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-----BEGIN PGP SIGNATURE----- iHQEABYIAB0WIQQqUNBr3gm4hGXdBJlZ7Krx/gZQ6wUCYpwEZAAKCRBZ7Krx/gZQ 691uAP0QnwO0lOYOa41MfQ6QnzPbiYcffqtUuTJBWyfs8+WnugD2NNGQP7Zjtin9 q0wcv2KA6yY7qgu7RCCbxU/7J0YdCg== =ywuh -----END PGP SIGNATURE----- Merge tag 'pull-18-rc1-work.fd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull file descriptor updates from Al Viro. - Descriptor handling cleanups * tag 'pull-18-rc1-work.fd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: Unify the primitives for file descriptor closing fs: remove fget_many and fput_many interface io_uring_enter(): don't leave f.flags uninitialized
433 lines
11 KiB
C
433 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* linux/fs/file_table.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
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*/
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#include <linux/string.h>
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#include <linux/slab.h>
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#include <linux/file.h>
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#include <linux/fdtable.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/security.h>
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#include <linux/cred.h>
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#include <linux/eventpoll.h>
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#include <linux/rcupdate.h>
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#include <linux/mount.h>
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#include <linux/capability.h>
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#include <linux/cdev.h>
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#include <linux/fsnotify.h>
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#include <linux/sysctl.h>
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#include <linux/percpu_counter.h>
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#include <linux/percpu.h>
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#include <linux/task_work.h>
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#include <linux/ima.h>
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#include <linux/swap.h>
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#include <linux/kmemleak.h>
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#include <linux/atomic.h>
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#include "internal.h"
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/* sysctl tunables... */
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static struct files_stat_struct files_stat = {
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.max_files = NR_FILE
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};
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/* SLAB cache for file structures */
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static struct kmem_cache *filp_cachep __read_mostly;
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static struct percpu_counter nr_files __cacheline_aligned_in_smp;
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static void file_free_rcu(struct rcu_head *head)
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{
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struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
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put_cred(f->f_cred);
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kmem_cache_free(filp_cachep, f);
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}
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static inline void file_free(struct file *f)
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{
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security_file_free(f);
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if (!(f->f_mode & FMODE_NOACCOUNT))
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percpu_counter_dec(&nr_files);
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call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
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}
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/*
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* Return the total number of open files in the system
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*/
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static long get_nr_files(void)
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{
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return percpu_counter_read_positive(&nr_files);
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}
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/*
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* Return the maximum number of open files in the system
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*/
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unsigned long get_max_files(void)
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{
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return files_stat.max_files;
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}
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EXPORT_SYMBOL_GPL(get_max_files);
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
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/*
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* Handle nr_files sysctl
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*/
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static int proc_nr_files(struct ctl_table *table, int write, void *buffer,
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size_t *lenp, loff_t *ppos)
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{
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files_stat.nr_files = get_nr_files();
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return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
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}
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static struct ctl_table fs_stat_sysctls[] = {
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{
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.procname = "file-nr",
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.data = &files_stat,
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.maxlen = sizeof(files_stat),
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.mode = 0444,
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.proc_handler = proc_nr_files,
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},
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{
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.procname = "file-max",
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.data = &files_stat.max_files,
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.maxlen = sizeof(files_stat.max_files),
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.mode = 0644,
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.proc_handler = proc_doulongvec_minmax,
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.extra1 = SYSCTL_LONG_ZERO,
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.extra2 = SYSCTL_LONG_MAX,
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},
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{
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.procname = "nr_open",
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.data = &sysctl_nr_open,
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.maxlen = sizeof(unsigned int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &sysctl_nr_open_min,
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.extra2 = &sysctl_nr_open_max,
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},
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{ }
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};
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static int __init init_fs_stat_sysctls(void)
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{
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register_sysctl_init("fs", fs_stat_sysctls);
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if (IS_ENABLED(CONFIG_BINFMT_MISC)) {
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struct ctl_table_header *hdr;
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hdr = register_sysctl_mount_point("fs/binfmt_misc");
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kmemleak_not_leak(hdr);
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}
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return 0;
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}
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fs_initcall(init_fs_stat_sysctls);
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#endif
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static struct file *__alloc_file(int flags, const struct cred *cred)
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{
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struct file *f;
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int error;
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f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
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if (unlikely(!f))
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return ERR_PTR(-ENOMEM);
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f->f_cred = get_cred(cred);
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error = security_file_alloc(f);
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if (unlikely(error)) {
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file_free_rcu(&f->f_u.fu_rcuhead);
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return ERR_PTR(error);
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}
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atomic_long_set(&f->f_count, 1);
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rwlock_init(&f->f_owner.lock);
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spin_lock_init(&f->f_lock);
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mutex_init(&f->f_pos_lock);
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f->f_flags = flags;
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f->f_mode = OPEN_FMODE(flags);
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/* f->f_version: 0 */
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return f;
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}
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/* Find an unused file structure and return a pointer to it.
