xref: /openbmc/linux/fs/proc/inode.c (revision 861e10be) 
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 	void *ns;
35 
36 	truncate_inode_pages(&inode->i_data, 0);
37 	clear_inode(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 	ns = PROC_I(inode)->ns;
54 	if (ns_ops && ns)
55 		ns_ops->put(ns);
56 }
57 
58 static struct kmem_cache * proc_inode_cachep;
59 
60 static struct inode *proc_alloc_inode(struct super_block *sb)
61 {
62 	struct proc_inode *ei;
63 	struct inode *inode;
64 
65 	ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
66 	if (!ei)
67 		return NULL;
68 	ei->pid = NULL;
69 	ei->fd = 0;
70 	ei->op.proc_get_link = NULL;
71 	ei->pde = NULL;
72 	ei->sysctl = NULL;
73 	ei->sysctl_entry = NULL;
74 	ei->ns = NULL;
75 	ei->ns_ops = NULL;
76 	inode = &ei->vfs_inode;
77 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
78 	return inode;
79 }
80 
81 static void proc_i_callback(struct rcu_head *head)
82 {
83 	struct inode *inode = container_of(head, struct inode, i_rcu);
84 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
85 }
86 
87 static void proc_destroy_inode(struct inode *inode)
88 {
89 	call_rcu(&inode->i_rcu, proc_i_callback);
90 }
91 
92 static void init_once(void *foo)
93 {
94 	struct proc_inode *ei = (struct proc_inode *) foo;
95 
96 	inode_init_once(&ei->vfs_inode);
97 }
98 
99 void __init proc_init_inodecache(void)
100 {
101 	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
102 					     sizeof(struct proc_inode),
103 					     0, (SLAB_RECLAIM_ACCOUNT|
104 						SLAB_MEM_SPREAD|SLAB_PANIC),
105 					     init_once);
106 }
107 
108 static int proc_show_options(struct seq_file *seq, struct dentry *root)
109 {
110 	struct super_block *sb = root->d_sb;
111 	struct pid_namespace *pid = sb->s_fs_info;
112 
113 	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
114 		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
115 	if (pid->hide_pid != 0)
116 		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
117 
118 	return 0;
119 }
120 
121 static const struct super_operations proc_sops = {
122 	.alloc_inode	= proc_alloc_inode,
123 	.destroy_inode	= proc_destroy_inode,
124 	.drop_inode	= generic_delete_inode,
125 	.evict_inode	= proc_evict_inode,
126 	.statfs		= simple_statfs,
127 	.remount_fs	= proc_remount,
128 	.show_options	= proc_show_options,
129 };
130 
131 static void __pde_users_dec(struct proc_dir_entry *pde)
132 {
133 	pde->pde_users--;
134 	if (pde->pde_unload_completion && pde->pde_users == 0)
135 		complete(pde->pde_unload_completion);
136 }
137 
138 void pde_users_dec(struct proc_dir_entry *pde)
139 {
140 	spin_lock(&pde->pde_unload_lock);
141 	__pde_users_dec(pde);
142 	spin_unlock(&pde->pde_unload_lock);
143 }
144 
145 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
146 {
147 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
148 	loff_t rv = -EINVAL;
149 	loff_t (*llseek)(struct file *, loff_t, int);
150 
151 	spin_lock(&pde->pde_unload_lock);
152 	/*
153 	 * remove_proc_entry() is going to delete PDE (as part of module
154 	 * cleanup sequence). No new callers into module allowed.
155 	 */
156 	if (!pde->proc_fops) {
157 		spin_unlock(&pde->pde_unload_lock);
158 		return rv;
159 	}
160 	/*
161 	 * Bump refcount so that remove_proc_entry will wail for ->llseek to
162 	 * complete.
163 	 */
164 	pde->pde_users++;
165 	/*
166 	 * Save function pointer under lock, to protect against ->proc_fops
167 	 * NULL'ifying right after ->pde_unload_lock is dropped.
