xref: /openbmc/linux/fs/proc/inode.c (revision b9ccfda2) 
1 /*
2  *  linux/fs/proc/inode.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  */
6 
7 #include <linux/time.h>
8 #include <linux/proc_fs.h>
9 #include <linux/kernel.h>
10 #include <linux/pid_namespace.h>
11 #include <linux/mm.h>
12 #include <linux/string.h>
13 #include <linux/stat.h>
14 #include <linux/completion.h>
15 #include <linux/poll.h>
16 #include <linux/file.h>
17 #include <linux/limits.h>
18 #include <linux/init.h>
19 #include <linux/module.h>
20 #include <linux/sysctl.h>
21 #include <linux/seq_file.h>
22 #include <linux/slab.h>
23 #include <linux/mount.h>
24 
25 #include <asm/uaccess.h>
26 
27 #include "internal.h"
28 
29 static void proc_evict_inode(struct inode *inode)
30 {
31 	struct proc_dir_entry *de;
32 	struct ctl_table_header *head;
33 	const struct proc_ns_operations *ns_ops;
34 
35 	truncate_inode_pages(&inode->i_data, 0);
36 	clear_inode(inode);
37 
38 	/* Stop tracking associated processes */
39 	put_pid(PROC_I(inode)->pid);
40 
41 	/* Let go of any associated proc directory entry */
42 	de = PROC_I(inode)->pde;
43 	if (de)
44 		pde_put(de);
45 	head = PROC_I(inode)->sysctl;
46 	if (head) {
47 		rcu_assign_pointer(PROC_I(inode)->sysctl, NULL);
48 		sysctl_head_put(head);
49 	}
50 	/* Release any associated namespace */
51 	ns_ops = PROC_I(inode)->ns_ops;
52 	if (ns_ops && ns_ops->put)
53 		ns_ops->put(PROC_I(inode)->ns);
54 }
55 
56 static struct kmem_cache * proc_inode_cachep;
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 = (struct proc_inode *)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 = NULL;
73 	ei->ns_ops = NULL;
74 	inode = &ei->vfs_inode;
75 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
76 	return inode;
77 }
78 
79 static void proc_i_callback(struct rcu_head *head)
80 {
81 	struct inode *inode = container_of(head, struct inode, i_rcu);
82 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
83 }
84 
85 static void proc_destroy_inode(struct inode *inode)
86 {
87 	call_rcu(&inode->i_rcu, proc_i_callback);
88 }
89 
90 static void init_once(void *foo)
91 {
92 	struct proc_inode *ei = (struct proc_inode *) foo;
93 
94 	inode_init_once(&ei->vfs_inode);
95 }
96 
97 void __init proc_init_inodecache(void)
98 {
99 	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
100 					     sizeof(struct proc_inode),
101 					     0, (SLAB_RECLAIM_ACCOUNT|
102 						SLAB_MEM_SPREAD|SLAB_PANIC),
103 					     init_once);
104 }
105 
106 static int proc_show_options(struct seq_file *seq, struct dentry *root)
107 {
108 	struct super_block *sb = root->d_sb;
109 	struct pid_namespace *pid = sb->s_fs_info;
110 
111 	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
112 		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
113 	if (pid->hide_pid != 0)
114 		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
115 
116 	return 0;
117 }
118 
119 static const struct super_operations proc_sops = {
120 	.alloc_inode	= proc_alloc_inode,
121 	.destroy_inode	= proc_destroy_inode,
122 	.drop_inode	= generic_delete_inode,
123 	.evict_inode	= proc_evict_inode,
124 	.statfs		= simple_statfs,
125 	.remount_fs	= proc_remount,
126 	.show_options	= proc_show_options,
127 };
128 
129 static void __pde_users_dec(struct proc_dir_entry *pde)
130 {
131 	pde->pde_users--;
132 	if (pde->pde_unload_completion && pde->pde_users == 0)
133 		complete(pde->pde_unload_completion);
134 }
135 
136 void pde_users_dec(struct proc_dir_entry *pde)
137 {
138 	spin_lock(&pde->pde_unload_lock);
139 	__pde_users_dec(pde);
140 	spin_unlock(&pde->pde_unload_lock);
141 }
142 
143 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
144 {
145 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
146 	loff_t rv = -EINVAL;
147 	loff_t (*llseek)(struct file *, loff_t, int);
148 
149 	spin_lock(&pde->pde_unload_lock);
150 	/*
151 	 * remove_proc_entry() is going to delete PDE (as part of module
152 	 * cleanup sequence). No new callers into module allowed.
