xref: /openbmc/linux/fs/proc/inode.c (revision 9cdb81c7) 
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/system.h>
26 #include <asm/uaccess.h>
27 
28 #include "internal.h"
29 
30 static void proc_evict_inode(struct inode *inode)
31 {
32 	struct proc_dir_entry *de;
33 	struct ctl_table_header *head;
34 	const struct proc_ns_operations *ns_ops;
35 
36 	truncate_inode_pages(&inode->i_data, 0);
37 	end_writeback(inode);
38 
39 	/* Stop tracking associated processes */
40 	put_pid(PROC_I(inode)->pid);
41 
42 	/* Let go of any associated proc directory entry */
43 	de = PROC_I(inode)->pde;
44 	if (de)
45 		pde_put(de);
46 	head = PROC_I(inode)->sysctl;
47 	if (head) {
48 		rcu_assign_pointer(PROC_I(inode)->sysctl, NULL);
49 		sysctl_head_put(head);
50 	}
51 	/* Release any associated namespace */
52 	ns_ops = PROC_I(inode)->ns_ops;
53 	if (ns_ops && ns_ops->put)
54 		ns_ops->put(PROC_I(inode)->ns);
55 }
56 
57 static struct kmem_cache * proc_inode_cachep;
58 
59 static struct inode *proc_alloc_inode(struct super_block *sb)
60 {
61 	struct proc_inode *ei;
62 	struct inode *inode;
63 
64 	ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
65 	if (!ei)
66 		return NULL;
67 	ei->pid = NULL;
68 	ei->fd = 0;
69 	ei->op.proc_get_link = NULL;
70 	ei->pde = NULL;
71 	ei->sysctl = NULL;
72 	ei->sysctl_entry = NULL;
73 	ei->ns = NULL;
74 	ei->ns_ops = NULL;
75 	inode = &ei->vfs_inode;
76 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
77 	return inode;
78 }
79 
80 static void proc_i_callback(struct rcu_head *head)
81 {
82 	struct inode *inode = container_of(head, struct inode, i_rcu);
83 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
84 }
85 
86 static void proc_destroy_inode(struct inode *inode)
87 {
88 	call_rcu(&inode->i_rcu, proc_i_callback);
89 }
90 
91 static void init_once(void *foo)
92 {
93 	struct proc_inode *ei = (struct proc_inode *) foo;
94 
95 	inode_init_once(&ei->vfs_inode);
96 }
97 
98 void __init proc_init_inodecache(void)
99 {
100 	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
101 					     sizeof(struct proc_inode),
102 					     0, (SLAB_RECLAIM_ACCOUNT|
103 						SLAB_MEM_SPREAD|SLAB_PANIC),
104 					     init_once);
105 }
106 
107 static int proc_show_options(struct seq_file *seq, struct dentry *root)
108 {
109 	struct super_block *sb = root->d_sb;
110 	struct pid_namespace *pid = sb->s_fs_info;
111 
112 	if (pid->pid_gid)
113 		seq_printf(seq, ",gid=%lu", (unsigned long)pid->pid_gid);
114 	if (pid->hide_pid != 0)
115 		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
116 
117 	return 0;
118 }
119 
120 static const struct super_operations proc_sops = {
121 	.alloc_inode	= proc_alloc_inode,
122 	.destroy_inode	= proc_destroy_inode,
123 	.drop_inode	= generic_delete_inode,
124 	.evict_inode	= proc_evict_inode,
125 	.statfs		= simple_statfs,
126 	.remount_fs	= proc_remount,
127 	.show_options	= proc_show_options,
128 };
129 
130 static void __pde_users_dec(struct proc_dir_entry *pde)
131 {
132 	pde->pde_users--;
133 	if (pde->pde_unload_completion && pde->pde_users == 0)
134 		complete(pde->pde_unload_completion);
135 }
136 
137 void pde_users_dec(struct proc_dir_entry *pde)
138 {
139 	spin_lock(&pde->pde_unload_lock);
140 	__pde_users_dec(pde);
141 	spin_unlock(&pde->pde_unload_lock);
142 }
143 
144 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
145 {
146 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
147 	loff_t rv = -EINVAL;
148 	loff_t (*llseek)(struct file *, loff_t, int);
149 
150 	spin_lock(&pde->pde_unload_lock);
151 	/*
152 	 * remove_proc_entry() is going to delete PDE (as part of module
153 	 * cleanup sequence). No new callers into module allowed.
