xref: /linux/fs/proc/inode.c (revision 2ba9268dd603d23e17643437b2246acb6844953b) 
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/printk.h>
17 #include <linux/file.h>
18 #include <linux/limits.h>
19 #include <linux/init.h>
20 #include <linux/module.h>
21 #include <linux/sysctl.h>
22 #include <linux/seq_file.h>
23 #include <linux/slab.h>
24 #include <linux/mount.h>
25 #include <linux/magic.h>
26 #include <linux/namei.h>
27 
28 #include <asm/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 	head = PROC_I(inode)->sysctl;
48 	if (head) {
49 		RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);
50 		sysctl_head_put(head);
51 	}
52 }
53 
54 static struct kmem_cache * proc_inode_cachep;
55 
56 static struct inode *proc_alloc_inode(struct super_block *sb)
57 {
58 	struct proc_inode *ei;
59 	struct inode *inode;
60 
61 	ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
62 	if (!ei)
63 		return NULL;
64 	ei->pid = NULL;
65 	ei->fd = 0;
66 	ei->op.proc_get_link = NULL;
67 	ei->pde = NULL;
68 	ei->sysctl = NULL;
69 	ei->sysctl_entry = NULL;
70 	ei->ns_ops = NULL;
71 	inode = &ei->vfs_inode;
72 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
73 	return inode;
74 }
75 
76 static void proc_i_callback(struct rcu_head *head)
77 {
78 	struct inode *inode = container_of(head, struct inode, i_rcu);
79 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
80 }
81 
82 static void proc_destroy_inode(struct inode *inode)
83 {
84 	call_rcu(&inode->i_rcu, proc_i_callback);
85 }
86 
87 static void init_once(void *foo)
88 {
89 	struct proc_inode *ei = (struct proc_inode *) foo;
90 
91 	inode_init_once(&ei->vfs_inode);
92 }
93 
94 void __init proc_init_inodecache(void)
95 {
96 	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
97 					     sizeof(struct proc_inode),
98 					     0, (SLAB_RECLAIM_ACCOUNT|
99 						SLAB_MEM_SPREAD|SLAB_PANIC),
100 					     init_once);
101 }
102 
103 static int proc_show_options(struct seq_file *seq, struct dentry *root)
104 {
105 	struct super_block *sb = root->d_sb;
106 	struct pid_namespace *pid = sb->s_fs_info;
107 
108 	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
109 		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
110 	if (pid->hide_pid != 0)
111 		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
112 
113 	return 0;
114 }
115 
116 static const struct super_operations proc_sops = {
117 	.alloc_inode	= proc_alloc_inode,
118 	.destroy_inode	= proc_destroy_inode,
119 	.drop_inode	= generic_delete_inode,
120 	.evict_inode	= proc_evict_inode,
121 	.statfs		= simple_statfs,
122 	.remount_fs	= proc_remount,
123 	.show_options	= proc_show_options,
124 };
125 
126 enum {BIAS = -1U<<31};
127 
128 static inline int use_pde(struct proc_dir_entry *pde)
129 {
130 	return atomic_inc_unless_negative(&pde->in_use);
131 }
132 
133 static void unuse_pde(struct proc_dir_entry *pde)
134 {
135 	if (atomic_dec_return(&pde->in_use) == BIAS)
136 		complete(pde->pde_unload_completion);
137 }
138 
139 /* pde is locked */
140 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
141 {
142 	if (pdeo->closing) {
143 		/* somebody else is doing that, just wait */
144 		DECLARE_COMPLETION_ONSTACK(c);
145 		pdeo->c = &c;
146 		spin_unlock(&pde->pde_unload_lock);
147 		wait_for_completion(&c);
148 		spin_lock(&pde->pde_unload_lock);
149 	} else {
150 		struct file *file;
151 		pdeo->closing = 1;
152 		spin_unlock(&pde->pde_unload_lock);
153 		file = pdeo->file;
154 		pde->proc_fops->release(file_inode(file), file);
155 		spin_lock(&pde->pde_unload_lock);
156 		list_del_init(&pdeo->lh);
157 		if (pdeo->c)
158 			complete(pdeo->c);
159 		kfree(pdeo);
160 	}
161 }
162 
163 void proc_entry_rundown(struct proc_dir_entry *de)
164 {
165 	DECLARE_COMPLETION_ONSTACK(c);
166 	/* Wait until all existing callers into module are done. */
167 	de->pde_unload_completion = &c;
168 	if (atomic_add_return(BIAS, &de->in_use) != BIAS)
169 		wait_for_completion(&c);
170 
171 	spin_lock(&de->pde_unload_lock);
172 	while (!list_empty(&de->pde_openers)) {
173 		struct pde_opener *pdeo;
174 		pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
175 		close_pdeo(de, pdeo);
