xref: /openbmc/linux/fs/proc/inode.c (revision 4a3fad70) 
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/time.h>
9 #include <linux/proc_fs.h>
10 #include <linux/kernel.h>
11 #include <linux/pid_namespace.h>
12 #include <linux/mm.h>
13 #include <linux/string.h>
14 #include <linux/stat.h>
15 #include <linux/completion.h>
16 #include <linux/poll.h>
17 #include <linux/printk.h>
18 #include <linux/file.h>
19 #include <linux/limits.h>
20 #include <linux/init.h>
21 #include <linux/module.h>
22 #include <linux/sysctl.h>
23 #include <linux/seq_file.h>
24 #include <linux/slab.h>
25 #include <linux/mount.h>
26 #include <linux/magic.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 
37 	truncate_inode_pages_final(&inode->i_data);
38 	clear_inode(inode);
39 
40 	/* Stop tracking associated processes */
41 	put_pid(PROC_I(inode)->pid);
42 
43 	/* Let go of any associated proc directory entry */
44 	de = PDE(inode);
45 	if (de)
46 		pde_put(de);
47 
48 	head = PROC_I(inode)->sysctl;
49 	if (head) {
50 		RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);
51 		proc_sys_evict_inode(inode, head);
52 	}
53 }
54 
55 static struct kmem_cache * proc_inode_cachep;
56 
57 static struct inode *proc_alloc_inode(struct super_block *sb)
58 {
59 	struct proc_inode *ei;
60 	struct inode *inode;
61 
62 	ei = kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
63 	if (!ei)
64 		return NULL;
65 	ei->pid = NULL;
66 	ei->fd = 0;
67 	ei->op.proc_get_link = NULL;
68 	ei->pde = NULL;
69 	ei->sysctl = NULL;
70 	ei->sysctl_entry = NULL;
71 	ei->ns_ops = NULL;
72 	inode = &ei->vfs_inode;
73 	return inode;
74 }
75 
76 static void proc_i_callback(struct rcu_head *head)
77 {
78 	struct inode *inode = container_of(head, struct inode, i_rcu);
79 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
80 }
81 
82 static void proc_destroy_inode(struct inode *inode)
83 {
84 	call_rcu(&inode->i_rcu, proc_i_callback);
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_inodecache(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 }
103 
104 static int proc_show_options(struct seq_file *seq, struct dentry *root)
105 {
106 	struct super_block *sb = root->d_sb;
107 	struct pid_namespace *pid = sb->s_fs_info;
108 
109 	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
110 		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
111 	if (pid->hide_pid != HIDEPID_OFF)
112 		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
113 
114 	return 0;
115 }
116 
117 static const struct super_operations proc_sops = {
118 	.alloc_inode	= proc_alloc_inode,
119 	.destroy_inode	= proc_destroy_inode,
120 	.drop_inode	= generic_delete_inode,
121 	.evict_inode	= proc_evict_inode,
122 	.statfs		= simple_statfs,
123 	.remount_fs	= proc_remount,
124 	.show_options	= proc_show_options,
125 };
126 
127 enum {BIAS = -1U<<31};
128 
129 static inline int use_pde(struct proc_dir_entry *pde)
130 {
131 	return atomic_inc_unless_negative(&pde->in_use);
132 }
133 
134 static void unuse_pde(struct proc_dir_entry *pde)
135 {
136 	if (atomic_dec_return(&pde->in_use) == BIAS)
137 		complete(pde->pde_unload_completion);
138 }
139 
140 /* pde is locked */
141 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
142 {
143 	/*
144 	 * close() (proc_reg_release()) can't delete an entry and proceed:
145 	 * ->release hook needs to be available at the right moment.
146 	 *
147 	 * rmmod (remove_proc_entry() et al) can't delete an entry and proceed:
148 	 * "struct file" needs to be available at the right moment.
149 	 *
150 	 * Therefore, first process to enter this function does ->release() and
151 	 * signals its completion to the other process which does nothing.
