xref: /openbmc/linux/fs/proc/inode.c (revision d2ba09c1) 
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(struct proc_dir_entry), 0, SLAB_PANIC,
109 		offsetof(struct proc_dir_entry, inline_name),
110 		sizeof_field(struct proc_dir_entry, inline_name), NULL);
111 }
112 
113 static int proc_show_options(struct seq_file *seq, struct dentry *root)
114 {
115 	struct super_block *sb = root->d_sb;
116 	struct pid_namespace *pid = sb->s_fs_info;
117 
118 	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
119 		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
120 	if (pid->hide_pid != HIDEPID_OFF)
121 		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
122 
123 	return 0;
124 }
125 
126 static const struct super_operations proc_sops = {
127 	.alloc_inode	= proc_alloc_inode,
128 	.destroy_inode	= proc_destroy_inode,
129 	.drop_inode	= generic_delete_inode,
130 	.evict_inode	= proc_evict_inode,
131 	.statfs		= simple_statfs,
132 	.remount_fs	= proc_remount,
133 	.show_options	= proc_show_options,
134 };
135 
136 enum {BIAS = -1U<<31};
137 
138 static inline int use_pde(struct proc_dir_entry *pde)
139 {
140 	return likely(atomic_inc_unless_negative(&pde->in_use));
141 }
142 
143 static void unuse_pde(struct proc_dir_entry *pde)
144 {
145 	if (unlikely(atomic_dec_return(&pde->in_use) == BIAS))
146 		complete(pde->pde_unload_completion);
147 }
148 
149 /* pde is locked on entry, unlocked on exit */
150 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
151 {
152 	/*
153 	 * close() (proc_reg_release()) can't delete an entry and proceed:
154 	 * ->release hook needs to be available at the right moment.
155 	 *
156 	 * rmmod (remove_proc_entry() et al) can't delete an entry and proceed:
157 	 * "struct file" needs to be available at the right moment.
158 	 *
159 	 * Therefore, first process to enter this function does ->release() and
160 	 * signals its completion to the other process which does nothing.
161 	 */
162 	if (pdeo->closing) {
163 		/* somebody else is doing that, just wait */
164 		DECLARE_COMPLETION_ONSTACK(c);
165 		pdeo->c = &c;
166 		spin_unlock(&pde->pde_unload_lock);
167 		wait_for_completion(&c);
168 	} else {
169 		struct file *file;
170 		struct completion *c;
171 
172 		pdeo->closing = true;
173 		spin_unlock(&pde->pde_unload_lock);
174 		file = pdeo->file;
175 		pde->proc_fops->release(file_inode(file), file);
176 		spin_lock(&pde->pde_unload_lock);
177 		/* After ->release. */
178 		list_del(&pdeo->lh);
179 		c = pdeo->c;
180 		spin_unlock(&pde->pde_unload_lock);
181 		if (unlikely(c))
182 			complete(c);
183 		kmem_cache_free(pde_opener_cache, pdeo);
184 	}
185 }
186 
187 void proc_entry_rundown(struct proc_dir_entry *de)
188 {
189 	DECLARE_COMPLETION_ONSTACK(c);
190 	/* Wait until all existing callers into module are done. */
191 	de->pde_unload_completion = &c;
192 	if (atomic_add_return(BIAS, &de->in_use) != BIAS)
193 		wait_for_completion(&c);
194 
195 	/* ->pde_openers list can't grow from now on. */
196 
197 	spin_lock(&de->pde_unload_lock);
198 	while (!list_empty(&de->pde_openers)) {
199 		struct pde_opener *pdeo;
200 		pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
201 		close_pdeo(de, pdeo);
202 		spin_lock(&de->pde_unload_lock);
203 	}
204 	spin_unlock(&de->pde_unload_lock);
205 }
206 
207 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
208 {
209 	struct proc_dir_entry *pde = PDE(file_inode(file));
210 	loff_t rv = -EINVAL;
211 	if (use_pde(pde)) {
212 		loff_t (*llseek)(struct file *, loff_t, int);
213 		llseek = pde->proc_fops->llseek;
214 		if (!llseek)
215 			llseek = default_llseek;
216 		rv = llseek(file, offset, whence);
217 		unuse_pde(pde);
218 	}
219 	return rv;
220 }
221 
