xref: /openbmc/linux/fs/proc/inode.c (revision f9a82c48) 
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 
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 __ro_after_init;
56 static struct kmem_cache *pde_opener_cache __ro_after_init;
57 
58 static struct inode *proc_alloc_inode(struct super_block *sb)
59 {
60 	struct proc_inode *ei;
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 	return &ei->vfs_inode;
73 }
74 
75 static void proc_i_callback(struct rcu_head *head)
76 {
77 	struct inode *inode = container_of(head, struct inode, i_rcu);
78 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
79 }
80 
81 static void proc_destroy_inode(struct inode *inode)
82 {
83 	call_rcu(&inode->i_rcu, proc_i_callback);
84 }
85 
86 static void init_once(void *foo)
87 {
88 	struct proc_inode *ei = (struct proc_inode *) foo;
89 
90 	inode_init_once(&ei->vfs_inode);
91 }
92 
93 void __init proc_init_kmemcache(void)
94 {
95 	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
96 					     sizeof(struct proc_inode),
97 					     0, (SLAB_RECLAIM_ACCOUNT|
98 						SLAB_MEM_SPREAD|SLAB_ACCOUNT|
99 						SLAB_PANIC),
100 					     init_once);
101 	pde_opener_cache =
102 		kmem_cache_create("pde_opener", sizeof(struct pde_opener), 0,
103 				  SLAB_ACCOUNT|SLAB_PANIC, NULL);
104 	proc_dir_entry_cache = kmem_cache_create_usercopy(
105 		"proc_dir_entry", SIZEOF_PDE, 0, SLAB_PANIC,
106 		offsetof(struct proc_dir_entry, inline_name),
107 		SIZEOF_PDE_INLINE_NAME, NULL);
108 	BUILD_BUG_ON(sizeof(struct proc_dir_entry) >= SIZEOF_PDE);
109 }
110 
111 static int proc_show_options(struct seq_file *seq, struct dentry *root)
112 {
113 	struct super_block *sb = root->d_sb;
114 	struct pid_namespace *pid = sb->s_fs_info;
115 
116 	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
117 		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
118 	if (pid->hide_pid != HIDEPID_OFF)
119 		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
120 
121 	return 0;
122 }
123 
124 const struct super_operations proc_sops = {
125 	.alloc_inode	= proc_alloc_inode,
126 	.destroy_inode	= proc_destroy_inode,
127 	.drop_inode	= generic_delete_inode,
128 	.evict_inode	= proc_evict_inode,
129 	.statfs		= simple_statfs,
130 	.show_options	= proc_show_options,
131 };
132 
133 enum {BIAS = -1U<<31};
134 
135 static inline int use_pde(struct proc_dir_entry *pde)
136 {
137 	return likely(atomic_inc_unless_negative(&pde->in_use));
138 }
139 
140 static void unuse_pde(struct proc_dir_entry *pde)
141 {
142 	if (unlikely(atomic_dec_return(&pde->in_use) == BIAS))
143 		complete(pde->pde_unload_completion);
144 }
145 
146 /* pde is locked on entry, unlocked on exit */
147 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
148 {
149 	/*
150 	 * close() (proc_reg_release()) can't delete an entry and proceed:
151 	 * ->release hook needs to be available at the right moment.
152 	 *
153 	 * rmmod (remove_proc_entry() et al) can't delete an entry and proceed:
154 	 * "struct file" needs to be available at the right moment.
155 	 *
156 	 * Therefore, first process to enter this function does ->release() and
157 	 * signals its completion to the other process which does nothing.
