blob: 385bfd31512a17f4e4c6869a3ee8f32c456cd327 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/file_table.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
6 */
7
8#include <linux/string.h>
9#include <linux/slab.h>
10#include <linux/file.h>
Al Viro9f3acc32008-04-24 07:44:08 -040011#include <linux/fdtable.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070012#include <linux/init.h>
13#include <linux/module.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070014#include <linux/fs.h>
15#include <linux/security.h>
16#include <linux/eventpoll.h>
Dipankar Sarmaab2af1f2005-09-09 13:04:13 -070017#include <linux/rcupdate.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070018#include <linux/mount.h>
Randy Dunlap16f7e0f2006-01-11 12:17:46 -080019#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070020#include <linux/cdev.h>
Robert Love0eeca282005-07-12 17:06:03 -040021#include <linux/fsnotify.h>
Dipankar Sarma529bf6b2006-03-07 21:55:35 -080022#include <linux/sysctl.h>
Nick Piggin6416ccb2010-08-18 04:37:38 +100023#include <linux/lglock.h>
Dipankar Sarma529bf6b2006-03-07 21:55:35 -080024#include <linux/percpu_counter.h>
Nick Piggin6416ccb2010-08-18 04:37:38 +100025#include <linux/percpu.h>
Al Viro4a9d4b02012-06-24 09:56:45 +040026#include <linux/hardirq.h>
27#include <linux/task_work.h>
Al Viro0552f872009-12-16 04:53:03 -050028#include <linux/ima.h>
Dipankar Sarma529bf6b2006-03-07 21:55:35 -080029
Arun Sharma600634972011-07-26 16:09:06 -070030#include <linux/atomic.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070031
Eric Parise81e3f42009-12-04 15:47:36 -050032#include "internal.h"
33
Linus Torvalds1da177e2005-04-16 15:20:36 -070034/* sysctl tunables... */
35struct files_stat_struct files_stat = {
36 .max_files = NR_FILE
37};
38
Eric Dumazetb6b3fde2008-12-10 09:35:45 -080039/* SLAB cache for file structures */
40static struct kmem_cache *filp_cachep __read_mostly;
41
Dipankar Sarma529bf6b2006-03-07 21:55:35 -080042static struct percpu_counter nr_files __cacheline_aligned_in_smp;
Linus Torvalds1da177e2005-04-16 15:20:36 -070043
Al Viro5c33b182012-07-20 23:05:59 +040044static void file_free_rcu(struct rcu_head *head)
Dipankar Sarmaab2af1f2005-09-09 13:04:13 -070045{
David Howellsd76b0d92008-11-14 10:39:25 +110046 struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
47
48 put_cred(f->f_cred);
Dipankar Sarmaab2af1f2005-09-09 13:04:13 -070049 kmem_cache_free(filp_cachep, f);
50}
51
Linus Torvalds1da177e2005-04-16 15:20:36 -070052static inline void file_free(struct file *f)
53{
Dipankar Sarma529bf6b2006-03-07 21:55:35 -080054 percpu_counter_dec(&nr_files);
Eric Dumazet2f512012005-10-30 15:02:16 -080055 call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
Linus Torvalds1da177e2005-04-16 15:20:36 -070056}
57
Dipankar Sarma529bf6b2006-03-07 21:55:35 -080058/*
59 * Return the total number of open files in the system
60 */
Eric Dumazet518de9b2010-10-26 14:22:44 -070061static long get_nr_files(void)
Dipankar Sarma529bf6b2006-03-07 21:55:35 -080062{
63 return percpu_counter_read_positive(&nr_files);
64}
65
66/*
67 * Return the maximum number of open files in the system
68 */
Eric Dumazet518de9b2010-10-26 14:22:44 -070069unsigned long get_max_files(void)
Dipankar Sarma529bf6b2006-03-07 21:55:35 -080070{
71 return files_stat.max_files;
72}
73EXPORT_SYMBOL_GPL(get_max_files);
74
75/*
76 * Handle nr_files sysctl
77 */
78#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
Joe Perches1f7e0612014-06-06 14:38:05 -070079int proc_nr_files(struct ctl_table *table, int write,
Dipankar Sarma529bf6b2006-03-07 21:55:35 -080080 void __user *buffer, size_t *lenp, loff_t *ppos)
81{
82 files_stat.nr_files = get_nr_files();
Eric Dumazet518de9b2010-10-26 14:22:44 -070083 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
Dipankar Sarma529bf6b2006-03-07 21:55:35 -080084}
85#else
Joe Perches1f7e0612014-06-06 14:38:05 -070086int proc_nr_files(struct ctl_table *table, int write,
Dipankar Sarma529bf6b2006-03-07 21:55:35 -080087 void __user *buffer, size_t *lenp, loff_t *ppos)
88{
89 return -ENOSYS;
90}
91#endif
92
Linus Torvalds1da177e2005-04-16 15:20:36 -070093/* Find an unused file structure and return a pointer to it.
