xref: /openbmc/linux/fs/proc/inode.c (revision 160b8e75) 
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 
58 static struct inode *proc_alloc_inode(struct super_block *sb)
59 {
60 	struct proc_inode *ei;
61 	struct inode *inode;
62 
63 	ei = kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
64 	if (!ei)
65 		return NULL;
66 	ei->pid = NULL;
67 	ei->fd = 0;
68 	ei->op.proc_get_link = NULL;
69 	ei->pde = NULL;
70 	ei->sysctl = NULL;
71 	ei->sysctl_entry = NULL;
72 	ei->ns_ops = NULL;
73 	inode = &ei->vfs_inode;
74 	return inode;
75 }
76 
77 static void proc_i_callback(struct rcu_head *head)
78 {
79 	struct inode *inode = container_of(head, struct inode, i_rcu);
80 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
81 }
82 
83 static void proc_destroy_inode(struct inode *inode)
84 {
85 	call_rcu(&inode->i_rcu, proc_i_callback);
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_inodecache(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 }
104 
105 static int proc_show_options(struct seq_file *seq, struct dentry *root)
106 {
107 	struct super_block *sb = root->d_sb;
108 	struct pid_namespace *pid = sb->s_fs_info;
109 
110 	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
111 		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
112 	if (pid->hide_pid != HIDEPID_OFF)
113 		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
114 
115 	return 0;
116 }
117 
118 static const struct super_operations proc_sops = {
119 	.alloc_inode	= proc_alloc_inode,
120 	.destroy_inode	= proc_destroy_inode,
121 	.drop_inode	= generic_delete_inode,
122 	.evict_inode	= proc_evict_inode,
123 	.statfs		= simple_statfs,
124 	.remount_fs	= proc_remount,
125 	.show_options	= proc_show_options,
126 };
127 
128 enum {BIAS = -1U<<31};
129 
130 static inline int use_pde(struct proc_dir_entry *pde)
131 {
132 	return likely(atomic_inc_unless_negative(&pde->in_use));
133 }
134 
135 static void unuse_pde(struct proc_dir_entry *pde)
136 {
137 	if (unlikely(atomic_dec_return(&pde->in_use) == BIAS))
138 		complete(pde->pde_unload_completion);
139 }
140 
141 /* pde is locked */
142 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
143 {
144 	/*
145 	 * close() (proc_reg_release()) can't delete an entry and proceed:
146 	 * ->release hook needs to be available at the right moment.
147 	 *
148 	 * rmmod (remove_proc_entry() et al) can't delete an entry and proceed:
149 	 * "struct file" needs to be available at the right moment.
150 	 *
151 	 * Therefore, first process to enter this function does ->release() and
152 	 * signals its completion to the other process which does nothing.
153 	 */
154 	if (pdeo->closing) {
155 		/* somebody else is doing that, just wait */
156 		DECLARE_COMPLETION_ONSTACK(c);
157 		pdeo->c = &c;
158 		spin_unlock(&pde->pde_unload_lock);
159 		wait_for_completion(&c);
160 		spin_lock(&pde->pde_unload_lock);
161 	} else {
162 		struct file *file;
163 		pdeo->closing = true;
164 		spin_unlock(&pde->pde_unload_lock);
165 		file = pdeo->file;
166 		pde->proc_fops->release(file_inode(file), file);
167 		spin_lock(&pde->pde_unload_lock);
168 		/* After ->release. */
169 		list_del(&pdeo->lh);
170 		if (unlikely(pdeo->c))
171 			complete(pdeo->c);
172 		kfree(pdeo);
173 	}
174 }
175 
176 void proc_entry_rundown(struct proc_dir_entry *de)
177 {
178 	DECLARE_COMPLETION_ONSTACK(c);
179 	/* Wait until all existing callers into module are done. */
180 	de->pde_unload_completion = &c;
181 	if (atomic_add_return(BIAS, &de->in_use) != BIAS)
182 		wait_for_completion(&c);
183 
184 	/* ->pde_openers list can't grow from now on. */
185 
186 	spin_lock(&de->pde_unload_lock);
187 	while (!list_empty(&de->pde_openers)) {
188 		struct pde_opener *pdeo;
189 		pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
190 		close_pdeo(de, pdeo);
191 	}
192 	spin_unlock(&de->pde_unload_lock);
193 }
194 
195 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
196 {
197 	struct proc_dir_entry *pde = PDE(file_inode(file));
