xref: /linux/fs/proc/inode.c (revision f788bb2fb915a79eae0a160580766ba52984d61f) 
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/bug.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 	struct proc_inode *ei = PROC_I(inode);
38 
39 	truncate_inode_pages_final(&inode->i_data);
40 	clear_inode(inode);
41 
42 	/* Stop tracking associated processes */
43 	if (ei->pid) {
44 		proc_pid_evict_inode(ei);
45 		ei->pid = NULL;
46 	}
47 
48 	/* Let go of any associated proc directory entry */
49 	de = ei->pde;
50 	if (de) {
51 		pde_put(de);
52 		ei->pde = NULL;
53 	}
54 
55 	head = ei->sysctl;
56 	if (head) {
57 		RCU_INIT_POINTER(ei->sysctl, NULL);
58 		proc_sys_evict_inode(inode, head);
59 	}
60 }
61 
62 static struct kmem_cache *proc_inode_cachep __ro_after_init;
63 static struct kmem_cache *pde_opener_cache __ro_after_init;
64 
65 static struct inode *proc_alloc_inode(struct super_block *sb)
66 {
67 	struct proc_inode *ei;
68 
69 	ei = kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
70 	if (!ei)
71 		return NULL;
72 	ei->pid = NULL;
73 	ei->fd = 0;
74 	ei->op.proc_get_link = NULL;
75 	ei->pde = NULL;
76 	ei->sysctl = NULL;
77 	ei->sysctl_entry = NULL;
78 	INIT_HLIST_NODE(&ei->sibling_inodes);
79 	ei->ns_ops = NULL;
80 	return &ei->vfs_inode;
81 }
82 
83 static void proc_free_inode(struct inode *inode)
84 {
85 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
86 }
87 
88 static void init_once(void *foo)
89 {
90 	struct proc_inode *ei = (struct proc_inode *) foo;
91 
92 	inode_init_once(&ei->vfs_inode);
93 }
94 
95 void __init proc_init_kmemcache(void)
96 {
97 	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
98 					     sizeof(struct proc_inode),
99 					     0, (SLAB_RECLAIM_ACCOUNT|
100 						SLAB_MEM_SPREAD|SLAB_ACCOUNT|
101 						SLAB_PANIC),
102 					     init_once);
103 	pde_opener_cache =
104 		kmem_cache_create("pde_opener", sizeof(struct pde_opener), 0,
105 				  SLAB_ACCOUNT|SLAB_PANIC, NULL);
106 	proc_dir_entry_cache = kmem_cache_create_usercopy(
107 		"proc_dir_entry", SIZEOF_PDE, 0, SLAB_PANIC,
108 		offsetof(struct proc_dir_entry, inline_name),
109 		SIZEOF_PDE_INLINE_NAME, NULL);
110 	BUILD_BUG_ON(sizeof(struct proc_dir_entry) >= SIZEOF_PDE);
111 }
112 
113 void proc_invalidate_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock)
114 {
115 	struct inode *inode;
116 	struct proc_inode *ei;
117 	struct hlist_node *node;
118 	struct super_block *old_sb = NULL;
119 
120 	rcu_read_lock();
121 	for (;;) {
122 		struct super_block *sb;
123 		node = hlist_first_rcu(inodes);
124 		if (!node)
125 			break;
126 		ei = hlist_entry(node, struct proc_inode, sibling_inodes);
127 		spin_lock(lock);
128 		hlist_del_init_rcu(&ei->sibling_inodes);
129 		spin_unlock(lock);
130 
131 		inode = &ei->vfs_inode;
132 		sb = inode->i_sb;
133 		if ((sb != old_sb) && !atomic_inc_not_zero(&sb->s_active))
134 			continue;
135 		inode = igrab(inode);
136 		rcu_read_unlock();
137 		if (sb != old_sb) {
138 			if (old_sb)
139 				deactivate_super(old_sb);
140 			old_sb = sb;
141 		}
142 		if (unlikely(!inode)) {
143 			rcu_read_lock();
144 			continue;
145 		}
146 
147 		if (S_ISDIR(inode->i_mode)) {
148 			struct dentry *dir = d_find_any_alias(inode);
149 			if (dir) {
150 				d_invalidate(dir);
151 				dput(dir);
152 			}
153 		} else {
154 			struct dentry *dentry;
155 			while ((dentry = d_find_alias(inode))) {
156 				d_invalidate(dentry);
157 				dput(dentry);
158 			}
159 		}
160 		iput(inode);
161 
