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1/*
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>
11#include <linux/fdtable.h>
12#include <linux/init.h>
13#include <linux/module.h>
14#include <linux/fs.h>
15#include <linux/security.h>
16#include <linux/eventpoll.h>
17#include <linux/rcupdate.h>
18#include <linux/mount.h>
19#include <linux/capability.h>
20#include <linux/cdev.h>
21#include <linux/fsnotify.h>
22#include <linux/sysctl.h>
23#include <linux/percpu_counter.h>
24#include <linux/percpu.h>
25#include <linux/hardirq.h>
26#include <linux/task_work.h>
27#include <linux/ima.h>
28#include <linux/swap.h>
29
30#include <linux/atomic.h>
31
32#include "internal.h"
33
34/* sysctl tunables... */
35struct files_stat_struct files_stat = {
36 .max_files = NR_FILE
37};
38
39/* SLAB cache for file structures */
40static struct kmem_cache *filp_cachep __read_mostly;
41
42static struct percpu_counter nr_files __cacheline_aligned_in_smp;
43
44static void file_free_rcu(struct rcu_head *head)
45{
46 struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
47
48 put_cred(f->f_cred);
49 kmem_cache_free(filp_cachep, f);
50}
51
52static inline void file_free(struct file *f)
53{
54 percpu_counter_dec(&nr_files);
55 call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
56}
57
58/*
59 * Return the total number of open files in the system
60 */
61static long get_nr_files(void)
62{
63 return percpu_counter_read_positive(&nr_files);
64}
65
66/*
67 * Return the maximum number of open files in the system
68 */
69unsigned long get_max_files(void)
70{
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)
79int proc_nr_files(struct ctl_table *table, int write,
80 void __user *buffer, size_t *lenp, loff_t *ppos)
81{
82 files_stat.nr_files = get_nr_files();
83 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
84}
85#else
86int proc_nr_files(struct ctl_table *table, int write,
87 void __user *buffer, size_t *lenp, loff_t *ppos)
88{
89 return -ENOSYS;
90}
91#endif
92
93/* Find an unused file structure and return a pointer to it.
94 * 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.
96 *
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.
102 */
103struct file *get_empty_filp(void)
104{
105 const struct cred *cred = current_cred();
106 static long old_max;
107 struct file *f;
108 int error;
109
110 /*
111 * Privileged users can go above max_files
112 */
113 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 */
118 if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
119 goto over;
120 }
121
122 f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
123 if (unlikely(!f))
124 return ERR_PTR(-ENOMEM);
125
126 percpu_counter_inc(&nr_files);
127 f->f_cred = get_cred(cred);
128 error = security_file_alloc(f);
129 if (unlikely(error)) {
130 file_free(f);
131 return ERR_PTR(error);
132 }
133
134 atomic_long_set(&f->f_count, 1);
135 rwlock_init(&f->f_owner.lock);
136 spin_lock_init(&f->f_lock);
137 mutex_init(&f->f_pos_lock);
138 eventpoll_init_file(f);
139 /* f->f_version: 0 */
140 return f;
141
142over:
143 /* Ran out of filps - report that */
144 if (get_nr_files() > old_max) {
145 pr_info("VFS: file-max limit %lu reached\n", get_max_files());
146 old_max = get_nr_files();
147 }
148 return ERR_PTR(-ENFILE);
149}
150
151/**
152 * alloc_file - allocate and initialize a 'struct file'
153 *
154 * @path: the (dentry, vfsmount) pair for 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 */
158struct file *alloc_file(const struct path *path, fmode_t mode,
159 const struct file_operations *fop)
160{
161 struct file *file;
162
163 file = get_empty_filp();
164 if (IS_ERR(file))
165 return file;
166
167 file->f_path = *path;
168 file->f_inode = path->dentry->d_inode;
169 file->f_mapping = path->dentry->d_inode->i_mapping;
170 if ((mode & FMODE_READ) &&
171 likely(fop->read || fop->read_iter))
172 mode |= FMODE_CAN_READ;
173 if ((mode & FMODE_WRITE) &&
174 likely(fop->write || fop->write_iter))
175 mode |= FMODE_CAN_WRITE;
176 file->f_mode = mode;
177 file->f_op = fop;
178 if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
179 i_readcount_inc(path->dentry->d_inode);
180 return file;
181}
182EXPORT_SYMBOL(alloc_file);
183
184/* the real guts of fput() - releasing the last reference to file
185 */
186static void __fput(struct file *file)
187{
188 struct dentry *dentry = file->f_path.dentry;
189 struct vfsmount *mnt = file->f_path.mnt;
190 struct inode *inode = file->f_inode;
191
192 might_sleep();
193
194 fsnotify_close(file);
195 /*
196 * The function eventpoll_release() should be the first called
197 * in the file cleanup chain.