153 	 */
154 	if (!pde->proc_fops) {
155 		spin_unlock(&pde->pde_unload_lock);
156 		return rv;
157 	}
158 	/*
159 	 * Bump refcount so that remove_proc_entry will wail for ->llseek to
160 	 * complete.
161 	 */
162 	pde->pde_users++;
163 	/*
164 	 * Save function pointer under lock, to protect against ->proc_fops
165 	 * NULL'ifying right after ->pde_unload_lock is dropped.
166 	 */
167 	llseek = pde->proc_fops->llseek;
168 	spin_unlock(&pde->pde_unload_lock);
169 
170 	if (!llseek)
171 		llseek = default_llseek;
172 	rv = llseek(file, offset, whence);
173 
174 	pde_users_dec(pde);
175 	return rv;
176 }
177 
178 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
179 {
180 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
181 	ssize_t rv = -EIO;
182 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
183 
184 	spin_lock(&pde->pde_unload_lock);
185 	if (!pde->proc_fops) {
186 		spin_unlock(&pde->pde_unload_lock);
187 		return rv;
188 	}
189 	pde->pde_users++;
190 	read = pde->proc_fops->read;
191 	spin_unlock(&pde->pde_unload_lock);
192 
193 	if (read)
194 		rv = read(file, buf, count, ppos);
195 
196 	pde_users_dec(pde);
197 	return rv;
198 }
199 
200 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
201 {
202 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
203 	ssize_t rv = -EIO;
204 	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
205 
206 	spin_lock(&pde->pde_unload_lock);
207 	if (!pde->proc_fops) {
208 		spin_unlock(&pde->pde_unload_lock);
209 		return rv;
210 	}
211 	pde->pde_users++;
212 	write = pde->proc_fops->write;
213 	spin_unlock(&pde->pde_unload_lock);
214 
215 	if (write)
216 		rv = write(file, buf, count, ppos);
217 
218 	pde_users_dec(pde);
219 	return rv;
220 }
221 
222 static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
223 {
224 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
225 	unsigned int rv = DEFAULT_POLLMASK;
226 	unsigned int (*poll)(struct file *, struct poll_table_struct *);
227 
228 	spin_lock(&pde->pde_unload_lock);
229 	if (!pde->proc_fops) {
230 		spin_unlock(&pde->pde_unload_lock);
231 		return rv;
232 	}
233 	pde->pde_users++;
234 	poll = pde->proc_fops->poll;
235 	spin_unlock(&pde->pde_unload_lock);
236 
237 	if (poll)
238 		rv = poll(file, pts);
239 
240 	pde_users_dec(pde);
241 	return rv;
242 }
243 
244 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
245 {
246 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
247 	long rv = -ENOTTY;
248 	long (*ioctl)(struct file *, unsigned int, unsigned long);
249 
250 	spin_lock(&pde->pde_unload_lock);
251 	if (!pde->proc_fops) {
252 		spin_unlock(&pde->pde_unload_lock);
253 		return rv;
254 	}
255 	pde->pde_users++;
256 	ioctl = pde->proc_fops->unlocked_ioctl;
257 	spin_unlock(&pde->pde_unload_lock);
258 
259 	if (ioctl)
260 		rv = ioctl(file, cmd, arg);
261 
262 	pde_users_dec(pde);
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->f_path.dentry->d_inode);
270 	long rv = -ENOTTY;
271 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
272 
273 	spin_lock(&pde->pde_unload_lock);
274 	if (!pde->proc_fops) {
275 		spin_unlock(&pde->pde_unload_lock);
276 		return rv;
277 	}
278 	pde->pde_users++;
279 	compat_ioctl = pde->proc_fops->compat_ioctl;
280 	spin_unlock(&pde->pde_unload_lock);