Al Viro1afc99b2013-02-14 20:41:04 -050094 * Returns an error pointer if some error happend e.g. we over file
95 * structures limit, run out of memory or operation is not permitted.
Dave Hansen430e2852008-02-15 14:37:26 -080096 *
97 * Be very careful using this. You are responsible for
98 * getting write access to any mount that you might assign
99 * to this filp, if it is opened for write. If this is not
100 * done, you will imbalance int the mount's writer count
101 * and a warning at __fput() time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 */
103struct file *get_empty_filp(void)
104{
David Howells86a264a2008-11-14 10:39:18 +1100105 const struct cred *cred = current_cred();
Eric Dumazet518de9b2010-10-26 14:22:44 -0700106 static long old_max;
Al Viro1afc99b2013-02-14 20:41:04 -0500107 struct file *f;
108 int error;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109
110 /*
111 * Privileged users can go above max_files
112 */
Dipankar Sarma529bf6b2006-03-07 21:55:35 -0800113 if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
114 /*
115 * percpu_counters are inaccurate. Do an expensive check before
116 * we go and fail.
117 */
Peter Zijlstra52d9f3b2007-10-16 23:25:44 -0700118 if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
Dipankar Sarma529bf6b2006-03-07 21:55:35 -0800119 goto over;
120 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121
Denis Cheng4975e452007-10-16 23:26:19 -0700122 f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
Al Viro1afc99b2013-02-14 20:41:04 -0500123 if (unlikely(!f))
124 return ERR_PTR(-ENOMEM);
Kirill Korotaevaf4d2ec2005-06-23 00:09:50 -0700125
Dipankar Sarma529bf6b2006-03-07 21:55:35 -0800126 percpu_counter_inc(&nr_files);
Tetsuo Handa78d29782011-02-04 18:13:24 +0000127 f->f_cred = get_cred(cred);
Al Viro1afc99b2013-02-14 20:41:04 -0500128 error = security_file_alloc(f);
129 if (unlikely(error)) {
130 file_free(f);
131 return ERR_PTR(error);
132 }
Kirill Korotaevaf4d2ec2005-06-23 00:09:50 -0700133
Al Viro516e0cc2008-07-26 00:39:17 -0400134 atomic_long_set(&f->f_count, 1);
Benjamin LaHaise5a6b79512006-03-23 03:01:03 -0800135 rwlock_init(&f->f_owner.lock);
Jonathan Corbet68499912009-02-06 13:52:43 -0700136 spin_lock_init(&f->f_lock);
Linus Torvalds9c225f22014-03-03 09:36:58 -0800137 mutex_init(&f->f_pos_lock);
Benjamin LaHaise5a6b79512006-03-23 03:01:03 -0800138 eventpoll_init_file(f);
139 /* f->f_version: 0 */
Kirill Korotaevaf4d2ec2005-06-23 00:09:50 -0700140 return f;
141
142over:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143 /* Ran out of filps - report that */
Dipankar Sarma529bf6b2006-03-07 21:55:35 -0800144 if (get_nr_files() > old_max) {
Eric Dumazet518de9b2010-10-26 14:22:44 -0700145 pr_info("VFS: file-max limit %lu reached\n", get_max_files());
Dipankar Sarma529bf6b2006-03-07 21:55:35 -0800146 old_max = get_nr_files();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147 }
Al Viro1afc99b2013-02-14 20:41:04 -0500148 return ERR_PTR(-ENFILE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149}
150
Dave Hansence8d2cd2007-10-16 23:31:13 -0700151/**
152 * alloc_file - allocate and initialize a 'struct file'
153 * @mnt: the vfsmount on which the file will reside
154 * @dentry: the dentry representing the new file
155 * @mode: the mode with which the new file will be opened
156 * @fop: the 'struct file_operations' for the new file
157 *
158 * Use this instead of get_empty_filp() to get a new
159 * 'struct file'. Do so because of the same initialization
160 * pitfalls reasons listed for init_file(). This is a
161 * preferred interface to using init_file().
162 *
163 * If all the callers of init_file() are eliminated, its
164 * code should be moved into this function.