152 	 */
153 	if (pdeo->closing) {
154 		/* somebody else is doing that, just wait */
155 		DECLARE_COMPLETION_ONSTACK(c);
156 		pdeo->c = &c;
157 		spin_unlock(&pde->pde_unload_lock);
158 		wait_for_completion(&c);
159 		spin_lock(&pde->pde_unload_lock);
160 	} else {
161 		struct file *file;
162 		pdeo->closing = true;
163 		spin_unlock(&pde->pde_unload_lock);
164 		file = pdeo->file;
165 		pde->proc_fops->release(file_inode(file), file);
166 		spin_lock(&pde->pde_unload_lock);
167 		/* After ->release. */
168 		list_del(&pdeo->lh);
169 		if (pdeo->c)
170 			complete(pdeo->c);
171 		kfree(pdeo);
172 	}
173 }
174 
175 void proc_entry_rundown(struct proc_dir_entry *de)
176 {
177 	DECLARE_COMPLETION_ONSTACK(c);
178 	/* Wait until all existing callers into module are done. */
179 	de->pde_unload_completion = &c;
180 	if (atomic_add_return(BIAS, &de->in_use) != BIAS)
181 		wait_for_completion(&c);
182 
183 	/* ->pde_openers list can't grow from now on. */
184 
185 	spin_lock(&de->pde_unload_lock);
186 	while (!list_empty(&de->pde_openers)) {
187 		struct pde_opener *pdeo;
188 		pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
189 		close_pdeo(de, pdeo);
190 	}
191 	spin_unlock(&de->pde_unload_lock);
192 }
193 
194 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
195 {
196 	struct proc_dir_entry *pde = PDE(file_inode(file));
197 	loff_t rv = -EINVAL;
198 	if (use_pde(pde)) {
199 		loff_t (*llseek)(struct file *, loff_t, int);
200 		llseek = pde->proc_fops->llseek;
201 		if (!llseek)
202 			llseek = default_llseek;
203 		rv = llseek(file, offset, whence);
204 		unuse_pde(pde);
205 	}
206 	return rv;
207 }
208 
209 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
210 {
211 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
212 	struct proc_dir_entry *pde = PDE(file_inode(file));
213 	ssize_t rv = -EIO;
214 	if (use_pde(pde)) {
215 		read = pde->proc_fops->read;
216 		if (read)
217 			rv = read(file, buf, count, ppos);
218 		unuse_pde(pde);
219 	}
220 	return rv;
221 }
222 
223 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
224 {
225 	ssize_t (*write)(struct file *, const 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 		write = pde->proc_fops->write;
230 		if (write)
231 			rv = write(file, buf, count, ppos);
232 		unuse_pde(pde);
233 	}
234 	return rv;
235 }
236 
237 static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
238 {
239 	struct proc_dir_entry *pde = PDE(file_inode(file));
240 	unsigned int rv = DEFAULT_POLLMASK;
241 	unsigned int (*poll)(struct file *, struct poll_table_struct *);
242 	if (use_pde(pde)) {
243 		poll = pde->proc_fops->poll;
244 		if (poll)
245 			rv = poll(file, pts);
246 		unuse_pde(pde);
247 	}
248 	return rv;
249 }
250 
251 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
252 {
253 	struct proc_dir_entry *pde = PDE(file_inode(file));
254 	long rv = -ENOTTY;
255 	long (*ioctl)(struct file *, unsigned int, unsigned long);
256 	if (use_pde(pde)) {
257 		ioctl = pde->proc_fops->unlocked_ioctl;
258 		if (ioctl)
259 			rv = ioctl(file, cmd, arg);
260 		unuse_pde(pde);
261 	}
262 	return rv;
263 }
264 
265 #ifdef CONFIG_COMPAT
266 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
267 {
268 	struct proc_dir_entry *pde = PDE(file_inode(file));
269 	long rv = -ENOTTY;
270 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
271 	if (use_pde(pde)) {
