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cd9253c23a
If we have 2 threads that are using the same file descriptor and one of
them is doing direct IO writes while the other is doing fsync, we have a
race where we can end up either:
1) Attempt a fsync without holding the inode's lock, triggering an
assertion failures when assertions are enabled;
2) Do an invalid memory access from the fsync task because the file private
points to memory allocated on stack by the direct IO task and it may be
used by the fsync task after the stack was destroyed.
The race happens like this:
1) A user space program opens a file descriptor with O_DIRECT;
2) The program spawns 2 threads using libpthread for example;
3) One of the threads uses the file descriptor to do direct IO writes,
while the other calls fsync using the same file descriptor.
4) Call task A the thread doing direct IO writes and task B the thread
doing fsyncs;
5) Task A does a direct IO write, and at btrfs_direct_write() sets the
file's private to an on stack allocated private with the member
'fsync_skip_inode_lock' set to true;
6) Task B enters btrfs_sync_file() and sees that there's a private
structure associated to the file which has 'fsync_skip_inode_lock' set
to true, so it skips locking the inode's VFS lock;
7) Task A completes the direct IO write, and resets the file's private to
NULL since it had no prior private and our private was stack allocated.
Then it unlocks the inode's VFS lock;
8) Task B enters btrfs_get_ordered_extents_for_logging(), then the
assertion that checks the inode's VFS lock is held fails, since task B
never locked it and task A has already unlocked it.
The stack trace produced is the following:
assertion failed: inode_is_locked(&inode->vfs_inode), in fs/btrfs/ordered-data.c:983
------------[ cut here ]------------
kernel BUG at fs/btrfs/ordered-data.c:983!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP PTI
CPU: 9 PID: 5072 Comm: worker Tainted: G U OE 6.10.5-1-default #1 openSUSE Tumbleweed 69f48d427608e1c09e60ea24c6c55e2ca1b049e8
Hardware name: Acer Predator PH315-52/Covini_CFS, BIOS V1.12 07/28/2020
RIP: 0010:btrfs_get_ordered_extents_for_logging.cold+0x1f/0x42 [btrfs]
Code: 50 d6 86 c0 e8 (...)
RSP: 0018:ffff9e4a03dcfc78 EFLAGS: 00010246
RAX: 0000000000000054 RBX: ffff9078a9868e98 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff907dce4a7800 RDI: ffff907dce4a7800
RBP: ffff907805518800 R08: 0000000000000000 R09: ffff9e4a03dcfb38
R10: ffff9e4a03dcfb30 R11: 0000000000000003 R12: ffff907684ae7800
R13: 0000000000000001 R14: ffff90774646b600 R15: 0000000000000000
FS: 00007f04b96006c0(0000) GS:ffff907dce480000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f32acbfc000 CR3: 00000001fd4fa005 CR4: 00000000003726f0
Call Trace:
<TASK>
? __die_body.cold+0x14/0x24
? die+0x2e/0x50
? do_trap+0xca/0x110
? do_error_trap+0x6a/0x90
? btrfs_get_ordered_extents_for_logging.cold+0x1f/0x42 [btrfs bb26272d49b4cdc847cf3f7faadd459b62caee9a]
? exc_invalid_op+0x50/0x70
? btrfs_get_ordered_extents_for_logging.cold+0x1f/0x42 [btrfs bb26272d49b4cdc847cf3f7faadd459b62caee9a]
? asm_exc_invalid_op+0x1a/0x20
? btrfs_get_ordered_extents_for_logging.cold+0x1f/0x42 [btrfs bb26272d49b4cdc847cf3f7faadd459b62caee9a]
? btrfs_get_ordered_extents_for_logging.cold+0x1f/0x42 [btrfs bb26272d49b4cdc847cf3f7faadd459b62caee9a]
btrfs_sync_file+0x21a/0x4d0 [btrfs bb26272d49b4cdc847cf3f7faadd459b62caee9a]
? __seccomp_filter+0x31d/0x4f0
__x64_sys_fdatasync+0x4f/0x90
do_syscall_64+0x82/0x160
? do_futex+0xcb/0x190
? __x64_sys_futex+0x10e/0x1d0
? switch_fpu_return+0x4f/0xd0
? syscall_exit_to_user_mode+0x72/0x220
? do_syscall_64+0x8e/0x160
? syscall_exit_to_user_mode+0x72/0x220
? do_syscall_64+0x8e/0x160
? syscall_exit_to_user_mode+0x72/0x220
? do_syscall_64+0x8e/0x160
? syscall_exit_to_user_mode+0x72/0x220
? do_syscall_64+0x8e/0x160
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Another problem here is if task B grabs the private pointer and then uses
it after task A has finished, since the private was allocated in the stack
of task A, it results in some invalid memory access with a hard to predict
result.
