xref: /openbmc/linux/fs/proc/inode.c (revision 165f2d28) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  linux/fs/proc/inode.c
4  *
5  *  Copyright (C) 1991, 1992  Linus Torvalds
6  */
7 
8 #include <linux/cache.h>
9 #include <linux/time.h>
10 #include <linux/proc_fs.h>
11 #include <linux/kernel.h>
12 #include <linux/pid_namespace.h>
13 #include <linux/mm.h>
14 #include <linux/string.h>
15 #include <linux/stat.h>
16 #include <linux/completion.h>
17 #include <linux/poll.h>
18 #include <linux/printk.h>
19 #include <linux/file.h>
20 #include <linux/limits.h>
21 #include <linux/init.h>
22 #include <linux/module.h>
23 #include <linux/sysctl.h>
24 #include <linux/seq_file.h>
25 #include <linux/slab.h>
26 #include <linux/mount.h>
27 
28 #include <linux/uaccess.h>
29 
30 #include "internal.h"
31 
32 static void proc_evict_inode(struct inode *inode)
33 {
34 	struct proc_dir_entry *de;
35 	struct ctl_table_header *head;
36 	struct proc_inode *ei = PROC_I(inode);
37 
38 	truncate_inode_pages_final(&inode->i_data);
39 	clear_inode(inode);
40 
41 	/* Stop tracking associated processes */
42 	if (ei->pid) {
43 		proc_pid_evict_inode(ei);
44 		ei->pid = NULL;
45 	}
46 
47 	/* Let go of any associated proc directory entry */
48 	de = ei->pde;
49 	if (de) {
50 		pde_put(de);
51 		ei->pde = NULL;
52 	}
53 
54 	head = ei->sysctl;
55 	if (head) {
56 		RCU_INIT_POINTER(ei->sysctl, NULL);
57 		proc_sys_evict_inode(inode, head);
58 	}
59 }
60 
61 static struct kmem_cache *proc_inode_cachep __ro_after_init;
62 static struct kmem_cache *pde_opener_cache __ro_after_init;
63 
64 static struct inode *proc_alloc_inode(struct super_block *sb)
65 {
66 	struct proc_inode *ei;
67 
68 	ei = kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
69 	if (!ei)
70 		return NULL;
71 	ei->pid = NULL;
72 	ei->fd = 0;
73 	ei->op.proc_get_link = NULL;
74 	ei->pde = NULL;
75 	ei->sysctl = NULL;
76 	ei->sysctl_entry = NULL;
77 	INIT_HLIST_NODE(&ei->sibling_inodes);
78 	ei->ns_ops = NULL;
79 	return &ei->vfs_inode;
80 }
81 
82 static void proc_free_inode(struct inode *inode)
83 {
84 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
85 }
86 
87 static void init_once(void *foo)
88 {
89 	struct proc_inode *ei = (struct proc_inode *) foo;
90 
91 	inode_init_once(&ei->vfs_inode);
92 }
93 
94 void __init proc_init_kmemcache(void)
95 {
96 	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
97 					     sizeof(struct proc_inode),
98 					     0, (SLAB_RECLAIM_ACCOUNT|
99 						SLAB_MEM_SPREAD|SLAB_ACCOUNT|
100 						SLAB_PANIC),
101 					     init_once);
102 	pde_opener_cache =
103 		kmem_cache_create("pde_opener", sizeof(struct pde_opener), 0,
104 				  SLAB_ACCOUNT|SLAB_PANIC, NULL);
105 	proc_dir_entry_cache = kmem_cache_create_usercopy(
106 		"proc_dir_entry", SIZEOF_PDE, 0, SLAB_PANIC,
107 		offsetof(struct proc_dir_entry, inline_name),
108 		SIZEOF_PDE_INLINE_NAME, NULL);
109 	BUILD_BUG_ON(sizeof(struct proc_dir_entry) >= SIZEOF_PDE);
110 }
111 
112 void proc_invalidate_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock)
113 {
114 	struct inode *inode;
115 	struct proc_inode *ei;
116 	struct hlist_node *node;
117 	struct super_block *old_sb = NULL;
118 
119 	rcu_read_lock();
120 	for (;;) {
121 		struct super_block *sb;
122 		node = hlist_first_rcu(inodes);
123 		if (!node)
124 			break;
125 		ei = hlist_entry(node, struct proc_inode, sibling_inodes);
126 		spin_lock(lock);
127 		hlist_del_init_rcu(&ei->sibling_inodes);
128 		spin_unlock(lock);
129 
130 		inode = &ei->vfs_inode;
