on return from munmap() will
2850  		 * not exceed its limit; but let map_count go just above
2851  		 * its limit temporarily, to help free resources as expected.
2852  		 */
2853  		if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2854  			return -ENOMEM;
2855  
2856  		error = __split_vma(mm, vma, start, 0);
2857  		if (error)
2858  			return error;
2859  		prev = vma;
2860  	}
2861  
2862  	/* Does it split the last one? */
2863  	last = find_vma(mm, end);
2864  	if (last && end > last->vm_start) {
2865  		int error = __split_vma(mm, last, end, 1);
2866  		if (error)
2867  			return error;
2868  	}
2869  	vma = vma_next(mm, prev);
2870  
2871  	if (unlikely(uf)) {
2872  		/*
2873  		 * If userfaultfd_unmap_prep returns an error the vmas
2874  		 * will remain splitted, but userland will get a
2875  		 * highly unexpected error anyway. This is no
2876  		 * different than the case where the first of the two
2877  		 * __split_vma fails, but we don't undo the first
2878  		 * split, despite we could. This is unlikely enough
2879  		 * failure that it's not worth optimizing it for.
2880  		 */
2881  		int error = userfaultfd_unmap_prep(vma, start, end, uf);
2882  		if (error)
2883  			return error;
2884  	}
2885  
2886  	/*
2887  	 * unlock any mlock()ed ranges before detaching vmas
2888  	 */
2889  	if (mm->locked_vm) {
2890  		struct vm_area_struct *tmp = vma;
2891  		while (tmp && tmp->vm_start < end) {
2892  			if (tmp->vm_flags & VM_LOCKED) {
2893  				mm->locked_vm -= vma_pages(tmp);
2894  				munlock_vma_pages_all(tmp);
2895  			}
2896  
2897  			tmp = tmp->vm_next;
2898  		}
2899  	}
2900  
2901  	/* Detach vmas from rbtree */
2902  	if (!detach_vmas_to_be_unmapped(mm, vma, prev, end))
2903  		downgrade = false;
2904  
2905  	if (downgrade)
2906  		mmap_write_downgrade(mm);
2907  
2908  	unmap_region(mm, vma, prev, start, end);
2909  
2910  	/* Fix up all other VM information */
2911  	remove_vma_list(mm, vma);
2912  
2913  	return downgrade ? 1 : 0;
2914  }
2915  
2916  int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
2917  	      struct list_head *uf)
2918  {
2919  	return __do_munmap(mm, start, len, uf, false);
2920  }
2921  
2922  static int __vm_munmap(unsigned long start, size_t len, bool downgrade)
2923  {
2924  	int ret;
2925  	struct mm_struct *mm = current->mm;
2926  	LIST_HEAD(uf);
2927  
2928  	if (mmap_write_lock_killable(mm))
2929  		return -EINTR;
2930  
2931  	ret = __do_munmap(mm, start, len, &uf, downgrade);
2932  	/*
2933  	 * Returning 1 indicates mmap_lock is downgraded.
2934  	 * But 1 is not legal return value of vm_munmap() and munmap(), reset
2935  	 * it to 0 before return.
2936  	 */
2937  	if (ret == 1) {
2938  		mmap_read_unlock(mm);
2939  		ret = 0;
2940  	} else
2941  		mmap_write_unlock(mm);
2942  
2943  	userfaultfd_unmap_complete(mm, &uf);
2944  	return ret;
2945  }
2946  
2947  int vm_munmap(unsigned long start, size_t len)
2948  {
2949  	return __vm_munmap(start, len, false);
2950  }
2951  EXPORT_SYMBOL(vm_munmap);
2952  
2953  SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2954  {
2955  	addr = untagged_addr(addr);
2956  	profile_munmap(addr);
2957  	return __vm_munmap(addr, len, true);
2958  }
2959  
2960  
2961  /*
2962   * Emulation of deprecated remap_file_pages() syscall.