272 		compat_ioctl = pde->proc_fops->compat_ioctl;
273 		if (compat_ioctl)
274 			rv = compat_ioctl(file, cmd, arg);
275 		unuse_pde(pde);
276 	}
277 	return rv;
278 }
279 #endif
280 
281 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
282 {
283 	struct proc_dir_entry *pde = PDE(file_inode(file));
284 	int rv = -EIO;
285 	int (*mmap)(struct file *, struct vm_area_struct *);
286 	if (use_pde(pde)) {
287 		mmap = pde->proc_fops->mmap;
288 		if (mmap)
289 			rv = mmap(file, vma);
290 		unuse_pde(pde);
291 	}
292 	return rv;
293 }
294 
295 static unsigned long
296 proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
297 			   unsigned long len, unsigned long pgoff,
298 			   unsigned long flags)
299 {
300 	struct proc_dir_entry *pde = PDE(file_inode(file));
301 	unsigned long rv = -EIO;
302 
303 	if (use_pde(pde)) {
304 		typeof(proc_reg_get_unmapped_area) *get_area;
305 
306 		get_area = pde->proc_fops->get_unmapped_area;
307 #ifdef CONFIG_MMU
308 		if (!get_area)
309 			get_area = current->mm->get_unmapped_area;
310 #endif
311 
312 		if (get_area)
313 			rv = get_area(file, orig_addr, len, pgoff, flags);
314 		else
315 			rv = orig_addr;
316 		unuse_pde(pde);
317 	}
318 	return rv;
319 }
320 
321 static int proc_reg_open(struct inode *inode, struct file *file)
322 {
323 	struct proc_dir_entry *pde = PDE(inode);
324 	int rv = 0;
325 	int (*open)(struct inode *, struct file *);
326 	int (*release)(struct inode *, struct file *);
327 	struct pde_opener *pdeo;
328 
329 	/*
330 	 * Ensure that
331 	 * 1) PDE's ->release hook will be called no matter what
332 	 *    either normally by close()/->release, or forcefully by
333 	 *    rmmod/remove_proc_entry.
334 	 *
335 	 * 2) rmmod isn't blocked by opening file in /proc and sitting on
336 	 *    the descriptor (including "rmmod foo </proc/foo" scenario).
337 	 *
338 	 * Save every "struct file" with custom ->release hook.
339 	 */
340 	pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
341 	if (!pdeo)
342 		return -ENOMEM;
343 
344 	if (!use_pde(pde)) {
345 		kfree(pdeo);
346 		return -ENOENT;
347 	}
348 	open = pde->proc_fops->open;
349 	release = pde->proc_fops->release;
350 
351 	if (open)
352 		rv = open(inode, file);
353 
354 	if (rv == 0 && release) {
355 		/* To know what to release. */
356 		pdeo->file = file;
357 		pdeo->closing = false;
358 		pdeo->c = NULL;
359 		spin_lock(&pde->pde_unload_lock);
360 		list_add(&pdeo->lh, &pde->pde_openers);
361 		spin_unlock(&pde->pde_unload_lock);
362 	} else
363 		kfree(pdeo);
364 
365 	unuse_pde(pde);
366 	return rv;
367 }
368 
369 static int proc_reg_release(struct inode *inode, struct file *file)
370 {
371 	struct proc_dir_entry *pde = PDE(inode);
372 	struct pde_opener *pdeo;
373 	spin_lock(&pde->pde_unload_lock);
374 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
375 		if (pdeo->file == file) {
376 			close_pdeo(pde, pdeo);
377 			break;
378 		}
379 	}
380 	spin_unlock(&pde->pde_unload_lock);
381 	return 0;
382 }
383 
384 static const struct file_operations proc_reg_file_ops = {
385 	.llseek		= proc_reg_llseek,
386 	.read		= proc_reg_read,
387 	.write		= proc_reg_write,
388 	.poll		= proc_reg_poll,
389 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
390 #ifdef CONFIG_COMPAT
391 	.compat_ioctl	= proc_reg_compat_ioctl,
392 #endif
393 	.mmap		= proc_reg_mmap,
394 	.get_unmapped_area = proc_reg_get_unmapped_area,
395 	.open		= proc_reg_open,