198 	loff_t rv = -EINVAL;
199 	if (use_pde(pde)) {
200 		loff_t (*llseek)(struct file *, loff_t, int);
201 		llseek = pde->proc_fops->llseek;
202 		if (!llseek)
203 			llseek = default_llseek;
204 		rv = llseek(file, offset, whence);
205 		unuse_pde(pde);
206 	}
207 	return rv;
208 }
209 
210 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
211 {
212 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
213 	struct proc_dir_entry *pde = PDE(file_inode(file));
214 	ssize_t rv = -EIO;
215 	if (use_pde(pde)) {
216 		read = pde->proc_fops->read;
217 		if (read)
218 			rv = read(file, buf, count, ppos);
219 		unuse_pde(pde);
220 	}
221 	return rv;
222 }
223 
224 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
225 {
226 	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
227 	struct proc_dir_entry *pde = PDE(file_inode(file));
228 	ssize_t rv = -EIO;
229 	if (use_pde(pde)) {
230 		write = pde->proc_fops->write;
231 		if (write)
232 			rv = write(file, buf, count, ppos);
233 		unuse_pde(pde);
234 	}
235 	return rv;
236 }
237 
238 static __poll_t proc_reg_poll(struct file *file, struct poll_table_struct *pts)
239 {
240 	struct proc_dir_entry *pde = PDE(file_inode(file));
241 	__poll_t rv = DEFAULT_POLLMASK;
242 	__poll_t (*poll)(struct file *, struct poll_table_struct *);
243 	if (use_pde(pde)) {
244 		poll = pde->proc_fops->poll;
245 		if (poll)
246 			rv = poll(file, pts);
247 		unuse_pde(pde);
248 	}
249 	return rv;
250 }
251 
252 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
253 {
254 	struct proc_dir_entry *pde = PDE(file_inode(file));
255 	long rv = -ENOTTY;
256 	long (*ioctl)(struct file *, unsigned int, unsigned long);
257 	if (use_pde(pde)) {
258 		ioctl = pde->proc_fops->unlocked_ioctl;
259 		if (ioctl)
260 			rv = ioctl(file, cmd, arg);
261 		unuse_pde(pde);
262 	}
263 	return rv;
264 }
265 
266 #ifdef CONFIG_COMPAT
267 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
268 {
269 	struct proc_dir_entry *pde = PDE(file_inode(file));
270 	long rv = -ENOTTY;
271 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
272 	if (use_pde(pde)) {
273 		compat_ioctl = pde->proc_fops->compat_ioctl;
274 		if (compat_ioctl)
275 			rv = compat_ioctl(file, cmd, arg);
276 		unuse_pde(pde);
277 	}
278 	return rv;
279 }
280 #endif
281 
282 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
283 {
284 	struct proc_dir_entry *pde = PDE(file_inode(file));
285 	int rv = -EIO;
286 	int (*mmap)(struct file *, struct vm_area_struct *);
287 	if (use_pde(pde)) {
288 		mmap = pde->proc_fops->mmap;
289 		if (mmap)
290 			rv = mmap(file, vma);
291 		unuse_pde(pde);
292 	}
293 	return rv;
294 }
295 
296 static unsigned long
297 proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
298 			   unsigned long len, unsigned long pgoff,
299 			   unsigned long flags)
300 {
301 	struct proc_dir_entry *pde = PDE(file_inode(file));
302 	unsigned long rv = -EIO;
303 
304 	if (use_pde(pde)) {
305 		typeof(proc_reg_get_unmapped_area) *get_area;
306 
307 		get_area = pde->proc_fops->get_unmapped_area;
308 #ifdef CONFIG_MMU
309 		if (!get_area)
310 			get_area = current->mm->get_unmapped_area;
311 #endif
312 
313 		if (get_area)
314 			rv = get_area(file, orig_addr, len, pgoff, flags);
315 		else
316 			rv = orig_addr;
317 		unuse_pde(pde);
318 	}
319 	return rv;
320 }
321 
322 static int proc_reg_open(struct inode *inode, struct file *file)
323 {
324 	struct proc_dir_entry *pde = PDE(inode);
325 	int rv = 0;
326 	int (*open)(struct inode *, struct file *);
327 	int (*release)(struct inode *, struct file *);
328 	struct pde_opener *pdeo;
329 
330 	/*
331 	 * Ensure that
332 	 * 1) PDE's ->release hook will be called no matter what
333 	 *    either normally by close()/->release, or forcefully by
334 	 *    rmmod/remove_proc_entry.
335 	 *
336 	 * 2) rmmod isn't blocked by opening file in /proc and sitting on
337 	 *    the descriptor (including "rmmod foo </proc/foo" scenario).
338 	 *
339 	 * Save every "struct file" with custom ->release hook.
