496 lines
12 KiB
C
496 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* linux/fs/file_table.c
|
|
*
|
|
* Copyright (C) 1991, 1992 Linus Torvalds
|
|
* Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
|
|
*/
|
|
|
|
#include <linux/string.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/file.h>
|
|
#include <linux/fdtable.h>
|
|
#include <linux/init.h>
|
|
#include <linux/module.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/filelock.h>
|
|
#include <linux/security.h>
|
|
#include <linux/cred.h>
|
|
#include <linux/eventpoll.h>
|
|
#include <linux/rcupdate.h>
|
|
#include <linux/mount.h>
|
|
#include <linux/capability.h>
|
|
#include <linux/cdev.h>
|
|
#include <linux/fsnotify.h>
|
|
#include <linux/sysctl.h>
|
|
#include <linux/percpu_counter.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/task_work.h>
|
|
#include <linux/ima.h>
|
|
#include <linux/swap.h>
|
|
#include <linux/kmemleak.h>
|
|
|
|
#include <linux/atomic.h>
|
|
|
|
#include "internal.h"
|
|
|
|
/* sysctl tunables... */
|
|
static struct files_stat_struct files_stat = {
|
|
.max_files = NR_FILE
|
|
};
|
|
|
|
/* SLAB cache for file structures */
|
|
static struct kmem_cache *filp_cachep __read_mostly;
|
|
|
|
static struct percpu_counter nr_files __cacheline_aligned_in_smp;
|
|
|
|
/* Container for backing file with optional real path */
|
|
struct backing_file {
|
|
struct file file;
|
|
struct path real_path;
|
|
};
|
|
|
|
static inline struct backing_file *backing_file(struct file *f)
|
|
{
|
|
return container_of(f, struct backing_file, file);
|
|
}
|
|
|
|
struct path *backing_file_real_path(struct file *f)
|
|
{
|
|
return &backing_file(f)->real_path;
|
|
}
|
|
EXPORT_SYMBOL_GPL(backing_file_real_path);
|
|
|
|
static void file_free_rcu(struct rcu_head *head)
|
|
{
|
|
struct file *f = container_of(head, struct file, f_rcuhead);
|
|
|
|
put_cred(f->f_cred);
|
|
if (unlikely(f->f_mode & FMODE_BACKING))
|
|
kfree(backing_file(f));
|
|
else
|
|
kmem_cache_free(filp_cachep, f);
|
|
}
|
|
|
|
static inline void file_free(struct file *f)
|
|
{
|
|
security_file_free(f);
|
|
if (unlikely(f->f_mode & FMODE_BACKING))
|
|
path_put(backing_file_real_path(f));
|
|
if (likely(!(f->f_mode & FMODE_NOACCOUNT)))
|
|
percpu_counter_dec(&nr_files);
|
|
call_rcu(&f->f_rcuhead, file_free_rcu);
|
|
}
|
|
|
|
/*
|
|
* Return the total number of open files in the system
|
|
*/
|
|
static long get_nr_files(void)
|
|
{
|
|
return percpu_counter_read_positive(&nr_files);
|
|
}
|
|
|
|
/*
|
|
* Return the maximum number of open files in the system
|
|
*/
|
|
unsigned long get_max_files(void)
|
|
{
|
|
return files_stat.max_files;
|
|
}
|
|
EXPORT_SYMBOL_GPL(get_max_files);
|
|
|
|
#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
|
|
|
|
/*
|
|
* Handle nr_files sysctl
|
|
*/
|
|
static int proc_nr_files(struct ctl_table *table, int write, void *buffer,
|
|
size_t *lenp, loff_t *ppos)
|
|
{
|
|
files_stat.nr_files = get_nr_files();
|
|
return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
|
|
}
|
|
|
|
static struct ctl_table fs_stat_sysctls[] = {
|
|
{
|
|
.procname = "file-nr",
|
|
.data = &files_stat,
|
|
.maxlen = sizeof(files_stat),
|
|
.mode = 0444,
|
|
.proc_handler = proc_nr_files,
|
|
},
|
|
{
|
|
.procname = "file-max",
|
|
.data = &files_stat.max_files,
|
|
.maxlen = sizeof(files_stat.max_files),
|
|
.mode = 0644,
|
|
.proc_handler = proc_doulongvec_minmax,
|
|
.extra1 = SYSCTL_LONG_ZERO,
|
|
.extra2 = SYSCTL_LONG_MAX,
|
|
},
|
|
{
|
|