131 		sb = inode->i_sb;
132 		if ((sb != old_sb) && !atomic_inc_not_zero(&sb->s_active))
133 			continue;
134 		inode = igrab(inode);
135 		rcu_read_unlock();
136 		if (sb != old_sb) {
137 			if (old_sb)
138 				deactivate_super(old_sb);
139 			old_sb = sb;
140 		}
141 		if (unlikely(!inode)) {
142 			rcu_read_lock();
143 			continue;
144 		}
145 
146 		if (S_ISDIR(inode->i_mode)) {
147 			struct dentry *dir = d_find_any_alias(inode);
148 			if (dir) {
149 				d_invalidate(dir);
150 				dput(dir);
151 			}
152 		} else {
153 			struct dentry *dentry;
154 			while ((dentry = d_find_alias(inode))) {
155 				d_invalidate(dentry);
156 				dput(dentry);
157 			}
158 		}
159 		iput(inode);
160 
161 		rcu_read_lock();
162 	}
163 	rcu_read_unlock();
164 	if (old_sb)
165 		deactivate_super(old_sb);
166 }
167 
168 static int proc_show_options(struct seq_file *seq, struct dentry *root)
169 {
170 	struct super_block *sb = root->d_sb;
171 	struct pid_namespace *pid = sb->s_fs_info;
172 
173 	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
174 		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
175 	if (pid->hide_pid != HIDEPID_OFF)
176 		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
177 
178 	return 0;
179 }
180 
181 const struct super_operations proc_sops = {
182 	.alloc_inode	= proc_alloc_inode,
183 	.free_inode	= proc_free_inode,
184 	.drop_inode	= generic_delete_inode,
185 	.evict_inode	= proc_evict_inode,
186 	.statfs		= simple_statfs,
187 	.show_options	= proc_show_options,
188 };
189 
190 enum {BIAS = -1U<<31};
191 
192 static inline int use_pde(struct proc_dir_entry *pde)
193 {
194 	return likely(atomic_inc_unless_negative(&pde->in_use));
195 }
196 
197 static void unuse_pde(struct proc_dir_entry *pde)
198 {
199 	if (unlikely(atomic_dec_return(&pde->in_use) == BIAS))
200 		complete(pde->pde_unload_completion);
201 }
202 
203 /* pde is locked on entry, unlocked on exit */
204 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
205 	__releases(&pde->pde_unload_lock)
206 {
207 	/*
208 	 * close() (proc_reg_release()) can't delete an entry and proceed:
209 	 * ->release hook needs to be available at the right moment.
210 	 *
211 	 * rmmod (remove_proc_entry() et al) can't delete an entry and proceed:
212 	 * "struct file" needs to be available at the right moment.
213 	 *
214 	 * Therefore, first process to enter this function does ->release() and
215 	 * signals its completion to the other process which does nothing.
216 	 */
217 	if (pdeo->closing) {
218 		/* somebody else is doing that, just wait */
219 		DECLARE_COMPLETION_ONSTACK(c);
220 		pdeo->c = &c;
221 		spin_unlock(&pde->pde_unload_lock);
222 		wait_for_completion(&c);
223 	} else {
224 		struct file *file;
225 		struct completion *c;
226 
227 		pdeo->closing = true;
228 		spin_unlock(&pde->pde_unload_lock);
229 		file = pdeo->file;
230 		pde->proc_ops->proc_release(file_inode(file), file);
231 		spin_lock(&pde->pde_unload_lock);
232 		/* After ->release. */
233 		list_del(&pdeo->lh);
234 		c = pdeo->c;
235 		spin_unlock(&pde->pde_unload_lock);
236 		if (unlikely(c))
237 			complete(c);
238 		kmem_cache_free(pde_opener_cache, pdeo);
239 	}
240 }
241 
242 void proc_entry_rundown(struct proc_dir_entry *de)
243 {
244 	DECLARE_COMPLETION_ONSTACK(c);
245 	/* Wait until all existing callers into module are done. */
246 	de->pde_unload_completion = &c;
247 	if (atomic_add_return(BIAS, &de->in_use) != BIAS)
248 		wait_for_completion(&c);
249 
250 	/* ->pde_openers list can't grow from now on. */