2963   */
2964  SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
2965  		unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
2966  {
2967  
2968  	struct mm_struct *mm = current->mm;
2969  	struct vm_area_struct *vma;
2970  	unsigned long populate = 0;
2971  	unsigned long ret = -EINVAL;
2972  	struct file *file;
2973  
2974  	pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.rst.\n",
2975  		     current->comm, current->pid);
2976  
2977  	if (prot)
2978  		return ret;
2979  	start = start & PAGE_MASK;
2980  	size = size & PAGE_MASK;
2981  
2982  	if (start + size <= start)
2983  		return ret;
2984  
2985  	/* Does pgoff wrap? */
2986  	if (pgoff + (size >> PAGE_SHIFT) < pgoff)
2987  		return ret;
2988  
2989  	if (mmap_write_lock_killable(mm))
2990  		return -EINTR;
2991  
2992  	vma = find_vma(mm, start);
2993  
2994  	if (!vma || !(vma->vm_flags & VM_SHARED))
2995  		goto out;
2996  
2997  	if (start < vma->vm_start)
2998  		goto out;
2999  
3000  	if (start + size > vma->vm_end) {
3001  		struct vm_area_struct *next;
3002  
3003  		for (next = vma->vm_next; next; next = next->vm_next) {
3004  			/* hole between vmas ? */
3005  			if (next->vm_start != next->vm_prev->vm_end)
3006  				goto out;
3007  
3008  			if (next->vm_file != vma->vm_file)
3009  				goto out;
3010  
3011  			if (next->vm_flags != vma->vm_flags)
3012  				goto out;
3013  
3014  			if (start + size <= next->vm_end)
3015  				break;
3016  		}
3017  
3018  		if (!next)
3019  			goto out;
3020  	}
3021  
3022  	prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
3023  	prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
3024  	prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
3025  
3026  	flags &= MAP_NONBLOCK;
3027  	flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
3028  	if (vma->vm_flags & VM_LOCKED) {
3029  		struct vm_area_struct *tmp;
3030  		flags |= MAP_LOCKED;
3031  
3032  		/* drop PG_Mlocked flag for over-mapped range */
3033  		for (tmp = vma; tmp->vm_start >= start + size;
3034  				tmp = tmp->vm_next) {
3035  			/*
3036  			 * Split pmd and munlock page on the border
3037  			 * of the range.
3038  			 */
3039  			vma_adjust_trans_huge(tmp, start, start + size, 0);
3040  
3041  			munlock_vma_pages_range(tmp,
3042  					max(tmp->vm_start, start),
3043  					min(tmp->vm_end, start + size));
3044  		}
3045  	}
3046  
3047  	file = get_file(vma->vm_file);
3048  	ret = do_mmap(vma->vm_file, start, size,
3049  			prot, flags, pgoff, &populate, NULL);
3050  	fput(file);
3051  out:
3052  	mmap_write_unlock(mm);
3053  	if (populate)
3054  		mm_populate(ret, populate);
3055  	if (!IS_ERR_VALUE(ret))
3056  		ret = 0;
3057  	return ret;
3058  }
3059  
3060  /*
3061   *  this is really a simplified "do_mmap".  it only handles
3062   *  anonymous maps.  eventually we may be able to do some
3063   *  brk-specific accounting here.
3064   */
3065  static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long flags, struct list_head *uf)
3066  {
3067  	struct mm_struct *mm = current->mm;
3068  	struct vm_area_struct *vma, *prev;
3069  	struct rb_node **rb_link, *rb_parent;
3070  	pgoff_t pgoff = addr >> PAGE_SHIFT;
3071  	int error;
3072  	unsigned long mapped_addr;
3073  
3074  	/* Until we need other flags, refuse anything except VM_EXEC. */
3075  	if ((flags & (~VM_EXEC)) != 0)
3076  		return -EINVAL;
3077  	flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
3078  
3079  	mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
3080  	if (IS_ERR_VALUE(mapped_addr))
3081  		return mapped_addr;
3082  
3083  	error = mlock_future_check(mm, mm->def_flags, len);
3084  	if (error)
3085  		return error;
3086  
3087  	/* Clear old maps, set up prev, rb_link, rb_parent, and uf */
3088  	if (munmap_vma_range(mm, addr, len, &prev, &rb_link, &rb_parent, uf))
3089  		return -ENOMEM;
3090  
3091  	/* Check against address space limits *after* clearing old maps... */
3092  	if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
3093  		return -ENOMEM;
3094  
3095  	if (mm->map_count > sysctl_max_map_count)
3096  		return -ENOMEM;
