xref: /openbmc/linux/fs/proc/inode.c (revision 6d99a79c) 
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 #include <linux/magic.h>
28 
29 #include <linux/uaccess.h>
30 
31 #include "internal.h"
32 
33 static void proc_evict_inode(struct inode *inode)
34 {
35 	struct proc_dir_entry *de;
36 	struct ctl_table_header *head;
37 
38 	truncate_inode_pages_final(&inode->i_data);
39 	clear_inode(inode);
40 
41 	/* Stop tracking associated processes */
42 	put_pid(PROC_I(inode)->pid);
43 
44 	/* Let go of any associated proc directory entry */
45 	de = PDE(inode);
46 	if (de)
47 		pde_put(de);
48 
49 	head = PROC_I(inode)->sysctl;
50 	if (head) {
51 		RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);
52 		proc_sys_evict_inode(inode, head);
53 	}
54 }
55 
56 static struct kmem_cache *proc_inode_cachep __ro_after_init;
57 static struct kmem_cache *pde_opener_cache __ro_after_init;
58 
59 static struct inode *proc_alloc_inode(struct super_block *sb)
60 {
61 	struct proc_inode *ei;
62 	struct inode *inode;
63 
64 	ei = kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
65 	if (!ei)
66 		return NULL;
67 	ei->pid = NULL;
68 	ei->fd = 0;
69 	ei->op.proc_get_link = NULL;
70 	ei->pde = NULL;
71 	ei->sysctl = NULL;
72 	ei->sysctl_entry = NULL;
73 	ei->ns_ops = NULL;
74 	inode = &ei->vfs_inode;
75 	return inode;
76 }
77 
78 static void proc_i_callback(struct rcu_head *head)
79 {
80 	struct inode *inode = container_of(head, struct inode, i_rcu);
81 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
82 }
83 
84 static void proc_destroy_inode(struct inode *inode)
85 {
86 	call_rcu(&inode->i_rcu, proc_i_callback);
87 }
88 
89 static void init_once(void *foo)
90 {
91 	struct proc_inode *ei = (struct proc_inode *) foo;
92 
93 	inode_init_once(&ei->vfs_inode);
94 }
95 
96 void __init proc_init_kmemcache(void)
97 {
98 	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
99 					     sizeof(struct proc_inode),
100 					     0, (SLAB_RECLAIM_ACCOUNT|
101 						SLAB_MEM_SPREAD|SLAB_ACCOUNT|
102 						SLAB_PANIC),
103 					     init_once);
104 	pde_opener_cache =
105 		kmem_cache_create("pde_opener", sizeof(struct pde_opener), 0,
106 				  SLAB_ACCOUNT|SLAB_PANIC, NULL);
107 	proc_dir_entry_cache = kmem_cache_create_usercopy(
108 		"proc_dir_entry", SIZEOF_PDE, 0, SLAB_PANIC,
109 		offsetof(struct proc_dir_entry, inline_name),
110 		SIZEOF_PDE_INLINE_NAME, NULL);
111 	BUILD_BUG_ON(sizeof(struct proc_dir_entry) >= SIZEOF_PDE);
112 }
113 
114 static int proc_show_options(struct seq_file *seq, struct dentry *root)
115 {
116 	struct super_block *sb = root->d_sb;
117 	struct pid_namespace *pid = sb->s_fs_info;
118 
119 	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
120 		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
121 	if (pid->hide_pid != HIDEPID_OFF)
122 		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
123 
124 	return 0;
125 }
126 
127 static const struct super_operations proc_sops = {
128 	.alloc_inode	= proc_alloc_inode,
129 	.destroy_inode	= proc_destroy_inode,
130 	.drop_inode	= generic_delete_inode,
131 	.evict_inode	= proc_evict_inode,
132 	.statfs		= simple_statfs,
133 	.remount_fs	= proc_remount,
134 	.show_options	= proc_show_options,
135 };
136 
137 enum {BIAS = -1U<<31};
138 
139 static inline int use_pde(struct proc_dir_entry *pde)
140 {
141 	return likely(atomic_inc_unless_negative(&pde->in_use));
142 }
143 
144 static void unuse_pde(struct proc_dir_entry *pde)
145 {
146 	if (unlikely(atomic_dec_return(&pde->in_use) == BIAS))
147 		complete(pde->pde_unload_completion);
148 }
149 
150 /* pde is locked on entry, unlocked on exit */
151 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
152 {
153 	/*
154 	 * close() (proc_reg_release()) can't delete an entry and proceed:
155 	 * ->release hook needs to be available at the right moment.