.procname = "nr_open",
|
|
.data = &sysctl_nr_open,
|
|
.maxlen = sizeof(unsigned int),
|
|
.mode = 0644,
|
|
.proc_handler = proc_dointvec_minmax,
|
|
.extra1 = &sysctl_nr_open_min,
|
|
.extra2 = &sysctl_nr_open_max,
|
|
},
|
|
{ }
|
|
};
|
|
|
|
static int __init init_fs_stat_sysctls(void)
|
|
{
|
|
register_sysctl_init("fs", fs_stat_sysctls);
|
|
if (IS_ENABLED(CONFIG_BINFMT_MISC)) {
|
|
struct ctl_table_header *hdr;
|
|
hdr = register_sysctl_mount_point("fs/binfmt_misc");
|
|
kmemleak_not_leak(hdr);
|
|
}
|
|
return 0;
|
|
}
|
|
fs_initcall(init_fs_stat_sysctls);
|
|
#endif
|
|
|
|
static int init_file(struct file *f, int flags, const struct cred *cred)
|
|
{
|
|
int error;
|
|
|
|
f->f_cred = get_cred(cred);
|
|
error = security_file_alloc(f);
|
|
if (unlikely(error)) {
|
|
put_cred(f->f_cred);
|
|
return error;
|
|
}
|
|
|
|
atomic_long_set(&f->f_count, 1);
|
|
rwlock_init(&f->f_owner.lock);
|
|
spin_lock_init(&f->f_lock);
|
|
mutex_init(&f->f_pos_lock);
|
|
f->f_flags = flags;
|
|
f->f_mode = OPEN_FMODE(flags);
|
|
/* f->f_version: 0 */
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* Find an unused file structure and return a pointer to it.
|
|
* Returns an error pointer if some error happend e.g. we over file
|
|
* structures limit, run out of memory or operation is not permitted.
|
|
*
|
|
* Be very careful using this. You are responsible for
|
|
* getting write access to any mount that you might assign
|
|
* to this filp, if it is opened for write. If this is not
|
|
* done, you will imbalance int the mount's writer count
|
|
* and a warning at __fput() time.
|
|
*/
|
|
struct file *alloc_empty_file(int flags, const struct cred *cred)
|
|
{
|
|
static long old_max;
|
|
struct file *f;
|
|
int error;
|
|
|
|
/*
|
|
* Privileged users can go above max_files
|
|
*/
|
|
if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
|
|
/*
|
|
* percpu_counters are inaccurate. Do an expensive check before
|
|
* we go and fail.
|
|
*/
|
|
if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
|
|
goto over;
|
|
}
|
|
|
|
f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
|
|
if (unlikely(!f))
|
|
return ERR_PTR(-ENOMEM);
|
|
|
|
error = init_file(f, flags, cred);
|
|
if (unlikely(error)) {
|
|
kmem_cache_free(filp_cachep, f);
|
|
return ERR_PTR(error);
|
|
}
|
|
|
|
percpu_counter_inc(&nr_files);
|
|
|
|
return f;
|
|
|
|
over:
|
|
/* Ran out of filps - report that */
|
|
if (get_nr_files() > old_max) {
|
|
pr_info("VFS: file-max limit %lu reached\n", get_max_files());
|
|
old_max = get_nr_files();
|
|
}
|
|
return ERR_PTR(-ENFILE);
|
|
}
|
|
|
|
/*
|
|
* Variant of alloc_empty_file() that doesn't check and modify nr_files.
|
|
*
|
|
* This is only for kernel internal use, and the allocate file must not be
|
|
* installed into file tables or such.
|
|
*/
|
|
struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred)
|
|
{
|
|
struct file *f;
|
|
int error;
|
|
|
|
f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
|
|
if (unlikely(!f))
|
|
return ERR_PTR(-ENOMEM);
|
|
|
|
error = init_file(f, flags, cred);
|
|
if (unlikely(error)) {
|
|
kmem_cache_free(filp_cachep, f);
|
|
return ERR_PTR(error);
|
|
}
|
|
|
|
f->f_mode |= FMODE_NOACCOUNT;
|
|
|
|
return f;
|
|
}
|
|
|
|
/*
|
|
* Variant of alloc_empty_file() that allocates a backing_file container
|
|
* and doesn't check and modify nr_files.
|
|
*
|
|
* This is only for kernel internal use, and the allocate file must not be
|
|
* installed into file tables or such.