165 */
Al Viro2c48b9c2009-08-09 00:52:35 +0400166struct file *alloc_file(struct path *path, fmode_t mode,
167 const struct file_operations *fop)
Dave Hansence8d2cd2007-10-16 23:31:13 -0700168{
169 struct file *file;
Dave Hansence8d2cd2007-10-16 23:31:13 -0700170
171 file = get_empty_filp();
Al Viro1afc99b2013-02-14 20:41:04 -0500172 if (IS_ERR(file))
Anatol Pomozov39b65252012-09-12 20:11:55 -0700173 return file;
Dave Hansence8d2cd2007-10-16 23:31:13 -0700174
Al Viro2c48b9c2009-08-09 00:52:35 +0400175 file->f_path = *path;
Al Virodd379782013-03-01 19:48:30 -0500176 file->f_inode = path->dentry->d_inode;
Al Viro2c48b9c2009-08-09 00:52:35 +0400177 file->f_mapping = path->dentry->d_inode->i_mapping;
Al Viro293bc982014-02-11 18:37:41 -0500178 if ((mode & FMODE_READ) &&
179 likely(fop->read || fop->aio_read || fop->read_iter))
Al Viro7f7f25e2014-02-11 17:49:24 -0500180 mode |= FMODE_CAN_READ;
Al Viro293bc982014-02-11 18:37:41 -0500181 if ((mode & FMODE_WRITE) &&
182 likely(fop->write || fop->aio_write || fop->write_iter))
Al Viro7f7f25e2014-02-11 17:49:24 -0500183 mode |= FMODE_CAN_WRITE;
Dave Hansence8d2cd2007-10-16 23:31:13 -0700184 file->f_mode = mode;
185 file->f_op = fop;
Mimi Zohar890275b52010-11-02 10:13:07 -0400186 if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
187 i_readcount_inc(path->dentry->d_inode);
Al Viro3d1e4632009-08-08 23:56:29 +0400188 return file;
Dave Hansence8d2cd2007-10-16 23:31:13 -0700189}
Roland Dreier73efc462009-12-16 12:43:11 -0800190EXPORT_SYMBOL(alloc_file);
Dave Hansence8d2cd2007-10-16 23:31:13 -0700191
Al Virod7065da2010-05-26 15:13:55 -0400192/* the real guts of fput() - releasing the last reference to file
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193 */
Al Virod7065da2010-05-26 15:13:55 -0400194static void __fput(struct file *file)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700195{
Josef "Jeff" Sipek0f7fc9e2006-12-08 02:36:35 -0800196 struct dentry *dentry = file->f_path.dentry;
197 struct vfsmount *mnt = file->f_path.mnt;
David Howellsc77cece2013-06-13 23:37:49 +0100198 struct inode *inode = file->f_inode;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700199
200 might_sleep();
Robert Love0eeca282005-07-12 17:06:03 -0400201
202 fsnotify_close(file);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700203 /*
204 * The function eventpoll_release() should be the first called
205 * in the file cleanup chain.
206 */
207 eventpoll_release(file);
Jeff Layton78ed8a12014-02-03 12:13:08 -0500208 locks_remove_file(file);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700209
Al Viro233e70f2008-10-31 23:28:30 +0000210 if (unlikely(file->f_flags & FASYNC)) {
Al Viro72c2d532013-09-22 16:27:52 -0400211 if (file->f_op->fasync)
Al Viro233e70f2008-10-31 23:28:30 +0000212 file->f_op->fasync(-1, file, 0);
213 }
Mimi Zohar4199d352011-03-16 22:48:43 -0400214 ima_file_free(file);
Al Viro72c2d532013-09-22 16:27:52 -0400215 if (file->f_op->release)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216 file->f_op->release(inode, file);
217 security_file_free(file);
Miklos Szeredi60ed8cf2011-03-16 18:17:54 +0100218 if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
219 !(file->f_mode & FMODE_PATH))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700220 cdev_put(inode->i_cdev);
Miklos Szeredi60ed8cf2011-03-16 18:17:54 +0100221 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222 fops_put(file->f_op);
Eric W. Biederman609d7fa2006-10-02 02:17:15 -0700223 put_pid(file->f_owner.pid);
Mimi Zohar890275b52010-11-02 10:13:07 -0400224 if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
225 i_readcount_dec(inode);
Al Viro83f936c2014-03-14 12:02:47 -0400226 if (file->f_mode & FMODE_WRITER) {
227 put_write_access(inode);
228 __mnt_drop_write(mnt);
229 }
Josef "Jeff" Sipek0f7fc9e2006-12-08 02:36:35 -0800230 file->f_path.dentry = NULL;
231 file->f_path.mnt = NULL;
Al Virodd379782013-03-01 19:48:30 -0500232 file->f_inode = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233 file_free(file);
234 dput(dentry);
235 mntput(mnt);
236}
237
Oleg Nesterov4f5e65a2013-07-08 14:24:16 -0700238static LLIST_HEAD(delayed_fput_list);
Al Viro4a9d4b02012-06-24 09:56:45 +0400239static void delayed_fput(struct work_struct *unused)
240{
Oleg Nesterov4f5e65a2013-07-08 14:24:16 -0700241 struct llist_node *node = llist_del_all(&delayed_fput_list);
242 struct llist_node *next;
243
244 for (; node; node = next) {
245 next = llist_next(node);
246 __fput(llist_entry(node, struct file, f_u.fu_llist));
Al Viro4a9d4b02012-06-24 09:56:45 +0400247 }
248}
249
250static void ____fput(struct callback_head *work)
251{
252 __fput(container_of(work, struct file, f_u.fu_rcuhead));
253}
254
255/*
256 * If kernel thread really needs to have the final fput() it has done
257 * to complete, call this. The only user right now is the boot - we
258 * *do* need to make sure our writes to binaries on initramfs has
259 * not left us with opened struct file waiting for __fput() - execve()
260 * won't work without that. Please, don't add more callers without
261 * very good reasons; in particular, never call that with locks
262 * held and never call that from a thread that might need to do
263 * some work on any kind of umount.