156 	 *
157 	 * rmmod (remove_proc_entry() et al) can't delete an entry and proceed:
158 	 * "struct file" needs to be available at the right moment.
159 	 *
160 	 * Therefore, first process to enter this function does ->release() and
161 	 * signals its completion to the other process which does nothing.
162 	 */
163 	if (pdeo->closing) {
164 		/* somebody else is doing that, just wait */
165 		DECLARE_COMPLETION_ONSTACK(c);
166 		pdeo->c = &c;
167 		spin_unlock(&pde->pde_unload_lock);
168 		wait_for_completion(&c);
169 	} else {
170 		struct file *file;
171 		struct completion *c;
172 
173 		pdeo->closing = true;
174 		spin_unlock(&pde->pde_unload_lock);
175 		file = pdeo->file;
176 		pde->proc_fops->release(file_inode(file), file);
177 		spin_lock(&pde->pde_unload_lock);
178 		/* After ->release. */
179 		list_del(&pdeo->lh);
180 		c = pdeo->c;
181 		spin_unlock(&pde->pde_unload_lock);
182 		if (unlikely(c))
183 			complete(c);
184 		kmem_cache_free(pde_opener_cache, pdeo);
185 	}
186 }
187 
188 void proc_entry_rundown(struct proc_dir_entry *de)
189 {
190 	DECLARE_COMPLETION_ONSTACK(c);
191 	/* Wait until all existing callers into module are done. */
192 	de->pde_unload_completion = &c;
193 	if (atomic_add_return(BIAS, &de->in_use) != BIAS)
194 		wait_for_completion(&c);
195 
196 	/* ->pde_openers list can't grow from now on. */
197 
198 	spin_lock(&de->pde_unload_lock);
199 	while (!list_empty(&de->pde_openers)) {
200 		struct pde_opener *pdeo;
201 		pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
202 		close_pdeo(de, pdeo);
203 		spin_lock(&de->pde_unload_lock);
204 	}
205 	spin_unlock(&de->pde_unload_lock);
206 }
207 
208 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
209 {
210 	struct proc_dir_entry *pde = PDE(file_inode(file));
211 	loff_t rv = -EINVAL;
212 	if (use_pde(pde)) {
213 		loff_t (*llseek)(struct file *, loff_t, int);
214 		llseek = pde->proc_fops->llseek;
215 		if (!llseek)
216 			llseek = default_llseek;
217 		rv = llseek(file, offset, whence);
218 		unuse_pde(pde);
219 	}
220 	return rv;
221 }
222 
223 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
224 {
225 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
226 	struct proc_dir_entry *pde = PDE(file_inode(file));
227 	ssize_t rv = -EIO;
228 	if (use_pde(pde)) {
229 		read = pde->proc_fops->read;
230 		if (read)
231 			rv = read(file, buf, count, ppos);
232 		unuse_pde(pde);
233 	}
234 	return rv;
235 }
236 
237 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
238 {
239 	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
240 	struct proc_dir_entry *pde = PDE(file_inode(file));
241 	ssize_t rv = -EIO;
242 	if (use_pde(pde)) {
243 		write = pde->proc_fops->write;
244 		if (write)
245 			rv = write(file, buf, count, ppos);
246 		unuse_pde(pde);
247 	}
248 	return rv;
249 }
250 
251 static __poll_t proc_reg_poll(struct file *file, struct poll_table_struct *pts)
252 {
253 	struct proc_dir_entry *pde = PDE(file_inode(file));
254 	__poll_t rv = DEFAULT_POLLMASK;
255 	__poll_t (*poll)(struct file *, struct poll_table_struct *);
256 	if (use_pde(pde)) {
257 		poll = pde->proc_fops->poll;
258 		if (poll)
259 			rv = poll(file, pts);
260 		unuse_pde(pde);
261 	}
262 	return rv;
263 }
264 
265 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
266 {
267 	struct proc_dir_entry *pde = PDE(file_inode(file));
268 	long rv = -ENOTTY;
269 	long (*ioctl)(struct file *, unsigned int, unsigned long);
270 	if (use_pde(pde)) {
271 		ioctl = pde->proc_fops->unlocked_ioctl;
272 		if (ioctl)
273 			rv = ioctl(file, cmd, arg);
274 		unuse_pde(pde);
275 	}
276 	return rv;
277 }
