Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-only
2 : /*
3 : * linux/fs/file_table.c
4 : *
5 : * Copyright (C) 1991, 1992 Linus Torvalds
6 : * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
7 : */
8 :
9 : #include <linux/string.h>
10 : #include <linux/slab.h>
11 : #include <linux/file.h>
12 : #include <linux/fdtable.h>
13 : #include <linux/init.h>
14 : #include <linux/module.h>
15 : #include <linux/fs.h>
16 : #include <linux/filelock.h>
17 : #include <linux/security.h>
18 : #include <linux/cred.h>
19 : #include <linux/eventpoll.h>
20 : #include <linux/rcupdate.h>
21 : #include <linux/mount.h>
22 : #include <linux/capability.h>
23 : #include <linux/cdev.h>
24 : #include <linux/fsnotify.h>
25 : #include <linux/sysctl.h>
26 : #include <linux/percpu_counter.h>
27 : #include <linux/percpu.h>
28 : #include <linux/task_work.h>
29 : #include <linux/ima.h>
30 : #include <linux/swap.h>
31 : #include <linux/kmemleak.h>
32 :
33 : #include <linux/atomic.h>
34 :
35 : #include "internal.h"
36 :
37 : /* sysctl tunables... */
38 : static struct files_stat_struct files_stat = {
39 : .max_files = NR_FILE
40 : };
41 :
42 : /* SLAB cache for file structures */
43 : static struct kmem_cache *filp_cachep __read_mostly;
44 :
45 : static struct percpu_counter nr_files __cacheline_aligned_in_smp;
46 :
47 0 : static void file_free_rcu(struct rcu_head *head)
48 : {
49 0 : struct file *f = container_of(head, struct file, f_rcuhead);
50 :
51 0 : put_cred(f->f_cred);
52 0 : kmem_cache_free(filp_cachep, f);
53 0 : }
54 :
55 0 : static inline void file_free(struct file *f)
56 : {
57 0 : security_file_free(f);
58 0 : if (!(f->f_mode & FMODE_NOACCOUNT))
59 0 : percpu_counter_dec(&nr_files);
60 0 : call_rcu(&f->f_rcuhead, file_free_rcu);
61 0 : }
62 :
63 : /*
64 : * Return the total number of open files in the system
65 : */
66 : static long get_nr_files(void)
67 : {
68 0 : return percpu_counter_read_positive(&nr_files);
69 : }
70 :
71 : /*
72 : * Return the maximum number of open files in the system
73 : */
74 0 : unsigned long get_max_files(void)
75 : {
76 0 : return files_stat.max_files;
77 : }
78 : EXPORT_SYMBOL_GPL(get_max_files);
79 :
80 : #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
81 :
82 : /*
83 : * Handle nr_files sysctl
84 : */
85 0 : static int proc_nr_files(struct ctl_table *table, int write, void *buffer,
86 : size_t *lenp, loff_t *ppos)
87 : {
88 0 : files_stat.nr_files = get_nr_files();
89 0 : return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
90 : }
91 :
92 : static struct ctl_table fs_stat_sysctls[] = {
93 : {
94 : .procname = "file-nr",
95 : .data = &files_stat,
96 : .maxlen = sizeof(files_stat),
97 : .mode = 0444,
98 : .proc_handler = proc_nr_files,
99 : },
100 : {
101 : .procname = "file-max",
102 : .data = &files_stat.max_files,
103 : .maxlen = sizeof(files_stat.max_files),
104 : .mode = 0644,
105 : .proc_handler = proc_doulongvec_minmax,
106 : .extra1 = SYSCTL_LONG_ZERO,