|
|
*/
|
|
struct file *alloc_empty_backing_file(int flags, const struct cred *cred)
|
|
{
|
|
struct backing_file *ff;
|
|
int error;
|
|
|
|
ff = kzalloc(sizeof(struct backing_file), GFP_KERNEL);
|
|
if (unlikely(!ff))
|
|
return ERR_PTR(-ENOMEM);
|
|
|
|
error = init_file(&ff->file, flags, cred);
|
|
if (unlikely(error)) {
|
|
kfree(ff);
|
|
return ERR_PTR(error);
|
|
}
|
|
|
|
ff->file.f_mode |= FMODE_BACKING | FMODE_NOACCOUNT;
|
|
return &ff->file;
|
|
}
|
|
|
|
/**
|
|
* alloc_file - allocate and initialize a 'struct file'
|
|
*
|
|
* @path: the (dentry, vfsmount) pair for the new file
|
|
* @flags: O_... flags with which the new file will be opened
|
|
* @fop: the 'struct file_operations' for the new file
|
|
*/
|
|
static struct file *alloc_file(const struct path *path, int flags,
|
|
const struct file_operations *fop)
|
|
{
|
|
struct file *file;
|
|
|
|
file = alloc_empty_file(flags, current_cred());
|
|
if (IS_ERR(file))
|
|
return file;
|
|
|
|
file->f_path = *path;
|
|
file->f_inode = path->dentry->d_inode;
|
|
file->f_mapping = path->dentry->d_inode->i_mapping;
|
|
file->f_wb_err = filemap_sample_wb_err(file->f_mapping);
|
|
file->f_sb_err = file_sample_sb_err(file);
|
|
if (fop->llseek)
|
|
file->f_mode |= FMODE_LSEEK;
|
|
if ((file->f_mode & FMODE_READ) &&
|
|
likely(fop->read || fop->read_iter))
|
|
file->f_mode |= FMODE_CAN_READ;
|
|
if ((file->f_mode & FMODE_WRITE) &&
|
|
likely(fop->write || fop->write_iter))
|
|
file->f_mode |= FMODE_CAN_WRITE;
|
|
file->f_iocb_flags = iocb_flags(file);
|
|
file->f_mode |= FMODE_OPENED;
|
|
file->f_op = fop;
|
|
if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
|
|
i_readcount_inc(path->dentry->d_inode);
|
|
return file;
|
|
}
|
|
|
|
struct file *alloc_file_pseudo(struct inode *inode, struct vfsmount *mnt,
|
|
const char *name, int flags,
|
|
const struct file_operations *fops)
|
|
{
|
|
static const struct dentry_operations anon_ops = {
|
|
.d_dname = simple_dname
|
|
};
|
|
struct qstr this = QSTR_INIT(name, strlen(name));
|
|
struct path path;
|
|
struct file *file;
|
|
|
|
path.dentry = d_alloc_pseudo(mnt->mnt_sb, &this);
|
|
if (!path.dentry)
|
|
return ERR_PTR(-ENOMEM);
|
|
if (!mnt->mnt_sb->s_d_op)
|
|
d_set_d_op(path.dentry, &anon_ops);
|
|
path.mnt = mntget(mnt);
|
|
d_instantiate(path.dentry, inode);
|
|
file = alloc_file(&path, flags, fops);
|
|
if (IS_ERR(file)) {
|
|
ihold(inode);
|
|
path_put(&path);
|
|
}
|
|
return file;
|
|
}
|
|
EXPORT_SYMBOL(alloc_file_pseudo);
|
|
|
|
struct file *alloc_file_clone(struct file *base, int flags,
|
|
const struct file_operations *fops)
|
|
{
|
|
struct file *f = alloc_file(&base->f_path, flags, fops);
|
|
if (!IS_ERR(f)) {
|
|
path_get(&f->f_path);
|
|
f->f_mapping = base->f_mapping;
|
|
}
|
|
return f;
|
|
}
|
|
|
|
/* the real guts of fput() - releasing the last reference to file
|
|
*/
|
|
static void __fput(struct file *file)
|
|
{
|
|
struct dentry *dentry = file->f_path.dentry;
|
|
struct vfsmount *mnt = file->f_path.mnt;
|
|
struct inode *inode = file->f_inode;
|
|
fmode_t mode = file->f_mode;
|
|
|
|
if (unlikely(!(file->f_mode & FMODE_OPENED)))
|
|
goto out;
|
|
|
|
might_sleep();
|
|
|
|
fsnotify_close(file);
|
|
/*
|
|
* The function eventpoll_release() should be the first called
|
|
* in the file cleanup chain.