340 	 */
341 	pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
342 	if (!pdeo)
343 		return -ENOMEM;
344 
345 	if (!use_pde(pde)) {
346 		kfree(pdeo);
347 		return -ENOENT;
348 	}
349 	open = pde->proc_fops->open;
350 	release = pde->proc_fops->release;
351 
352 	if (open)
353 		rv = open(inode, file);
354 
355 	if (rv == 0 && release) {
356 		/* To know what to release. */
357 		pdeo->file = file;
358 		pdeo->closing = false;
359 		pdeo->c = NULL;
360 		spin_lock(&pde->pde_unload_lock);
361 		list_add(&pdeo->lh, &pde->pde_openers);
362 		spin_unlock(&pde->pde_unload_lock);
363 	} else
364 		kfree(pdeo);
365 
366 	unuse_pde(pde);
367 	return rv;
368 }
369 
370 static int proc_reg_release(struct inode *inode, struct file *file)
371 {
372 	struct proc_dir_entry *pde = PDE(inode);
373 	struct pde_opener *pdeo;
374 	spin_lock(&pde->pde_unload_lock);
375 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
376 		if (pdeo->file == file) {
377 			close_pdeo(pde, pdeo);
378 			break;
379 		}
380 	}
381 	spin_unlock(&pde->pde_unload_lock);
382 	return 0;
383 }
384 
385 static const struct file_operations proc_reg_file_ops = {
386 	.llseek		= proc_reg_llseek,
387 	.read		= proc_reg_read,
388 	.write		= proc_reg_write,
389 	.poll		= proc_reg_poll,
390 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
391 #ifdef CONFIG_COMPAT
392 	.compat_ioctl	= proc_reg_compat_ioctl,
393 #endif
394 	.mmap		= proc_reg_mmap,
395 	.get_unmapped_area = proc_reg_get_unmapped_area,
396 	.open		= proc_reg_open,
397 	.release	= proc_reg_release,
398 };
399 
400 #ifdef CONFIG_COMPAT
401 static const struct file_operations proc_reg_file_ops_no_compat = {
402 	.llseek		= proc_reg_llseek,
403 	.read		= proc_reg_read,
404 	.write		= proc_reg_write,
405 	.poll		= proc_reg_poll,
406 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
407 	.mmap		= proc_reg_mmap,
408 	.get_unmapped_area = proc_reg_get_unmapped_area,
409 	.open		= proc_reg_open,
410 	.release	= proc_reg_release,
411 };
412 #endif
413 
414 static void proc_put_link(void *p)
415 {
416 	unuse_pde(p);
417 }
418 
419 static const char *proc_get_link(struct dentry *dentry,
420 				 struct inode *inode,
421 				 struct delayed_call *done)
422 {
423 	struct proc_dir_entry *pde = PDE(inode);
424 	if (!use_pde(pde))
425 		return ERR_PTR(-EINVAL);
426 	set_delayed_call(done, proc_put_link, pde);
427 	return pde->data;
428 }
429 
430 const struct inode_operations proc_link_inode_operations = {
431 	.get_link	= proc_get_link,
432 };
433 
434 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
435 {
436 	struct inode *inode = new_inode_pseudo(sb);
437 
438 	if (inode) {
439 		inode->i_ino = de->low_ino;
440 		inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
441 		PROC_I(inode)->pde = de;
442 
443 		if (is_empty_pde(de)) {
444 			make_empty_dir_inode(inode);
445 			return inode;
446 		}
447 		if (de->mode) {
448 			inode->i_mode = de->mode;
449 			inode->i_uid = de->uid;
450 			inode->i_gid = de->gid;
451 		}
452 		if (de->size)
453 			inode->i_size = de->size;
454 		if (de->nlink)
455 			set_nlink(inode, de->nlink);
456 		WARN_ON(!de->proc_iops);
457 		inode->i_op = de->proc_iops;
458 		if (de->proc_fops) {
459 			if (S_ISREG(inode->i_mode)) {
460 #ifdef CONFIG_COMPAT
461 				if (!de->proc_fops->compat_ioctl)
462 					inode->i_fop =
463 						&proc_reg_file_ops_no_compat;
464 				else
465 #endif
466 					inode->i_fop = &proc_reg_file_ops;
467 			} else {
468 				inode->i_fop = de->proc_fops;
469 			}
470 		}
471 	} else
472 	       pde_put(de);
473 	return inode;
474 }
475 
476 int proc_fill_super(struct super_block *s, void *data, int silent)
477 {
478 	struct pid_namespace *ns = get_pid_ns(s->s_fs_info);
479 	struct inode *root_inode;
480 	int ret;
481 
482 	if (!proc_parse_options(data, ns))
483 		return -EINVAL;
484 
485 	/* User space would break if executables or devices appear on proc */
486 	s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
487 	s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
488 	s->s_blocksize = 1024;
489 	s->s_blocksize_bits = 10;
490 	s->s_magic = PROC_SUPER_MAGIC;
491 	s->s_op = &proc_sops;
492 	s->s_time_gran = 1;
493 
494 	/*
495 	 * procfs isn't actually a stacking filesystem; however, there is
496 	 * too much magic going on inside it to permit stacking things on
497 	 * top of it
498 	 */
499 	s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
500 
501 	pde_get(&proc_root);
502 	root_inode = proc_get_inode(s, &proc_root);
503 	if (!root_inode) {
504 		pr_err("proc_fill_super: get root inode failed\n");
505 		return -ENOMEM;
506 	}
507 
508 	s->s_root = d_make_root(root_inode);
509 	if (!s->s_root) {
510 		pr_err("proc_fill_super: allocate dentry failed\n");
511 		return -ENOMEM;
512 	}
513 
514 	ret = proc_setup_self(s);
515 	if (ret) {
516 		return ret;
517 	}
518 	return proc_setup_thread_self(s);
519 }
520