154 	 */
155 	if (!pde->proc_fops) {
156 		spin_unlock(&pde->pde_unload_lock);
157 		return rv;
158 	}
159 	/*
160 	 * Bump refcount so that remove_proc_entry will wail for ->llseek to
161 	 * complete.
162 	 */
163 	pde->pde_users++;
164 	/*
165 	 * Save function pointer under lock, to protect against ->proc_fops
166 	 * NULL'ifying right after ->pde_unload_lock is dropped.
167 	 */
168 	llseek = pde->proc_fops->llseek;
169 	spin_unlock(&pde->pde_unload_lock);
170 
171 	if (!llseek)
172 		llseek = default_llseek;
173 	rv = llseek(file, offset, whence);
174 
175 	pde_users_dec(pde);
176 	return rv;
177 }
178 
179 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
180 {
181 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
182 	ssize_t rv = -EIO;
183 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
184 
185 	spin_lock(&pde->pde_unload_lock);
186 	if (!pde->proc_fops) {
187 		spin_unlock(&pde->pde_unload_lock);
188 		return rv;
189 	}
190 	pde->pde_users++;
191 	read = pde->proc_fops->read;
192 	spin_unlock(&pde->pde_unload_lock);
193 
194 	if (read)
195 		rv = read(file, buf, count, ppos);
196 
197 	pde_users_dec(pde);
198 	return rv;
199 }
200 
201 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
202 {
203 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
204 	ssize_t rv = -EIO;
205 	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
206 
207 	spin_lock(&pde->pde_unload_lock);
208 	if (!pde->proc_fops) {
209 		spin_unlock(&pde->pde_unload_lock);
210 		return rv;
211 	}
212 	pde->pde_users++;
213 	write = pde->proc_fops->write;
214 	spin_unlock(&pde->pde_unload_lock);
215 
216 	if (write)
217 		rv = write(file, buf, count, ppos);
218 
219 	pde_users_dec(pde);
220 	return rv;
221 }
222 
223 static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
224 {
225 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
226 	unsigned int rv = DEFAULT_POLLMASK;
227 	unsigned int (*poll)(struct file *, struct poll_table_struct *);
228 
229 	spin_lock(&pde->pde_unload_lock);
230 	if (!pde->proc_fops) {
231 		spin_unlock(&pde->pde_unload_lock);
232 		return rv;
233 	}
234 	pde->pde_users++;
235 	poll = pde->proc_fops->poll;
236 	spin_unlock(&pde->pde_unload_lock);
237 
238 	if (poll)
239 		rv = poll(file, pts);
240 
241 	pde_users_dec(pde);
242 	return rv;
243 }
244 
245 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
246 {
247 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
248 	long rv = -ENOTTY;
249 	long (*ioctl)(struct file *, unsigned int, unsigned long);
250 
251 	spin_lock(&pde->pde_unload_lock);
252 	if (!pde->proc_fops) {
253 		spin_unlock(&pde->pde_unload_lock);
254 		return rv;
255 	}
256 	pde->pde_users++;
257 	ioctl = pde->proc_fops->unlocked_ioctl;
258 	spin_unlock(&pde->pde_unload_lock);
259 
260 	if (ioctl)
261 		rv = ioctl(file, cmd, arg);
262 
263 	pde_users_dec(pde);
264 	return rv;
265 }
266 
267 #ifdef CONFIG_COMPAT
268 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
269 {
270 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
271 	long rv = -ENOTTY;
272 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
273 
274 	spin_lock(&pde->pde_unload_lock);
275 	if (!pde->proc_fops) {
276 		spin_unlock(&pde->pde_unload_lock);
277 		return rv;
278 	}
279 	pde->pde_users++;