3097  
3098  	if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
3099  		return -ENOMEM;
3100  
3101  	/* Can we just expand an old private anonymous mapping? */
3102  	vma = vma_merge(mm, prev, addr, addr + len, flags,
3103  			NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX);
3104  	if (vma)
3105  		goto out;
3106  
3107  	/*
3108  	 * create a vma struct for an anonymous mapping
3109  	 */
3110  	vma = vm_area_alloc(mm);
3111  	if (!vma) {
3112  		vm_unacct_memory(len >> PAGE_SHIFT);
3113  		return -ENOMEM;
3114  	}
3115  
3116  	vma_set_anonymous(vma);
3117  	vma->vm_start = addr;
3118  	vma->vm_end = addr + len;
3119  	vma->vm_pgoff = pgoff;
3120  	vma->vm_flags = flags;
3121  	vma->vm_page_prot = vm_get_page_prot(flags);
3122  	vma_link(mm, vma, prev, rb_link, rb_parent);
3123  out:
3124  	perf_event_mmap(vma);
3125  	mm->total_vm += len >> PAGE_SHIFT;
3126  	mm->data_vm += len >> PAGE_SHIFT;
3127  	if (flags & VM_LOCKED)
3128  		mm->locked_vm += (len >> PAGE_SHIFT);
3129  	vma->vm_flags |= VM_SOFTDIRTY;
3130  	return 0;
3131  }
3132  
3133  int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
3134  {
3135  	struct mm_struct *mm = current->mm;
3136  	unsigned long len;
3137  	int ret;
3138  	bool populate;
3139  	LIST_HEAD(uf);
3140  
3141  	len = PAGE_ALIGN(request);
3142  	if (len < request)
3143  		return -ENOMEM;
3144  	if (!len)
3145  		return 0;
3146  
3147  	if (mmap_write_lock_killable(mm))
3148  		return -EINTR;
3149  
3150  	ret = do_brk_flags(addr, len, flags, &uf);
3151  	populate = ((mm->def_flags & VM_LOCKED) != 0);
3152  	mmap_write_unlock(mm);
3153  	userfaultfd_unmap_complete(mm, &uf);
3154  	if (populate && !ret)
3155  		mm_populate(addr, len);
3156  	return ret;
3157  }
3158  EXPORT_SYMBOL(vm_brk_flags);
3159  
3160  int vm_brk(unsigned long addr, unsigned long len)
3161  {
3162  	return vm_brk_flags(addr, len, 0);
3163  }
3164  EXPORT_SYMBOL(vm_brk);
3165  
3166  /* Release all mmaps. */
3167  void exit_mmap(struct mm_struct *mm)
3168  {
3169  	struct mmu_gather tlb;
3170  	struct vm_area_struct *vma;
3171  	unsigned long nr_accounted = 0;
3172  
3173  	/* mm's last user has gone, and its about to be pulled down */
3174  	mmu_notifier_release(mm);
3175  
3176  	if (unlikely(mm_is_oom_victim(mm))) {
3177  		/*
3178  		 * Manually reap the mm to free as much memory as possible.
3179  		 * Then, as the oom reaper does, set MMF_OOM_SKIP to disregard
3180  		 * this mm from further consideration.  Taking mm->mmap_lock for
3181  		 * write after setting MMF_OOM_SKIP will guarantee that the oom
3182  		 * reaper will not run on this mm again after mmap_lock is
3183  		 * dropped.
3184  		 *
3185  		 * Nothing can be holding mm->mmap_lock here and the above call
3186  		 * to mmu_notifier_release(mm) ensures mmu notifier callbacks in
3187  		 * __oom_reap_task_mm() will not block.
3188  		 *
3189  		 * This needs to be done before calling munlock_vma_pages_all(),
3190  		 * which clears VM_LOCKED, otherwise the oom reaper cannot
3191  		 * reliably test it.
3192  		 */
3193  		(void)__oom_reap_task_mm(mm);
3194  
3195  		set_bit(MMF_OOM_SKIP, &mm->flags);
3196  		mmap_write_lock(mm);
3197  		mmap_write_unlock(mm);
3198  	}
3199  
3200  	if (mm->locked_vm) {
3201  		vma = mm->mmap;
3202  		while (vma) {
3203  			if (vma->vm_flags & VM_LOCKED)
3204  				munlock_vma_pages_all(vma);
3205  			vma = vma->vm_next;
3206  		}
3207  	}
3208  
3209  	arch_exit_mmap(mm);
3210  
3211  	vma = mm->mmap;
3212  	if (!vma)	/* Can happen if dup_mmap() received an OOM */
3213  		return;
3214  
3215  	lru_add_drain();
3216  	flush_cache_mm(mm);
3217  	tlb_gather_mmu(&tlb, mm, 0, -1);
3218  	/* update_hiwater_rss(mm) here? but nobody should be looking */
3219  	/* Use -1 here to ensure all VMAs in the mm are unmapped */
3220  	unmap_vmas(&tlb, vma, 0, -1);
3221  	free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
3222  	tlb_finish_mmu(&tlb, 0, -1);
3223  
3224  	/*
3225  	 * Walk the list again, actually closing and freeing it,
3226  	 * with preemption enabled, without holding any MM locks.