168 	 */
169 	llseek = pde->proc_fops->llseek;
170 	spin_unlock(&pde->pde_unload_lock);
171 
172 	if (!llseek)
173 		llseek = default_llseek;
174 	rv = llseek(file, offset, whence);
175 
176 	pde_users_dec(pde);
177 	return rv;
178 }
179 
180 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
181 {
182 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
183 	ssize_t rv = -EIO;
184 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
185 
186 	spin_lock(&pde->pde_unload_lock);
187 	if (!pde->proc_fops) {
188 		spin_unlock(&pde->pde_unload_lock);
189 		return rv;
190 	}
191 	pde->pde_users++;
192 	read = pde->proc_fops->read;
193 	spin_unlock(&pde->pde_unload_lock);
194 
195 	if (read)
196 		rv = read(file, buf, count, ppos);
197 
198 	pde_users_dec(pde);
199 	return rv;
200 }
201 
202 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
203 {
204 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
205 	ssize_t rv = -EIO;
206 	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
207 
208 	spin_lock(&pde->pde_unload_lock);
209 	if (!pde->proc_fops) {
210 		spin_unlock(&pde->pde_unload_lock);
211 		return rv;
212 	}
213 	pde->pde_users++;
214 	write = pde->proc_fops->write;
215 	spin_unlock(&pde->pde_unload_lock);
216 
217 	if (write)
218 		rv = write(file, buf, count, ppos);
219 
220 	pde_users_dec(pde);
221 	return rv;
222 }
223 
224 static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
225 {
226 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
227 	unsigned int rv = DEFAULT_POLLMASK;
228 	unsigned int (*poll)(struct file *, struct poll_table_struct *);
229 
230 	spin_lock(&pde->pde_unload_lock);
231 	if (!pde->proc_fops) {
232 		spin_unlock(&pde->pde_unload_lock);
233 		return rv;
234 	}
235 	pde->pde_users++;
236 	poll = pde->proc_fops->poll;
237 	spin_unlock(&pde->pde_unload_lock);
238 
239 	if (poll)
240 		rv = poll(file, pts);
241 
242 	pde_users_dec(pde);
243 	return rv;
244 }
245 
246 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
247 {
248 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
249 	long rv = -ENOTTY;
250 	long (*ioctl)(struct file *, unsigned int, unsigned long);
251 
252 	spin_lock(&pde->pde_unload_lock);
253 	if (!pde->proc_fops) {
254 		spin_unlock(&pde->pde_unload_lock);
255 		return rv;
256 	}
257 	pde->pde_users++;
258 	ioctl = pde->proc_fops->unlocked_ioctl;
259 	spin_unlock(&pde->pde_unload_lock);
260 
261 	if (ioctl)
262 		rv = ioctl(file, cmd, arg);
263 
264 	pde_users_dec(pde);
265 	return rv;
266 }
267 
268 #ifdef CONFIG_COMPAT
269 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
270 {
271 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
272 	long rv = -ENOTTY;
273 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
274 
275 	spin_lock(&pde->pde_unload_lock);
276 	if (!pde->proc_fops) {
277 		spin_unlock(&pde->pde_unload_lock);
278 		return rv;
279 	}
280 	pde->pde_users++;
281 	compat_ioctl = pde->proc_fops->compat_ioctl;
282 	spin_unlock(&pde->pde_unload_lock);
283 
284 	if (compat_ioctl)
285 		rv = compat_ioctl(file, cmd, arg);
286 
287 	pde_users_dec(pde);
288 	return rv;
289 }
290 #endif
291 
292 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
293 {
294 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
295 	int rv = -EIO;
296 	int (*mmap)(struct file *, struct vm_area_struct *);
297 
298 	spin_lock(&pde->pde_unload_lock);
299 	if (!pde->proc_fops) {
300 		spin_unlock(&pde->pde_unload_lock);
301 		return rv;
302 	}
303 	pde->pde_users++;
304 	mmap = pde->proc_fops->mmap;
305 	spin_unlock(&pde->pde_unload_lock);
306 
307 	if (mmap)
308 		rv = mmap(file, vma);
309 
310 	pde_users_dec(pde);
311 	return rv;
312 }
313 
314 static int proc_reg_open(struct inode *inode, struct file *file)
315 {
316 	struct proc_dir_entry *pde = PDE(inode);
317 	int rv = 0;
318 	int (*open)(struct inode *, struct file *);
319 	int (*release)(struct inode *, struct file *);
320 	struct pde_opener *pdeo;
321 
322 	/*
323 	 * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
324 	 * sequence. ->release won't be called because ->proc_fops will be
325 	 * cleared. Depending on complexity of ->release, consequences vary.
