linux-stable/fs/file_table.c
Linus Torvalds cc4a875cf3 lsm/stable-6.9 PR 20240312
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Merge tag 'lsm-pr-20240312' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm

Pull lsm updates from Paul Moore:

 - Promote IMA/EVM to a proper LSM

   This is the bulk of the diffstat, and the source of all the changes
   in the VFS code. Prior to the start of the LSM stacking work it was
   important that IMA/EVM were separate from the rest of the LSMs,
   complete with their own hooks, infrastructure, etc. as it was the
   only way to enable IMA/EVM at the same time as a LSM.

   However, now that the bulk of the LSM infrastructure supports
   multiple simultaneous LSMs, we can simplify things greatly by
   bringing IMA/EVM into the LSM infrastructure as proper LSMs. This is
   something I've wanted to see happen for quite some time and Roberto
   was kind enough to put in the work to make it happen.

 - Use the LSM hook default values to simplify the call_int_hook() macro

   Previously the call_int_hook() macro required callers to supply a
   default return value, despite a default value being specified when
   the LSM hook was defined.

   This simplifies the macro by using the defined default return value
   which makes life easier for callers and should also reduce the number
   of return value bugs in the future (we've had a few pop up recently,
   hence this work).

 - Use the KMEM_CACHE() macro instead of kmem_cache_create()

   The guidance appears to be to use the KMEM_CACHE() macro when
   possible and there is no reason why we can't use the macro, so let's
   use it.

 - Fix a number of comment typos in the LSM hook comment blocks

   Not much to say here, we fixed some questionable grammar decisions in
   the LSM hook comment blocks.

* tag 'lsm-pr-20240312' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm: (28 commits)
  cred: Use KMEM_CACHE() instead of kmem_cache_create()
  lsm: use default hook return value in call_int_hook()
  lsm: fix typos in security/security.c comment headers
  integrity: Remove LSM
  ima: Make it independent from 'integrity' LSM
  evm: Make it independent from 'integrity' LSM
  evm: Move to LSM infrastructure
  ima: Move IMA-Appraisal to LSM infrastructure
  ima: Move to LSM infrastructure
  integrity: Move integrity_kernel_module_request() to IMA
  security: Introduce key_post_create_or_update hook
  security: Introduce inode_post_remove_acl hook
  security: Introduce inode_post_set_acl hook
  security: Introduce inode_post_create_tmpfile hook
  security: Introduce path_post_mknod hook
  security: Introduce file_release hook
  security: Introduce file_post_open hook
  security: Introduce inode_post_removexattr hook
  security: Introduce inode_post_setattr hook
  security: Align inode_setattr hook definition with EVM
  ...
2024-03-12 20:03:34 -07:00

535 lines
13 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/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 __ro_after_init;
static struct percpu_counter nr_files __cacheline_aligned_in_smp;
/* Container for backing file with optional user path */
struct backing_file {
struct file file;
struct path user_path;
};
static inline struct backing_file *backing_file(struct file *f)
{
return container_of(f, struct backing_file, file);
}
struct path *backing_file_user_path(struct file *f)
{
return &backing_file(f)->user_path;
}
EXPORT_SYMBOL_GPL(backing_file_user_path);
static inline void file_free(struct file *f)
{
security_file_free(f);
if (likely(!(f->f_mode & FMODE_NOACCOUNT)))
percpu_counter_dec(&nr_files);
put_cred(f->f_cred);
if (unlikely(f->f_mode & FMODE_BACKING)) {
path_put(backing_file_user_path(f));
kfree(backing_file(f));
} else {
kmem_cache_free(filp_cachep, f);
}
}
/*
* 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;
}
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 */
/*
* We're SLAB_TYPESAFE_BY_RCU so initialize f_count last. While
* fget-rcu pattern users need to be able to handle spurious
* refcount bumps we should reinitialize the reused file first.
*/
atomic_long_set(&f->f_count, 1);
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;
}
/**
* file_init_path - initialize a 'struct file' based on path
*
* @file: the file to set up
* @path: the (dentry, vfsmount) pair for the new file
* @fop: the 'struct file_operations' for the new file
*/
static void file_init_path(struct file *file, const struct path *path,
const struct file_operations *fop)
{
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);
}
/**
* 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))
file_init_path(file, path, fop);
return file;
}
static inline int alloc_path_pseudo(const char *name, struct inode *inode,
struct vfsmount *mnt, struct path *path)
{
struct qstr this = QSTR_INIT(name, strlen(name));
path->dentry = d_alloc_pseudo(mnt->mnt_sb, &this);
if (!path->dentry)
return -ENOMEM;
path->mnt = mntget(mnt);
d_instantiate(path->dentry, inode);
return 0;
}
struct file *alloc_file_pseudo(struct inode *inode, struct vfsmount *mnt,
const char *name, int flags,
const struct file_operations *fops)
{
int ret;
struct path path;
struct file *file;
ret = alloc_path_pseudo(name, inode, mnt, &path);
if (ret)
return ERR_PTR(ret);
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_pseudo_noaccount(struct inode *inode,
struct vfsmount *mnt, const char *name,
int flags,
const struct file_operations *fops)
{
int ret;
struct path path;
struct file *file;
ret = alloc_path_pseudo(name, inode, mnt, &path);
if (ret)
return ERR_PTR(ret);
file = alloc_empty_file_noaccount(flags, current_cred());
if (IS_ERR(file)) {
ihold(inode);
path_put(&path);
return file;
}
file_init_path(file, &path, fops);
return file;
}
EXPORT_SYMBOL_GPL(alloc_file_pseudo_noaccount);
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);
security_file_release(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_task_work));
}
/*
* 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 (unlikely(!(file->f_mode & (FMODE_BACKING | FMODE_OPENED)))) {
file_free(file);
return;
}
if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
init_task_work(&file->f_task_work, ____fput);
if (!task_work_add(task, &file->f_task_work, 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))
__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_TYPESAFE_BY_RCU | 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);
}