[syzbot] possible deadlock in blkdev_put (3)

From: syzbot
Date: Sat Mar 12 2022 - 11:31:27 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 68453767131a ARM: Spectre-BHB: provide empty stub for non-..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17bd4709700000
kernel config: https://syzkaller.appspot.com/x/.config?x=16438642a37fea1
dashboard link: https://syzkaller.appspot.com/bug?extid=6479585dfd4dedd3f7e1
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.2

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+6479585dfd4dedd3f7e1@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
5.17.0-rc7-syzkaller-00227-g68453767131a #0 Not tainted
------------------------------------------------------
udevd/6428 is trying to acquire lock:
ffff88801d66a938 ((wq_completion)loop3){+.+.}-{0:0}, at: flush_workqueue+0x172/0x16b0 kernel/workqueue.c:2827

but task is already holding lock:
ffff88801ab90918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xf8/0x7a0 block/bdev.c:902

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #6 (&disk->open_mutex){+.+.}-{3:3}:
lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5639
__mutex_lock_common+0x1d5/0x2590 kernel/locking/mutex.c:600
__mutex_lock kernel/locking/mutex.c:733 [inline]
mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:785
blkdev_get_by_dev+0x169/0xd70 block/bdev.c:804
swsusp_check+0xb0/0x3f0 kernel/power/swap.c:1526
software_resume+0xc8/0x3d0 kernel/power/hibernate.c:979
resume_store+0xdc/0x120 kernel/power/hibernate.c:1181
kernfs_fop_write_iter+0x3b6/0x510 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2074 [inline]
new_sync_write fs/read_write.c:503 [inline]
vfs_write+0xb11/0xe90 fs/read_write.c:590
ksys_write+0x18f/0x2c0 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #5 (system_transition_mutex/1){+.+.}-{3:3}:
lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5639
__mutex_lock_common+0x1d5/0x2590 kernel/locking/mutex.c:600
__mutex_lock kernel/locking/mutex.c:733 [inline]
mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:785
software_resume+0x7a/0x3d0 kernel/power/hibernate.c:934
resume_store+0xdc/0x120 kernel/power/hibernate.c:1181
kernfs_fop_write_iter+0x3b6/0x510 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2074 [inline]
new_sync_write fs/read_write.c:503 [inline]
vfs_write+0xb11/0xe90 fs/read_write.c:590
ksys_write+0x18f/0x2c0 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #4 (&of->mutex){+.+.}-{3:3}:
lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5639
__mutex_lock_common+0x1d5/0x2590 kernel/locking/mutex.c:600
__mutex_lock kernel/locking/mutex.c:733 [inline]
mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:785
kernfs_seq_start+0x50/0x3b0 fs/kernfs/file.c:112
seq_read_iter+0x3cd/0xd30 fs/seq_file.c:225
call_read_iter include/linux/fs.h:2068 [inline]
new_sync_read fs/read_write.c:400 [inline]
vfs_read+0xaf9/0xe60 fs/read_write.c:481
ksys_read+0x18f/0x2c0 fs/read_write.c:619
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #3 (&p->lock){+.+.}-{3:3}:
lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5639
__mutex_lock_common+0x1d5/0x2590 kernel/locking/mutex.c:600
__mutex_lock kernel/locking/mutex.c:733 [inline]
mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:785
seq_read_iter+0xad/0xd30 fs/seq_file.c:182
call_read_iter include/linux/fs.h:2068 [inline]
generic_file_splice_read+0x482/0x760 fs/splice.c:311
do_splice_to fs/splice.c:796 [inline]
splice_direct_to_actor+0x45f/0xd00 fs/splice.c:870
do_splice_direct+0x291/0x3e0 fs/splice.c:979
do_sendfile+0x6fe/0x1040 fs/read_write.c:1245
__do_sys_sendfile64 fs/read_write.c:1310 [inline]
__se_sys_sendfile64+0x171/0x1d0 fs/read_write.c:1296
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #2 (sb_writers#3){.+.+}-{0:0}:
lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5639
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1722 [inline]
sb_start_write include/linux/fs.h:1792 [inline]
file_start_write include/linux/fs.h:2937 [inline]
lo_write_bvec drivers/block/loop.c:243 [inline]
lo_write_simple drivers/block/loop.c:266 [inline]
do_req_filebacked drivers/block/loop.c:495 [inline]
loop_handle_cmd drivers/block/loop.c:1852 [inline]
loop_process_work+0x167f/0x22b0 drivers/block/loop.c:1892
process_one_work+0x86c/0x1190 kernel/workqueue.c:2307
worker_thread+0xab1/0x1300 kernel/workqueue.c:2454
kthread+0x2a3/0x2d0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30