281 
282 	if (compat_ioctl)
283 		rv = compat_ioctl(file, cmd, arg);
284 
285 	pde_users_dec(pde);
286 	return rv;
287 }
288 #endif
289 
290 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
291 {
292 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
293 	int rv = -EIO;
294 	int (*mmap)(struct file *, struct vm_area_struct *);
295 
296 	spin_lock(&pde->pde_unload_lock);
297 	if (!pde->proc_fops) {
298 		spin_unlock(&pde->pde_unload_lock);
299 		return rv;
300 	}
301 	pde->pde_users++;
302 	mmap = pde->proc_fops->mmap;
303 	spin_unlock(&pde->pde_unload_lock);
304 
305 	if (mmap)
306 		rv = mmap(file, vma);
307 
308 	pde_users_dec(pde);
309 	return rv;
310 }
311 
312 static int proc_reg_open(struct inode *inode, struct file *file)
313 {
314 	struct proc_dir_entry *pde = PDE(inode);
315 	int rv = 0;
316 	int (*open)(struct inode *, struct file *);
317 	int (*release)(struct inode *, struct file *);
318 	struct pde_opener *pdeo;
319 
320 	/*
321 	 * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
322 	 * sequence. ->release won't be called because ->proc_fops will be
323 	 * cleared. Depending on complexity of ->release, consequences vary.
324 	 *
325 	 * We can't wait for mercy when close will be done for real, it's
326 	 * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
327 	 * by hand in remove_proc_entry(). For this, save opener's credentials
328 	 * for later.
329 	 */
330 	pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
331 	if (!pdeo)
332 		return -ENOMEM;
333 
334 	spin_lock(&pde->pde_unload_lock);
335 	if (!pde->proc_fops) {
336 		spin_unlock(&pde->pde_unload_lock);
337 		kfree(pdeo);
338 		return -ENOENT;
339 	}
340 	pde->pde_users++;
341 	open = pde->proc_fops->open;
342 	release = pde->proc_fops->release;
343 	spin_unlock(&pde->pde_unload_lock);
344 
345 	if (open)
346 		rv = open(inode, file);
347 
348 	spin_lock(&pde->pde_unload_lock);
349 	if (rv == 0 && release) {
350 		/* To know what to release. */
351 		pdeo->inode = inode;
352 		pdeo->file = file;
353 		/* Strictly for "too late" ->release in proc_reg_release(). */
354 		pdeo->release = release;
355 		list_add(&pdeo->lh, &pde->pde_openers);
356 	} else
357 		kfree(pdeo);
358 	__pde_users_dec(pde);
359 	spin_unlock(&pde->pde_unload_lock);
360 	return rv;
361 }
362 
363 static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
364 					struct inode *inode, struct file *file)
365 {
366 	struct pde_opener *pdeo;
367 
368 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
369 		if (pdeo->inode == inode && pdeo->file == file)
370 			return pdeo;
371 	}
372 	return NULL;
373 }
374 
375 static int proc_reg_release(struct inode *inode, struct file *file)
376 {
377 	struct proc_dir_entry *pde = PDE(inode);
378 	int rv = 0;
379 	int (*release)(struct inode *, struct file *);
380 	struct pde_opener *pdeo;
381 
382 	spin_lock(&pde->pde_unload_lock);
383 	pdeo = find_pde_opener(pde, inode, file);
384 	if (!pde->proc_fops) {
385 		/*
386 		 * Can't simply exit, __fput() will think that everything is OK,
387 		 * and move on to freeing struct file. remove_proc_entry() will
388 		 * find slacker in opener's list and will try to do non-trivial
389 		 * things with struct file. Therefore, remove opener from list.