251 
252 	spin_lock(&de->pde_unload_lock);
253 	while (!list_empty(&de->pde_openers)) {
254 		struct pde_opener *pdeo;
255 		pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
256 		close_pdeo(de, pdeo);
257 		spin_lock(&de->pde_unload_lock);
258 	}
259 	spin_unlock(&de->pde_unload_lock);
260 }
261 
262 static loff_t pde_lseek(struct proc_dir_entry *pde, struct file *file, loff_t offset, int whence)
263 {
264 	typeof_member(struct proc_ops, proc_lseek) lseek;
265 
266 	lseek = pde->proc_ops->proc_lseek;
267 	if (!lseek)
268 		lseek = default_llseek;
269 	return lseek(file, offset, whence);
270 }
271 
272 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
273 {
274 	struct proc_dir_entry *pde = PDE(file_inode(file));
275 	loff_t rv = -EINVAL;
276 
277 	if (pde_is_permanent(pde)) {
278 		return pde_lseek(pde, file, offset, whence);
279 	} else if (use_pde(pde)) {
280 		rv = pde_lseek(pde, file, offset, whence);
281 		unuse_pde(pde);
282 	}
283 	return rv;
284 }
285 
286 static ssize_t pde_read(struct proc_dir_entry *pde, struct file *file, char __user *buf, size_t count, loff_t *ppos)
287 {
288 	typeof_member(struct proc_ops, proc_read) read;
289 
290 	read = pde->proc_ops->proc_read;
291 	if (read)
292 		return read(file, buf, count, ppos);
293 	return -EIO;
294 }
295 
296 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
297 {
298 	struct proc_dir_entry *pde = PDE(file_inode(file));
299 	ssize_t rv = -EIO;
300 
301 	if (pde_is_permanent(pde)) {
302 		return pde_read(pde, file, buf, count, ppos);
303 	} else if (use_pde(pde)) {
304 		rv = pde_read(pde, file, buf, count, ppos);
305 		unuse_pde(pde);
306 	}
307 	return rv;
308 }
309 
310 static ssize_t pde_write(struct proc_dir_entry *pde, struct file *file, const char __user *buf, size_t count, loff_t *ppos)
311 {
312 	typeof_member(struct proc_ops, proc_write) write;
313 
314 	write = pde->proc_ops->proc_write;
315 	if (write)
316 		return write(file, buf, count, ppos);
317 	return -EIO;
318 }
319 
320 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
321 {
322 	struct proc_dir_entry *pde = PDE(file_inode(file));
323 	ssize_t rv = -EIO;
324 
325 	if (pde_is_permanent(pde)) {
326 		return pde_write(pde, file, buf, count, ppos);
327 	} else if (use_pde(pde)) {
328 		rv = pde_write(pde, file, buf, count, ppos);
329 		unuse_pde(pde);
330 	}
331 	return rv;
332 }
333 
334 static __poll_t pde_poll(struct proc_dir_entry *pde, struct file *file, struct poll_table_struct *pts)
335 {
336 	typeof_member(struct proc_ops, proc_poll) poll;
337 
338 	poll = pde->proc_ops->proc_poll;
339 	if (poll)
340 		return poll(file, pts);
341 	return DEFAULT_POLLMASK;
342 }
343 
344 static __poll_t proc_reg_poll(struct file *file, struct poll_table_struct *pts)
345 {
346 	struct proc_dir_entry *pde = PDE(file_inode(file));
347 	__poll_t rv = DEFAULT_POLLMASK;
348 
349 	if (pde_is_permanent(pde)) {
350 		return pde_poll(pde, file, pts);
351 	} else if (use_pde(pde)) {
352 		rv = pde_poll(pde, file, pts);
353 		unuse_pde(pde);
354 	}
355 	return rv;
356 }
357 
358 static long pde_ioctl(struct proc_dir_entry *pde, struct file *file, unsigned int cmd, unsigned long arg)
359 {
360 	typeof_member(struct proc_ops, proc_ioctl) ioctl;
361 
362 	ioctl = pde->proc_ops->proc_ioctl;
363 	if (ioctl)
364 		return ioctl(file, cmd, arg);
365 	return -ENOTTY;
366 }
367 
368 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
369 {
370 	struct proc_dir_entry *pde = PDE(file_inode(file));
371 	long rv = -ENOTTY;
372 