222 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
223 {
224 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
225 	struct proc_dir_entry *pde = PDE(file_inode(file));
226 	ssize_t rv = -EIO;
227 	if (use_pde(pde)) {
228 		read = pde->proc_fops->read;
229 		if (read)
230 			rv = read(file, buf, count, ppos);
231 		unuse_pde(pde);
232 	}
233 	return rv;
234 }
235 
236 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
237 {
238 	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
239 	struct proc_dir_entry *pde = PDE(file_inode(file));
240 	ssize_t rv = -EIO;
241 	if (use_pde(pde)) {
242 		write = pde->proc_fops->write;
243 		if (write)
244 			rv = write(file, buf, count, ppos);
245 		unuse_pde(pde);
246 	}
247 	return rv;
248 }
249 
250 static __poll_t proc_reg_poll(struct file *file, struct poll_table_struct *pts)
251 {
252 	struct proc_dir_entry *pde = PDE(file_inode(file));
253 	__poll_t rv = DEFAULT_POLLMASK;
254 	__poll_t (*poll)(struct file *, struct poll_table_struct *);
255 	if (use_pde(pde)) {
256 		poll = pde->proc_fops->poll;
257 		if (poll)
258 			rv = poll(file, pts);
259 		unuse_pde(pde);
260 	}
261 	return rv;
262 }
263 
264 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
265 {
266 	struct proc_dir_entry *pde = PDE(file_inode(file));
267 	long rv = -ENOTTY;
268 	long (*ioctl)(struct file *, unsigned int, unsigned long);
269 	if (use_pde(pde)) {
270 		ioctl = pde->proc_fops->unlocked_ioctl;
271 		if (ioctl)
272 			rv = ioctl(file, cmd, arg);
273 		unuse_pde(pde);
274 	}
275 	return rv;
276 }
277 
278 #ifdef CONFIG_COMPAT
279 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
280 {
281 	struct proc_dir_entry *pde = PDE(file_inode(file));
282 	long rv = -ENOTTY;
283 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
284 	if (use_pde(pde)) {
285 		compat_ioctl = pde->proc_fops->compat_ioctl;
286 		if (compat_ioctl)
287 			rv = compat_ioctl(file, cmd, arg);
288 		unuse_pde(pde);
289 	}
290 	return rv;
291 }
292 #endif
293 
294 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
295 {
296 	struct proc_dir_entry *pde = PDE(file_inode(file));
297 	int rv = -EIO;
298 	int (*mmap)(struct file *, struct vm_area_struct *);
299 	if (use_pde(pde)) {
300 		mmap = pde->proc_fops->mmap;
301 		if (mmap)
302 			rv = mmap(file, vma);
303 		unuse_pde(pde);
304 	}
305 	return rv;
306 }
307 
308 static unsigned long
309 proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
310 			   unsigned long len, unsigned long pgoff,
311 			   unsigned long flags)
312 {
313 	struct proc_dir_entry *pde = PDE(file_inode(file));
314 	unsigned long rv = -EIO;
315 
316 	if (use_pde(pde)) {
317 		typeof(proc_reg_get_unmapped_area) *get_area;
318 
319 		get_area = pde->proc_fops->get_unmapped_area;
320 #ifdef CONFIG_MMU
321 		if (!get_area)
322 			get_area = current->mm->get_unmapped_area;
323 #endif
324 
325 		if (get_area)
326 			rv = get_area(file, orig_addr, len, pgoff, flags);
327 		else
328 			rv = orig_addr;
329 		unuse_pde(pde);
330 	}
331 	return rv;
332 }
333 
334 static int proc_reg_open(struct inode *inode, struct file *file)
335 {
336 	struct proc_dir_entry *pde = PDE(inode);
337 	int rv = 0;
338 	int (*open)(struct inode *, struct file *);
339 	int (*release)(struct inode *, struct file *);
340 	struct pde_opener *pdeo;
341 
342 	/*
343 	 * Ensure that
344 	 * 1) PDE's ->release hook will be called no matter what
345 	 *    either normally by close()/->release, or forcefully by
346 	 *    rmmod/remove_proc_entry.
347 	 *
348 	 * 2) rmmod isn't blocked by opening file in /proc and sitting on
349 	 *    the descriptor (including "rmmod foo </proc/foo" scenario).
350 	 *
351 	 * Save every "struct file" with custom ->release hook.
