xref: /openbmc/linux/fs/proc/inode.c (revision 93dc544c) 
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/mm.h>
11 #include <linux/string.h>
12 #include <linux/stat.h>
13 #include <linux/completion.h>
14 #include <linux/poll.h>
15 #include <linux/file.h>
16 #include <linux/limits.h>
17 #include <linux/init.h>
18 #include <linux/module.h>
19 #include <linux/smp_lock.h>
20 #include <linux/sysctl.h>
21 
22 #include <asm/system.h>
23 #include <asm/uaccess.h>
24 
25 #include "internal.h"
26 
27 struct proc_dir_entry *de_get(struct proc_dir_entry *de)
28 {
29 	atomic_inc(&de->count);
30 	return de;
31 }
32 
33 /*
34  * Decrements the use count and checks for deferred deletion.
35  */
36 void de_put(struct proc_dir_entry *de)
37 {
38 	lock_kernel();
39 	if (!atomic_read(&de->count)) {
40 		printk("de_put: entry %s already free!\n", de->name);
41 		unlock_kernel();
42 		return;
43 	}
44 
45 	if (atomic_dec_and_test(&de->count))
46 		free_proc_entry(de);
47 	unlock_kernel();
48 }
49 
50 /*
51  * Decrement the use count of the proc_dir_entry.
52  */
53 static void proc_delete_inode(struct inode *inode)
54 {
55 	struct proc_dir_entry *de;
56 
57 	truncate_inode_pages(&inode->i_data, 0);
58 
59 	/* Stop tracking associated processes */
60 	put_pid(PROC_I(inode)->pid);
61 
62 	/* Let go of any associated proc directory entry */
63 	de = PROC_I(inode)->pde;
64 	if (de) {
65 		if (de->owner)
66 			module_put(de->owner);
67 		de_put(de);
68 	}
69 	if (PROC_I(inode)->sysctl)
70 		sysctl_head_put(PROC_I(inode)->sysctl);
71 	clear_inode(inode);
72 }
73 
74 struct vfsmount *proc_mnt;
75 
76 static struct kmem_cache * proc_inode_cachep;
77 
78 static struct inode *proc_alloc_inode(struct super_block *sb)
79 {
80 	struct proc_inode *ei;
81 	struct inode *inode;
82 
83 	ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
84 	if (!ei)
85 		return NULL;
86 	ei->pid = NULL;
87 	ei->fd = 0;
88 	ei->op.proc_get_link = NULL;
89 	ei->pde = NULL;
90 	ei->sysctl = NULL;
91 	ei->sysctl_entry = NULL;
92 	inode = &ei->vfs_inode;
93 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
94 	return inode;
95 }
96 
97 static void proc_destroy_inode(struct inode *inode)
98 {
99 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
100 }
101 
102 static void init_once(void *foo)
103 {
104 	struct proc_inode *ei = (struct proc_inode *) foo;
105 
106 	inode_init_once(&ei->vfs_inode);
107 }
108 
109 int __init proc_init_inodecache(void)
110 {
111 	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
112 					     sizeof(struct proc_inode),
113 					     0, (SLAB_RECLAIM_ACCOUNT|
114 						SLAB_MEM_SPREAD|SLAB_PANIC),
115 					     init_once);
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 	.delete_inode	= proc_delete_inode,
124 	.statfs		= simple_statfs,
125 };
126 
127 static void __pde_users_dec(struct proc_dir_entry *pde)
128 {
129 	pde->pde_users--;
130 	if (pde->pde_unload_completion && pde->pde_users == 0)
131 		complete(pde->pde_unload_completion);
132 }
133 
134 static void pde_users_dec(struct proc_dir_entry *pde)
135 {
136 	spin_lock(&pde->pde_unload_lock);
137 	__pde_users_dec(pde);
138 	spin_unlock(&pde->pde_unload_lock);
139 }
140 
141 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
142 {
143 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
144 	loff_t rv = -EINVAL;
145 	loff_t (*llseek)(struct file *, loff_t, int);
146 
147 	spin_lock(&pde->pde_unload_lock);
148 	/*
149 	 * remove_proc_entry() is going to delete PDE (as part of module
150 	 * cleanup sequence). No new callers into module allowed.