373 	if (pde_is_permanent(pde)) {
374 		return pde_ioctl(pde, file, cmd, arg);
375 	} else if (use_pde(pde)) {
376 		rv = pde_ioctl(pde, file, cmd, arg);
377 		unuse_pde(pde);
378 	}
379 	return rv;
380 }
381 
382 #ifdef CONFIG_COMPAT
383 static long pde_compat_ioctl(struct proc_dir_entry *pde, struct file *file, unsigned int cmd, unsigned long arg)
384 {
385 	typeof_member(struct proc_ops, proc_compat_ioctl) compat_ioctl;
386 
387 	compat_ioctl = pde->proc_ops->proc_compat_ioctl;
388 	if (compat_ioctl)
389 		return compat_ioctl(file, cmd, arg);
390 	return -ENOTTY;
391 }
392 
393 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
394 {
395 	struct proc_dir_entry *pde = PDE(file_inode(file));
396 	long rv = -ENOTTY;
397 	if (pde_is_permanent(pde)) {
398 		return pde_compat_ioctl(pde, file, cmd, arg);
399 	} else if (use_pde(pde)) {
400 		rv = pde_compat_ioctl(pde, file, cmd, arg);
401 		unuse_pde(pde);
402 	}
403 	return rv;
404 }
405 #endif
406 
407 static int pde_mmap(struct proc_dir_entry *pde, struct file *file, struct vm_area_struct *vma)
408 {
409 	typeof_member(struct proc_ops, proc_mmap) mmap;
410 
411 	mmap = pde->proc_ops->proc_mmap;
412 	if (mmap)
413 		return mmap(file, vma);
414 	return -EIO;
415 }
416 
417 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
418 {
419 	struct proc_dir_entry *pde = PDE(file_inode(file));
420 	int rv = -EIO;
421 
422 	if (pde_is_permanent(pde)) {
423 		return pde_mmap(pde, file, vma);
424 	} else if (use_pde(pde)) {
425 		rv = pde_mmap(pde, file, vma);
426 		unuse_pde(pde);
427 	}
428 	return rv;
429 }
430 
431 static unsigned long
432 pde_get_unmapped_area(struct proc_dir_entry *pde, struct file *file, unsigned long orig_addr,
433 			   unsigned long len, unsigned long pgoff,
434 			   unsigned long flags)
435 {
436 	typeof_member(struct proc_ops, proc_get_unmapped_area) get_area;
437 
438 	get_area = pde->proc_ops->proc_get_unmapped_area;
439 #ifdef CONFIG_MMU
440 	if (!get_area)
441 		get_area = current->mm->get_unmapped_area;
442 #endif
443 	if (get_area)
444 		return get_area(file, orig_addr, len, pgoff, flags);
445 	return orig_addr;
446 }
447 
448 static unsigned long
449 proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
450 			   unsigned long len, unsigned long pgoff,
451 			   unsigned long flags)
452 {
453 	struct proc_dir_entry *pde = PDE(file_inode(file));
454 	unsigned long rv = -EIO;
455 
456 	if (pde_is_permanent(pde)) {
457 		return pde_get_unmapped_area(pde, file, orig_addr, len, pgoff, flags);
458 	} else if (use_pde(pde)) {
459 		rv = pde_get_unmapped_area(pde, file, orig_addr, len, pgoff, flags);
460 		unuse_pde(pde);
461 	}
462 	return rv;
463 }
464 
465 static int proc_reg_open(struct inode *inode, struct file *file)
466 {
467 	struct proc_dir_entry *pde = PDE(inode);
468 	int rv = 0;
469 	typeof_member(struct proc_ops, proc_open) open;
470 	typeof_member(struct proc_ops, proc_release) release;
471 	struct pde_opener *pdeo;
472 
473 	if (pde_is_permanent(pde)) {
474 		open = pde->proc_ops->proc_open;
475 		if (open)
476 			rv = open(inode, file);
477 		return rv;
478 	}
479 
480 	/*
481 	 * Ensure that
482 	 * 1) PDE's ->release hook will be called no matter what
483 	 *    either normally by close()/->release, or forcefully by
484 	 *    rmmod/remove_proc_entry.
485 	 *
486 	 * 2) rmmod isn't blocked by opening file in /proc and sitting on
487 	 *    the descriptor (including "rmmod foo </proc/foo" scenario).
488 	 *
489 	 * Save every "struct file" with custom ->release hook.