264 */
265void flush_delayed_fput(void)
266{
267 delayed_fput(NULL);
268}
269
Al Viroc7314d72013-10-20 08:44:39 -0400270static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
Al Viro4a9d4b02012-06-24 09:56:45 +0400271
Al Virod7065da2010-05-26 15:13:55 -0400272void fput(struct file *file)
273{
Al Viro4a9d4b02012-06-24 09:56:45 +0400274 if (atomic_long_dec_and_test(&file->f_count)) {
275 struct task_struct *task = current;
Oleg Nesterove7b2c402013-06-14 21:09:47 +0200276
Oleg Nesterove7b2c402013-06-14 21:09:47 +0200277 if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
278 init_task_work(&file->f_u.fu_rcuhead, ____fput);
279 if (!task_work_add(task, &file->f_u.fu_rcuhead, true))
280 return;
Andrew Morton64372502013-07-08 14:24:15 -0700281 /*
282 * After this task has run exit_task_work(),
Andrew Mortonbe49b302013-09-11 14:24:34 -0700283 * task_work_add() will fail. Fall through to delayed
Andrew Morton64372502013-07-08 14:24:15 -0700284 * fput to avoid leaking *file.
285 */
Al Viro4a9d4b02012-06-24 09:56:45 +0400286 }
Oleg Nesterov4f5e65a2013-07-08 14:24:16 -0700287
288 if (llist_add(&file->f_u.fu_llist, &delayed_fput_list))
Al Viroc7314d72013-10-20 08:44:39 -0400289 schedule_delayed_work(&delayed_fput_work, 1);
Al Viro4a9d4b02012-06-24 09:56:45 +0400290 }
291}
292
293/*
294 * synchronous analog of fput(); for kernel threads that might be needed
295 * in some umount() (and thus can't use flush_delayed_fput() without
296 * risking deadlocks), need to wait for completion of __fput() and know
297 * for this specific struct file it won't involve anything that would
298 * need them. Use only if you really need it - at the very least,
299 * don't blindly convert fput() by kernel thread to that.
300 */
301void __fput_sync(struct file *file)
302{
303 if (atomic_long_dec_and_test(&file->f_count)) {
304 struct task_struct *task = current;
Al Viro4a9d4b02012-06-24 09:56:45 +0400305 BUG_ON(!(task->flags & PF_KTHREAD));
Al Virod7065da2010-05-26 15:13:55 -0400306 __fput(file);
Al Viro4a9d4b02012-06-24 09:56:45 +0400307 }
Al Virod7065da2010-05-26 15:13:55 -0400308}
309
310EXPORT_SYMBOL(fput);
311
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312void put_filp(struct file *file)
313{
Al Viro516e0cc2008-07-26 00:39:17 -0400314 if (atomic_long_dec_and_test(&file->f_count)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700315 security_file_free(file);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316 file_free(file);
317 }
318}
319
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320void __init files_init(unsigned long mempages)
321{
Eric Dumazet518de9b2010-10-26 14:22:44 -0700322 unsigned long n;
Eric Dumazetb6b3fde2008-12-10 09:35:45 -0800323
324 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
325 SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
326
327 /*
328 * One file with associated inode and dcache is very roughly 1K.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700329 * Per default don't use more than 10% of our memory for files.
330 */
331
332 n = (mempages * (PAGE_SIZE / 1024)) / 10;
Eric Dumazet518de9b2010-10-26 14:22:44 -0700333 files_stat.max_files = max_t(unsigned long, n, NR_FILE);
Mingming Cao0216bfc2006-06-23 02:05:41 -0700334 percpu_counter_init(&nr_files, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700335}