151 	 */
152 	if (!pde->proc_fops) {
153 		spin_unlock(&pde->pde_unload_lock);
154 		return rv;
155 	}
156 	/*
157 	 * Bump refcount so that remove_proc_entry will wail for ->llseek to
158 	 * complete.
159 	 */
160 	pde->pde_users++;
161 	/*
162 	 * Save function pointer under lock, to protect against ->proc_fops
163 	 * NULL'ifying right after ->pde_unload_lock is dropped.
164 	 */
165 	llseek = pde->proc_fops->llseek;
166 	spin_unlock(&pde->pde_unload_lock);
167 
168 	if (!llseek)
169 		llseek = default_llseek;
170 	rv = llseek(file, offset, whence);
171 
172 	pde_users_dec(pde);
173 	return rv;
174 }
175 
176 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
177 {
178 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
179 	ssize_t rv = -EIO;
180 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
181 
182 	spin_lock(&pde->pde_unload_lock);
183 	if (!pde->proc_fops) {
184 		spin_unlock(&pde->pde_unload_lock);
185 		return rv;
186 	}
187 	pde->pde_users++;
188 	read = pde->proc_fops->read;
189 	spin_unlock(&pde->pde_unload_lock);
190 
191 	if (read)
192 		rv = read(file, buf, count, ppos);
193 
194 	pde_users_dec(pde);
195 	return rv;
196 }
197 
198 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
199 {
200 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
201 	ssize_t rv = -EIO;
202 	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
203 
204 	spin_lock(&pde->pde_unload_lock);
205 	if (!pde->proc_fops) {
206 		spin_unlock(&pde->pde_unload_lock);
207 		return rv;
208 	}
209 	pde->pde_users++;
210 	write = pde->proc_fops->write;
211 	spin_unlock(&pde->pde_unload_lock);
212 
213 	if (write)
214 		rv = write(file, buf, count, ppos);
215 
216 	pde_users_dec(pde);
217 	return rv;
218 }
219 
220 static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
221 {
222 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
223 	unsigned int rv = DEFAULT_POLLMASK;
224 	unsigned int (*poll)(struct file *, struct poll_table_struct *);
225 
226 	spin_lock(&pde->pde_unload_lock);
227 	if (!pde->proc_fops) {
228 		spin_unlock(&pde->pde_unload_lock);
229 		return rv;
230 	}
231 	pde->pde_users++;
232 	poll = pde->proc_fops->poll;
233 	spin_unlock(&pde->pde_unload_lock);
234 
235 	if (poll)
236 		rv = poll(file, pts);
237 
238 	pde_users_dec(pde);
239 	return rv;
240 }
241 
242 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
243 {
244 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
245 	long rv = -ENOTTY;
246 	long (*unlocked_ioctl)(struct file *, unsigned int, unsigned long);
247 	int (*ioctl)(struct inode *, struct file *, unsigned int, unsigned long);
248 
249 	spin_lock(&pde->pde_unload_lock);
250 	if (!pde->proc_fops) {
251 		spin_unlock(&pde->pde_unload_lock);
252 		return rv;
253 	}
254 	pde->pde_users++;
255 	unlocked_ioctl = pde->proc_fops->unlocked_ioctl;
256 	ioctl = pde->proc_fops->ioctl;
257 	spin_unlock(&pde->pde_unload_lock);
258 
259 	if (unlocked_ioctl) {
260 		rv = unlocked_ioctl(file, cmd, arg);
261 		if (rv == -ENOIOCTLCMD)
262 			rv = -EINVAL;
263 	} else if (ioctl) {
264 		lock_kernel();
265 		rv = ioctl(file->f_path.dentry->d_inode, file, cmd, arg);
266 		unlock_kernel();
267 	}
268 
269 	pde_users_dec(pde);
270 	return rv;
271 }
272 
273 #ifdef CONFIG_COMPAT
274 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
275 {
276 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
277 	long rv = -ENOTTY;
278 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
279 
280 	spin_lock(&pde->pde_unload_lock);
