[v6.6] INFO: task hung in blkdev_put

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d96eb99e2f0e Linux 6.6.99
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11c164f0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=bfd82343ac39d3b
dashboard link: https://syzkaller.appspot.com/bug?extid=810a82ba4601be510bde
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/11b332f11d00/disk-d96eb99e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8a063193b98f/vmlinux-d96eb99e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b36214b822e5/bzImage-d96eb99e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+810a82...@syzkaller.appspotmail.com

INFO: task syz.1.7394:534 blocked for more than 143 seconds.
Not tainted 6.6.99-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.7394 state:D stack:27912 pid:534 ppid:20914 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x14e2/0x4580 kernel/sched/core.c:6700
schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6833
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x6b7/0xcc0 kernel/locking/mutex.c:747
blkdev_put+0xff/0x760 block/bdev.c:927
blkdev_release+0x84/0x90 block/fops.c:604
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1ce/0x250 kernel/task_work.c:239
get_signal+0x1235/0x1400 kernel/signal.c:2678
arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe8f3b8e9a9
RSP: 002b:00007fe8f4aae038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: 0000000000000000 RBX: 00007fe8f3db5fa0 RCX: 00007fe8f3b8e9a9
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003
RBP: 00007fe8f3c10d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fe8f3db5fa0 R15: 00007fffc6c36558
</TASK>
INFO: task syz.1.7394:539 blocked for more than 143 seconds.
Not tainted 6.6.99-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.7394 state:D stack:27912 pid:539 ppid:20914 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x14e2/0x4580 kernel/sched/core.c:6700
schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6833
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x6b7/0xcc0 kernel/locking/mutex.c:747
blkdev_get_by_dev+0x121/0x600 block/bdev.c:788
blkdev_open+0x152/0x360 block/fops.c:589
do_dentry_open+0x8c6/0x1500 fs/open.c:929
do_open fs/namei.c:3632 [inline]
path_openat+0x274b/0x3190 fs/namei.c:3789
do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
do_sys_open fs/open.c:1434 [inline]
__do_sys_openat fs/open.c:1450 [inline]
__se_sys_openat fs/open.c:1445 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1445
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe8f3b8d310
RSP: 002b:00007fe8f4a6bb70 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000100 RCX: 00007fe8f3b8d310
RDX: 0000000000000100 RSI: 00007fe8f4a6bc10 RDI: 00000000ffffff9c
RBP: 00007fe8f4a6bc10 R08: 0000000000000000 R09: 002364626e2f7665
R10: 0000000000000000 R11: 0000000000000293 R12: cccccccccccccccd
R13: 0000000000000001 R14: 00007fe8f3db6160 R15: 00007fffc6c36558
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
1 lock held by dhcpcd/5454:
2 locks held by getty/5551:
#0: ffff88814ccf30a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x425/0x1380 drivers/tty/n_tty.c:2217
2 locks held by kworker/u4:13/22542:
#0: ffff8880b8e3c458 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:558
#1: ffff8880b8e288c8 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x39c/0x6d0 kernel/sched/psi.c:998
1 lock held by udevd/383:
#0: ffff888021cf34c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x121/0x600 block/bdev.c:788
1 lock held by syz.1.7394/534:
#0: ffff888021cf34c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xff/0x760 block/bdev.c:927
1 lock held by syz.1.7394/539:
#0: ffff888021cf34c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x121/0x600 block/bdev.c:788