107 : .extra2 = SYSCTL_LONG_MAX,
108 : },
109 : {
110 : .procname = "nr_open",
111 : .data = &sysctl_nr_open,
112 : .maxlen = sizeof(unsigned int),
113 : .mode = 0644,
114 : .proc_handler = proc_dointvec_minmax,
115 : .extra1 = &sysctl_nr_open_min,
116 : .extra2 = &sysctl_nr_open_max,
117 : },
118 : { }
119 : };
120 :
121 1 : static int __init init_fs_stat_sysctls(void)
122 : {
123 1 : register_sysctl_init("fs", fs_stat_sysctls);
124 : if (IS_ENABLED(CONFIG_BINFMT_MISC)) {
125 : struct ctl_table_header *hdr;
126 : hdr = register_sysctl_mount_point("fs/binfmt_misc");
127 : kmemleak_not_leak(hdr);
128 : }
129 1 : return 0;
130 : }
131 : fs_initcall(init_fs_stat_sysctls);
132 : #endif
133 :
134 0 : static struct file *__alloc_file(int flags, const struct cred *cred)
135 : {
136 : struct file *f;
137 : int error;
138 :
139 0 : f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
140 0 : if (unlikely(!f))
141 : return ERR_PTR(-ENOMEM);
142 :
143 0 : f->f_cred = get_cred(cred);
144 0 : error = security_file_alloc(f);
145 : if (unlikely(error)) {
146 : file_free_rcu(&f->f_rcuhead);
147 : return ERR_PTR(error);
148 : }
149 :
150 0 : atomic_long_set(&f->f_count, 1);
151 : rwlock_init(&f->f_owner.lock);
152 0 : spin_lock_init(&f->f_lock);
153 0 : mutex_init(&f->f_pos_lock);
154 0 : f->f_flags = flags;
155 0 : f->f_mode = OPEN_FMODE(flags);
156 : /* f->f_version: 0 */
157 :
158 0 : return f;
159 : }
160 :
161 : /* Find an unused file structure and return a pointer to it.
162 : * Returns an error pointer if some error happend e.g. we over file
163 : * structures limit, run out of memory or operation is not permitted.
164 : *
165 : * Be very careful using this. You are responsible for
166 : * getting write access to any mount that you might assign
167 : * to this filp, if it is opened for write. If this is not
168 : * done, you will imbalance int the mount's writer count
169 : * and a warning at __fput() time.
170 : */
171 0 : struct file *alloc_empty_file(int flags, const struct cred *cred)
172 : {
173 : static long old_max;
174 : struct file *f;
175 :
176 : /*
177 : * Privileged users can go above max_files
178 : */
179 0 : if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
180 : /*
181 : * percpu_counters are inaccurate. Do an expensive check before
182 : * we go and fail.
183 : */
184 0 : if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
185 : goto over;
186 : }
187 :
188 0 : f = __alloc_file(flags, cred);
189 0 : if (!IS_ERR(f))
190 0 : percpu_counter_inc(&nr_files);
191 :
192 : return f;
193 :
194 : over:
195 : /* Ran out of filps - report that */
196 0 : if (get_nr_files() > old_max) {
197 0 : pr_info("VFS: file-max limit %lu reached\n", get_max_files());
198 0 : old_max = get_nr_files();
199 : }
200 : return ERR_PTR(-ENFILE);
201 : }
202 :
203 : /*
204 : * Variant of alloc_empty_file() that doesn't check and modify nr_files.
205 : *
206 : * Should not be used unless there's a very good reason to do so.