162 		rcu_read_lock();
163 	}
164 	rcu_read_unlock();
165 	if (old_sb)
166 		deactivate_super(old_sb);
167 }
168 
169 static inline const char *hidepid2str(enum proc_hidepid v)
170 {
171 	switch (v) {
172 		case HIDEPID_OFF: return "off";
173 		case HIDEPID_NO_ACCESS: return "noaccess";
174 		case HIDEPID_INVISIBLE: return "invisible";
175 		case HIDEPID_NOT_PTRACEABLE: return "ptraceable";
176 	}
177 	WARN_ONCE(1, "bad hide_pid value: %d\n", v);
178 	return "unknown";
179 }
180 
181 static int proc_show_options(struct seq_file *seq, struct dentry *root)
182 {
183 	struct proc_fs_info *fs_info = proc_sb_info(root->d_sb);
184 
185 	if (!gid_eq(fs_info->pid_gid, GLOBAL_ROOT_GID))
186 		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fs_info->pid_gid));
187 	if (fs_info->hide_pid != HIDEPID_OFF)
188 		seq_printf(seq, ",hidepid=%s", hidepid2str(fs_info->hide_pid));
189 	if (fs_info->pidonly != PROC_PIDONLY_OFF)
190 		seq_printf(seq, ",subset=pid");
191 
192 	return 0;
193 }
194 
195 const struct super_operations proc_sops = {
196 	.alloc_inode	= proc_alloc_inode,
197 	.free_inode	= proc_free_inode,
198 	.drop_inode	= generic_delete_inode,
199 	.evict_inode	= proc_evict_inode,
200 	.statfs		= simple_statfs,
201 	.show_options	= proc_show_options,
202 };
203 
204 enum {BIAS = -1U<<31};
205 
206 static inline int use_pde(struct proc_dir_entry *pde)
207 {
208 	return likely(atomic_inc_unless_negative(&pde->in_use));
209 }
210 
211 static void unuse_pde(struct proc_dir_entry *pde)
212 {
213 	if (unlikely(atomic_dec_return(&pde->in_use) == BIAS))
214 		complete(pde->pde_unload_completion);
215 }
216 
217 /* pde is locked on entry, unlocked on exit */
218 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
219 	__releases(&pde->pde_unload_lock)
220 {
221 	/*
222 	 * close() (proc_reg_release()) can't delete an entry and proceed:
223 	 * ->release hook needs to be available at the right moment.
224 	 *
225 	 * rmmod (remove_proc_entry() et al) can't delete an entry and proceed:
226 	 * "struct file" needs to be available at the right moment.
227 	 *
228 	 * Therefore, first process to enter this function does ->release() and
229 	 * signals its completion to the other process which does nothing.
230 	 */
231 	if (pdeo->closing) {
232 		/* somebody else is doing that, just wait */
233 		DECLARE_COMPLETION_ONSTACK(c);
234 		pdeo->c = &c;
235 		spin_unlock(&pde->pde_unload_lock);
236 		wait_for_completion(&c);
237 	} else {
238 		struct file *file;
239 		struct completion *c;
240 
241 		pdeo->closing = true;
242 		spin_unlock(&pde->pde_unload_lock);
243 		file = pdeo->file;
244 		pde->proc_ops->proc_release(file_inode(file), file);
245 		spin_lock(&pde->pde_unload_lock);
246 		/* After ->release. */
247 		list_del(&pdeo->lh);
248 		c = pdeo->c;
249 		spin_unlock(&pde->pde_unload_lock);
250 		if (unlikely(c))
251 			complete(c);
252 		kmem_cache_free(pde_opener_cache, pdeo);
253 	}
254 }
255 
256 void proc_entry_rundown(struct proc_dir_entry *de)
257 {
258 	DECLARE_COMPLETION_ONSTACK(c);
259 	/* Wait until all existing callers into module are done. */
260 	de->pde_unload_completion = &c;
261 	if (atomic_add_return(BIAS, &de->in_use) != BIAS)
262 		wait_for_completion(&c);
263 
264 	/* ->pde_openers list can't grow from now on. */
265 
266 	spin_lock(&de->pde_unload_lock);
267 	while (!list_empty(&de->pde_openers)) {
268 		struct pde_opener *pdeo;
269 		pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
270 		close_pdeo(de, pdeo);