3227  	 */
3228  	while (vma) {
3229  		if (vma->vm_flags & VM_ACCOUNT)
3230  			nr_accounted += vma_pages(vma);
3231  		vma = remove_vma(vma);
3232  		cond_resched();
3233  	}
3234  	vm_unacct_memory(nr_accounted);
3235  }
3236  
3237  /* Insert vm structure into process list sorted by address
3238   * and into the inode's i_mmap tree.  If vm_file is non-NULL
3239   * then i_mmap_rwsem is taken here.
3240   */
3241  int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
3242  {
3243  	struct vm_area_struct *prev;
3244  	struct rb_node **rb_link, *rb_parent;
3245  
3246  	if (find_vma_links(mm, vma->vm_start, vma->vm_end,
3247  			   &prev, &rb_link, &rb_parent))
3248  		return -ENOMEM;
3249  	if ((vma->vm_flags & VM_ACCOUNT) &&
3250  	     security_vm_enough_memory_mm(mm, vma_pages(vma)))
3251  		return -ENOMEM;
3252  
3253  	/*
3254  	 * The vm_pgoff of a purely anonymous vma should be irrelevant
3255  	 * until its first write fault, when page's anon_vma and index
3256  	 * are set.  But now set the vm_pgoff it will almost certainly
3257  	 * end up with (unless mremap moves it elsewhere before that
3258  	 * first wfault), so /proc/pid/maps tells a consistent story.
3259  	 *
3260  	 * By setting it to reflect the virtual start address of the
3261  	 * vma, merges and splits can happen in a seamless way, just
3262  	 * using the existing file pgoff checks and manipulations.
3263  	 * Similarly in do_mmap and in do_brk_flags.
3264  	 */
3265  	if (vma_is_anonymous(vma)) {
3266  		BUG_ON(vma->anon_vma);
3267  		vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
3268  	}
3269  
3270  	vma_link(mm, vma, prev, rb_link, rb_parent);
3271  	return 0;
3272  }
3273  
3274  /*
3275   * Copy the vma structure to a new location in the same mm,
3276   * prior to moving page table entries, to effect an mremap move.
3277   */
3278  struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
3279  	unsigned long addr, unsigned long len, pgoff_t pgoff,
3280  	bool *need_rmap_locks)
3281  {
3282  	struct vm_area_struct *vma = *vmap;
3283  	unsigned long vma_start = vma->vm_start;
3284  	struct mm_struct *mm = vma->vm_mm;
3285  	struct vm_area_struct *new_vma, *prev;
3286  	struct rb_node **rb_link, *rb_parent;
3287  	bool faulted_in_anon_vma = true;
3288  
3289  	/*
3290  	 * If anonymous vma has not yet been faulted, update new pgoff
3291  	 * to match new location, to increase its chance of merging.
3292  	 */
3293  	if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
3294  		pgoff = addr >> PAGE_SHIFT;
3295  		faulted_in_anon_vma = false;
3296  	}
3297  
3298  	if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
3299  		return NULL;	/* should never get here */
3300  	new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
3301  			    vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
3302  			    vma->vm_userfaultfd_ctx);
3303  	if (new_vma) {
3304  		/*
3305  		 * Source vma may have been merged into new_vma
3306  		 */
3307  		if (unlikely(vma_start >= new_vma->vm_start &&
3308  			     vma_start < new_vma->vm_end)) {
3309  			/*
3310  			 * The only way we can get a vma_merge with
3311  			 * self during an mremap is if the vma hasn't
3312  			 * been faulted in yet and we were allowed to
3313  			 * reset the dst vma->vm_pgoff to the
3314  			 * destination address of the mremap to allow
3315  			 * the merge to happen. mremap must change the
3316  			 * vm_pgoff linearity between src and dst vmas
3317  			 * (in turn preventing a vma_merge) to be
3318  			 * safe. It is only safe to keep the vm_pgoff
3319  			 * linear if there are no pages mapped yet.