280 	compat_ioctl = pde->proc_fops->compat_ioctl;
281 	spin_unlock(&pde->pde_unload_lock);
282 
283 	if (compat_ioctl)
284 		rv = compat_ioctl(file, cmd, arg);
285 
286 	pde_users_dec(pde);
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->f_path.dentry->d_inode);
294 	int rv = -EIO;
295 	int (*mmap)(struct file *, struct vm_area_struct *);
296 
297 	spin_lock(&pde->pde_unload_lock);
298 	if (!pde->proc_fops) {
299 		spin_unlock(&pde->pde_unload_lock);
300 		return rv;
301 	}
302 	pde->pde_users++;
303 	mmap = pde->proc_fops->mmap;
304 	spin_unlock(&pde->pde_unload_lock);
305 
306 	if (mmap)
307 		rv = mmap(file, vma);
308 
309 	pde_users_dec(pde);
310 	return rv;
311 }
312 
313 static int proc_reg_open(struct inode *inode, struct file *file)
314 {
315 	struct proc_dir_entry *pde = PDE(inode);
316 	int rv = 0;
317 	int (*open)(struct inode *, struct file *);
318 	int (*release)(struct inode *, struct file *);
319 	struct pde_opener *pdeo;
320 
321 	/*
322 	 * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
323 	 * sequence. ->release won't be called because ->proc_fops will be
324 	 * cleared. Depending on complexity of ->release, consequences vary.
325 	 *
326 	 * We can't wait for mercy when close will be done for real, it's
327 	 * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
328 	 * by hand in remove_proc_entry(). For this, save opener's credentials
329 	 * for later.
330 	 */
331 	pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
332 	if (!pdeo)
333 		return -ENOMEM;
334 
335 	spin_lock(&pde->pde_unload_lock);
336 	if (!pde->proc_fops) {
337 		spin_unlock(&pde->pde_unload_lock);
338 		kfree(pdeo);
339 		return -ENOENT;
340 	}
341 	pde->pde_users++;
342 	open = pde->proc_fops->open;
343 	release = pde->proc_fops->release;
344 	spin_unlock(&pde->pde_unload_lock);
345 
346 	if (open)
347 		rv = open(inode, file);
348 
349 	spin_lock(&pde->pde_unload_lock);
350 	if (rv == 0 && release) {
351 		/* To know what to release. */
352 		pdeo->inode = inode;
353 		pdeo->file = file;
354 		/* Strictly for "too late" ->release in proc_reg_release(). */
355 		pdeo->release = release;
356 		list_add(&pdeo->lh, &pde->pde_openers);
357 	} else
358 		kfree(pdeo);
359 	__pde_users_dec(pde);
360 	spin_unlock(&pde->pde_unload_lock);
361 	return rv;
362 }
363 
364 static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
365 					struct inode *inode, struct file *file)
366 {
367 	struct pde_opener *pdeo;
368 
369 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
370 		if (pdeo->inode == inode && pdeo->file == file)
371 			return pdeo;
372 	}
373 	return NULL;
374 }
375 
376 static int proc_reg_release(struct inode *inode, struct file *file)
377 {
378 	struct proc_dir_entry *pde = PDE(inode);
379 	int rv = 0;
380 	int (*release)(struct inode *, struct file *);
381 	struct pde_opener *pdeo;
382 
383 	spin_lock(&pde->pde_unload_lock);
384 	pdeo = find_pde_opener(pde, inode, file);
385 	if (!pde->proc_fops) {
386 		/*
387 		 * Can't simply exit, __fput() will think that everything is OK,
388 		 * and move on to freeing struct file. remove_proc_entry() will
389 		 * find slacker in opener's list and will try to do non-trivial
390 		 * things with struct file. Therefore, remove opener from list.