271 		spin_lock(&de->pde_unload_lock);
272 	}
273 	spin_unlock(&de->pde_unload_lock);
274 }
275 
276 static loff_t pde_lseek(struct proc_dir_entry *pde, struct file *file, loff_t offset, int whence)
277 {
278 	typeof_member(struct proc_ops, proc_lseek) lseek;
279 
280 	lseek = pde->proc_ops->proc_lseek;
281 	if (!lseek)
282 		lseek = default_llseek;
283 	return lseek(file, offset, whence);
284 }
285 
286 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
287 {
288 	struct proc_dir_entry *pde = PDE(file_inode(file));
289 	loff_t rv = -EINVAL;
290 
291 	if (pde_is_permanent(pde)) {
292 		return pde_lseek(pde, file, offset, whence);
293 	} else if (use_pde(pde)) {
294 		rv = pde_lseek(pde, file, offset, whence);
295 		unuse_pde(pde);
296 	}
297 	return rv;
298 }
299 
300 static ssize_t pde_read(struct proc_dir_entry *pde, struct file *file, char __user *buf, size_t count, loff_t *ppos)
301 {
302 	typeof_member(struct proc_ops, proc_read) read;
303 
304 	read = pde->proc_ops->proc_read;
305 	if (read)
306 		return read(file, buf, count, ppos);
307 	return -EIO;
308 }
309 
310 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
311 {
312 	struct proc_dir_entry *pde = PDE(file_inode(file));
313 	ssize_t rv = -EIO;
314 
315 	if (pde_is_permanent(pde)) {
316 		return pde_read(pde, file, buf, count, ppos);
317 	} else if (use_pde(pde)) {
318 		rv = pde_read(pde, file, buf, count, ppos);
319 		unuse_pde(pde);
320 	}
321 	return rv;
322 }
323 
324 static ssize_t pde_write(struct proc_dir_entry *pde, struct file *file, const char __user *buf, size_t count, loff_t *ppos)
325 {
326 	typeof_member(struct proc_ops, proc_write) write;
327 
328 	write = pde->proc_ops->proc_write;
329 	if (write)
330 		return write(file, buf, count, ppos);
331 	return -EIO;
332 }
333 
334 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
335 {
336 	struct proc_dir_entry *pde = PDE(file_inode(file));
337 	ssize_t rv = -EIO;
338 
339 	if (pde_is_permanent(pde)) {
340 		return pde_write(pde, file, buf, count, ppos);
341 	} else if (use_pde(pde)) {
342 		rv = pde_write(pde, file, buf, count, ppos);
343 		unuse_pde(pde);
344 	}
345 	return rv;
346 }
347 
348 static __poll_t pde_poll(struct proc_dir_entry *pde, struct file *file, struct poll_table_struct *pts)
349 {
350 	typeof_member(struct proc_ops, proc_poll) poll;
351 
352 	poll = pde->proc_ops->proc_poll;
353 	if (poll)
354 		return poll(file, pts);
355 	return DEFAULT_POLLMASK;
356 }
357 
358 static __poll_t proc_reg_poll(struct file *file, struct poll_table_struct *pts)
359 {
360 	struct proc_dir_entry *pde = PDE(file_inode(file));
361 	__poll_t rv = DEFAULT_POLLMASK;
362 
363 	if (pde_is_permanent(pde)) {
364 		return pde_poll(pde, file, pts);
365 	} else if (use_pde(pde)) {
366 		rv = pde_poll(pde, file, pts);
367 		unuse_pde(pde);
368 	}
369 	return rv;
370 }
371 
372 static long pde_ioctl(struct proc_dir_entry *pde, struct file *file, unsigned int cmd, unsigned long arg)
373 {
374 	typeof_member(struct proc_ops, proc_ioctl) ioctl;
375 
376 	ioctl = pde->proc_ops->proc_ioctl;
377 	if (ioctl)
378 		return ioctl(file, cmd, arg);
379 	return -ENOTTY;
380 }
381 
382 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
383 {
384 	struct proc_dir_entry *pde = PDE(file_inode(file));
385 	long rv = -ENOTTY;
386 
387 	if (pde_is_permanent(pde)) {
388 		return pde_ioctl(pde, file, cmd, arg);
389 	} else if (use_pde(pde)) {
390 		rv = pde_ioctl(pde, file, cmd, arg);
391 		unuse_pde(pde);