3320  			 */
3321  			VM_BUG_ON_VMA(faulted_in_anon_vma, new_vma);
3322  			*vmap = vma = new_vma;
3323  		}
3324  		*need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
3325  	} else {
3326  		new_vma = vm_area_dup(vma);
3327  		if (!new_vma)
3328  			goto out;
3329  		new_vma->vm_start = addr;
3330  		new_vma->vm_end = addr + len;
3331  		new_vma->vm_pgoff = pgoff;
3332  		if (vma_dup_policy(vma, new_vma))
3333  			goto out_free_vma;
3334  		if (anon_vma_clone(new_vma, vma))
3335  			goto out_free_mempol;
3336  		if (new_vma->vm_file)
3337  			get_file(new_vma->vm_file);
3338  		if (new_vma->vm_ops && new_vma->vm_ops->open)
3339  			new_vma->vm_ops->open(new_vma);
3340  		vma_link(mm, new_vma, prev, rb_link, rb_parent);
3341  		*need_rmap_locks = false;
3342  	}
3343  	return new_vma;
3344  
3345  out_free_mempol:
3346  	mpol_put(vma_policy(new_vma));
3347  out_free_vma:
3348  	vm_area_free(new_vma);
3349  out:
3350  	return NULL;
3351  }
3352  
3353  /*
3354   * Return true if the calling process may expand its vm space by the passed
3355   * number of pages
3356   */
3357  bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
3358  {
3359  	if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
3360  		return false;
3361  
3362  	if (is_data_mapping(flags) &&
3363  	    mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) {
3364  		/* Workaround for Valgrind */
3365  		if (rlimit(RLIMIT_DATA) == 0 &&
3366  		    mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT)
3367  			return true;
3368  
3369  		pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits%s.\n",
3370  			     current->comm, current->pid,
3371  			     (mm->data_vm + npages) << PAGE_SHIFT,
3372  			     rlimit(RLIMIT_DATA),
3373  			     ignore_rlimit_data ? "" : " or use boot option ignore_rlimit_data");
3374  
3375  		if (!ignore_rlimit_data)
3376  			return false;
3377  	}
3378  
3379  	return true;
3380  }
3381  
3382  void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
3383  {
3384  	mm->total_vm += npages;
3385  
3386  	if (is_exec_mapping(flags))
3387  		mm->exec_vm += npages;
3388  	else if (is_stack_mapping(flags))
3389  		mm->stack_vm += npages;
3390  	else if (is_data_mapping(flags))
3391  		mm->data_vm += npages;
3392  }
3393  
3394  static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
3395  
3396  /*
3397   * Having a close hook prevents vma merging regardless of flags.
3398   */
3399  static void special_mapping_close(struct vm_area_struct *vma)
3400  {
3401  }
3402  
3403  static const char *special_mapping_name(struct vm_area_struct *vma)
3404  {
3405  	return ((struct vm_special_mapping *)vma->vm_private_data)->name;
3406  }
3407  
3408  static int special_mapping_mremap(struct vm_area_struct *new_vma,
3409  				  unsigned long flags)
3410  {
3411  	struct vm_special_mapping *sm = new_vma->vm_private_data;
3412  
3413  	if (flags & MREMAP_DONTUNMAP)
3414  		return -EINVAL;
3415  
3416  	if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))
3417  		return -EFAULT;
3418  
3419  	if (sm->mremap)
3420  		return sm->mremap(sm, new_vma);
3421  
3422  	return 0;
3423  }
3424  
3425  static int special_mapping_split(struct vm_area_struct *vma, unsigned long addr)
3426  {
3427  	/*
3428  	 * Forbid splitting special mappings - kernel has expectations over
3429  	 * the number of pages in mapping. Together with VM_DONTEXPAND
3430  	 * the size of vma should stay the same over the special mapping's
3431  	 * lifetime.
3432  	 */
3433  	return -EINVAL;
3434  }
3435  
3436  static const struct vm_operations_struct special_mapping_vmops = {
3437  	.close = special_mapping_close,
3438  	.fault = special_mapping_fault,
3439  	.mremap = special_mapping_mremap,
3440  	.name = special_mapping_name,
3441  	/* vDSO code relies that VVAR can't be accessed remotely */
3442  	.access = NULL,
3443  	.may_split = special_mapping_split,
3444  };
3445  
3446  static const struct vm_operations_struct legacy_special_mapping_vmops = {
3447  	.close = special_mapping_close,
3448  	.fault = special_mapping_fault,
3449  };
3450  
3451  static vm_fault_t special_mapping_fault(struct vm_fault *vmf)
3452  {
3453  	struct vm_area_struct *vma = vmf->vma;
3454  	pgoff_t pgoff;
3455  	struct page **pages;
3456  
3457  	if (vma->vm_ops == &legacy_special_mapping_vmops) {
3458  		pages = vma->vm_private_data;
3459  	} else {
3460  		struct vm_special_mapping *sm = vma->vm_private_data;
3461  
3462  		if (sm->fault)
3463  			return sm->fault(sm, vmf->vma, vmf);
3464  
3465  		pages = sm->pages;