This issue, triggering the assertion, was observed with QEMU workloads by
two users in the Link tags below.
Fix this by not relying on a file's private to pass information to fsync
that it should skip locking the inode and instead pass this information
through a special value stored in current->journal_info. This is safe
because in the relevant section of the direct IO write path we are not
holding a transaction handle, so current->journal_info is NULL.
The following C program triggers the issue:
$ cat repro.c
/* Get the O_DIRECT definition. */
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdint.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <pthread.h>
static int fd;
static ssize_t do_write(int fd, const void *buf, size_t count, off_t offset)
{
while (count > 0) {
ssize_t ret;
ret = pwrite(fd, buf, count, offset);
if (ret < 0) {
if (errno == EINTR)
continue;
return ret;
}
count -= ret;
buf += ret;
}
return 0;
}
static void *fsync_loop(void *arg)
{
while (1) {
int ret;
ret = fsync(fd);
if (ret != 0) {
perror("Fsync failed");
exit(6);
}
}
}
int main(int argc, char *argv[])
{
long pagesize;
void *write_buf;
pthread_t fsyncer;
int ret;
if (argc != 2) {
fprintf(stderr, "Use: %s <file path>\n", argv[0]);
return 1;
}
fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC | O_DIRECT, 0666);
if (fd == -1) {
perror("Failed to open/create file");
return 1;
}
pagesize = sysconf(_SC_PAGE_SIZE);
if (pagesize == -1) {
perror("Failed to get page size");
return 2;
}
ret = posix_memalign(&write_buf, pagesize, pagesize);
if (ret) {
perror("Failed to allocate buffer");
return 3;
}
ret = pthread_create(&fsyncer, NULL, fsync_loop, NULL);
if (ret != 0) {
fprintf(stderr, "Failed to create writer thread: %d\n", ret);
return 4;
}
while (1) {
ret = do_write(fd, write_buf, pagesize, 0);
if (ret != 0) {
perror("Write failed");
exit(5);
}
}
return 0;
}
$ mkfs.btrfs -f /dev/sdi
$ mount /dev/sdi /mnt/sdi
$ timeout 10 ./repro /mnt/sdi/foo
Usually the race is triggered within less than 1 second. A test case for
fstests will follow soon.
Reported-by: Paulo Dias <paulo.miguel.dias@gmail.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=219187
Reported-by: Andreas Jahn <jahn-andi@web.de>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=219199
Reported-by: syzbot+4704b3cc972bd76024f1@syzkaller.appspotmail.com
Link: https://lore.kernel.org/linux-btrfs/00000000000044ff540620d7dee2@google.com/
Fixes: 939b656bc8 ("btrfs: fix corruption after buffer fault in during direct IO append write")
CC: stable@vger.kernel.org # 5.15+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
299 lines
9.4 KiB
C
299 lines
9.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (C) 2007 Oracle. All rights reserved.
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*/
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#ifndef BTRFS_TRANSACTION_H
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#define BTRFS_TRANSACTION_H
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#include <linux/atomic.h>
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#include <linux/refcount.h>
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#include <linux/list.h>
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#include <linux/time64.h>
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#include <linux/mutex.h>
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#include <linux/wait.h>
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#include "btrfs_inode.h"
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#include "delayed-ref.h"
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#include "extent-io-tree.h"
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#include "block-rsv.h"
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#include "messages.h"
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#include "misc.h"
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struct dentry;
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struct inode;
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struct btrfs_pending_snapshot;
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struct btrfs_fs_info;
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struct btrfs_root_item;
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struct btrfs_root;
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struct btrfs_path;
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/*
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* Signal that a direct IO write is in progress, to avoid deadlock for sync
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* direct IO writes when fsync is called during the direct IO write path.