278 
279 #ifdef CONFIG_COMPAT
280 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
281 {
282 	struct proc_dir_entry *pde = PDE(file_inode(file));
283 	long rv = -ENOTTY;
284 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
285 	if (use_pde(pde)) {
286 		compat_ioctl = pde->proc_fops->compat_ioctl;
287 		if (compat_ioctl)
288 			rv = compat_ioctl(file, cmd, arg);
289 		unuse_pde(pde);
290 	}
291 	return rv;
292 }
293 #endif
294 
295 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
296 {
297 	struct proc_dir_entry *pde = PDE(file_inode(file));
298 	int rv = -EIO;
299 	int (*mmap)(struct file *, struct vm_area_struct *);
300 	if (use_pde(pde)) {
301 		mmap = pde->proc_fops->mmap;
302 		if (mmap)
303 			rv = mmap(file, vma);
304 		unuse_pde(pde);
305 	}
306 	return rv;
307 }
308 
309 static unsigned long
310 proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
311 			   unsigned long len, unsigned long pgoff,
312 			   unsigned long flags)
313 {
314 	struct proc_dir_entry *pde = PDE(file_inode(file));
315 	unsigned long rv = -EIO;
316 
317 	if (use_pde(pde)) {
318 		typeof(proc_reg_get_unmapped_area) *get_area;
319 
320 		get_area = pde->proc_fops->get_unmapped_area;
321 #ifdef CONFIG_MMU
322 		if (!get_area)
323 			get_area = current->mm->get_unmapped_area;
324 #endif
325 
326 		if (get_area)
327 			rv = get_area(file, orig_addr, len, pgoff, flags);
328 		else
329 			rv = orig_addr;
330 		unuse_pde(pde);
331 	}
332 	return rv;
333 }
334 
335 static int proc_reg_open(struct inode *inode, struct file *file)
336 {
337 	struct proc_dir_entry *pde = PDE(inode);
338 	int rv = 0;
339 	int (*open)(struct inode *, struct file *);
340 	int (*release)(struct inode *, struct file *);
341 	struct pde_opener *pdeo;
342 
343 	/*
344 	 * Ensure that
345 	 * 1) PDE's ->release hook will be called no matter what
346 	 *    either normally by close()/->release, or forcefully by
347 	 *    rmmod/remove_proc_entry.
348 	 *
349 	 * 2) rmmod isn't blocked by opening file in /proc and sitting on
350 	 *    the descriptor (including "rmmod foo </proc/foo" scenario).
351 	 *
352 	 * Save every "struct file" with custom ->release hook.
353 	 */
354 	if (!use_pde(pde))
355 		return -ENOENT;
356 
357 	release = pde->proc_fops->release;
358 	if (release) {
359 		pdeo = kmem_cache_alloc(pde_opener_cache, GFP_KERNEL);
360 		if (!pdeo) {
361 			rv = -ENOMEM;
362 			goto out_unuse;
363 		}
364 	}
365 
366 	open = pde->proc_fops->open;
367 	if (open)
368 		rv = open(inode, file);
369 
370 	if (release) {
371 		if (rv == 0) {
372 			/* To know what to release. */
373 			pdeo->file = file;
374 			pdeo->closing = false;
375 			pdeo->c = NULL;
376 			spin_lock(&pde->pde_unload_lock);
377 			list_add(&pdeo->lh, &pde->pde_openers);
378 			spin_unlock(&pde->pde_unload_lock);
379 		} else
380 			kmem_cache_free(pde_opener_cache, pdeo);
381 	}
382 
383 out_unuse:
384 	unuse_pde(pde);
385 	return rv;
386 }
387 
388 static int proc_reg_release(struct inode *inode, struct file *file)
389 {
390 	struct proc_dir_entry *pde = PDE(inode);
391 	struct pde_opener *pdeo;
392 	spin_lock(&pde->pde_unload_lock);
393 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
394 		if (pdeo->file == file) {
395 			close_pdeo(pde, pdeo);
396 			return 0;
397 		}
398 	}
399 	spin_unlock(&pde->pde_unload_lock);
400 	return 0;
401 }
402 
403 static const struct file_operations proc_reg_file_ops = {
404 	.llseek		= proc_reg_llseek,
405 	.read		= proc_reg_read,
406 	.write		= proc_reg_write,
407 	.poll		= proc_reg_poll,
408 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
409 #ifdef CONFIG_COMPAT