198 */
199 eventpoll_release(file);
200 locks_remove_file(file);
201
202 if (unlikely(file->f_flags & FASYNC)) {
203 if (file->f_op->fasync)
204 file->f_op->fasync(-1, file, 0);
205 }
206 ima_file_free(file);
207 if (file->f_op->release)
208 file->f_op->release(inode, file);
209 security_file_free(file);
210 if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
211 !(file->f_mode & FMODE_PATH))) {
212 cdev_put(inode->i_cdev);
213 }
214 fops_put(file->f_op);
215 put_pid(file->f_owner.pid);
216 if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
217 i_readcount_dec(inode);
218 if (file->f_mode & FMODE_WRITER) {
219 put_write_access(inode);
220 __mnt_drop_write(mnt);
221 }
222 file->f_path.dentry = NULL;
223 file->f_path.mnt = NULL;
224 file->f_inode = NULL;
225 file_free(file);
226 dput(dentry);
227 mntput(mnt);
228}
229
230static LLIST_HEAD(delayed_fput_list);
231static void delayed_fput(struct work_struct *unused)
232{
233 struct llist_node *node = llist_del_all(&delayed_fput_list);
234 struct llist_node *next;
235
236 for (; node; node = next) {
237 next = llist_next(node);
238 __fput(llist_entry(node, struct file, f_u.fu_llist));
239 }
240}
241
242static void ____fput(struct callback_head *work)
243{
244 __fput(container_of(work, struct file, f_u.fu_rcuhead));
245}
246
247/*
248 * If kernel thread really needs to have the final fput() it has done
249 * to complete, call this. The only user right now is the boot - we
250 * *do* need to make sure our writes to binaries on initramfs has
251 * not left us with opened struct file waiting for __fput() - execve()
252 * won't work without that. Please, don't add more callers without
253 * very good reasons; in particular, never call that with locks
254 * held and never call that from a thread that might need to do
255 * some work on any kind of umount.
256 */
257void flush_delayed_fput(void)
258{
259 delayed_fput(NULL);
260}
261
262static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
263
264void fput(struct file *file)
265{
266 if (atomic_long_dec_and_test(&file->f_count)) {
267 struct task_struct *task = current;
268
269 if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
270 init_task_work(&file->f_u.fu_rcuhead, ____fput);
271 if (!task_work_add(task, &file->f_u.fu_rcuhead, true))
272 return;
273 /*
274 * After this task has run exit_task_work(),
275 * task_work_add() will fail. Fall through to delayed
276 * fput to avoid leaking *file.
277 */
278 }
279
280 if (llist_add(&file->f_u.fu_llist, &delayed_fput_list))
281 schedule_delayed_work(&delayed_fput_work, 1);
282 }
283}
284
285/*
286 * synchronous analog of fput(); for kernel threads that might be needed
287 * in some umount() (and thus can't use flush_delayed_fput() without
288 * risking deadlocks), need to wait for completion of __fput() and know
289 * for this specific struct file it won't involve anything that would
290 * need them. Use only if you really need it - at the very least,
291 * don't blindly convert fput() by kernel thread to that.
292 */
293void __fput_sync(struct file *file)
294{
295 if (atomic_long_dec_and_test(&file->f_count)) {
296 struct task_struct *task = current;
297 BUG_ON(!(task->flags & PF_KTHREAD));
298 __fput(file);
299 }
300}
301
302EXPORT_SYMBOL(fput);
303
304void put_filp(struct file *file)
305{
306 if (atomic_long_dec_and_test(&file->f_count)) {
307 security_file_free(file);
308 file_free(file);
309 }
310}
311
312void __init files_init(void)
313{
314 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
315 SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
316 percpu_counter_init(&nr_files, 0, GFP_KERNEL);
317}
318
319/*
320 * One file with associated inode and dcache is very roughly 1K. Per default
321 * do not use more than 10% of our memory for files.