392 	}
393 	return rv;
394 }
395 
396 #ifdef CONFIG_COMPAT
397 static long pde_compat_ioctl(struct proc_dir_entry *pde, struct file *file, unsigned int cmd, unsigned long arg)
398 {
399 	typeof_member(struct proc_ops, proc_compat_ioctl) compat_ioctl;
400 
401 	compat_ioctl = pde->proc_ops->proc_compat_ioctl;
402 	if (compat_ioctl)
403 		return compat_ioctl(file, cmd, arg);
404 	return -ENOTTY;
405 }
406 
407 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
408 {
409 	struct proc_dir_entry *pde = PDE(file_inode(file));
410 	long rv = -ENOTTY;
411 	if (pde_is_permanent(pde)) {
412 		return pde_compat_ioctl(pde, file, cmd, arg);
413 	} else if (use_pde(pde)) {
414 		rv = pde_compat_ioctl(pde, file, cmd, arg);
415 		unuse_pde(pde);
416 	}
417 	return rv;
418 }
419 #endif
420 
421 static int pde_mmap(struct proc_dir_entry *pde, struct file *file, struct vm_area_struct *vma)
422 {
423 	typeof_member(struct proc_ops, proc_mmap) mmap;
424 
425 	mmap = pde->proc_ops->proc_mmap;
426 	if (mmap)
427 		return mmap(file, vma);
428 	return -EIO;
429 }
430 
431 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
432 {
433 	struct proc_dir_entry *pde = PDE(file_inode(file));
434 	int rv = -EIO;
435 
436 	if (pde_is_permanent(pde)) {
437 		return pde_mmap(pde, file, vma);
438 	} else if (use_pde(pde)) {
439 		rv = pde_mmap(pde, file, vma);
440 		unuse_pde(pde);
441 	}
442 	return rv;
443 }
444 
445 static unsigned long
446 pde_get_unmapped_area(struct proc_dir_entry *pde, struct file *file, unsigned long orig_addr,
447 			   unsigned long len, unsigned long pgoff,
448 			   unsigned long flags)
449 {
450 	typeof_member(struct proc_ops, proc_get_unmapped_area) get_area;
451 
452 	get_area = pde->proc_ops->proc_get_unmapped_area;
453 #ifdef CONFIG_MMU
454 	if (!get_area)
455 		get_area = current->mm->get_unmapped_area;
456 #endif
457 	if (get_area)
458 		return get_area(file, orig_addr, len, pgoff, flags);
459 	return orig_addr;
460 }
461 
462 static unsigned long
463 proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
464 			   unsigned long len, unsigned long pgoff,
465 			   unsigned long flags)
466 {
467 	struct proc_dir_entry *pde = PDE(file_inode(file));
468 	unsigned long rv = -EIO;
469 
470 	if (pde_is_permanent(pde)) {
471 		return pde_get_unmapped_area(pde, file, orig_addr, len, pgoff, flags);
472 	} else if (use_pde(pde)) {
473 		rv = pde_get_unmapped_area(pde, file, orig_addr, len, pgoff, flags);
474 		unuse_pde(pde);
475 	}
476 	return rv;
477 }
478 
479 static int proc_reg_open(struct inode *inode, struct file *file)
480 {
481 	struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
482 	struct proc_dir_entry *pde = PDE(inode);
483 	int rv = 0;
484 	typeof_member(struct proc_ops, proc_open) open;
485 	typeof_member(struct proc_ops, proc_release) release;
486 	struct pde_opener *pdeo;
487 
488 	if (pde_is_permanent(pde)) {
489 		open = pde->proc_ops->proc_open;
490 		if (open)
491 			rv = open(inode, file);
492 		return rv;
493 	}
494 
495 	if (fs_info->pidonly == PROC_PIDONLY_ON)
496 		return -ENOENT;
497 
498 	/*
499 	 * Ensure that
500 	 * 1) PDE's ->release hook will be called no matter what
501 	 *    either normally by close()/->release, or forcefully by
502 	 *    rmmod/remove_proc_entry.
503 	 *
504 	 * 2) rmmod isn't blocked by opening file in /proc and sitting on
505 	 *    the descriptor (including "rmmod foo </proc/foo" scenario).
506 	 *
507 	 * Save every "struct file" with custom ->release hook.
