xref: /openbmc/linux/fs/proc/inode.c (revision a2cce7a9) 
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 
27 #include <asm/uaccess.h>
28 
29 #include "internal.h"
30 
31 static void proc_evict_inode(struct inode *inode)
32 {
33 	struct proc_dir_entry *de;
34 	struct ctl_table_header *head;
35 
36 	truncate_inode_pages_final(&inode->i_data);
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 = PDE(inode);
44 	if (de)
45 		pde_put(de);
46 	head = PROC_I(inode)->sysctl;
47 	if (head) {
48 		RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);
49 		sysctl_head_put(head);
50 	}
51 }
52 
53 static struct kmem_cache * proc_inode_cachep;
54 
55 static struct inode *proc_alloc_inode(struct super_block *sb)
56 {
57 	struct proc_inode *ei;
58 	struct inode *inode;
59 
60 	ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
61 	if (!ei)
62 		return NULL;
63 	ei->pid = NULL;
64 	ei->fd = 0;
65 	ei->op.proc_get_link = NULL;
66 	ei->pde = NULL;
67 	ei->sysctl = NULL;
68 	ei->sysctl_entry = NULL;
69 	ei->ns_ops = NULL;
70 	inode = &ei->vfs_inode;
71 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
72 	return inode;
73 }
74 
75 static void proc_i_callback(struct rcu_head *head)
76 {
77 	struct inode *inode = container_of(head, struct inode, i_rcu);
78 	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
79 }
80 
81 static void proc_destroy_inode(struct inode *inode)
82 {
83 	call_rcu(&inode->i_rcu, proc_i_callback);
84 }
85 
86 static void init_once(void *foo)
87 {
88 	struct proc_inode *ei = (struct proc_inode *) foo;
89 
90 	inode_init_once(&ei->vfs_inode);
91 }
92 
93 void __init proc_init_inodecache(void)
94 {
95 	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
96 					     sizeof(struct proc_inode),
97 					     0, (SLAB_RECLAIM_ACCOUNT|
98 						SLAB_MEM_SPREAD|SLAB_PANIC),
99 					     init_once);
100 }
101 
102 static int proc_show_options(struct seq_file *seq, struct dentry *root)
103 {
104 	struct super_block *sb = root->d_sb;
105 	struct pid_namespace *pid = sb->s_fs_info;
106 
107 	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
108 		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
109 	if (pid->hide_pid != 0)
110 		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
111 
112 	return 0;
113 }
114 
115 static const struct super_operations proc_sops = {
116 	.alloc_inode	= proc_alloc_inode,
117 	.destroy_inode	= proc_destroy_inode,
118 	.drop_inode	= generic_delete_inode,
119 	.evict_inode	= proc_evict_inode,
120 	.statfs		= simple_statfs,
121 	.remount_fs	= proc_remount,
122 	.show_options	= proc_show_options,
123 };
124 
125 enum {BIAS = -1U<<31};
126 
127 static inline int use_pde(struct proc_dir_entry *pde)
128 {
129 	return atomic_inc_unless_negative(&pde->in_use);
130 }
131 
132 static void unuse_pde(struct proc_dir_entry *pde)
133 {
134 	if (atomic_dec_return(&pde->in_use) == BIAS)
135 		complete(pde->pde_unload_completion);
136 }
137 
138 /* pde is locked */
139 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
140 {
141 	if (pdeo->closing) {
142 		/* somebody else is doing that, just wait */
143 		DECLARE_COMPLETION_ONSTACK(c);
144 		pdeo->c = &c;
145 		spin_unlock(&pde->pde_unload_lock);
146 		wait_for_completion(&c);
147 		spin_lock(&pde->pde_unload_lock);
148 	} else {
149 		struct file *file;
150 		pdeo->closing = 1;
151 		spin_unlock(&pde->pde_unload_lock);
152 		file = pdeo->file;
153 		pde->proc_fops->release(file_inode(file), file);
154 		spin_lock(&pde->pde_unload_lock);
155 		list_del_init(&pdeo->lh);
156 		if (pdeo->c)
157 			complete(pdeo->c);
158 		kfree(pdeo);
159 	}
160 }
161 
162 void proc_entry_rundown(struct proc_dir_entry *de)
163 {
164 	DECLARE_COMPLETION_ONSTACK(c);
165 	/* Wait until all existing callers into module are done. */
166 	de->pde_unload_completion = &c;
167 	if (atomic_add_return(BIAS, &de->in_use) != BIAS)
168 		wait_for_completion(&c);
169 
170 	spin_lock(&de->pde_unload_lock);
171 	while (!list_empty(&de->pde_openers)) {
172 		struct pde_opener *pdeo;
173 		pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
174 		close_pdeo(de, pdeo);
175 	}