176 	}
177 	spin_unlock(&de->pde_unload_lock);
178 }
179 
180 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
181 {
182 	struct proc_dir_entry *pde = PDE(file_inode(file));
183 	loff_t rv = -EINVAL;
184 	if (use_pde(pde)) {
185 		loff_t (*llseek)(struct file *, loff_t, int);
186 		llseek = pde->proc_fops->llseek;
187 		if (!llseek)
188 			llseek = default_llseek;
189 		rv = llseek(file, offset, whence);
190 		unuse_pde(pde);
191 	}
192 	return rv;
193 }
194 
195 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
196 {
197 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
198 	struct proc_dir_entry *pde = PDE(file_inode(file));
199 	ssize_t rv = -EIO;
200 	if (use_pde(pde)) {
201 		read = pde->proc_fops->read;
202 		if (read)
203 			rv = read(file, buf, count, ppos);
204 		unuse_pde(pde);
205 	}
206 	return rv;
207 }
208 
209 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
210 {
211 	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
212 	struct proc_dir_entry *pde = PDE(file_inode(file));
213 	ssize_t rv = -EIO;
214 	if (use_pde(pde)) {
215 		write = pde->proc_fops->write;
216 		if (write)
217 			rv = write(file, buf, count, ppos);
218 		unuse_pde(pde);
219 	}
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_inode(file));
226 	unsigned int rv = DEFAULT_POLLMASK;
227 	unsigned int (*poll)(struct file *, struct poll_table_struct *);
228 	if (use_pde(pde)) {
229 		poll = pde->proc_fops->poll;
230 		if (poll)
231 			rv = poll(file, pts);
232 		unuse_pde(pde);
233 	}
234 	return rv;
235 }
236 
237 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
238 {
239 	struct proc_dir_entry *pde = PDE(file_inode(file));
240 	long rv = -ENOTTY;
241 	long (*ioctl)(struct file *, unsigned int, unsigned long);
242 	if (use_pde(pde)) {
243 		ioctl = pde->proc_fops->unlocked_ioctl;
244 		if (ioctl)
245 			rv = ioctl(file, cmd, arg);
246 		unuse_pde(pde);
247 	}
248 	return rv;
249 }
250 
251 #ifdef CONFIG_COMPAT
252 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
253 {
254 	struct proc_dir_entry *pde = PDE(file_inode(file));
255 	long rv = -ENOTTY;
256 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
257 	if (use_pde(pde)) {
258 		compat_ioctl = pde->proc_fops->compat_ioctl;
259 		if (compat_ioctl)
260 			rv = compat_ioctl(file, cmd, arg);
261 		unuse_pde(pde);
262 	}
263 	return rv;
264 }
265 #endif
266 
267 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
268 {
269 	struct proc_dir_entry *pde = PDE(file_inode(file));
270 	int rv = -EIO;
271 	int (*mmap)(struct file *, struct vm_area_struct *);
272 	if (use_pde(pde)) {
273 		mmap = pde->proc_fops->mmap;
274 		if (mmap)
275 			rv = mmap(file, vma);
276 		unuse_pde(pde);
277 	}
278 	return rv;
279 }
280 
281 static unsigned long
282 proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
283 			   unsigned long len, unsigned long pgoff,
284 			   unsigned long flags)
285 {
286 	struct proc_dir_entry *pde = PDE(file_inode(file));
287 	unsigned long rv = -EIO;
288 
289 	if (use_pde(pde)) {
290 		typeof(proc_reg_get_unmapped_area) *get_area;
291 
292 		get_area = pde->proc_fops->get_unmapped_area;
293 #ifdef CONFIG_MMU
294 		if (!get_area)
295 			get_area = current->mm->get_unmapped_area;
296 #endif
297 
298 		if (get_area)
299 			rv = get_area(file, orig_addr, len, pgoff, flags);
300 		else
301 			rv = orig_addr;
302 		unuse_pde(pde);
303 	}
304 	return rv;
305 }
306 
307 static int proc_reg_open(struct inode *inode, struct file *file)
308 {
309 	struct proc_dir_entry *pde = PDE(inode);
310 	int rv = 0;
311 	int (*open)(struct inode *, struct file *);
312 	int (*release)(struct inode *, struct file *);
313 	struct pde_opener *pdeo;
314 
315 	/*
316 	 * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
317 	 * sequence. ->release won't be called because ->proc_fops will be
318 	 * cleared. Depending on complexity of ->release, consequences vary.
319 	 *
320 	 * We can't wait for mercy when close will be done for real, it's
321 	 * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
322 	 * by hand in remove_proc_entry(). For this, save opener's credentials
323 	 * for later.