396 	.release	= proc_reg_release,
397 };
398 
399 #ifdef CONFIG_COMPAT
400 static const struct file_operations proc_reg_file_ops_no_compat = {
401 	.llseek		= proc_reg_llseek,
402 	.read		= proc_reg_read,
403 	.write		= proc_reg_write,
404 	.poll		= proc_reg_poll,
405 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
406 	.mmap		= proc_reg_mmap,
407 	.get_unmapped_area = proc_reg_get_unmapped_area,
408 	.open		= proc_reg_open,
409 	.release	= proc_reg_release,
410 };
411 #endif
412 
413 static void proc_put_link(void *p)
414 {
415 	unuse_pde(p);
416 }
417 
418 static const char *proc_get_link(struct dentry *dentry,
419 				 struct inode *inode,
420 				 struct delayed_call *done)
421 {
422 	struct proc_dir_entry *pde = PDE(inode);
423 	if (unlikely(!use_pde(pde)))
424 		return ERR_PTR(-EINVAL);
425 	set_delayed_call(done, proc_put_link, pde);
426 	return pde->data;
427 }
428 
429 const struct inode_operations proc_link_inode_operations = {
430 	.get_link	= proc_get_link,
431 };
432 
433 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
434 {
435 	struct inode *inode = new_inode_pseudo(sb);
436 
437 	if (inode) {
438 		inode->i_ino = de->low_ino;
439 		inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
440 		PROC_I(inode)->pde = de;
441 
442 		if (is_empty_pde(de)) {
443 			make_empty_dir_inode(inode);
444 			return inode;
445 		}
446 		if (de->mode) {
447 			inode->i_mode = de->mode;
448 			inode->i_uid = de->uid;
449 			inode->i_gid = de->gid;
450 		}
451 		if (de->size)
452 			inode->i_size = de->size;
453 		if (de->nlink)
454 			set_nlink(inode, de->nlink);
455 		WARN_ON(!de->proc_iops);
456 		inode->i_op = de->proc_iops;
457 		if (de->proc_fops) {
458 			if (S_ISREG(inode->i_mode)) {
459 #ifdef CONFIG_COMPAT
460 				if (!de->proc_fops->compat_ioctl)
461 					inode->i_fop =
462 						&proc_reg_file_ops_no_compat;
463 				else
464 #endif
465 					inode->i_fop = &proc_reg_file_ops;
466 			} else {
467 				inode->i_fop = de->proc_fops;
468 			}
469 		}
470 	} else
471 	       pde_put(de);
472 	return inode;
473 }
474 
475 int proc_fill_super(struct super_block *s, void *data, int silent)
476 {
477 	struct pid_namespace *ns = get_pid_ns(s->s_fs_info);
478 	struct inode *root_inode;
479 	int ret;
480 
481 	if (!proc_parse_options(data, ns))
482 		return -EINVAL;
483 
484 	/* User space would break if executables or devices appear on proc */
485 	s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
486 	s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
487 	s->s_blocksize = 1024;
488 	s->s_blocksize_bits = 10;
489 	s->s_magic = PROC_SUPER_MAGIC;
490 	s->s_op = &proc_sops;
491 	s->s_time_gran = 1;
492 
493 	/*
494 	 * procfs isn't actually a stacking filesystem; however, there is
495 	 * too much magic going on inside it to permit stacking things on
496 	 * top of it
497 	 */
498 	s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
499 
500 	pde_get(&proc_root);
501 	root_inode = proc_get_inode(s, &proc_root);
502 	if (!root_inode) {
503 		pr_err("proc_fill_super: get root inode failed\n");
504 		return -ENOMEM;
505 	}
506 
507 	s->s_root = d_make_root(root_inode);
508 	if (!s->s_root) {
509 		pr_err("proc_fill_super: allocate dentry failed\n");
510 		return -ENOMEM;
511 	}
512 
513 	ret = proc_setup_self(s);
514 	if (ret) {
515 		return ret;
516 	}
517 	return proc_setup_thread_self(s);
518 }
519