[syzbot] possible deadlock in blkdev_put (2)

From: syzbot
Date: Sat Nov 27 2021 - 02:15:53 EST

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Hello,

syzbot found the following issue on:

HEAD commit: f81e94e91878 Add linux-next specific files for 20211125
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16366216b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=be9183de0824e4d7
dashboard link: https://syzkaller.appspot.com/bug?extid=643e4ce4b6ad1347d372
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, 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+643e4ce4b6ad1347d372@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
5.16.0-rc2-next-20211125-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.3/8204 is trying to acquire lock:
ffff88807df21138 ((wq_completion)loop3){+.+.}-{0:0}, at: flush_workqueue+0xe1/0x15b0 kernel/workqueue.c:2816

but task is already holding lock:
ffff88801a822918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0x97/0x9e0 block/bdev.c:913

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #6 (&disk->open_mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:607 [inline]
__mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
blkdev_get_by_dev.part.0+0x24e/0xb50 block/bdev.c:818
blkdev_get_by_dev+0x6b/0x80 block/bdev.c:858
swsusp_check+0x97/0x2f0 kernel/power/swap.c:1520
software_resume.part.0+0x102/0x1f0 kernel/power/hibernate.c:979
software_resume kernel/power/hibernate.c:86 [inline]
resume_store+0x161/0x190 kernel/power/hibernate.c:1181
kobj_attr_store+0x50/0x80 lib/kobject.c:856
sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:136
kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2162 [inline]
new_sync_write+0x429/0x660 fs/read_write.c:503
vfs_write+0x7cd/0xae0 fs/read_write.c:590
ksys_write+0x12d/0x250 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #5 (system_transition_mutex/1){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:607 [inline]
__mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
software_resume.part.0+0x19/0x1f0 kernel/power/hibernate.c:934
software_resume kernel/power/hibernate.c:86 [inline]
resume_store+0x161/0x190 kernel/power/hibernate.c:1181
kobj_attr_store+0x50/0x80 lib/kobject.c:856
sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:136
kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2162 [inline]
new_sync_write+0x429/0x660 fs/read_write.c:503
vfs_write+0x7cd/0xae0 fs/read_write.c:590
ksys_write+0x12d/0x250 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #4 (&of->mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:607 [inline]
__mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
kernfs_seq_start+0x4b/0x260 fs/kernfs/file.c:112
seq_read_iter+0x2c7/0x1240 fs/seq_file.c:225
kernfs_fop_read_iter+0x44f/0x5f0 fs/kernfs/file.c:241
call_read_iter include/linux/fs.h:2156 [inline]
new_sync_read+0x421/0x6e0 fs/read_write.c:400
vfs_read+0x35c/0x600 fs/read_write.c:481
ksys_read+0x12d/0x250 fs/read_write.c:619
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #3 (&p->lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:607 [inline]
__mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
seq_read_iter+0xdf/0x1240 fs/seq_file.c:182
kernfs_fop_read_iter+0x44f/0x5f0 fs/kernfs/file.c:241
call_read_iter include/linux/fs.h:2156 [inline]
generic_file_splice_read+0x453/0x6d0 fs/splice.c:311
do_splice_to+0x1bf/0x250 fs/splice.c:796
splice_direct_to_actor+0x2c2/0x8c0 fs/splice.c:870
do_splice_direct+0x1b3/0x280 fs/splice.c:979
do_sendfile+0xaf2/0x1250 fs/read_write.c:1245
__do_sys_sendfile64 fs/read_write.c:1310 [inline]
__se_sys_sendfile64 fs/read_write.c:1296 [inline]
__x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1296
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #2 (sb_writers#3){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1810 [inline]
sb_start_write include/linux/fs.h:1880 [inline]
file_start_write include/linux/fs.h:3008 [inline]
lo_write_bvec drivers/block/loop.c:242 [inline]
lo_write_simple drivers/block/loop.c:265 [inline]
do_req_filebacked drivers/block/loop.c:494 [inline]
loop_handle_cmd drivers/block/loop.c:1846 [inline]
loop_process_work+0x1499/0x1db0 drivers/block/loop.c:1886
process_one_work+0x9b2/0x1690 kernel/workqueue.c:2299
worker_thread+0x658/0x11f0 kernel/workqueue.c:2446
kthread+0x405/0x4f0 kernel/kthread.c:345
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

-> #1 ((work_completion)(&lo->rootcg_work)){+.+.}-{0:0}:
process_one_work+0x921/0x1690 kernel/workqueue.c:2275
worker_thread+0x658/0x11f0 kernel/workqueue.c:2446
kthread+0x405/0x4f0 kernel/kthread.c:345
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

-> #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 kernel/locking/lockdep.c:3801 [inline]
__lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5027
lock_acquire kernel/locking/lockdep.c:5637 [inline]
lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
flush_workqueue+0x110/0x15b0 kernel/workqueue.c:2819
drain_workqueue+0x1a5/0x3c0 kernel/workqueue.c:2984
destroy_workqueue+0x71/0x800 kernel/workqueue.c:4421
__loop_clr_fd+0x1ab/0xe20 drivers/block/loop.c:1118
lo_release+0x1ac/0x1f0 drivers/block/loop.c:1750
blkdev_put_whole block/bdev.c:694 [inline]
blkdev_put+0x2fb/0x9e0 block/bdev.c:955
deactivate_locked_super+0x94/0x160 fs/super.c:335
deactivate_super+0xad/0xd0 fs/super.c:366
cleanup_mnt+0x3a2/0x540 fs/namespace.c:1137
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
do_syscall_64+0x42/0xb0 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 syz-executor.3/8204:
#0: ffff88801a822918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0x97/0x9e0 block/bdev.c:913

stack backtrace:
CPU: 0 PID: 8204 Comm: syz-executor.3 Not tainted 5.16.0-rc2-next-20211125-syzkaller #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+0xcd/0x134 lib/dump_stack.c:106
check_noncircular+0x25f/0x2e0 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 kernel/locking/lockdep.c:3801 [inline]
__lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5027
lock_acquire kernel/locking/lockdep.c:5637 [inline]
lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
flush_workqueue+0x110/0x15b0 kernel/workqueue.c:2819
drain_workqueue+0x1a5/0x3c0 kernel/workqueue.c:2984
destroy_workqueue+0x71/0x800 kernel/workqueue.c:4421
__loop_clr_fd+0x1ab/0xe20 drivers/block/loop.c:1118
lo_release+0x1ac/0x1f0 drivers/block/loop.c:1750
blkdev_put_whole block/bdev.c:694 [inline]
blkdev_put+0x2fb/0x9e0 block/bdev.c:955
deactivate_locked_super+0x94/0x160 fs/super.c:335
deactivate_super+0xad/0xd0 fs/super.c:366
cleanup_mnt+0x3a2/0x540 fs/namespace.c:1137
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7fcdf7077f57
Code: ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 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:00007ffc24b336f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007fcdf7077f57
RDX: 00007ffc24b337ca RSI: 000000000000000a RDI: 00007ffc24b337c0
RBP: 00007ffc24b337c0 R08: 00000000ffffffff R09: 00007ffc24b33590
R10: 0000555555c00903 R11: 0000000000000246 R12: 00007fcdf70d0105
R13: 00007ffc24b34880 R14: 0000555555c00810 R15: 00007ffc24b348c0
</TASK>

---
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Next message: Noah Goldstein: "Re: [PATCH v3] x86/lib: Optimize 8x loop and memory clobbers in csum_partial.c"
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