158 	 */
159 	if (pdeo->closing) {
160 		/* somebody else is doing that, just wait */
161 		DECLARE_COMPLETION_ONSTACK(c);
162 		pdeo->c = &c;
163 		spin_unlock(&pde->pde_unload_lock);
164 		wait_for_completion(&c);
165 	} else {
166 		struct file *file;
167 		struct completion *c;
168 
169 		pdeo->closing = true;
170 		spin_unlock(&pde->pde_unload_lock);
171 		file = pdeo->file;
172 		pde->proc_fops->release(file_inode(file), file);
173 		spin_lock(&pde->pde_unload_lock);
174 		/* After ->release. */
175 		list_del(&pdeo->lh);
176 		c = pdeo->c;
177 		spin_unlock(&pde->pde_unload_lock);
178 		if (unlikely(c))
179 			complete(c);
180 		kmem_cache_free(pde_opener_cache, pdeo);
181 	}
182 }
183 
184 void proc_entry_rundown(struct proc_dir_entry *de)
185 {
186 	DECLARE_COMPLETION_ONSTACK(c);
187 	/* Wait until all existing callers into module are done. */
188 	de->pde_unload_completion = &c;
189 	if (atomic_add_return(BIAS, &de->in_use) != BIAS)
190 		wait_for_completion(&c);
191 
192 	/* ->pde_openers list can't grow from now on. */
193 
194 	spin_lock(&de->pde_unload_lock);
195 	while (!list_empty(&de->pde_openers)) {
196 		struct pde_opener *pdeo;
197 		pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
198 		close_pdeo(de, pdeo);
199 		spin_lock(&de->pde_unload_lock);
200 	}
201 	spin_unlock(&de->pde_unload_lock);
202 }
203 
204 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
205 {
206 	struct proc_dir_entry *pde = PDE(file_inode(file));
207 	loff_t rv = -EINVAL;
208 	if (use_pde(pde)) {
209 		loff_t (*llseek)(struct file *, loff_t, int);
210 		llseek = pde->proc_fops->llseek;
211 		if (!llseek)
212 			llseek = default_llseek;
213 		rv = llseek(file, offset, whence);
214 		unuse_pde(pde);
215 	}
216 	return rv;
217 }
218 
219 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
220 {
221 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
222 	struct proc_dir_entry *pde = PDE(file_inode(file));
223 	ssize_t rv = -EIO;
224 	if (use_pde(pde)) {
225 		read = pde->proc_fops->read;
226 		if (read)
227 			rv = read(file, buf, count, ppos);
228 		unuse_pde(pde);
229 	}
230 	return rv;
231 }
232 
233 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
234 {
235 	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
236 	struct proc_dir_entry *pde = PDE(file_inode(file));
237 	ssize_t rv = -EIO;
238 	if (use_pde(pde)) {
239 		write = pde->proc_fops->write;
240 		if (write)
241 			rv = write(file, buf, count, ppos);
242 		unuse_pde(pde);
243 	}
244 	return rv;
245 }
246 
247 static __poll_t proc_reg_poll(struct file *file, struct poll_table_struct *pts)
248 {
249 	struct proc_dir_entry *pde = PDE(file_inode(file));
250 	__poll_t rv = DEFAULT_POLLMASK;
251 	__poll_t (*poll)(struct file *, struct poll_table_struct *);
252 	if (use_pde(pde)) {
253 		poll = pde->proc_fops->poll;
254 		if (poll)
255 			rv = poll(file, pts);
256 		unuse_pde(pde);
257 	}
258 	return rv;
259 }
260 
261 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
262 {
263 	struct proc_dir_entry *pde = PDE(file_inode(file));
264 	long rv = -ENOTTY;
265 	long (*ioctl)(struct file *, unsigned int, unsigned long);
266 	if (use_pde(pde)) {
267 		ioctl = pde->proc_fops->unlocked_ioctl;
268 		if (ioctl)
269 			rv = ioctl(file, cmd, arg);
270 		unuse_pde(pde);
271 	}
272 	return rv;
273 }
274 
275 #ifdef CONFIG_COMPAT
276 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
277 {
278 	struct proc_dir_entry *pde = PDE(file_inode(file));
279 	long rv = -ENOTTY;
280 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
281 	if (use_pde(pde)) {
282 		compat_ioctl = pde->proc_fops->compat_ioctl;
283 		if (compat_ioctl)
284 			rv = compat_ioctl(file, cmd, arg);
285 		unuse_pde(pde);
286 	}
287 	return rv;
288 }
289 #endif
290 
291 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
292 {
293 	struct proc_dir_entry *pde = PDE(file_inode(file));
294 	int rv = -EIO;
295 	int (*mmap)(struct file *, struct vm_area_struct *);
296 	if (use_pde(pde)) {
297 		mmap = pde->proc_fops->mmap;
298 		if (mmap)
299 			rv = mmap(file, vma);
300 		unuse_pde(pde);
301 	}
302 	return rv;
303 }
304 
305 static unsigned long
306 proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
307 			   unsigned long len, unsigned long pgoff,
308 			   unsigned long flags)
309 {
310 	struct proc_dir_entry *pde = PDE(file_inode(file));
311 	unsigned long rv = -EIO;
312 
313 	if (use_pde(pde)) {
314 		typeof(proc_reg_get_unmapped_area) *get_area;
315 
316 		get_area = pde->proc_fops->get_unmapped_area;
317 #ifdef CONFIG_MMU
318 		if (!get_area)
319 			get_area = current->mm->get_unmapped_area;
320 #endif
321 
322 		if (get_area)
323 			rv = get_area(file, orig_addr, len, pgoff, flags);
324 		else
325 			rv = orig_addr;
326 		unuse_pde(pde);
327 	}
328 	return rv;
329 }
330 
331 static int proc_reg_open(struct inode *inode, struct file *file)
332 {
333 	struct proc_dir_entry *pde = PDE(inode);
334 	int rv = 0;
335 	int (*open)(struct inode *, struct file *);
336 	int (*release)(struct inode *, struct file *);
337 	struct pde_opener *pdeo;
338 
339 	/*
340 	 * Ensure that
341 	 * 1) PDE's ->release hook will be called no matter what
342 	 *    either normally by close()/->release, or forcefully by
343 	 *    rmmod/remove_proc_entry.