3466  	}
3467  
3468  	for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
3469  		pgoff--;
3470  
3471  	if (*pages) {
3472  		struct page *page = *pages;
3473  		get_page(page);
3474  		vmf->page = page;
3475  		return 0;
3476  	}
3477  
3478  	return VM_FAULT_SIGBUS;
3479  }
3480  
3481  static struct vm_area_struct *__install_special_mapping(
3482  	struct mm_struct *mm,
3483  	unsigned long addr, unsigned long len,
3484  	unsigned long vm_flags, void *priv,
3485  	const struct vm_operations_struct *ops)
3486  {
3487  	int ret;
3488  	struct vm_area_struct *vma;
3489  
3490  	vma = vm_area_alloc(mm);
3491  	if (unlikely(vma == NULL))
3492  		return ERR_PTR(-ENOMEM);
3493  
3494  	vma->vm_start = addr;
3495  	vma->vm_end = addr + len;
3496  
3497  	vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND | VM_SOFTDIRTY;
3498  	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
3499  
3500  	vma->vm_ops = ops;
3501  	vma->vm_private_data = priv;
3502  
3503  	ret = insert_vm_struct(mm, vma);
3504  	if (ret)
3505  		goto out;
3506  
3507  	vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
3508  
3509  	perf_event_mmap(vma);
3510  
3511  	return vma;
3512  
3513  out:
3514  	vm_area_free(vma);
3515  	return ERR_PTR(ret);
3516  }
3517  
3518  bool vma_is_special_mapping(const struct vm_area_struct *vma,
3519  	const struct vm_special_mapping *sm)
3520  {
3521  	return vma->vm_private_data == sm &&
3522  		(vma->vm_ops == &special_mapping_vmops ||
3523  		 vma->vm_ops == &legacy_special_mapping_vmops);
3524  }
3525  
3526  /*
3527   * Called with mm->mmap_lock held for writing.
3528   * Insert a new vma covering the given region, with the given flags.
3529   * Its pages are supplied by the given array of struct page *.
3530   * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
3531   * The region past the last page supplied will always produce SIGBUS.
3532   * The array pointer and the pages it points to are assumed to stay alive
3533   * for as long as this mapping might exist.
3534   */
3535  struct vm_area_struct *_install_special_mapping(
3536  	struct mm_struct *mm,
3537  	unsigned long addr, unsigned long len,
3538  	unsigned long vm_flags, const struct vm_special_mapping *spec)
3539  {
3540  	return __install_special_mapping(mm, addr, len, vm_flags, (void *)spec,
3541  					&special_mapping_vmops);
3542  }
3543  
3544  int install_special_mapping(struct mm_struct *mm,
3545  			    unsigned long addr, unsigned long len,
3546  			    unsigned long vm_flags, struct page **pages)
3547  {
3548  	struct vm_area_struct *vma = __install_special_mapping(
3549  		mm, addr, len, vm_flags, (void *)pages,
3550  		&legacy_special_mapping_vmops);
3551  
3552  	return PTR_ERR_OR_ZERO(vma);
3553  }
3554  
3555  static DEFINE_MUTEX(mm_all_locks_mutex);
3556  
3557  static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
3558  {
3559  	if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
3560  		/*
3561  		 * The LSB of head.next can't change from under us
3562  		 * because we hold the mm_all_locks_mutex.
3563  		 */
3564  		down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_lock);
3565  		/*
3566  		 * We can safely modify head.next after taking the
3567  		 * anon_vma->root->rwsem. If some other vma in this mm shares
3568  		 * the same anon_vma we won't take it again.
3569  		 *
3570  		 * No need of atomic instructions here, head.next
3571  		 * can't change from under us thanks to the
3572  		 * anon_vma->root->rwsem.
3573  		 */
3574  		if (__test_and_set_bit(0, (unsigned long *)
3575  				       &anon_vma->root->rb_root.rb_root.rb_node))
3576  			BUG();
3577  	}
3578  }
3579  
3580  static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
3581  {
3582  	if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3583  		/*
3584  		 * AS_MM_ALL_LOCKS can't change from under us because
3585  		 * we hold the mm_all_locks_mutex.
3586  		 *
3587  		 * Operations on ->flags have to be atomic because
3588  		 * even if AS_MM_ALL_LOCKS is stable thanks to the
3589  		 * mm_all_locks_mutex, there may be other cpus
3590  		 * changing other bitflags in parallel to us.
3591  		 */
3592  		if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
3593  			BUG();
3594  		down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_lock);
3595  	}
3596  }
3597  
3598  /*
3599   * This operation locks against the VM for all pte/vma/mm related
3600   * operations that could ever happen on a certain mm. This includes
3601   * vmtruncate, try_to_unmap, and all page faults.