352 	 */
353 	if (!use_pde(pde))
354 		return -ENOENT;
355 
356 	release = pde->proc_fops->release;
357 	if (release) {
358 		pdeo = kmem_cache_alloc(pde_opener_cache, GFP_KERNEL);
359 		if (!pdeo) {
360 			rv = -ENOMEM;
361 			goto out_unuse;
362 		}
363 	}
364 
365 	open = pde->proc_fops->open;
366 	if (open)
367 		rv = open(inode, file);
368 
369 	if (release) {
370 		if (rv == 0) {
371 			/* To know what to release. */
372 			pdeo->file = file;
373 			pdeo->closing = false;
374 			pdeo->c = NULL;
375 			spin_lock(&pde->pde_unload_lock);
376 			list_add(&pdeo->lh, &pde->pde_openers);
377 			spin_unlock(&pde->pde_unload_lock);
378 		} else
379 			kmem_cache_free(pde_opener_cache, pdeo);
380 	}
381 
382 out_unuse:
383 	unuse_pde(pde);
384 	return rv;
385 }
386 
387 static int proc_reg_release(struct inode *inode, struct file *file)
388 {
389 	struct proc_dir_entry *pde = PDE(inode);
390 	struct pde_opener *pdeo;
391 	spin_lock(&pde->pde_unload_lock);
392 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
393 		if (pdeo->file == file) {
394 			close_pdeo(pde, pdeo);
395 			return 0;
396 		}
397 	}
398 	spin_unlock(&pde->pde_unload_lock);
399 	return 0;
400 }
401 
402 static const struct file_operations proc_reg_file_ops = {
403 	.llseek		= proc_reg_llseek,
404 	.read		= proc_reg_read,
405 	.write		= proc_reg_write,
406 	.poll		= proc_reg_poll,
407 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
408 #ifdef CONFIG_COMPAT
409 	.compat_ioctl	= proc_reg_compat_ioctl,
410 #endif
411 	.mmap		= proc_reg_mmap,
412 	.get_unmapped_area = proc_reg_get_unmapped_area,
413 	.open		= proc_reg_open,
414 	.release	= proc_reg_release,
415 };
416 
417 #ifdef CONFIG_COMPAT
418 static const struct file_operations proc_reg_file_ops_no_compat = {
419 	.llseek		= proc_reg_llseek,
420 	.read		= proc_reg_read,
421 	.write		= proc_reg_write,
422 	.poll		= proc_reg_poll,
423 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
424 	.mmap		= proc_reg_mmap,
425 	.get_unmapped_area = proc_reg_get_unmapped_area,
426 	.open		= proc_reg_open,
427 	.release	= proc_reg_release,
428 };
429 #endif
430 
431 static void proc_put_link(void *p)
432 {
433 	unuse_pde(p);
434 }
435 
436 static const char *proc_get_link(struct dentry *dentry,
437 				 struct inode *inode,
438 				 struct delayed_call *done)
439 {
440 	struct proc_dir_entry *pde = PDE(inode);
441 	if (!use_pde(pde))
442 		return ERR_PTR(-EINVAL);
443 	set_delayed_call(done, proc_put_link, pde);
444 	return pde->data;
445 }
446 
447 const struct inode_operations proc_link_inode_operations = {
448 	.get_link	= proc_get_link,
449 };
450 
451 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
452 {
453 	struct inode *inode = new_inode_pseudo(sb);
454 
455 	if (inode) {
456 		inode->i_ino = de->low_ino;
457 		inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
458 		PROC_I(inode)->pde = de;
459 
460 		if (is_empty_pde(de)) {
461 			make_empty_dir_inode(inode);
462 			return inode;
463 		}
464 		if (de->mode) {
465 			inode->i_mode = de->mode;
466 			inode->i_uid = de->uid;
467 			inode->i_gid = de->gid;
468 		}
469 		if (de->size)
470 			inode->i_size = de->size;
471 		if (de->nlink)
472 			set_nlink(inode, de->nlink);
473 		WARN_ON(!de->proc_iops);
474 		inode->i_op = de->proc_iops;
475 		if (de->proc_fops) {
476 			if (S_ISREG(inode->i_mode)) {
477 #ifdef CONFIG_COMPAT
478 				if (!de->proc_fops->compat_ioctl)
479 					inode->i_fop =
480 						&proc_reg_file_ops_no_compat;
481 				else
482 #endif
483 					inode->i_fop = &proc_reg_file_ops;
484 			} else {
485 				inode->i_fop = de->proc_fops;
486 			}
487 		}
488 	} else
489 	       pde_put(de);
490 	return inode;
491 }
492 
493 int proc_fill_super(struct super_block *s, void *data, int silent)
494 {
495 	struct pid_namespace *ns = get_pid_ns(s->s_fs_info);
496 	struct inode *root_inode;
497 	int ret;
498 
499 	if (!proc_parse_options(data, ns))
500 		return -EINVAL;
501 
502 	/* User space would break if executables or devices appear on proc */
503 	s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
504 	s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
505 	s->s_blocksize = 1024;
506 	s->s_blocksize_bits = 10;
507 	s->s_magic = PROC_SUPER_MAGIC;
508 	s->s_op = &proc_sops;
509 	s->s_time_gran = 1;
510 
511 	/*
512 	 * procfs isn't actually a stacking filesystem; however, there is
513 	 * too much magic going on inside it to permit stacking things on
514 	 * top of it
515 	 */
516 	s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
517 
518 	pde_get(&proc_root);
519 	root_inode = proc_get_inode(s, &proc_root);
520 	if (!root_inode) {
521 		pr_err("proc_fill_super: get root inode failed\n");
522 		return -ENOMEM;
523 	}
524 
525 	s->s_root = d_make_root(root_inode);
526 	if (!s->s_root) {
527 		pr_err("proc_fill_super: allocate dentry failed\n");
528 		return -ENOMEM;
529 	}
530 
531 	ret = proc_setup_self(s);
532 	if (ret) {
533 		return ret;
534 	}
535 	return proc_setup_thread_self(s);
536 }
537