|
|
*/
|
|
eventpoll_release(file);
|
|
locks_remove_file(file);
|
|
|
|
ima_file_free(file);
|
|
if (unlikely(file->f_flags & FASYNC)) {
|
|
if (file->f_op->fasync)
|
|
file->f_op->fasync(-1, file, 0);
|
|
}
|
|
if (file->f_op->release)
|
|
file->f_op->release(inode, file);
|
|
if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
|
|
!(mode & FMODE_PATH))) {
|
|
cdev_put(inode->i_cdev);
|
|
}
|
|
fops_put(file->f_op);
|
|
put_pid(file->f_owner.pid);
|
|
put_file_access(file);
|
|
dput(dentry);
|
|
if (unlikely(mode & FMODE_NEED_UNMOUNT))
|
|
dissolve_on_fput(mnt);
|
|
mntput(mnt);
|
|
out:
|
|
file_free(file);
|
|
}
|
|
|
|
static LLIST_HEAD(delayed_fput_list);
|
|
static void delayed_fput(struct work_struct *unused)
|
|
{
|
|
struct llist_node *node = llist_del_all(&delayed_fput_list);
|
|
struct file *f, *t;
|
|
|
|
llist_for_each_entry_safe(f, t, node, f_llist)
|
|
__fput(f);
|
|
}
|
|
|
|
static void ____fput(struct callback_head *work)
|
|
{
|
|
__fput(container_of(work, struct file, f_rcuhead));
|
|
}
|
|
|
|
/*
|
|
* If kernel thread really needs to have the final fput() it has done
|
|
* to complete, call this. The only user right now is the boot - we
|
|
* *do* need to make sure our writes to binaries on initramfs has
|
|
* not left us with opened struct file waiting for __fput() - execve()
|
|
* won't work without that. Please, don't add more callers without
|
|
* very good reasons; in particular, never call that with locks
|
|
* held and never call that from a thread that might need to do
|
|
* some work on any kind of umount.
|
|
*/
|
|
void flush_delayed_fput(void)
|
|
{
|
|
delayed_fput(NULL);
|
|
}
|
|
EXPORT_SYMBOL_GPL(flush_delayed_fput);
|
|
|
|
static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
|
|
|
|
void fput(struct file *file)
|
|
{
|
|
if (atomic_long_dec_and_test(&file->f_count)) {
|
|
struct task_struct *task = current;
|
|
|
|
if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
|
|
init_task_work(&file->f_rcuhead, ____fput);
|
|
if (!task_work_add(task, &file->f_rcuhead, TWA_RESUME))
|
|
return;
|
|
/*
|
|
* After this task has run exit_task_work(),
|
|
* task_work_add() will fail. Fall through to delayed
|
|
* fput to avoid leaking *file.
|
|
*/
|
|
}
|
|
|
|
if (llist_add(&file->f_llist, &delayed_fput_list))
|
|
schedule_delayed_work(&delayed_fput_work, 1);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* synchronous analog of fput(); for kernel threads that might be needed
|
|
* in some umount() (and thus can't use flush_delayed_fput() without
|
|
* risking deadlocks), need to wait for completion of __fput() and know
|
|
* for this specific struct file it won't involve anything that would
|
|
* need them. Use only if you really need it - at the very least,
|
|
* don't blindly convert fput() by kernel thread to that.
|
|
*/
|
|
void __fput_sync(struct file *file)
|
|
{
|
|
if (atomic_long_dec_and_test(&file->f_count)) {
|
|
struct task_struct *task = current;
|
|
BUG_ON(!(task->flags & PF_KTHREAD));
|
|
__fput(file);
|
|
}
|
|
}
|
|
|
|
EXPORT_SYMBOL(fput);
|
|
EXPORT_SYMBOL(__fput_sync);
|
|
|
|
void __init files_init(void)
|
|
{
|
|
filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
|
|
SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT, NULL);
|
|
percpu_counter_init(&nr_files, 0, GFP_KERNEL);
|
|
}
|
|
|
|
/*
|
|
* One file with associated inode and dcache is very roughly 1K. Per default
|
|
* do not use more than 10% of our memory for files.
|
|
*/
|
|
void __init files_maxfiles_init(void)
|
|
{
|
|
unsigned long n;
|
|
unsigned long nr_pages = totalram_pages();
|
|
unsigned long memreserve = (nr_pages - nr_free_pages()) * 3/2;
|
|
|
|
memreserve = min(memreserve, nr_pages - 1);
|
|
n = ((nr_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
|
|
|
|
files_stat.max_files = max_t(unsigned long, n, NR_FILE);
|
|
}
|