390 		 *
391 		 * But if opener is removed from list, who will ->release it?
392 		 */
393 		if (pdeo) {
394 			list_del(&pdeo->lh);
395 			spin_unlock(&pde->pde_unload_lock);
396 			rv = pdeo->release(inode, file);
397 			kfree(pdeo);
398 		} else
399 			spin_unlock(&pde->pde_unload_lock);
400 		return rv;
401 	}
402 	pde->pde_users++;
403 	release = pde->proc_fops->release;
404 	if (pdeo) {
405 		list_del(&pdeo->lh);
406 		kfree(pdeo);
407 	}
408 	spin_unlock(&pde->pde_unload_lock);
409 
410 	if (release)
411 		rv = release(inode, file);
412 
413 	pde_users_dec(pde);
414 	return rv;
415 }
416 
417 static const struct file_operations proc_reg_file_ops = {
418 	.llseek		= proc_reg_llseek,
419 	.read		= proc_reg_read,
420 	.write		= proc_reg_write,
421 	.poll		= proc_reg_poll,
422 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
423 #ifdef CONFIG_COMPAT
424 	.compat_ioctl	= proc_reg_compat_ioctl,
425 #endif
426 	.mmap		= proc_reg_mmap,
427 	.open		= proc_reg_open,
428 	.release	= proc_reg_release,
429 };
430 
431 #ifdef CONFIG_COMPAT
432 static const struct file_operations proc_reg_file_ops_no_compat = {
433 	.llseek		= proc_reg_llseek,
434 	.read		= proc_reg_read,
435 	.write		= proc_reg_write,
436 	.poll		= proc_reg_poll,
437 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
438 	.mmap		= proc_reg_mmap,
439 	.open		= proc_reg_open,
440 	.release	= proc_reg_release,
441 };
442 #endif
443 
444 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
445 {
446 	struct inode * inode;
447 
448 	inode = iget_locked(sb, de->low_ino);
449 	if (!inode)
450 		return NULL;
451 	if (inode->i_state & I_NEW) {
452 		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
453 		PROC_I(inode)->fd = 0;
454 		PROC_I(inode)->pde = de;
455 
456 		if (de->mode) {
457 			inode->i_mode = de->mode;
458 			inode->i_uid = de->uid;
459 			inode->i_gid = de->gid;
460 		}
461 		if (de->size)
462 			inode->i_size = de->size;
463 		if (de->nlink)
464 			set_nlink(inode, de->nlink);
465 		if (de->proc_iops)
466 			inode->i_op = de->proc_iops;
467 		if (de->proc_fops) {
468 			if (S_ISREG(inode->i_mode)) {
469 #ifdef CONFIG_COMPAT
470 				if (!de->proc_fops->compat_ioctl)
471 					inode->i_fop =
472 						&proc_reg_file_ops_no_compat;
473 				else
474 #endif
475 					inode->i_fop = &proc_reg_file_ops;
476 			} else {
477 				inode->i_fop = de->proc_fops;
478 			}
479 		}
480 		unlock_new_inode(inode);
481 	} else
482 	       pde_put(de);
483 	return inode;
484 }
485 
486 int proc_fill_super(struct super_block *s)
487 {
488 	s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
489 	s->s_blocksize = 1024;
490 	s->s_blocksize_bits = 10;
491 	s->s_magic = PROC_SUPER_MAGIC;
492 	s->s_op = &proc_sops;
493 	s->s_time_gran = 1;
494 
495 	pde_get(&proc_root);
496 	s->s_root = d_make_root(proc_get_inode(s, &proc_root));
497 	if (s->s_root)
498 		return 0;
499 
500 	printk("proc_read_super: get root inode failed\n");
501 	pde_put(&proc_root);
502 	return -ENOMEM;
503 }
504