322 */
323void __init files_maxfiles_init(void)
324{
325 unsigned long n;
326 unsigned long memreserve = (totalram_pages - nr_free_pages()) * 3/2;
327
328 memreserve = min(memreserve, totalram_pages - 1);
329 n = ((totalram_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
330
331 files_stat.max_files = max_t(unsigned long, n, NR_FILE);
332}
1/*
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>
11#include <linux/fdtable.h>
12#include <linux/init.h>
13#include <linux/module.h>
14#include <linux/fs.h>
15#include <linux/security.h>
16#include <linux/eventpoll.h>
17#include <linux/rcupdate.h>
18#include <linux/mount.h>
19#include <linux/capability.h>
20#include <linux/cdev.h>
21#include <linux/fsnotify.h>
22#include <linux/sysctl.h>
23#include <linux/lglock.h>
24#include <linux/percpu_counter.h>
25#include <linux/percpu.h>
26#include <linux/hardirq.h>
27#include <linux/task_work.h>
28#include <linux/ima.h>
29
30#include <linux/atomic.h>
31
32#include "internal.h"
33
34/* sysctl tunables... */
35struct files_stat_struct files_stat = {
36 .max_files = NR_FILE
37};
38
39/* SLAB cache for file structures */
40static struct kmem_cache *filp_cachep __read_mostly;
41
42static struct percpu_counter nr_files __cacheline_aligned_in_smp;
43
44static void file_free_rcu(struct rcu_head *head)
45{
46 struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
47
48 put_cred(f->f_cred);
49 kmem_cache_free(filp_cachep, f);
50}
51
52static inline void file_free(struct file *f)
53{
54 percpu_counter_dec(&nr_files);
55 call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
56}
57
58/*
59 * Return the total number of open files in the system
60 */
61static long get_nr_files(void)
62{
63 return percpu_counter_read_positive(&nr_files);
64}
65
66/*
67 * Return the maximum number of open files in the system
68 */
69unsigned long get_max_files(void)
70{
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)
79int proc_nr_files(ctl_table *table, int write,
80 void __user *buffer, size_t *lenp, loff_t *ppos)
81{
82 files_stat.nr_files = get_nr_files();
83 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
84}
85#else
86int proc_nr_files(ctl_table *table, int write,
87 void __user *buffer, size_t *lenp, loff_t *ppos)
88{
89 return -ENOSYS;
90}
91#endif
92
93/* Find an unused file structure and return a pointer to it.
94 * 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.
96 *
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.
102 */
103struct file *get_empty_filp(void)
104{
105 const struct cred *cred = current_cred();
106 static long old_max;
107 struct file *f;
108 int error;
109
110 /*
111 * Privileged users can go above max_files
112 */
113 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 */
118 if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
119 goto over;
120 }
121
122 f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
123 if (unlikely(!f))
124 return ERR_PTR(-ENOMEM);
125
126 percpu_counter_inc(&nr_files);
127 f->f_cred = get_cred(cred);
128 error = security_file_alloc(f);
129 if (unlikely(error)) {
130 file_free(f);
131 return ERR_PTR(error);
132 }
133
134 atomic_long_set(&f->f_count, 1);
135 rwlock_init(&f->f_owner.lock);
136 spin_lock_init(&f->f_lock);
137 mutex_init(&f->f_pos_lock);
138 eventpoll_init_file(f);
139 /* f->f_version: 0 */
140 return f;
141
142over:
143 /* Ran out of filps - report that */
144 if (get_nr_files() > old_max) {
145 pr_info("VFS: file-max limit %lu reached\n", get_max_files());
146 old_max = get_nr_files();
147 }
148 return ERR_PTR(-ENFILE);
149}
150
151/**
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 */
166struct file *alloc_file(struct path *path, fmode_t mode,
167 const struct file_operations *fop)
168{
169 struct file *file;
170
171 file = get_empty_filp();
172 if (IS_ERR(file))
173 return file;
174
175 file->f_path = *path;
176 file->f_inode = path->dentry->d_inode;
177 file->f_mapping = path->dentry->d_inode->i_mapping;
178 file->f_mode = mode;
179 file->f_op = fop;
180 if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
181 i_readcount_inc(path->dentry->d_inode);
182 return file;
183}
184EXPORT_SYMBOL(alloc_file);
185
186/* the real guts of fput() - releasing the last reference to file
187 */
188static void __fput(struct file *file)
189{
190 struct dentry *dentry = file->f_path.dentry;
191 struct vfsmount *mnt = file->f_path.mnt;
192 struct inode *inode = file->f_inode;
193
194 might_sleep();
195
196 fsnotify_close(file);
197 /*
198 * The function eventpoll_release() should be the first called
199 * in the file cleanup chain.