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*/
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#define BTRFS_TRANS_DIO_WRITE_STUB ((void *) 1)
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/* Radix-tree tag for roots that are part of the trasaction. */
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#define BTRFS_ROOT_TRANS_TAG 0
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enum btrfs_trans_state {
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TRANS_STATE_RUNNING,
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TRANS_STATE_COMMIT_PREP,
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TRANS_STATE_COMMIT_START,
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TRANS_STATE_COMMIT_DOING,
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TRANS_STATE_UNBLOCKED,
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TRANS_STATE_SUPER_COMMITTED,
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TRANS_STATE_COMPLETED,
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TRANS_STATE_MAX,
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};
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#define BTRFS_TRANS_HAVE_FREE_BGS 0
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#define BTRFS_TRANS_DIRTY_BG_RUN 1
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#define BTRFS_TRANS_CACHE_ENOSPC 2
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struct btrfs_transaction {
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u64 transid;
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/*
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* total external writers(USERSPACE/START/ATTACH) in this
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* transaction, it must be zero before the transaction is
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* being committed
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*/
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atomic_t num_extwriters;
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/*
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* total writers in this transaction, it must be zero before the
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* transaction can end
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*/
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atomic_t num_writers;
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refcount_t use_count;
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unsigned long flags;
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/* Be protected by fs_info->trans_lock when we want to change it. */
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enum btrfs_trans_state state;
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int aborted;
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struct list_head list;
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struct extent_io_tree dirty_pages;
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time64_t start_time;
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wait_queue_head_t writer_wait;
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wait_queue_head_t commit_wait;
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struct list_head pending_snapshots;
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struct list_head dev_update_list;
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struct list_head switch_commits;
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struct list_head dirty_bgs;
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/*
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* There is no explicit lock which protects io_bgs, rather its
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* consistency is implied by the fact that all the sites which modify
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* it do so under some form of transaction critical section, namely:
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*
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* - btrfs_start_dirty_block_groups - This function can only ever be
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* run by one of the transaction committers. Refer to
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* BTRFS_TRANS_DIRTY_BG_RUN usage in btrfs_commit_transaction
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*
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* - btrfs_write_dirty_blockgroups - this is called by
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* commit_cowonly_roots from transaction critical section
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* (TRANS_STATE_COMMIT_DOING)
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*
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* - btrfs_cleanup_dirty_bgs - called on transaction abort
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*/
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struct list_head io_bgs;
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struct list_head dropped_roots;
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struct extent_io_tree pinned_extents;
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/*
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* we need to make sure block group deletion doesn't race with
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* free space cache writeout. This mutex keeps them from stomping
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* on each other
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*/
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struct mutex cache_write_mutex;
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spinlock_t dirty_bgs_lock;
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/* Protected by spin lock fs_info->unused_bgs_lock. */
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struct list_head deleted_bgs;
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spinlock_t dropped_roots_lock;
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struct btrfs_delayed_ref_root delayed_refs;
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struct btrfs_fs_info *fs_info;
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/*
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* Number of ordered extents the transaction must wait for before
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* committing. These are ordered extents started by a fast fsync.
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*/
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atomic_t pending_ordered;
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wait_queue_head_t pending_wait;
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};
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enum {
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ENUM_BIT(__TRANS_FREEZABLE),
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ENUM_BIT(__TRANS_START),
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ENUM_BIT(__TRANS_ATTACH),
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ENUM_BIT(__TRANS_JOIN),
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ENUM_BIT(__TRANS_JOIN_NOLOCK),
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ENUM_BIT(__TRANS_DUMMY),
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ENUM_BIT(__TRANS_JOIN_NOSTART),
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};
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#define TRANS_START (__TRANS_START | __TRANS_FREEZABLE)
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#define TRANS_ATTACH (__TRANS_ATTACH)
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#define TRANS_JOIN (__TRANS_JOIN | __TRANS_FREEZABLE)
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#define TRANS_JOIN_NOLOCK (__TRANS_JOIN_NOLOCK)
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#define TRANS_JOIN_NOSTART (__TRANS_JOIN_NOSTART)
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#define TRANS_EXTWRITERS (__TRANS_START | __TRANS_ATTACH)
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struct btrfs_trans_handle {
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u64 transid;
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u64 bytes_reserved;
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u64 delayed_refs_bytes_reserved;
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u64 chunk_bytes_reserved;
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unsigned long delayed_ref_updates;
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unsigned long delayed_ref_csum_deletions;
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struct btrfs_transaction *transaction;
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struct btrfs_block_rsv *block_rsv;
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struct btrfs_block_rsv *orig_rsv;
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/* Set by a task that wants to create a snapshot. */
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struct btrfs_pending_snapshot *pending_snapshot;
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refcount_t use_count;
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unsigned int type;
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/*
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* Error code of transaction abort, set outside of locks and must use
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* the READ_ONCE/WRITE_ONCE access
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*/
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short aborted;
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bool adding_csums;
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bool allocating_chunk;
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bool removing_chunk;
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bool reloc_reserved;
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bool in_fsync;
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struct btrfs_fs_info *fs_info;
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struct list_head new_bgs;
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struct btrfs_block_rsv delayed_rsv;
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};
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/*
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* The abort status can be changed between calls and is not protected by locks.
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* This accepts btrfs_transaction and btrfs_trans_handle as types. Once it's
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* set to a non-zero value it does not change, so the macro should be in checks
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* but is not necessary for further reads of the value.