176 	spin_unlock(&de->pde_unload_lock);
177 }
178 
179 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
180 {
181 	struct proc_dir_entry *pde = PDE(file_inode(file));
182 	loff_t rv = -EINVAL;
183 	if (use_pde(pde)) {
184 		loff_t (*llseek)(struct file *, loff_t, int);
185 		llseek = pde->proc_fops->llseek;
186 		if (!llseek)
187 			llseek = default_llseek;
188 		rv = llseek(file, offset, whence);
189 		unuse_pde(pde);
190 	}
191 	return rv;
192 }
193 
194 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
195 {
196 	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
197 	struct proc_dir_entry *pde = PDE(file_inode(file));
198 	ssize_t rv = -EIO;
199 	if (use_pde(pde)) {
200 		read = pde->proc_fops->read;
201 		if (read)
202 			rv = read(file, buf, count, ppos);
203 		unuse_pde(pde);
204 	}
205 	return rv;
206 }
207 
208 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
209 {
210 	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
211 	struct proc_dir_entry *pde = PDE(file_inode(file));
212 	ssize_t rv = -EIO;
213 	if (use_pde(pde)) {
214 		write = pde->proc_fops->write;
215 		if (write)
216 			rv = write(file, buf, count, ppos);
217 		unuse_pde(pde);
218 	}
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_inode(file));
225 	unsigned int rv = DEFAULT_POLLMASK;
226 	unsigned int (*poll)(struct file *, struct poll_table_struct *);
227 	if (use_pde(pde)) {
228 		poll = pde->proc_fops->poll;
229 		if (poll)
230 			rv = poll(file, pts);
231 		unuse_pde(pde);
232 	}
233 	return rv;
234 }
235 
236 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
237 {
238 	struct proc_dir_entry *pde = PDE(file_inode(file));
239 	long rv = -ENOTTY;
240 	long (*ioctl)(struct file *, unsigned int, unsigned long);
241 	if (use_pde(pde)) {
242 		ioctl = pde->proc_fops->unlocked_ioctl;
243 		if (ioctl)
244 			rv = ioctl(file, cmd, arg);
245 		unuse_pde(pde);
246 	}
247 	return rv;
248 }
249 
250 #ifdef CONFIG_COMPAT
251 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
252 {
253 	struct proc_dir_entry *pde = PDE(file_inode(file));
254 	long rv = -ENOTTY;
255 	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
256 	if (use_pde(pde)) {
257 		compat_ioctl = pde->proc_fops->compat_ioctl;
258 		if (compat_ioctl)
259 			rv = compat_ioctl(file, cmd, arg);
260 		unuse_pde(pde);
261 	}
262 	return rv;
263 }
264 #endif
265 
266 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
267 {
268 	struct proc_dir_entry *pde = PDE(file_inode(file));
269 	int rv = -EIO;
270 	int (*mmap)(struct file *, struct vm_area_struct *);
271 	if (use_pde(pde)) {
272 		mmap = pde->proc_fops->mmap;
273 		if (mmap)
274 			rv = mmap(file, vma);
275 		unuse_pde(pde);
276 	}
277 	return rv;
278 }
279 
280 static unsigned long
281 proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
282 			   unsigned long len, unsigned long pgoff,
283 			   unsigned long flags)
284 {
285 	struct proc_dir_entry *pde = PDE(file_inode(file));
286 	unsigned long rv = -EIO;
287 
288 	if (use_pde(pde)) {
289 		typeof(proc_reg_get_unmapped_area) *get_area;
290 
291 		get_area = pde->proc_fops->get_unmapped_area;
292 #ifdef CONFIG_MMU
293 		if (!get_area)
294 			get_area = current->mm->get_unmapped_area;
295 #endif
296 
297 		if (get_area)
298 			rv = get_area(file, orig_addr, len, pgoff, flags);
299 		else
300 			rv = orig_addr;
301 		unuse_pde(pde);
302 	}
303 	return rv;
304 }
305 
306 static int proc_reg_open(struct inode *inode, struct file *file)
307 {
308 	struct proc_dir_entry *pde = PDE(inode);
309 	int rv = 0;
310 	int (*open)(struct inode *, struct file *);
311 	int (*release)(struct inode *, struct file *);
312 	struct pde_opener *pdeo;
313 
314 	/*
315 	 * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
316 	 * sequence. ->release won't be called because ->proc_fops will be
317 	 * cleared. Depending on complexity of ->release, consequences vary.
318 	 *
319 	 * We can't wait for mercy when close will be done for real, it's
320 	 * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
321 	 * by hand in remove_proc_entry(). For this, save opener's credentials
322 	 * for later.