200 */
201 eventpoll_release(file);
202 locks_remove_file(file);
203
204 if (unlikely(file->f_flags & FASYNC)) {
205 if (file->f_op->fasync)
206 file->f_op->fasync(-1, file, 0);
207 }
208 ima_file_free(file);
209 if (file->f_op->release)
210 file->f_op->release(inode, file);
211 security_file_free(file);
212 if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
213 !(file->f_mode & FMODE_PATH))) {
214 cdev_put(inode->i_cdev);
215 }
216 fops_put(file->f_op);
217 put_pid(file->f_owner.pid);
218 if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
219 i_readcount_dec(inode);
220 if (file->f_mode & FMODE_WRITER) {
221 put_write_access(inode);
222 __mnt_drop_write(mnt);
223 }
224 file->f_path.dentry = NULL;
225 file->f_path.mnt = NULL;
226 file->f_inode = NULL;
227 file_free(file);
228 dput(dentry);
229 mntput(mnt);
230}
231
232static LLIST_HEAD(delayed_fput_list);
233static void delayed_fput(struct work_struct *unused)
234{
235 struct llist_node *node = llist_del_all(&delayed_fput_list);
236 struct llist_node *next;
237
238 for (; node; node = next) {
239 next = llist_next(node);
240 __fput(llist_entry(node, struct file, f_u.fu_llist));
241 }
242}
243
244static void ____fput(struct callback_head *work)
245{
246 __fput(container_of(work, struct file, f_u.fu_rcuhead));
247}
248
249/*
250 * If kernel thread really needs to have the final fput() it has done
251 * to complete, call this. The only user right now is the boot - we
252 * *do* need to make sure our writes to binaries on initramfs has
253 * not left us with opened struct file waiting for __fput() - execve()
254 * won't work without that. Please, don't add more callers without
255 * very good reasons; in particular, never call that with locks
256 * held and never call that from a thread that might need to do
257 * some work on any kind of umount.
258 */
259void flush_delayed_fput(void)
260{
261 delayed_fput(NULL);
262}
263
264static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
265
266void fput(struct file *file)
267{
268 if (atomic_long_dec_and_test(&file->f_count)) {
269 struct task_struct *task = current;
270
271 if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
272 init_task_work(&file->f_u.fu_rcuhead, ____fput);
273 if (!task_work_add(task, &file->f_u.fu_rcuhead, true))
274 return;
275 /*
276 * After this task has run exit_task_work(),
277 * task_work_add() will fail. Fall through to delayed
278 * fput to avoid leaking *file.
279 */
280 }
281
282 if (llist_add(&file->f_u.fu_llist, &delayed_fput_list))
283 schedule_delayed_work(&delayed_fput_work, 1);
284 }
285}
286
287/*
288 * synchronous analog of fput(); for kernel threads that might be needed
289 * in some umount() (and thus can't use flush_delayed_fput() without
290 * risking deadlocks), need to wait for completion of __fput() and know
291 * for this specific struct file it won't involve anything that would
292 * need them. Use only if you really need it - at the very least,
293 * don't blindly convert fput() by kernel thread to that.
294 */
295void __fput_sync(struct file *file)
296{
297 if (atomic_long_dec_and_test(&file->f_count)) {
298 struct task_struct *task = current;
299 BUG_ON(!(task->flags & PF_KTHREAD));
300 __fput(file);
301 }
302}
303
304EXPORT_SYMBOL(fput);
305
306void put_filp(struct file *file)
307{
308 if (atomic_long_dec_and_test(&file->f_count)) {
309 security_file_free(file);
310 file_free(file);
311 }
312}
313
314void __init files_init(unsigned long mempages)
315{
316 unsigned long n;
317
318 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
319 SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
320
321 /*
322 * One file with associated inode and dcache is very roughly 1K.
323 * Per default don't use more than 10% of our memory for files.
324 */
325
326 n = (mempages * (PAGE_SIZE / 1024)) / 10;
327 files_stat.max_files = max_t(unsigned long, n, NR_FILE);
328 percpu_counter_init(&nr_files, 0);
329}