324 	 */
325 	pdeo = kzalloc(sizeof(struct pde_opener), GFP_KERNEL);
326 	if (!pdeo)
327 		return -ENOMEM;
328 
329 	if (!use_pde(pde)) {
330 		kfree(pdeo);
331 		return -ENOENT;
332 	}
333 	open = pde->proc_fops->open;
334 	release = pde->proc_fops->release;
335 
336 	if (open)
337 		rv = open(inode, file);
338 
339 	if (rv == 0 && release) {
340 		/* To know what to release. */
341 		pdeo->file = file;
342 		/* Strictly for "too late" ->release in proc_reg_release(). */
343 		spin_lock(&pde->pde_unload_lock);
344 		list_add(&pdeo->lh, &pde->pde_openers);
345 		spin_unlock(&pde->pde_unload_lock);
346 	} else
347 		kfree(pdeo);
348 
349 	unuse_pde(pde);
350 	return rv;
351 }
352 
353 static int proc_reg_release(struct inode *inode, struct file *file)
354 {
355 	struct proc_dir_entry *pde = PDE(inode);
356 	struct pde_opener *pdeo;
357 	spin_lock(&pde->pde_unload_lock);
358 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
359 		if (pdeo->file == file) {
360 			close_pdeo(pde, pdeo);
361 			break;
362 		}
363 	}
364 	spin_unlock(&pde->pde_unload_lock);
365 	return 0;
366 }
367 
368 static const struct file_operations proc_reg_file_ops = {
369 	.llseek		= proc_reg_llseek,
370 	.read		= proc_reg_read,
371 	.write		= proc_reg_write,
372 	.poll		= proc_reg_poll,
373 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
374 #ifdef CONFIG_COMPAT
375 	.compat_ioctl	= proc_reg_compat_ioctl,
376 #endif
377 	.mmap		= proc_reg_mmap,
378 	.get_unmapped_area = proc_reg_get_unmapped_area,
379 	.open		= proc_reg_open,
380 	.release	= proc_reg_release,
381 };
382 
383 #ifdef CONFIG_COMPAT
384 static const struct file_operations proc_reg_file_ops_no_compat = {
385 	.llseek		= proc_reg_llseek,
386 	.read		= proc_reg_read,
387 	.write		= proc_reg_write,
388 	.poll		= proc_reg_poll,
389 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
390 	.mmap		= proc_reg_mmap,
391 	.get_unmapped_area = proc_reg_get_unmapped_area,
392 	.open		= proc_reg_open,
393 	.release	= proc_reg_release,
394 };
395 #endif
396 
397 static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd)
398 {
399 	struct proc_dir_entry *pde = PDE(dentry->d_inode);
400 	if (unlikely(!use_pde(pde)))
401 		return ERR_PTR(-EINVAL);
402 	nd_set_link(nd, pde->data);
403 	return pde;
404 }
405 
406 static void proc_put_link(struct dentry *dentry, struct nameidata *nd, void *p)
407 {
408 	unuse_pde(p);
409 }
410 
411 const struct inode_operations proc_link_inode_operations = {
412 	.readlink	= generic_readlink,
413 	.follow_link	= proc_follow_link,
414 	.put_link	= proc_put_link,
415 };
416 
417 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
418 {
419 	struct inode *inode = new_inode_pseudo(sb);
420 
421 	if (inode) {
422 		inode->i_ino = de->low_ino;
423 		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
424 		PROC_I(inode)->pde = de;
425 
426 		if (de->mode) {
427 			inode->i_mode = de->mode;
428 			inode->i_uid = de->uid;
429 			inode->i_gid = de->gid;
430 		}
431 		if (de->size)
432 			inode->i_size = de->size;
433 		if (de->nlink)
434 			set_nlink(inode, de->nlink);
435 		WARN_ON(!de->proc_iops);
436 		inode->i_op = de->proc_iops;
437 		if (de->proc_fops) {
438 			if (S_ISREG(inode->i_mode)) {
439 #ifdef CONFIG_COMPAT
440 				if (!de->proc_fops->compat_ioctl)
441 					inode->i_fop =
442 						&proc_reg_file_ops_no_compat;
443 				else
444 #endif
445 					inode->i_fop = &proc_reg_file_ops;
446 			} else {
447 				inode->i_fop = de->proc_fops;
448 			}
449 		}
450 	} else
451 	       pde_put(de);
452 	return inode;
453 }
454 
455 int proc_fill_super(struct super_block *s)
456 {
457 	struct inode *root_inode;
458 	int ret;
459 
460 	s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
461 	s->s_blocksize = 1024;
462 	s->s_blocksize_bits = 10;
463 	s->s_magic = PROC_SUPER_MAGIC;
464 	s->s_op = &proc_sops;
465 	s->s_time_gran = 1;
466 
467 	pde_get(&proc_root);
468 	root_inode = proc_get_inode(s, &proc_root);
469 	if (!root_inode) {
470 		pr_err("proc_fill_super: get root inode failed\n");
471 		return -ENOMEM;
472 	}
473 
474 	s->s_root = d_make_root(root_inode);
475 	if (!s->s_root) {
476 		pr_err("proc_fill_super: allocate dentry failed\n");
477 		return -ENOMEM;
478 	}
479 
480 	ret = proc_setup_self(s);
481 	if (ret) {
482 		return ret;
483 	}
484 	return proc_setup_thread_self(s);
485 }
486