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* Returns an error pointer if some error happend e.g. we over file
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* structures limit, run out of memory or operation is not permitted.
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*
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* Be very careful using this. You are responsible for
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* getting write access to any mount that you might assign
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* to this filp, if it is opened for write. If this is not
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* done, you will imbalance int the mount's writer count
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* and a warning at __fput() time.
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*/
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struct file *alloc_empty_file(int flags, const struct cred *cred)
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{
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static long old_max;
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struct file *f;
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/*
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* Privileged users can go above max_files
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*/
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if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
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/*
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* percpu_counters are inaccurate. Do an expensive check before
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* we go and fail.
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*/
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if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
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goto over;
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}
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f = __alloc_file(flags, cred);
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if (!IS_ERR(f))
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percpu_counter_inc(&nr_files);
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return f;
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over:
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/* Ran out of filps - report that */
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if (get_nr_files() > old_max) {
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pr_info("VFS: file-max limit %lu reached\n", get_max_files());
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old_max = get_nr_files();
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}
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return ERR_PTR(-ENFILE);
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}
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/*
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* Variant of alloc_empty_file() that doesn't check and modify nr_files.
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*
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* Should not be used unless there's a very good reason to do so.
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*/
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struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred)
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{
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struct file *f = __alloc_file(flags, cred);
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if (!IS_ERR(f))
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f->f_mode |= FMODE_NOACCOUNT;
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return f;
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}
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/**
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* alloc_file - allocate and initialize a 'struct file'
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*
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* @path: the (dentry, vfsmount) pair for the new file
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* @flags: O_... flags with which the new file will be opened
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* @fop: the 'struct file_operations' for the new file
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*/
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static struct file *alloc_file(const struct path *path, int flags,
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const struct file_operations *fop)
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{
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struct file *file;
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file = alloc_empty_file(flags, current_cred());
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if (IS_ERR(file))
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return file;
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file->f_path = *path;
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file->f_inode = path->dentry->d_inode;
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file->f_mapping = path->dentry->d_inode->i_mapping;
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file->f_wb_err = filemap_sample_wb_err(file->f_mapping);
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file->f_sb_err = file_sample_sb_err(file);
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if ((file->f_mode & FMODE_READ) &&
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likely(fop->read || fop->read_iter))
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file->f_mode |= FMODE_CAN_READ;
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if ((file->f_mode & FMODE_WRITE) &&
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likely(fop->write || fop->write_iter))
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file->f_mode |= FMODE_CAN_WRITE;
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file->f_mode |= FMODE_OPENED;
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file->f_op = fop;
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if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
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i_readcount_inc(path->dentry->d_inode);
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return file;
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}
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struct file *alloc_file_pseudo(struct inode *inode, struct vfsmount *mnt,
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const char *name, int flags,
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const struct file_operations *fops)
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{
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static const struct dentry_operations anon_ops = {
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.d_dname = simple_dname
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};
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struct qstr this = QSTR_INIT(name, strlen(name));
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struct path path;
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struct file *file;
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path.dentry = d_alloc_pseudo(mnt->mnt_sb, &this);
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if (!path.dentry)
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return ERR_PTR(-ENOMEM);
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if (!mnt->mnt_sb->s_d_op)
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d_set_d_op(path.dentry, &anon_ops);
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path.mnt = mntget(mnt);
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d_instantiate(path.dentry, inode);
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file = alloc_file(&path, flags, fops);
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if (IS_ERR(file)) {
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ihold(inode);
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path_put(&path);
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}
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return file;
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}
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EXPORT_SYMBOL(alloc_file_pseudo);
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struct file *alloc_file_clone(struct file *base, int flags,
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const struct file_operations *fops)
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{
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struct file *f = alloc_file(&base->f_path, flags, fops);
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if (!IS_ERR(f)) {
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path_get(&f->f_path);
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f->f_mapping = base->f_mapping;
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}
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return f;
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}
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/* the real guts of fput() - releasing the last reference to file
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*/
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static void __fput(struct file *file)
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{
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struct dentry *dentry = file->f_path.dentry;
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struct vfsmount *mnt = file->f_path.mnt;
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struct inode *inode = file->f_inode;
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fmode_t mode = file->f_mode;
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if (unlikely(!(file->f_mode & FMODE_OPENED)))
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goto out;
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might_sleep();
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fsnotify_close(file);
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/*
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* The function eventpoll_release() should be the first called
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* in the file cleanup chain.