391 		 *
392 		 * But if opener is removed from list, who will ->release it?
393 		 */
394 		if (pdeo) {
395 			list_del(&pdeo->lh);
396 			spin_unlock(&pde->pde_unload_lock);
397 			rv = pdeo->release(inode, file);
398 			kfree(pdeo);
399 		} else
400 			spin_unlock(&pde->pde_unload_lock);
401 		return rv;
402 	}
403 	pde->pde_users++;
404 	release = pde->proc_fops->release;
405 	if (pdeo) {
406 		list_del(&pdeo->lh);
407 		kfree(pdeo);
408 	}
409 	spin_unlock(&pde->pde_unload_lock);
410 
411 	if (release)
412 		rv = release(inode, file);
413 
414 	pde_users_dec(pde);
415 	return rv;
416 }
417 
418 static const struct file_operations proc_reg_file_ops = {
419 	.llseek		= proc_reg_llseek,
420 	.read		= proc_reg_read,
421 	.write		= proc_reg_write,
422 	.poll		= proc_reg_poll,
423 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
424 #ifdef CONFIG_COMPAT
425 	.compat_ioctl	= proc_reg_compat_ioctl,
426 #endif
427 	.mmap		= proc_reg_mmap,
428 	.open		= proc_reg_open,
429 	.release	= proc_reg_release,
430 };
431 
432 #ifdef CONFIG_COMPAT
433 static const struct file_operations proc_reg_file_ops_no_compat = {
434 	.llseek		= proc_reg_llseek,
435 	.read		= proc_reg_read,
436 	.write		= proc_reg_write,
437 	.poll		= proc_reg_poll,
438 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
439 	.mmap		= proc_reg_mmap,
440 	.open		= proc_reg_open,
441 	.release	= proc_reg_release,
442 };
443 #endif
444 
445 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
446 {
447 	struct inode * inode;
448 
449 	inode = iget_locked(sb, de->low_ino);
450 	if (!inode)
451 		return NULL;
452 	if (inode->i_state & I_NEW) {
453 		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
454 		PROC_I(inode)->fd = 0;
455 		PROC_I(inode)->pde = de;
456 
457 		if (de->mode) {
458 			inode->i_mode = de->mode;
459 			inode->i_uid = de->uid;
460 			inode->i_gid = de->gid;
461 		}
462 		if (de->size)
463 			inode->i_size = de->size;
464 		if (de->nlink)
465 			set_nlink(inode, de->nlink);
466 		if (de->proc_iops)
467 			inode->i_op = de->proc_iops;
468 		if (de->proc_fops) {
469 			if (S_ISREG(inode->i_mode)) {
470 #ifdef CONFIG_COMPAT
471 				if (!de->proc_fops->compat_ioctl)
472 					inode->i_fop =
473 						&proc_reg_file_ops_no_compat;
474 				else
475 #endif
476 					inode->i_fop = &proc_reg_file_ops;
477 			} else {
478 				inode->i_fop = de->proc_fops;
479 			}
480 		}
481 		unlock_new_inode(inode);
482 	} else
483 	       pde_put(de);
484 	return inode;
485 }
486 
487 int proc_fill_super(struct super_block *s)
488 {
489 	s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
490 	s->s_blocksize = 1024;
491 	s->s_blocksize_bits = 10;
492 	s->s_magic = PROC_SUPER_MAGIC;
493 	s->s_op = &proc_sops;
494 	s->s_time_gran = 1;
495 
496 	pde_get(&proc_root);
497 	s->s_root = d_make_root(proc_get_inode(s, &proc_root));
498 	if (s->s_root)
499 		return 0;
500 
501 	printk("proc_read_super: get root inode failed\n");
502 	pde_put(&proc_root);
503 	return -ENOMEM;
504 }
505