508 	 */
509 	if (!use_pde(pde))
510 		return -ENOENT;
511 
512 	release = pde->proc_ops->proc_release;
513 	if (release) {
514 		pdeo = kmem_cache_alloc(pde_opener_cache, GFP_KERNEL);
515 		if (!pdeo) {
516 			rv = -ENOMEM;
517 			goto out_unuse;
518 		}
519 	}
520 
521 	open = pde->proc_ops->proc_open;
522 	if (open)
523 		rv = open(inode, file);
524 
525 	if (release) {
526 		if (rv == 0) {
527 			/* To know what to release. */
528 			pdeo->file = file;
529 			pdeo->closing = false;
530 			pdeo->c = NULL;
531 			spin_lock(&pde->pde_unload_lock);
532 			list_add(&pdeo->lh, &pde->pde_openers);
533 			spin_unlock(&pde->pde_unload_lock);
534 		} else
535 			kmem_cache_free(pde_opener_cache, pdeo);
536 	}
537 
538 out_unuse:
539 	unuse_pde(pde);
540 	return rv;
541 }
542 
543 static int proc_reg_release(struct inode *inode, struct file *file)
544 {
545 	struct proc_dir_entry *pde = PDE(inode);
546 	struct pde_opener *pdeo;
547 
548 	if (pde_is_permanent(pde)) {
549 		typeof_member(struct proc_ops, proc_release) release;
550 
551 		release = pde->proc_ops->proc_release;
552 		if (release) {
553 			return release(inode, file);
554 		}
555 		return 0;
556 	}
557 
558 	spin_lock(&pde->pde_unload_lock);
559 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
560 		if (pdeo->file == file) {
561 			close_pdeo(pde, pdeo);
562 			return 0;
563 		}
564 	}
565 	spin_unlock(&pde->pde_unload_lock);
566 	return 0;
567 }
568 
569 static const struct file_operations proc_reg_file_ops = {
570 	.llseek		= proc_reg_llseek,
571 	.read		= proc_reg_read,
572 	.write		= proc_reg_write,
573 	.poll		= proc_reg_poll,
574 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
575 #ifdef CONFIG_COMPAT
576 	.compat_ioctl	= proc_reg_compat_ioctl,
577 #endif
578 	.mmap		= proc_reg_mmap,
579 	.get_unmapped_area = proc_reg_get_unmapped_area,
580 	.open		= proc_reg_open,
581 	.release	= proc_reg_release,
582 };
583 
584 #ifdef CONFIG_COMPAT
585 static const struct file_operations proc_reg_file_ops_no_compat = {
586 	.llseek		= proc_reg_llseek,
587 	.read		= proc_reg_read,
588 	.write		= proc_reg_write,
589 	.poll		= proc_reg_poll,
590 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
591 	.mmap		= proc_reg_mmap,
592 	.get_unmapped_area = proc_reg_get_unmapped_area,
593 	.open		= proc_reg_open,
594 	.release	= proc_reg_release,
595 };
596 #endif
597 
598 static void proc_put_link(void *p)
599 {
600 	unuse_pde(p);
601 }
602 
603 static const char *proc_get_link(struct dentry *dentry,
604 				 struct inode *inode,
605 				 struct delayed_call *done)
606 {
607 	struct proc_dir_entry *pde = PDE(inode);
608 	if (!use_pde(pde))
609 		return ERR_PTR(-EINVAL);
610 	set_delayed_call(done, proc_put_link, pde);
611 	return pde->data;
612 }
613 
614 const struct inode_operations proc_link_inode_operations = {
615 	.get_link	= proc_get_link,
616 };
617 
618 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
619 {
620 	struct inode *inode = new_inode(sb);
621 
622 	if (inode) {
623 		inode->i_ino = de->low_ino;
624 		inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
625 		PROC_I(inode)->pde = de;
626 
627 		if (is_empty_pde(de)) {
628 			make_empty_dir_inode(inode);
629 			return inode;
630 		}
631 		if (de->mode) {
632 			inode->i_mode = de->mode;
633 			inode->i_uid = de->uid;
634 			inode->i_gid = de->gid;
635 		}
636 		if (de->size)
637 			inode->i_size = de->size;
638 		if (de->nlink)
639 			set_nlink(inode, de->nlink);
640 
641 		if (S_ISREG(inode->i_mode)) {
642 			inode->i_op = de->proc_iops;
643 			inode->i_fop = &proc_reg_file_ops;
644 #ifdef CONFIG_COMPAT
645 			if (!de->proc_ops->proc_compat_ioctl) {
646 				inode->i_fop = &proc_reg_file_ops_no_compat;
647 			}
648 #endif
649 		} else if (S_ISDIR(inode->i_mode)) {
650 			inode->i_op = de->proc_iops;
651 			inode->i_fop = de->proc_dir_ops;
652 		} else if (S_ISLNK(inode->i_mode)) {
653 			inode->i_op = de->proc_iops;
654 			inode->i_fop = NULL;
655 		} else
656 			BUG();
657 	} else
658 	       pde_put(de);
659 	return inode;
660 }
661