possible deadlock in ext4_file_write_iter (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a89b48fe9308 Linux 4.19.199
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11eb028e300000
kernel config: https://syzkaller.appspot.com/x/.config?x=72b91bfdb2e2b668
dashboard link: https://syzkaller.appspot.com/bug?extid=b2d6c8c9bd3814e427e0
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b2d6c8...@syzkaller.appspotmail.com

WARNING: possible circular locking dependency detected
attempt to access beyond end of device
4.19.199-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/10904 is trying to acquire lock:
0000000040005cae ((wq_completion)"dio/%s"sb->s_id){+.+.}, at: flush_workqueue+0xe8/0x13e0 kernel/workqueue.c:2658
loop1: rw=2049, want=80, limit=16

but task is already holding lock:
000000008805768d (&sb->s_type->i_mutex_key#10){++++}, at: inode_trylock include/linux/fs.h:768 [inline]
000000008805768d (&sb->s_type->i_mutex_key#10){++++}, at: ext4_file_write_iter+0x21f/0xf20 fs/ext4/file.c:238

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&sb->s_type->i_mutex_key#10){++++}:
inode_lock include/linux/fs.h:748 [inline]
__generic_file_fsync+0xb0/0x1f0 fs/libfs.c:989
ext4_sync_file+0xa35/0x1420 fs/ext4/fsync.c:118
vfs_fsync_range+0x13a/0x220 fs/sync.c:197
generic_write_sync include/linux/fs.h:2750 [inline]
dio_complete+0x763/0xac0 fs/direct-io.c:329
process_one_work+0x864/0x1570 kernel/workqueue.c:2153
worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

-> #1 ((work_completion)(&dio->complete_work)){+.+.}:
worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

-> #0 ((wq_completion)"dio/%s"sb->s_id){+.+.}:
flush_workqueue+0x117/0x13e0 kernel/workqueue.c:2661
drain_workqueue+0x1a5/0x460 kernel/workqueue.c:2826
destroy_workqueue+0x75/0x790 kernel/workqueue.c:4177
sb_init_dio_done_wq+0x72/0x90 fs/direct-io.c:634
do_blockdev_direct_IO fs/direct-io.c:1285 [inline]
__blockdev_direct_IO+0x5f55/0xef40 fs/direct-io.c:1419
ext4_direct_IO_write fs/ext4/inode.c:3777 [inline]
ext4_direct_IO+0xae4/0x1c50 fs/ext4/inode.c:3915
generic_file_direct_write+0x208/0x4a0 mm/filemap.c:3073
__generic_file_write_iter+0x2d0/0x610 mm/filemap.c:3252
ext4_file_write_iter+0x2fe/0xf20 fs/ext4/file.c:272
call_write_iter include/linux/fs.h:1821 [inline]
aio_write+0x37f/0x5c0 fs/aio.c:1574
__io_submit_one fs/aio.c:1858 [inline]
io_submit_one+0xecd/0x20c0 fs/aio.c:1909
__do_sys_io_submit fs/aio.c:1953 [inline]
__se_sys_io_submit+0x11b/0x4a0 fs/aio.c:1924
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
(wq_completion)"dio/%s"sb->s_id --> (work_completion)(&dio->complete_work) --> &sb->s_type->i_mutex_key#10

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sb->s_type->i_mutex_key#10);
lock((work_completion)(&dio->complete_work));
lock(&sb->s_type->i_mutex_key#10);
lock((wq_completion)"dio/%s"sb->s_id);

*** DEADLOCK ***

1 lock held by syz-executor.4/10904:
#0: 000000008805768d (&sb->s_type->i_mutex_key#10){++++}, at: inode_trylock include/linux/fs.h:768 [inline]
#0: 000000008805768d (&sb->s_type->i_mutex_key#10){++++}, at: ext4_file_write_iter+0x21f/0xf20 fs/ext4/file.c:238