344 	 *
345 	 * 2) rmmod isn't blocked by opening file in /proc and sitting on
346 	 *    the descriptor (including "rmmod foo </proc/foo" scenario).
347 	 *
348 	 * Save every "struct file" with custom ->release hook.
349 	 */
350 	if (!use_pde(pde))
351 		return -ENOENT;
352 
353 	release = pde->proc_fops->release;
354 	if (release) {
355 		pdeo = kmem_cache_alloc(pde_opener_cache, GFP_KERNEL);
356 		if (!pdeo) {
357 			rv = -ENOMEM;
358 			goto out_unuse;
359 		}
360 	}
361 
362 	open = pde->proc_fops->open;
363 	if (open)
364 		rv = open(inode, file);
365 
366 	if (release) {
367 		if (rv == 0) {
368 			/* To know what to release. */
369 			pdeo->file = file;
370 			pdeo->closing = false;
371 			pdeo->c = NULL;
372 			spin_lock(&pde->pde_unload_lock);
373 			list_add(&pdeo->lh, &pde->pde_openers);
374 			spin_unlock(&pde->pde_unload_lock);
375 		} else
376 			kmem_cache_free(pde_opener_cache, pdeo);
377 	}
378 
379 out_unuse:
380 	unuse_pde(pde);
381 	return rv;
382 }
383 
384 static int proc_reg_release(struct inode *inode, struct file *file)
385 {
386 	struct proc_dir_entry *pde = PDE(inode);
387 	struct pde_opener *pdeo;
388 	spin_lock(&pde->pde_unload_lock);
389 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
390 		if (pdeo->file == file) {
391 			close_pdeo(pde, pdeo);
392 			return 0;
393 		}
394 	}
395 	spin_unlock(&pde->pde_unload_lock);
396 	return 0;
397 }
398 
399 static const struct file_operations proc_reg_file_ops = {
400 	.llseek		= proc_reg_llseek,
401 	.read		= proc_reg_read,
402 	.write		= proc_reg_write,
403 	.poll		= proc_reg_poll,
404 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
405 #ifdef CONFIG_COMPAT
406 	.compat_ioctl	= proc_reg_compat_ioctl,
407 #endif
408 	.mmap		= proc_reg_mmap,
409 	.get_unmapped_area = proc_reg_get_unmapped_area,
410 	.open		= proc_reg_open,
411 	.release	= proc_reg_release,
412 };
413 
414 #ifdef CONFIG_COMPAT
415 static const struct file_operations proc_reg_file_ops_no_compat = {
416 	.llseek		= proc_reg_llseek,
417 	.read		= proc_reg_read,
418 	.write		= proc_reg_write,
419 	.poll		= proc_reg_poll,
420 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
421 	.mmap		= proc_reg_mmap,
422 	.get_unmapped_area = proc_reg_get_unmapped_area,
423 	.open		= proc_reg_open,
424 	.release	= proc_reg_release,
425 };
426 #endif
427 
428 static void proc_put_link(void *p)
429 {
430 	unuse_pde(p);
431 }
432 
433 static const char *proc_get_link(struct dentry *dentry,
434 				 struct inode *inode,
435 				 struct delayed_call *done)
436 {
437 	struct proc_dir_entry *pde = PDE(inode);
438 	if (!use_pde(pde))
439 		return ERR_PTR(-EINVAL);
440 	set_delayed_call(done, proc_put_link, pde);
441 	return pde->data;
442 }
443 
444 const struct inode_operations proc_link_inode_operations = {
445 	.get_link	= proc_get_link,
446 };
447 
448 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
449 {
450 	struct inode *inode = new_inode_pseudo(sb);
451 
452 	if (inode) {
453 		inode->i_ino = de->low_ino;
454 		inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
455 		PROC_I(inode)->pde = de;
456 
457 		if (is_empty_pde(de)) {
458 			make_empty_dir_inode(inode);
459 			return inode;
460 		}
461 		if (de->mode) {
462 			inode->i_mode = de->mode;
463 			inode->i_uid = de->uid;
464 			inode->i_gid = de->gid;
465 		}
466 		if (de->size)
467 			inode->i_size = de->size;
468 		if (de->nlink)
469 			set_nlink(inode, de->nlink);
470 		WARN_ON(!de->proc_iops);
471 		inode->i_op = de->proc_iops;
472 		if (de->proc_fops) {
473 			if (S_ISREG(inode->i_mode)) {
474 #ifdef CONFIG_COMPAT
475 				if (!de->proc_fops->compat_ioctl)
476 					inode->i_fop =
477 						&proc_reg_file_ops_no_compat;
478 				else
479 #endif
480 					inode->i_fop = &proc_reg_file_ops;
481 			} else {
482 				inode->i_fop = de->proc_fops;
483 			}
484 		}
485 	} else
486 	       pde_put(de);
487 	return inode;
488 }
489