281 	if (!pde->proc_fops) {
282 		spin_unlock(&pde->pde_unload_lock);
283 		return rv;
284 	}
285 	pde->pde_users++;
286 	compat_ioctl = pde->proc_fops->compat_ioctl;
287 	spin_unlock(&pde->pde_unload_lock);
288 
289 	if (compat_ioctl)
290 		rv = compat_ioctl(file, cmd, arg);
291 
292 	pde_users_dec(pde);
293 	return rv;
294 }
295 #endif
296 
297 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
298 {
299 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
300 	int rv = -EIO;
301 	int (*mmap)(struct file *, struct vm_area_struct *);
302 
303 	spin_lock(&pde->pde_unload_lock);
304 	if (!pde->proc_fops) {
305 		spin_unlock(&pde->pde_unload_lock);
306 		return rv;
307 	}
308 	pde->pde_users++;
309 	mmap = pde->proc_fops->mmap;
310 	spin_unlock(&pde->pde_unload_lock);
311 
312 	if (mmap)
313 		rv = mmap(file, vma);
314 
315 	pde_users_dec(pde);
316 	return rv;
317 }
318 
319 static int proc_reg_open(struct inode *inode, struct file *file)
320 {
321 	struct proc_dir_entry *pde = PDE(inode);
322 	int rv = 0;
323 	int (*open)(struct inode *, struct file *);
324 	int (*release)(struct inode *, struct file *);
325 	struct pde_opener *pdeo;
326 
327 	/*
328 	 * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
329 	 * sequence. ->release won't be called because ->proc_fops will be
330 	 * cleared. Depending on complexity of ->release, consequences vary.
331 	 *
332 	 * We can't wait for mercy when close will be done for real, it's
333 	 * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
334 	 * by hand in remove_proc_entry(). For this, save opener's credentials
335 	 * for later.
336 	 */
337 	pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
338 	if (!pdeo)
339 		return -ENOMEM;
340 
341 	spin_lock(&pde->pde_unload_lock);
342 	if (!pde->proc_fops) {
343 		spin_unlock(&pde->pde_unload_lock);
344 		kfree(pdeo);
345 		return rv;
346 	}
347 	pde->pde_users++;
348 	open = pde->proc_fops->open;
349 	release = pde->proc_fops->release;
350 	spin_unlock(&pde->pde_unload_lock);
351 
352 	if (open)
353 		rv = open(inode, file);
354 
355 	spin_lock(&pde->pde_unload_lock);
356 	if (rv == 0 && release) {
357 		/* To know what to release. */
358 		pdeo->inode = inode;
359 		pdeo->file = file;
360 		/* Strictly for "too late" ->release in proc_reg_release(). */
361 		pdeo->release = release;
362 		list_add(&pdeo->lh, &pde->pde_openers);
363 	} else
364 		kfree(pdeo);
365 	__pde_users_dec(pde);
366 	spin_unlock(&pde->pde_unload_lock);
367 	return rv;
368 }
369 
370 static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
371 					struct inode *inode, struct file *file)
372 {
373 	struct pde_opener *pdeo;
374 
375 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
376 		if (pdeo->inode == inode && pdeo->file == file)
377 			return pdeo;
378 	}
379 	return NULL;
380 }
381 
382 static int proc_reg_release(struct inode *inode, struct file *file)
383 {
384 	struct proc_dir_entry *pde = PDE(inode);
385 	int rv = 0;
386 	int (*release)(struct inode *, struct file *);
387 	struct pde_opener *pdeo;
388 
389 	spin_lock(&pde->pde_unload_lock);
390 	pdeo = find_pde_opener(pde, inode, file);
391 	if (!pde->proc_fops) {
392 		/*
393 		 * Can't simply exit, __fput() will think that everything is OK,
394 		 * and move on to freeing struct file. remove_proc_entry() will
395 		 * find slacker in opener's list and will try to do non-trivial
396 		 * things with struct file. Therefore, remove opener from list.
397 		 *
398 		 * But if opener is removed from list, who will ->release it?