326 	 *
327 	 * We can't wait for mercy when close will be done for real, it's
328 	 * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
329 	 * by hand in remove_proc_entry(). For this, save opener's credentials
330 	 * for later.
331 	 */
332 	pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
333 	if (!pdeo)
334 		return -ENOMEM;
335 
336 	spin_lock(&pde->pde_unload_lock);
337 	if (!pde->proc_fops) {
338 		spin_unlock(&pde->pde_unload_lock);
339 		kfree(pdeo);
340 		return -ENOENT;
341 	}
342 	pde->pde_users++;
343 	open = pde->proc_fops->open;
344 	release = pde->proc_fops->release;
345 	spin_unlock(&pde->pde_unload_lock);
346 
347 	if (open)
348 		rv = open(inode, file);
349 
350 	spin_lock(&pde->pde_unload_lock);
351 	if (rv == 0 && release) {
352 		/* To know what to release. */
353 		pdeo->inode = inode;
354 		pdeo->file = file;
355 		/* Strictly for "too late" ->release in proc_reg_release(). */
356 		pdeo->release = release;
357 		list_add(&pdeo->lh, &pde->pde_openers);
358 	} else
359 		kfree(pdeo);
360 	__pde_users_dec(pde);
361 	spin_unlock(&pde->pde_unload_lock);
362 	return rv;
363 }
364 
365 static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
366 					struct inode *inode, struct file *file)
367 {
368 	struct pde_opener *pdeo;
369 
370 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
371 		if (pdeo->inode == inode && pdeo->file == file)
372 			return pdeo;
373 	}
374 	return NULL;
375 }
376 
377 static int proc_reg_release(struct inode *inode, struct file *file)
378 {
379 	struct proc_dir_entry *pde = PDE(inode);
380 	int rv = 0;
381 	int (*release)(struct inode *, struct file *);
382 	struct pde_opener *pdeo;
383 
384 	spin_lock(&pde->pde_unload_lock);
385 	pdeo = find_pde_opener(pde, inode, file);
386 	if (!pde->proc_fops) {
387 		/*
388 		 * Can't simply exit, __fput() will think that everything is OK,
389 		 * and move on to freeing struct file. remove_proc_entry() will
390 		 * find slacker in opener's list and will try to do non-trivial
391 		 * things with struct file. Therefore, remove opener from list.
392 		 *
393 		 * But if opener is removed from list, who will ->release it?
394 		 */
395 		if (pdeo) {
396 			list_del(&pdeo->lh);
397 			spin_unlock(&pde->pde_unload_lock);
398 			rv = pdeo->release(inode, file);
399 			kfree(pdeo);
400 		} else
401 			spin_unlock(&pde->pde_unload_lock);
402 		return rv;
403 	}
404 	pde->pde_users++;
405 	release = pde->proc_fops->release;
406 	if (pdeo) {
407 		list_del(&pdeo->lh);
408 		kfree(pdeo);
409 	}
410 	spin_unlock(&pde->pde_unload_lock);
411 
412 	if (release)
413 		rv = release(inode, file);
414 
415 	pde_users_dec(pde);
416 	return rv;
417 }
418 
419 static const struct file_operations proc_reg_file_ops = {
420 	.llseek		= proc_reg_llseek,
421 	.read		= proc_reg_read,
422 	.write		= proc_reg_write,
423 	.poll		= proc_reg_poll,
424 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
425 #ifdef CONFIG_COMPAT
426 	.compat_ioctl	= proc_reg_compat_ioctl,
427 #endif
428 	.mmap		= proc_reg_mmap,
429 	.open		= proc_reg_open,
430 	.release	= proc_reg_release,
431 };
432 
433 #ifdef CONFIG_COMPAT
434 static const struct file_operations proc_reg_file_ops_no_compat = {
435 	.llseek		= proc_reg_llseek,
436 	.read		= proc_reg_read,
437 	.write		= proc_reg_write,
438 	.poll		= proc_reg_poll,
439 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
440 	.mmap		= proc_reg_mmap,
441 	.open		= proc_reg_open,
442 	.release	= proc_reg_release,
443 };
444 #endif
445 
446 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
447 {
448 	struct inode * inode;
449 
450 	inode = iget_locked(sb, de->low_ino);
451 	if (!inode)
452 		return NULL;
453 	if (inode->i_state & I_NEW) {
454 		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
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