stack backtrace:
CPU: 0 PID: 10904 Comm: syz-executor.4 Not tainted 4.19.199-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1222
check_prev_add kernel/locking/lockdep.c:1866 [inline]
check_prevs_add kernel/locking/lockdep.c:1979 [inline]
validate_chain kernel/locking/lockdep.c:2420 [inline]
__lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3416
lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
flush_workqueue+0x117/0x13e0 kernel/workqueue.c:2661
drain_workqueue+0x1a5/0x460 kernel/workqueue.c:2826
destroy_workqueue+0x75/0x790 kernel/workqueue.c:4177
sb_init_dio_done_wq+0x72/0x90 fs/direct-io.c:634
do_blockdev_direct_IO fs/direct-io.c:1285 [inline]
__blockdev_direct_IO+0x5f55/0xef40 fs/direct-io.c:1419
ext4_direct_IO_write fs/ext4/inode.c:3777 [inline]
ext4_direct_IO+0xae4/0x1c50 fs/ext4/inode.c:3915
generic_file_direct_write+0x208/0x4a0 mm/filemap.c:3073
__generic_file_write_iter+0x2d0/0x610 mm/filemap.c:3252
ext4_file_write_iter+0x2fe/0xf20 fs/ext4/file.c:272
call_write_iter include/linux/fs.h:1821 [inline]
aio_write+0x37f/0x5c0 fs/aio.c:1574
__io_submit_one fs/aio.c:1858 [inline]
io_submit_one+0xecd/0x20c0 fs/aio.c:1909
__do_sys_io_submit fs/aio.c:1953 [inline]
__se_sys_io_submit+0x11b/0x4a0 fs/aio.c:1924
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4665e9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007feba34e1188 EFLAGS: 00000246 ORIG_RAX: 00000000000000d1
RAX: ffffffffffffffda RBX: 000000000056c038 RCX: 00000000004665e9
RDX: 0000000020000540 RSI: 0000000000000002 RDI: 00007feba34b8000
RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c038
R13: 00007ffc8e2ad96f R14: 00007feba34e1300 R15: 0000000000022000
attempt to access beyond end of device
loop0: rw=2049, want=184, limit=16
attempt to access beyond end of device
attempt to access beyond end of device
attempt to access beyond end of device
loop5: rw=1, want=256, limit=16
loop3: rw=2049, want=184, limit=16
loop1: rw=2049, want=81, limit=16
attempt to access beyond end of device
loop1: rw=2049, want=82, limit=16
attempt to access beyond end of device
loop1: rw=2049, want=84, limit=16
attempt to access beyond end of device
loop1: rw=2049, want=85, limit=16
attempt to access beyond end of device
loop1: rw=2049, want=86, limit=16
attempt to access beyond end of device
loop1: rw=2049, want=87, limit=16
attempt to access beyond end of device
attempt to access beyond end of device
loop1: rw=2049, want=88, limit=16
attempt to access beyond end of device
loop1: rw=2049, want=89, limit=16
attempt to access beyond end of device
loop1: rw=2049, want=185, limit=16
loop0: rw=1, want=256, limit=16
attempt to access beyond end of device
loop3: rw=1, want=256, limit=16
attempt to access beyond end of device
loop1: rw=1, want=257, limit=16
attempt to access beyond end of device
loop2: rw=2049, want=184, limit=16
attempt to access beyond end of device
loop3: rw=2049, want=184, limit=16
attempt to access beyond end of device
loop0: rw=2049, want=184, limit=16
attempt to access beyond end of device
loop2: rw=1, want=256, limit=16
attempt to access beyond end of device
attempt to access beyond end of device
loop1: rw=2049, want=184, limit=16
loop4: rw=2049, want=184, limit=16
attempt to access beyond end of device
loop3: rw=1, want=256, limit=16
attempt to access beyond end of device
loop0: rw=1, want=256, limit=16
attempt to access beyond end of device
loop1: rw=1, want=256, limit=16
attempt to access beyond end of device
loop4: rw=1, want=256, limit=16
attempt to access beyond end of device
loop0: rw=2049, want=184, limit=16
attempt to access beyond end of device
loop1: rw=2049, want=184, limit=16
attempt to access beyond end of device
loop0: rw=1, want=256, limit=16
attempt to access beyond end of device
loop4: rw=2049, want=184, limit=16
attempt to access beyond end of device
loop1: rw=1, want=256, limit=16
Cannot find map_set index 0 as target
Cannot find map_set index 0 as target
attempt to access beyond end of device
loop4: rw=1, want=256, limit=16
Cannot find map_set index 0 as target
Cannot find map_set index 0 as target
attempt to access beyond end of device
loop4: rw=2049, want=184, limit=16
attempt to access beyond end of device
loop1: rw=2049, want=184, limit=16
Cannot find map_set index 0 as target
attempt to access beyond end of device
loop4: rw=1, want=256, limit=16
attempt to access beyond end of device
loop1: rw=1, want=256, limit=16


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.