3602   *
3603   * The caller must take the mmap_lock in write mode before calling
3604   * mm_take_all_locks(). The caller isn't allowed to release the
3605   * mmap_lock until mm_drop_all_locks() returns.
3606   *
3607   * mmap_lock in write mode is required in order to block all operations
3608   * that could modify pagetables and free pages without need of
3609   * altering the vma layout. It's also needed in write mode to avoid new
3610   * anon_vmas to be associated with existing vmas.
3611   *
3612   * A single task can't take more than one mm_take_all_locks() in a row
3613   * or it would deadlock.
3614   *
3615   * The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
3616   * mapping->flags avoid to take the same lock twice, if more than one
3617   * vma in this mm is backed by the same anon_vma or address_space.
3618   *
3619   * We take locks in following order, accordingly to comment at beginning
3620   * of mm/rmap.c:
3621   *   - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for
3622   *     hugetlb mapping);
3623   *   - all i_mmap_rwsem locks;
3624   *   - all anon_vma->rwseml
3625   *
3626   * We can take all locks within these types randomly because the VM code
3627   * doesn't nest them and we protected from parallel mm_take_all_locks() by
3628   * mm_all_locks_mutex.
3629   *
3630   * mm_take_all_locks() and mm_drop_all_locks are expensive operations
3631   * that may have to take thousand of locks.
3632   *
3633   * mm_take_all_locks() can fail if it's interrupted by signals.
3634   */
3635  int mm_take_all_locks(struct mm_struct *mm)
3636  {
3637  	struct vm_area_struct *vma;
3638  	struct anon_vma_chain *avc;
3639  
3640  	BUG_ON(mmap_read_trylock(mm));
3641  
3642  	mutex_lock(&mm_all_locks_mutex);
3643  
3644  	for (vma = mm->mmap; vma; vma = vma->vm_next) {
3645  		if (signal_pending(current))
3646  			goto out_unlock;
3647  		if (vma->vm_file && vma->vm_file->f_mapping &&
3648  				is_vm_hugetlb_page(vma))
3649  			vm_lock_mapping(mm, vma->vm_file->f_mapping);
3650  	}
3651  
3652  	for (vma = mm->mmap; vma; vma = vma->vm_next) {
3653  		if (signal_pending(current))
3654  			goto out_unlock;
3655  		if (vma->vm_file && vma->vm_file->f_mapping &&
3656  				!is_vm_hugetlb_page(vma))
3657  			vm_lock_mapping(mm, vma->vm_file->f_mapping);
3658  	}
3659  
3660  	for (vma = mm->mmap; vma; vma = vma->vm_next) {
3661  		if (signal_pending(current))
3662  			goto out_unlock;
3663  		if (vma->anon_vma)
3664  			list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3665  				vm_lock_anon_vma(mm, avc->anon_vma);
3666  	}
3667  
3668  	return 0;
3669  
3670  out_unlock:
3671  	mm_drop_all_locks(mm);
3672  	return -EINTR;
3673  }
3674  
3675  static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
3676  {
3677  	if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
3678  		/*
3679  		 * The LSB of head.next can't change to 0 from under
3680  		 * us because we hold the mm_all_locks_mutex.
3681  		 *
3682  		 * We must however clear the bitflag before unlocking
3683  		 * the vma so the users using the anon_vma->rb_root will
3684  		 * never see our bitflag.
3685  		 *
3686  		 * No need of atomic instructions here, head.next
3687  		 * can't change from under us until we release the
3688  		 * anon_vma->root->rwsem.
3689  		 */
3690  		if (!__test_and_clear_bit(0, (unsigned long *)
3691  					  &anon_vma->root->rb_root.rb_root.rb_node))
3692  			BUG();
3693  		anon_vma_unlock_write(anon_vma);
3694  	}
3695  }
3696  
3697  static void vm_unlock_mapping(struct address_space *mapping)
3698  {
3699  	if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3700  		/*
3701  		 * AS_MM_ALL_LOCKS can't change to 0 from under us
3702  		 * because we hold the mm_all_locks_mutex.
3703  		 */
3704  		i_mmap_unlock_write(mapping);
3705  		if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
3706  					&mapping->flags))
3707  			BUG();
3708  	}
3709  }
3710  
3711  /*
3712   * The mmap_lock cannot be released by the caller until
3713   * mm_drop_all_locks() returns.