-> #1 ((work_completion)(&lo->rootcg_work)){+.+.}-{0:0}:
lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5639
process_one_work+0x83c/0x1190 kernel/workqueue.c:2283
worker_thread+0xab1/0x1300 kernel/workqueue.c:2454
kthread+0x2a3/0x2d0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30

-> #0 ((wq_completion)loop3){+.+.}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3063 [inline]
check_prevs_add kernel/locking/lockdep.c:3186 [inline]
validate_chain+0x1dfb/0x8250 kernel/locking/lockdep.c:3801
__lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5027
lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5639
flush_workqueue+0x18e/0x16b0 kernel/workqueue.c:2827
drain_workqueue+0xc3/0x3a0 kernel/workqueue.c:2992
destroy_workqueue+0x7d/0xed0 kernel/workqueue.c:4429
__loop_clr_fd+0x1bd/0x980 drivers/block/loop.c:1124
blkdev_put+0x5a7/0x7a0
blkdev_close+0x58/0x80 block/fops.c:517
__fput+0x3fc/0x870 fs/file_table.c:317
task_work_run+0x146/0x1c0 kernel/task_work.c:164
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
exit_to_user_mode_prepare+0x209/0x220 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x2e/0x70 kernel/entry/common.c:300
do_syscall_64+0x53/0xd0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae

other info that might help us debug this:

Chain exists of:
(wq_completion)loop3 --> system_transition_mutex/1 --> &disk->open_mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&disk->open_mutex);
lock(system_transition_mutex/1);
lock(&disk->open_mutex);
lock((wq_completion)loop3);

*** DEADLOCK ***

1 lock held by udevd/6428:
#0: ffff88801ab90918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xf8/0x7a0 block/bdev.c:902

stack backtrace:
CPU: 0 PID: 6428 Comm: udevd Not tainted 5.17.0-rc7-syzkaller-00227-g68453767131a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1dc/0x2d8 lib/dump_stack.c:106
check_noncircular+0x2f9/0x3b0 kernel/locking/lockdep.c:2143
check_prev_add kernel/locking/lockdep.c:3063 [inline]
check_prevs_add kernel/locking/lockdep.c:3186 [inline]
validate_chain+0x1dfb/0x8250 kernel/locking/lockdep.c:3801
__lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5027
lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5639
flush_workqueue+0x18e/0x16b0 kernel/workqueue.c:2827
drain_workqueue+0xc3/0x3a0 kernel/workqueue.c:2992
destroy_workqueue+0x7d/0xed0 kernel/workqueue.c:4429
__loop_clr_fd+0x1bd/0x980 drivers/block/loop.c:1124
blkdev_put+0x5a7/0x7a0
blkdev_close+0x58/0x80 block/fops.c:517
__fput+0x3fc/0x870 fs/file_table.c:317
task_work_run+0x146/0x1c0 kernel/task_work.c:164
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
exit_to_user_mode_prepare+0x209/0x220 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x2e/0x70 kernel/entry/common.c:300
do_syscall_64+0x53/0xd0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f3819885fc3
Code: 48 ff ff ff b8 ff ff ff ff e9 3e ff ff ff 66 0f 1f 84 00 00 00 00 00 64 8b 04 25 18 00 00 00 85 c0 75 14 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8
RSP: 002b:00007ffc29e6f138 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 00007f381972e6a8 RCX: 00007f3819885fc3
RDX: 000000000000001c RSI: 00007ffc29e6e938 RDI: 0000000000000008
RBP: 000055f83c052190 R08: 0000000000000007 R09: 000055f83c057f00
R10: 00007f3819914fc0 R11: 0000000000000246 R12: 0000000000000002
R13: 000055f83c04c1b0 R14: 0000000000000008 R15: 000055f83c028910
</TASK>

---
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Next message: Joe Perches: "Re: [PATCH 1/5] x86/alternative: simplify DUMP_BYTES macro"
Previous message: Trevor Wu: "Re: [PATCH 4/5] ASoC: mediatek: mt8195: add machine driver with mt6359, max98390 and rt5682"
Next in thread: syzbot: "Re: [syzbot] possible deadlock in blkdev_put (3)"
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