490 	 */
491 	if (!use_pde(pde))
492 		return -ENOENT;
493 
494 	release = pde->proc_ops->proc_release;
495 	if (release) {
496 		pdeo = kmem_cache_alloc(pde_opener_cache, GFP_KERNEL);
497 		if (!pdeo) {
498 			rv = -ENOMEM;
499 			goto out_unuse;
500 		}
501 	}
502 
503 	open = pde->proc_ops->proc_open;
504 	if (open)
505 		rv = open(inode, file);
506 
507 	if (release) {
508 		if (rv == 0) {
509 			/* To know what to release. */
510 			pdeo->file = file;
511 			pdeo->closing = false;
512 			pdeo->c = NULL;
513 			spin_lock(&pde->pde_unload_lock);
514 			list_add(&pdeo->lh, &pde->pde_openers);
515 			spin_unlock(&pde->pde_unload_lock);
516 		} else
517 			kmem_cache_free(pde_opener_cache, pdeo);
518 	}
519 
520 out_unuse:
521 	unuse_pde(pde);
522 	return rv;
523 }
524 
525 static int proc_reg_release(struct inode *inode, struct file *file)
526 {
527 	struct proc_dir_entry *pde = PDE(inode);
528 	struct pde_opener *pdeo;
529 
530 	if (pde_is_permanent(pde)) {
531 		typeof_member(struct proc_ops, proc_release) release;
532 
533 		release = pde->proc_ops->proc_release;
534 		if (release) {
535 			return release(inode, file);
536 		}
537 		return 0;
538 	}
539 
540 	spin_lock(&pde->pde_unload_lock);
541 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
542 		if (pdeo->file == file) {
543 			close_pdeo(pde, pdeo);
544 			return 0;
545 		}
546 	}
547 	spin_unlock(&pde->pde_unload_lock);
548 	return 0;
549 }
550 
551 static const struct file_operations proc_reg_file_ops = {
552 	.llseek		= proc_reg_llseek,
553 	.read		= proc_reg_read,
554 	.write		= proc_reg_write,
555 	.poll		= proc_reg_poll,
556 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
557 #ifdef CONFIG_COMPAT
558 	.compat_ioctl	= proc_reg_compat_ioctl,
559 #endif
560 	.mmap		= proc_reg_mmap,
561 	.get_unmapped_area = proc_reg_get_unmapped_area,
562 	.open		= proc_reg_open,
563 	.release	= proc_reg_release,
564 };
565 
566 #ifdef CONFIG_COMPAT
567 static const struct file_operations proc_reg_file_ops_no_compat = {
568 	.llseek		= proc_reg_llseek,
569 	.read		= proc_reg_read,
570 	.write		= proc_reg_write,
571 	.poll		= proc_reg_poll,
572 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
573 	.mmap		= proc_reg_mmap,
574 	.get_unmapped_area = proc_reg_get_unmapped_area,
575 	.open		= proc_reg_open,
576 	.release	= proc_reg_release,
577 };
578 #endif
579 
580 static void proc_put_link(void *p)
581 {
582 	unuse_pde(p);
583 }
584 
585 static const char *proc_get_link(struct dentry *dentry,
586 				 struct inode *inode,
587 				 struct delayed_call *done)
588 {
589 	struct proc_dir_entry *pde = PDE(inode);
590 	if (!use_pde(pde))
591 		return ERR_PTR(-EINVAL);
592 	set_delayed_call(done, proc_put_link, pde);
593 	return pde->data;
594 }
595 
596 const struct inode_operations proc_link_inode_operations = {
597 	.get_link	= proc_get_link,
598 };
599 
600 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
601 {
602 	struct inode *inode = new_inode_pseudo(sb);
603 
604 	if (inode) {
605 		inode->i_ino = de->low_ino;
606 		inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
607 		PROC_I(inode)->pde = de;
608 
609 		if (is_empty_pde(de)) {
610 			make_empty_dir_inode(inode);
611 			return inode;
612 		}
613 		if (de->mode) {
614 			inode->i_mode = de->mode;
615 			inode->i_uid = de->uid;
616 			inode->i_gid = de->gid;
617 		}
618 		if (de->size)
619 			inode->i_size = de->size;
620 		if (de->nlink)
621 			set_nlink(inode, de->nlink);
622 
623 		if (S_ISREG(inode->i_mode)) {
624 			inode->i_op = de->proc_iops;
625 			inode->i_fop = &proc_reg_file_ops;
626 #ifdef CONFIG_COMPAT
627 			if (!de->proc_ops->proc_compat_ioctl) {
628 				inode->i_fop = &proc_reg_file_ops_no_compat;
629 			}
630 #endif
631 		} else if (S_ISDIR(inode->i_mode)) {
632 			inode->i_op = de->proc_iops;
633 			inode->i_fop = de->proc_dir_ops;
634 		} else if (S_ISLNK(inode->i_mode)) {
635 			inode->i_op = de->proc_iops;
636 			inode->i_fop = NULL;
637 		} else
638 			BUG();
639 	} else
640 	       pde_put(de);
641 	return inode;
642 }
643