410 	.compat_ioctl	= proc_reg_compat_ioctl,
411 #endif
412 	.mmap		= proc_reg_mmap,
413 	.get_unmapped_area = proc_reg_get_unmapped_area,
414 	.open		= proc_reg_open,
415 	.release	= proc_reg_release,
416 };
417 
418 #ifdef CONFIG_COMPAT
419 static const struct file_operations proc_reg_file_ops_no_compat = {
420 	.llseek		= proc_reg_llseek,
421 	.read		= proc_reg_read,
422 	.write		= proc_reg_write,
423 	.poll		= proc_reg_poll,
424 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
425 	.mmap		= proc_reg_mmap,
426 	.get_unmapped_area = proc_reg_get_unmapped_area,
427 	.open		= proc_reg_open,
428 	.release	= proc_reg_release,
429 };
430 #endif
431 
432 static void proc_put_link(void *p)
433 {
434 	unuse_pde(p);
435 }
436 
437 static const char *proc_get_link(struct dentry *dentry,
438 				 struct inode *inode,
439 				 struct delayed_call *done)
440 {
441 	struct proc_dir_entry *pde = PDE(inode);
442 	if (!use_pde(pde))
443 		return ERR_PTR(-EINVAL);
444 	set_delayed_call(done, proc_put_link, pde);
445 	return pde->data;
446 }
447 
448 const struct inode_operations proc_link_inode_operations = {
449 	.get_link	= proc_get_link,
450 };
451 
452 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
453 {
454 	struct inode *inode = new_inode_pseudo(sb);
455 
456 	if (inode) {
457 		inode->i_ino = de->low_ino;
458 		inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
459 		PROC_I(inode)->pde = de;
460 
461 		if (is_empty_pde(de)) {
462 			make_empty_dir_inode(inode);
463 			return inode;
464 		}
465 		if (de->mode) {
466 			inode->i_mode = de->mode;
467 			inode->i_uid = de->uid;
468 			inode->i_gid = de->gid;
469 		}
470 		if (de->size)
471 			inode->i_size = de->size;
472 		if (de->nlink)
473 			set_nlink(inode, de->nlink);
474 		WARN_ON(!de->proc_iops);
475 		inode->i_op = de->proc_iops;
476 		if (de->proc_fops) {
477 			if (S_ISREG(inode->i_mode)) {
478 #ifdef CONFIG_COMPAT
479 				if (!de->proc_fops->compat_ioctl)
480 					inode->i_fop =
481 						&proc_reg_file_ops_no_compat;
482 				else
483 #endif
484 					inode->i_fop = &proc_reg_file_ops;
485 			} else {
486 				inode->i_fop = de->proc_fops;
487 			}
488 		}
489 	} else
490 	       pde_put(de);
491 	return inode;
492 }
493 
494 int proc_fill_super(struct super_block *s, void *data, int silent)
495 {
496 	struct pid_namespace *ns = get_pid_ns(s->s_fs_info);
497 	struct inode *root_inode;
498 	int ret;
499 
500 	if (!proc_parse_options(data, ns))
501 		return -EINVAL;
502 
503 	/* User space would break if executables or devices appear on proc */
504 	s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
505 	s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
506 	s->s_blocksize = 1024;
507 	s->s_blocksize_bits = 10;
508 	s->s_magic = PROC_SUPER_MAGIC;
509 	s->s_op = &proc_sops;
510 	s->s_time_gran = 1;
511 
512 	/*
513 	 * procfs isn't actually a stacking filesystem; however, there is
514 	 * too much magic going on inside it to permit stacking things on
515 	 * top of it
516 	 */
517 	s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
518 
519 	/* procfs dentries and inodes don't require IO to create */
520 	s->s_shrink.seeks = 0;
521 
522 	pde_get(&proc_root);
523 	root_inode = proc_get_inode(s, &proc_root);
524 	if (!root_inode) {
525 		pr_err("proc_fill_super: get root inode failed\n");
526 		return -ENOMEM;
527 	}
528 
529 	s->s_root = d_make_root(root_inode);
530 	if (!s->s_root) {
531 		pr_err("proc_fill_super: allocate dentry failed\n");
532 		return -ENOMEM;
533 	}
534 
535 	ret = proc_setup_self(s);
536 	if (ret) {
537 		return ret;
538 	}
539 	return proc_setup_thread_self(s);
540 }
541