399 		 */
400 		if (pdeo) {
401 			list_del(&pdeo->lh);
402 			spin_unlock(&pde->pde_unload_lock);
403 			rv = pdeo->release(inode, file);
404 			kfree(pdeo);
405 		} else
406 			spin_unlock(&pde->pde_unload_lock);
407 		return rv;
408 	}
409 	pde->pde_users++;
410 	release = pde->proc_fops->release;
411 	if (pdeo) {
412 		list_del(&pdeo->lh);
413 		kfree(pdeo);
414 	}
415 	spin_unlock(&pde->pde_unload_lock);
416 
417 	if (release)
418 		rv = release(inode, file);
419 
420 	pde_users_dec(pde);
421 	return rv;
422 }
423 
424 static const struct file_operations proc_reg_file_ops = {
425 	.llseek		= proc_reg_llseek,
426 	.read		= proc_reg_read,
427 	.write		= proc_reg_write,
428 	.poll		= proc_reg_poll,
429 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
430 #ifdef CONFIG_COMPAT
431 	.compat_ioctl	= proc_reg_compat_ioctl,
432 #endif
433 	.mmap		= proc_reg_mmap,
434 	.open		= proc_reg_open,
435 	.release	= proc_reg_release,
436 };
437 
438 #ifdef CONFIG_COMPAT
439 static const struct file_operations proc_reg_file_ops_no_compat = {
440 	.llseek		= proc_reg_llseek,
441 	.read		= proc_reg_read,
442 	.write		= proc_reg_write,
443 	.poll		= proc_reg_poll,
444 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
445 	.mmap		= proc_reg_mmap,
446 	.open		= proc_reg_open,
447 	.release	= proc_reg_release,
448 };
449 #endif
450 
451 struct inode *proc_get_inode(struct super_block *sb, unsigned int ino,
452 				struct proc_dir_entry *de)
453 {
454 	struct inode * inode;
455 
456 	if (!try_module_get(de->owner))
457 		goto out_mod;
458 
459 	inode = iget_locked(sb, ino);
460 	if (!inode)
461 		goto out_ino;
462 	if (inode->i_state & I_NEW) {
463 		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
464 		PROC_I(inode)->fd = 0;
465 		PROC_I(inode)->pde = de;
466 
467 		if (de->mode) {
468 			inode->i_mode = de->mode;
469 			inode->i_uid = de->uid;
470 			inode->i_gid = de->gid;
471 		}
472 		if (de->size)
473 			inode->i_size = de->size;
474 		if (de->nlink)
475 			inode->i_nlink = de->nlink;
476 		if (de->proc_iops)
477 			inode->i_op = de->proc_iops;
478 		if (de->proc_fops) {
479 			if (S_ISREG(inode->i_mode)) {
480 #ifdef CONFIG_COMPAT
481 				if (!de->proc_fops->compat_ioctl)
482 					inode->i_fop =
483 						&proc_reg_file_ops_no_compat;
484 				else
485 #endif
486 					inode->i_fop = &proc_reg_file_ops;
487 			} else {
488 				inode->i_fop = de->proc_fops;
489 			}
490 		}
491 		unlock_new_inode(inode);
492 	} else
493 	       module_put(de->owner);
494 	return inode;
495 
496 out_ino:
497 	module_put(de->owner);
498 out_mod:
499 	return NULL;
500 }
501 
502 int proc_fill_super(struct super_block *s)
503 {
504 	struct inode * root_inode;
505 
506 	s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
507 	s->s_blocksize = 1024;
508 	s->s_blocksize_bits = 10;
509 	s->s_magic = PROC_SUPER_MAGIC;
510 	s->s_op = &proc_sops;
511 	s->s_time_gran = 1;
512 
513 	de_get(&proc_root);
514 	root_inode = proc_get_inode(s, PROC_ROOT_INO, &proc_root);
515 	if (!root_inode)
516 		goto out_no_root;
517 	root_inode->i_uid = 0;
518 	root_inode->i_gid = 0;
519 	s->s_root = d_alloc_root(root_inode);
520 	if (!s->s_root)
521 		goto out_no_root;
522 	return 0;
523 
524 out_no_root:
525 	printk("proc_read_super: get root inode failed\n");
526 	iput(root_inode);
527 	de_put(&proc_root);
528 	return -ENOMEM;
529 }
530