323 	 */
324 	pdeo = kzalloc(sizeof(struct pde_opener), GFP_KERNEL);
325 	if (!pdeo)
326 		return -ENOMEM;
327 
328 	if (!use_pde(pde)) {
329 		kfree(pdeo);
330 		return -ENOENT;
331 	}
332 	open = pde->proc_fops->open;
333 	release = pde->proc_fops->release;
334 
335 	if (open)
336 		rv = open(inode, file);
337 
338 	if (rv == 0 && release) {
339 		/* To know what to release. */
340 		pdeo->file = file;
341 		/* Strictly for "too late" ->release in proc_reg_release(). */
342 		spin_lock(&pde->pde_unload_lock);
343 		list_add(&pdeo->lh, &pde->pde_openers);
344 		spin_unlock(&pde->pde_unload_lock);
345 	} else
346 		kfree(pdeo);
347 
348 	unuse_pde(pde);
349 	return rv;
350 }
351 
352 static int proc_reg_release(struct inode *inode, struct file *file)
353 {
354 	struct proc_dir_entry *pde = PDE(inode);
355 	struct pde_opener *pdeo;
356 	spin_lock(&pde->pde_unload_lock);
357 	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
358 		if (pdeo->file == file) {
359 			close_pdeo(pde, pdeo);
360 			break;
361 		}
362 	}
363 	spin_unlock(&pde->pde_unload_lock);
364 	return 0;
365 }
366 
367 static const struct file_operations proc_reg_file_ops = {
368 	.llseek		= proc_reg_llseek,
369 	.read		= proc_reg_read,
370 	.write		= proc_reg_write,
371 	.poll		= proc_reg_poll,
372 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
373 #ifdef CONFIG_COMPAT
374 	.compat_ioctl	= proc_reg_compat_ioctl,
375 #endif
376 	.mmap		= proc_reg_mmap,
377 	.get_unmapped_area = proc_reg_get_unmapped_area,
378 	.open		= proc_reg_open,
379 	.release	= proc_reg_release,
380 };
381 
382 #ifdef CONFIG_COMPAT
383 static const struct file_operations proc_reg_file_ops_no_compat = {
384 	.llseek		= proc_reg_llseek,
385 	.read		= proc_reg_read,
386 	.write		= proc_reg_write,
387 	.poll		= proc_reg_poll,
388 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
389 	.mmap		= proc_reg_mmap,
390 	.get_unmapped_area = proc_reg_get_unmapped_area,
391 	.open		= proc_reg_open,
392 	.release	= proc_reg_release,
393 };
394 #endif
395 
396 static const char *proc_follow_link(struct dentry *dentry, void **cookie)
397 {
398 	struct proc_dir_entry *pde = PDE(d_inode(dentry));
399 	if (unlikely(!use_pde(pde)))
400 		return ERR_PTR(-EINVAL);
401 	*cookie = pde;
402 	return pde->data;
403 }
404 
405 static void proc_put_link(struct inode *unused, void *p)
406 {
407 	unuse_pde(p);
408 }
409 
410 const struct inode_operations proc_link_inode_operations = {
411 	.readlink	= generic_readlink,
412 	.follow_link	= proc_follow_link,
413 	.put_link	= proc_put_link,
414 };
415 
416 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
417 {
418 	struct inode *inode = new_inode_pseudo(sb);
419 
420 	if (inode) {
421 		inode->i_ino = de->low_ino;
422 		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
423 		PROC_I(inode)->pde = de;
424 
425 		if (is_empty_pde(de)) {
426 			make_empty_dir_inode(inode);
427 			return inode;
428 		}
429 		if (de->mode) {
430 			inode->i_mode = de->mode;
431 			inode->i_uid = de->uid;
432 			inode->i_gid = de->gid;
433 		}
434 		if (de->size)
435 			inode->i_size = de->size;
436 		if (de->nlink)
437 			set_nlink(inode, de->nlink);
438 		WARN_ON(!de->proc_iops);
439 		inode->i_op = de->proc_iops;
440 		if (de->proc_fops) {
441 			if (S_ISREG(inode->i_mode)) {
442 #ifdef CONFIG_COMPAT
443 				if (!de->proc_fops->compat_ioctl)
444 					inode->i_fop =
445 						&proc_reg_file_ops_no_compat;
446 				else
447 #endif
448 					inode->i_fop = &proc_reg_file_ops;
449 			} else {
450 				inode->i_fop = de->proc_fops;
451 			}
452 		}
453 	} else
454 	       pde_put(de);
455 	return inode;
456 }
457 
458 int proc_fill_super(struct super_block *s)
459 {
460 	struct inode *root_inode;
461 	int ret;
462 
463 	s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
464 	s->s_blocksize = 1024;
465 	s->s_blocksize_bits = 10;
466 	s->s_magic = PROC_SUPER_MAGIC;
467 	s->s_op = &proc_sops;
468 	s->s_time_gran = 1;
469 
470 	pde_get(&proc_root);
471 	root_inode = proc_get_inode(s, &proc_root);
472 	if (!root_inode) {
473 		pr_err("proc_fill_super: get root inode failed\n");
474 		return -ENOMEM;
475 	}
476 
477 	s->s_root = d_make_root(root_inode);
478 	if (!s->s_root) {
479 		pr_err("proc_fill_super: allocate dentry failed\n");
480 		return -ENOMEM;
481 	}
482 
483 	ret = proc_setup_self(s);
484 	if (ret) {
485 		return ret;
486 	}
487 	return proc_setup_thread_self(s);
488 }
489