3714   */
3715  void mm_drop_all_locks(struct mm_struct *mm)
3716  {
3717  	struct vm_area_struct *vma;
3718  	struct anon_vma_chain *avc;
3719  
3720  	BUG_ON(mmap_read_trylock(mm));
3721  	BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
3722  
3723  	for (vma = mm->mmap; vma; vma = vma->vm_next) {
3724  		if (vma->anon_vma)
3725  			list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3726  				vm_unlock_anon_vma(avc->anon_vma);
3727  		if (vma->vm_file && vma->vm_file->f_mapping)
3728  			vm_unlock_mapping(vma->vm_file->f_mapping);
3729  	}
3730  
3731  	mutex_unlock(&mm_all_locks_mutex);
3732  }
3733  
3734  /*
3735   * initialise the percpu counter for VM
3736   */
3737  void __init mmap_init(void)
3738  {
3739  	int ret;
3740  
3741  	ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
3742  	VM_BUG_ON(ret);
3743  }
3744  
3745  /*
3746   * Initialise sysctl_user_reserve_kbytes.
3747   *
3748   * This is intended to prevent a user from starting a single memory hogging
3749   * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
3750   * mode.
3751   *
3752   * The default value is min(3% of free memory, 128MB)
3753   * 128MB is enough to recover with sshd/login, bash, and top/kill.
3754   */
3755  static int init_user_reserve(void)
3756  {
3757  	unsigned long free_kbytes;
3758  
3759  	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3760  
3761  	sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
3762  	return 0;
3763  }
3764  subsys_initcall(init_user_reserve);
3765  
3766  /*
3767   * Initialise sysctl_admin_reserve_kbytes.
3768   *
3769   * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
3770   * to log in and kill a memory hogging process.
3771   *
3772   * Systems with more than 256MB will reserve 8MB, enough to recover
3773   * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
3774   * only reserve 3% of free pages by default.
3775   */
3776  static int init_admin_reserve(void)
3777  {
3778  	unsigned long free_kbytes;
3779  
3780  	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3781  
3782  	sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
3783  	return 0;
3784  }
3785  subsys_initcall(init_admin_reserve);
3786  
3787  /*
3788   * Reinititalise user and admin reserves if memory is added or removed.
3789   *
3790   * The default user reserve max is 128MB, and the default max for the
3791   * admin reserve is 8MB. These are usually, but not always, enough to
3792   * enable recovery from a memory hogging process using login/sshd, a shell,
3793   * and tools like top. It may make sense to increase or even disable the
3794   * reserve depending on the existence of swap or variations in the recovery
3795   * tools. So, the admin may have changed them.
3796   *
3797   * If memory is added and the reserves have been eliminated or increased above
3798   * the default max, then we'll trust the admin.
3799   *
3800   * If memory is removed and there isn't enough free memory, then we
3801   * need to reset the reserves.
3802   *
3803   * Otherwise keep the reserve set by the admin.
3804   */
3805  static int reserve_mem_notifier(struct notifier_block *nb,
3806  			     unsigned long action, void *data)
3807  {
3808  	unsigned long tmp, free_kbytes;
3809  
3810  	switch (action) {
3811  	case MEM_ONLINE:
3812  		/* Default max is 128MB. Leave alone if modified by operator. */
3813  		tmp = sysctl_user_reserve_kbytes;
3814  		if (0 < tmp && tmp < (1UL << 17))
3815  			init_user_reserve();
3816  
3817  		/* Default max is 8MB.  Leave alone if modified by operator. */
3818  		tmp = sysctl_admin_reserve_kbytes;
3819  		if (0 < tmp && tmp < (1UL << 13))
3820  			init_admin_reserve();
3821  
3822  		break;
3823  	case MEM_OFFLINE:
3824  		free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3825  
3826  		if (sysctl_user_reserve_kbytes > free_kbytes) {
3827  			init_user_reserve();
3828  			pr_info("vm.user_reserve_kbytes reset to %lu\n",
3829  				sysctl_user_reserve_kbytes);
3830  		}
3831  
3832  		if (sysctl_admin_reserve_kbytes > free_kbytes) {
3833  			init_admin_reserve();
3834  			pr_info("vm.admin_reserve_kbytes reset to %lu\n",
3835  				sysctl_admin_reserve_kbytes);
3836  		}
3837  		break;
3838  	default:
3839  		break;
3840  	}
3841  	return NOTIFY_OK;
3842  }
3843  
3844  static struct notifier_block reserve_mem_nb = {
3845  	.notifier_call = reserve_mem_notifier,
3846  };
3847  
3848  static int __meminit init_reserve_notifier(void)
3849  {
3850  	if (register_hotmemory_notifier(&reserve_mem_nb))
3851  		pr_err("Failed registering memory add/remove notifier for admin reserve\n");
3852  
3853  	return 0;
3854  }
3855  subsys_initcall(init_reserve_notifier);
3856