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*/
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#define TRANS_ABORTED(trans) (unlikely(READ_ONCE((trans)->aborted)))
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struct btrfs_pending_snapshot {
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struct dentry *dentry;
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struct btrfs_inode *dir;
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struct btrfs_root *root;
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struct btrfs_root_item *root_item;
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struct btrfs_root *snap;
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struct btrfs_qgroup_inherit *inherit;
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struct btrfs_path *path;
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/* block reservation for the operation */
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struct btrfs_block_rsv block_rsv;
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/* extra metadata reservation for relocation */
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int error;
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/* Preallocated anonymous block device number */
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dev_t anon_dev;
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bool readonly;
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struct list_head list;
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};
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static inline void btrfs_set_inode_last_trans(struct btrfs_trans_handle *trans,
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struct btrfs_inode *inode)
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{
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spin_lock(&inode->lock);
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inode->last_trans = trans->transaction->transid;
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inode->last_sub_trans = btrfs_get_root_log_transid(inode->root);
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inode->last_log_commit = inode->last_sub_trans - 1;
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spin_unlock(&inode->lock);
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}
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/*
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* Make qgroup codes to skip given qgroupid, means the old/new_roots for
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* qgroup won't contain the qgroupid in it.
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*/
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static inline void btrfs_set_skip_qgroup(struct btrfs_trans_handle *trans,
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u64 qgroupid)
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{
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struct btrfs_delayed_ref_root *delayed_refs;
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delayed_refs = &trans->transaction->delayed_refs;
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WARN_ON(delayed_refs->qgroup_to_skip);
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delayed_refs->qgroup_to_skip = qgroupid;
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}
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static inline void btrfs_clear_skip_qgroup(struct btrfs_trans_handle *trans)
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{
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struct btrfs_delayed_ref_root *delayed_refs;
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delayed_refs = &trans->transaction->delayed_refs;
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WARN_ON(!delayed_refs->qgroup_to_skip);
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delayed_refs->qgroup_to_skip = 0;
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}
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bool __cold abort_should_print_stack(int error);
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/*
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* Call btrfs_abort_transaction as early as possible when an error condition is
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* detected, that way the exact stack trace is reported for some errors.
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*/
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#define btrfs_abort_transaction(trans, error) \
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do { \
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bool __first = false; \
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/* Report first abort since mount */ \
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if (!test_and_set_bit(BTRFS_FS_STATE_TRANS_ABORTED, \
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&((trans)->fs_info->fs_state))) { \
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__first = true; \
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if (WARN(abort_should_print_stack(error), \
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KERN_ERR \
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"BTRFS: Transaction aborted (error %d)\n", \
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(error))) { \
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/* Stack trace printed. */ \
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} else { \
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btrfs_err((trans)->fs_info, \
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"Transaction aborted (error %d)", \
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(error)); \
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} \
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} \
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__btrfs_abort_transaction((trans), __func__, \
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__LINE__, (error), __first); \
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} while (0)
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int btrfs_end_transaction(struct btrfs_trans_handle *trans);
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struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
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unsigned int num_items);
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struct btrfs_trans_handle *btrfs_start_transaction_fallback_global_rsv(
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struct btrfs_root *root,
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unsigned int num_items);
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struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root);
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struct btrfs_trans_handle *btrfs_join_transaction_spacecache(struct btrfs_root *root);
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struct btrfs_trans_handle *btrfs_join_transaction_nostart(struct btrfs_root *root);
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struct btrfs_trans_handle *btrfs_attach_transaction(struct btrfs_root *root);
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struct btrfs_trans_handle *btrfs_attach_transaction_barrier(
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struct btrfs_root *root);
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int btrfs_wait_for_commit(struct btrfs_fs_info *fs_info, u64 transid);
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void btrfs_add_dead_root(struct btrfs_root *root);
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void btrfs_maybe_wake_unfinished_drop(struct btrfs_fs_info *fs_info);
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int btrfs_clean_one_deleted_snapshot(struct btrfs_fs_info *fs_info);
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int btrfs_commit_transaction(struct btrfs_trans_handle *trans);
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void btrfs_commit_transaction_async(struct btrfs_trans_handle *trans);
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int btrfs_commit_current_transaction(struct btrfs_root *root);
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int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans);
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bool btrfs_should_end_transaction(struct btrfs_trans_handle *trans);
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void btrfs_throttle(struct btrfs_fs_info *fs_info);
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int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
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struct btrfs_root *root);
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int btrfs_write_marked_extents(struct btrfs_fs_info *fs_info,
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struct extent_io_tree *dirty_pages, int mark);
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int btrfs_wait_tree_log_extents(struct btrfs_root *root, int mark);
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int btrfs_transaction_blocked(struct btrfs_fs_info *info);
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void btrfs_put_transaction(struct btrfs_transaction *transaction);
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void btrfs_add_dropped_root(struct btrfs_trans_handle *trans,
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struct btrfs_root *root);
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void btrfs_trans_release_chunk_metadata(struct btrfs_trans_handle *trans);
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void __cold __btrfs_abort_transaction(struct btrfs_trans_handle *trans,
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const char *function,
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unsigned int line, int error, bool first_hit);
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int __init btrfs_transaction_init(void);
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void __cold btrfs_transaction_exit(void);
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#endif
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