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*/
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eventpoll_release(file);
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locks_remove_file(file);
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ima_file_free(file);
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if (unlikely(file->f_flags & FASYNC)) {
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if (file->f_op->fasync)
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file->f_op->fasync(-1, file, 0);
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}
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if (file->f_op->release)
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file->f_op->release(inode, file);
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if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
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!(mode & FMODE_PATH))) {
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cdev_put(inode->i_cdev);
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}
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fops_put(file->f_op);
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put_pid(file->f_owner.pid);
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if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
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i_readcount_dec(inode);
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if (mode & FMODE_WRITER) {
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put_write_access(inode);
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__mnt_drop_write(mnt);
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}
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dput(dentry);
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if (unlikely(mode & FMODE_NEED_UNMOUNT))
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dissolve_on_fput(mnt);
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mntput(mnt);
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out:
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file_free(file);
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}
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static LLIST_HEAD(delayed_fput_list);
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static void delayed_fput(struct work_struct *unused)
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{
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struct llist_node *node = llist_del_all(&delayed_fput_list);
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struct file *f, *t;
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llist_for_each_entry_safe(f, t, node, f_u.fu_llist)
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__fput(f);
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}
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static void ____fput(struct callback_head *work)
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{
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__fput(container_of(work, struct file, f_u.fu_rcuhead));
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}
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/*
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* If kernel thread really needs to have the final fput() it has done
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* to complete, call this. The only user right now is the boot - we
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* *do* need to make sure our writes to binaries on initramfs has
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* not left us with opened struct file waiting for __fput() - execve()
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* won't work without that. Please, don't add more callers without
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* very good reasons; in particular, never call that with locks
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* held and never call that from a thread that might need to do
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* some work on any kind of umount.
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*/
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void flush_delayed_fput(void)
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{
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delayed_fput(NULL);
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}
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EXPORT_SYMBOL_GPL(flush_delayed_fput);
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static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
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void fput(struct file *file)
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{
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if (atomic_long_dec_and_test(&file->f_count)) {
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struct task_struct *task = current;
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if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
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init_task_work(&file->f_u.fu_rcuhead, ____fput);
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if (!task_work_add(task, &file->f_u.fu_rcuhead, TWA_RESUME))
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return;
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/*
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* After this task has run exit_task_work(),
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* task_work_add() will fail. Fall through to delayed
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* fput to avoid leaking *file.
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*/
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}
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if (llist_add(&file->f_u.fu_llist, &delayed_fput_list))
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schedule_delayed_work(&delayed_fput_work, 1);
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}
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}
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/*
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* synchronous analog of fput(); for kernel threads that might be needed
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* in some umount() (and thus can't use flush_delayed_fput() without
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* risking deadlocks), need to wait for completion of __fput() and know
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* for this specific struct file it won't involve anything that would
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* need them. Use only if you really need it - at the very least,
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* don't blindly convert fput() by kernel thread to that.
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*/
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void __fput_sync(struct file *file)
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{
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if (atomic_long_dec_and_test(&file->f_count)) {
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struct task_struct *task = current;
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BUG_ON(!(task->flags & PF_KTHREAD));
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__fput(file);
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}
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}
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EXPORT_SYMBOL(fput);
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EXPORT_SYMBOL(__fput_sync);
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void __init files_init(void)
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{
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filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
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SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT, NULL);
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percpu_counter_init(&nr_files, 0, GFP_KERNEL);
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}
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/*
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* One file with associated inode and dcache is very roughly 1K. Per default
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* do not use more than 10% of our memory for files.
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*/
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void __init files_maxfiles_init(void)
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{
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unsigned long n;
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unsigned long nr_pages = totalram_pages();
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unsigned long memreserve = (nr_pages - nr_free_pages()) * 3/2;
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memreserve = min(memreserve, nr_pages - 1);
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n = ((nr_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
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files_stat.max_files = max_t(unsigned long, n, NR_FILE);
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}
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