207 : */
208 0 : struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred)
209 : {
210 0 : struct file *f = __alloc_file(flags, cred);
211 :
212 0 : if (!IS_ERR(f))
213 0 : f->f_mode |= FMODE_NOACCOUNT;
214 :
215 0 : return f;
216 : }
217 :
218 : /**
219 : * alloc_file - allocate and initialize a 'struct file'
220 : *
221 : * @path: the (dentry, vfsmount) pair for the new file
222 : * @flags: O_... flags with which the new file will be opened
223 : * @fop: the 'struct file_operations' for the new file
224 : */
225 0 : static struct file *alloc_file(const struct path *path, int flags,
226 : const struct file_operations *fop)
227 : {
228 : struct file *file;
229 :
230 0 : file = alloc_empty_file(flags, current_cred());
231 0 : if (IS_ERR(file))
232 : return file;
233 :
234 0 : file->f_path = *path;
235 0 : file->f_inode = path->dentry->d_inode;
236 0 : file->f_mapping = path->dentry->d_inode->i_mapping;
237 0 : file->f_wb_err = filemap_sample_wb_err(file->f_mapping);
238 0 : file->f_sb_err = file_sample_sb_err(file);
239 0 : if (fop->llseek)
240 0 : file->f_mode |= FMODE_LSEEK;
241 0 : if ((file->f_mode & FMODE_READ) &&
242 0 : likely(fop->read || fop->read_iter))
243 0 : file->f_mode |= FMODE_CAN_READ;
244 0 : if ((file->f_mode & FMODE_WRITE) &&
245 0 : likely(fop->write || fop->write_iter))
246 0 : file->f_mode |= FMODE_CAN_WRITE;
247 0 : file->f_iocb_flags = iocb_flags(file);
248 0 : file->f_mode |= FMODE_OPENED;
249 0 : file->f_op = fop;
250 0 : if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
251 0 : i_readcount_inc(path->dentry->d_inode);
252 : return file;
253 : }
254 :
255 0 : struct file *alloc_file_pseudo(struct inode *inode, struct vfsmount *mnt,
256 : const char *name, int flags,
257 : const struct file_operations *fops)
258 : {
259 : static const struct dentry_operations anon_ops = {
260 : .d_dname = simple_dname
261 : };
262 0 : struct qstr this = QSTR_INIT(name, strlen(name));
263 : struct path path;
264 : struct file *file;
265 :
266 0 : path.dentry = d_alloc_pseudo(mnt->mnt_sb, &this);
267 0 : if (!path.dentry)
268 : return ERR_PTR(-ENOMEM);
269 0 : if (!mnt->mnt_sb->s_d_op)
270 0 : d_set_d_op(path.dentry, &anon_ops);
271 0 : path.mnt = mntget(mnt);
272 0 : d_instantiate(path.dentry, inode);
273 0 : file = alloc_file(&path, flags, fops);
274 0 : if (IS_ERR(file)) {
275 0 : ihold(inode);
276 0 : path_put(&path);
277 : }
278 : return file;
279 : }
280 : EXPORT_SYMBOL(alloc_file_pseudo);
281 :
282 0 : struct file *alloc_file_clone(struct file *base, int flags,
283 : const struct file_operations *fops)
284 : {
285 0 : struct file *f = alloc_file(&base->f_path, flags, fops);
286 0 : if (!IS_ERR(f)) {
287 0 : path_get(&f->f_path);
288 0 : f->f_mapping = base->f_mapping;
289 : }
290 0 : return f;
291 : }
292 :
293 : /* the real guts of fput() - releasing the last reference to file
294 : */
295 0 : static void __fput(struct file *file)
296 : {
297 0 : struct dentry *dentry = file->f_path.dentry;
298 0 : struct vfsmount *mnt = file->f_path.mnt;
299 0 : struct inode *inode = file->f_inode;
300 0 : fmode_t mode = file->f_mode;
301 :
302 0 : if (unlikely(!(file->f_mode & FMODE_OPENED)))
303 : goto out;
304 :
305 : might_sleep();
306 :
307 0 : fsnotify_close(file);
308 : /*
309 : * The function eventpoll_release() should be the first called
310 : * in the file cleanup chain.
311 : */
312 0 : eventpoll_release(file);
313 0 : locks_remove_file(file);
314 :
315 0 : ima_file_free(file);
316 0 : if (unlikely(file->f_flags & FASYNC)) {
317 0 : if (file->f_op->fasync)
318 0 : file->f_op->fasync(-1, file, 0);
319 : }
320 0 : if (file->f_op->release)
321 0 : file->f_op->release(inode, file);
322 0 : if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
323 : !(mode & FMODE_PATH))) {
324 0 : cdev_put(inode->i_cdev);
325 : }
326 0 : fops_put(file->f_op);
327 0 : put_pid(file->f_owner.pid);
328 0 : put_file_access(file);
329 0 : dput(dentry);
330 0 : if (unlikely(mode & FMODE_NEED_UNMOUNT))
331 0 : dissolve_on_fput(mnt);
332 0 : mntput(mnt);
333 : out:
334 0 : file_free(file);
335 0 : }
336 :
337 : static LLIST_HEAD(delayed_fput_list);
338 0 : static void delayed_fput(struct work_struct *unused)
339 : {
340 0 : struct llist_node *node = llist_del_all(&delayed_fput_list);
341 : struct file *f, *t;
342 :
343 0 : llist_for_each_entry_safe(f, t, node, f_llist)
344 0 : __fput(f);
345 0 : }
346 :
347 0 : static void ____fput(struct callback_head *work)
348 : {
349 0 : __fput(container_of(work, struct file, f_rcuhead));
350 0 : }
351 :
352 : /*
353 : * If kernel thread really needs to have the final fput() it has done
354 : * to complete, call this. The only user right now is the boot - we
355 : * *do* need to make sure our writes to binaries on initramfs has
356 : * not left us with opened struct file waiting for __fput() - execve()
357 : * won't work without that. Please, don't add more callers without
358 : * very good reasons; in particular, never call that with locks
359 : * held and never call that from a thread that might need to do
360 : * some work on any kind of umount.
361 : */
362 0 : void flush_delayed_fput(void)
363 : {
364 0 : delayed_fput(NULL);
365 0 : }
366 : EXPORT_SYMBOL_GPL(flush_delayed_fput);
367 :
368 : static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
369 :
370 0 : void fput(struct file *file)
371 : {
372 0 : if (atomic_long_dec_and_test(&file->f_count)) {
373 0 : struct task_struct *task = current;
374 :
375 0 : if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
376 0 : init_task_work(&file->f_rcuhead, ____fput);
377 0 : if (!task_work_add(task, &file->f_rcuhead, TWA_RESUME))
378 : return;
379 : /*
380 : * After this task has run exit_task_work(),
381 : * task_work_add() will fail. Fall through to delayed
382 : * fput to avoid leaking *file.
383 : */
384 : }
385 :
386 0 : if (llist_add(&file->f_llist, &delayed_fput_list))
387 : schedule_delayed_work(&delayed_fput_work, 1);
388 : }
389 : }
390 :
391 : /*
392 : * synchronous analog of fput(); for kernel threads that might be needed
393 : * in some umount() (and thus can't use flush_delayed_fput() without
394 : * risking deadlocks), need to wait for completion of __fput() and know
395 : * for this specific struct file it won't involve anything that would
396 : * need them. Use only if you really need it - at the very least,
397 : * don't blindly convert fput() by kernel thread to that.
398 : */
399 0 : void __fput_sync(struct file *file)
400 : {
401 0 : if (atomic_long_dec_and_test(&file->f_count)) {
402 0 : struct task_struct *task = current;
403 0 : BUG_ON(!(task->flags & PF_KTHREAD));
404 0 : __fput(file);
405 : }
406 0 : }
407 :
408 : EXPORT_SYMBOL(fput);
409 : EXPORT_SYMBOL(__fput_sync);
410 :
411 1 : void __init files_init(void)
412 : {
413 1 : filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
414 : SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT, NULL);
415 2 : percpu_counter_init(&nr_files, 0, GFP_KERNEL);
416 1 : }
417 :
418 : /*
419 : * One file with associated inode and dcache is very roughly 1K. Per default
420 : * do not use more than 10% of our memory for files.
421 : */
422 1 : void __init files_maxfiles_init(void)
423 : {
424 : unsigned long n;
425 1 : unsigned long nr_pages = totalram_pages();
426 1 : unsigned long memreserve = (nr_pages - nr_free_pages()) * 3/2;
427 :
428 1 : memreserve = min(memreserve, nr_pages - 1);
429 1 : n = ((nr_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
430 :
431 1 : files_stat.max_files = max_t(unsigned long, n, NR_FILE);
432 1 : }
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