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Not tainted 6.6.99-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x39b/0x3d0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
watchdog+0xf41/0xf80 kernel/hung_task.c:379
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 5454 Comm: dhcpcd Not tainted 6.6.99-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:preempt_count_add+0x0/0x1a0 kernel/sched/core.c:5836
Code: e9 5f ff ff ff 48 8b 0c 24 80 e1 07 80 c1 03 38 c1 7c 97 48 8b 3c 24 e8 5e 69 81 00 eb 8c e9 f1 fe ff ff 0f 1f 80 00 00 00 00 <f3> 0f 1e fa 41 57 41 56 53 49 bf 00 00 00 00 00 fc ff df 48 c7 c0
RSP: 0018:ffffc900035b7c38 EFLAGS: 00000002
RAX: 0000000000000001 RBX: ffff88805b8065c0 RCX: a620ff6741ae3f00
RDX: 0000000000000000 RSI: ffffffff8afc6660 RDI: 0000000000000001
RBP: ffffc900035b7cb8 R08: ffffffff8e4a7cef R09: 1ffffffff1c94f9d
R10: dffffc0000000000 R11: fffffbfff1c94f9e R12: ffff88802bf61e00
R13: dffffc0000000000 R14: 1ffff920006b6f88 R15: dffffc0000000000
FS: 00007f0c58bca740(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055d71ebd2078 CR3: 0000000078c73000 CR4: 00000000003506e0
Call Trace:
<TASK>
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:118 [inline]
_raw_spin_lock_irq+0x88/0xe0 kernel/locking/spinlock.c:170
spin_lock_irq include/linux/spinlock.h:376 [inline]
__set_current_blocked+0xeb/0x240 kernel/signal.c:3091
restore_saved_sigmask include/linux/sched/signal.h:550 [inline]
restore_saved_sigmask_unless include/linux/sched/signal.h:560 [inline]
poll_select_finish+0x1e7/0x5e0 fs/select.c:301
__do_sys_ppoll fs/select.c:1119 [inline]
__se_sys_ppoll+0x214/0x260 fs/select.c:1098
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0c58c54407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007fff01473020 EFLAGS: 00000202 ORIG_RAX: 000000000000010f
RAX: ffffffffffffffda RBX: 00007f0c58bca740 RCX: 00007f0c58c54407
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000555e0388e550
RBP: 00007fff01473360 R08: 0000000000000008 R09: 0000000000000000
R10: 00007fff01473360 R11: 0000000000000202 R12: 0000555df35ee5e0
R13: 0000555e03888df0 R14: 0000000000000000 R15: 00007fff01473110
</TASK>


---
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If you want to undo deduplication, reply with:
#syz undup

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: dbcb8d8e4163 Linux 6.6.100
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15b2a8a2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=293251cfa8d8100

dashboard link: https://syzkaller.appspot.com/bug?extid=810a82ba4601be510bde
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13aed4f0580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17aed4f0580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d0b56817a2c3/disk-dbcb8d8e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f0d646b2f7fa/vmlinux-dbcb8d8e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1e0b752a5011/bzImage-dbcb8d8e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+810a82...@syzkaller.appspotmail.com

INFO: task syz.0.97:6141 blocked for more than 143 seconds.
Not tainted 6.6.100-syzkaller #0

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.0.97 state:D stack:26760 pid:6141 ppid:5912 flags:0x00004006

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]

__schedule+0x14d2/0x44d0 kernel/sched/core.c:6700

schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6833
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x6b7/0xcc0 kernel/locking/mutex.c:747
blkdev_put+0xff/0x760 block/bdev.c:927
blkdev_release+0x84/0x90 block/fops.c:604
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1ce/0x250 kernel/task_work.c:239
get_signal+0x1235/0x1400 kernel/signal.c:2678
arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2

RIP: 0033:0x7fb15598e9a9
RSP: 002b:00007fb1567e7038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: 0000000000000000 RBX: 00007fb155bb5fa0 RCX: 00007fb15598e9a9

RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003

RBP: 00007fb155a10d69 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 0000000000000000 R14: 00007fb155bb5fa0 R15: 00007fffdffaef98

</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633

2 locks held by kworker/u5:1/5103:
#0: ffff888021b26538 ((wq_completion)nbd2-recv){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#0: ffff888021b26538 ((wq_completion)nbd2-recv){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
#1: ffffc900031c7d00 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#1: ffffc900031c7d00 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
2 locks held by getty/5558:
#0: ffff88802d5f50a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc900015c02f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x425/0x1380 drivers/tty/n_tty.c:2217
1 lock held by udevd/5819:
#0: ffff8881401264c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x121/0x600 block/bdev.c:788
1 lock held by udevd/5922:
#0: ffff888021dc04c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x121/0x600 block/bdev.c:788
1 lock held by udevd/5923:
#0: ffff888021cdb4c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x121/0x600 block/bdev.c:788
1 lock held by syz.0.97/6141:
#0: ffff8881401264c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xff/0x760 block/bdev.c:927
1 lock held by syz.1.211/6412:
#0: ffff888021cdb4c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xff/0x760 block/bdev.c:927

=============================================

NMI backtrace for cpu 0

CPU: 0 PID: 29 Comm: khungtaskd Not tainted 6.6.100-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x39b/0x3d0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
watchdog+0xf41/0xf80 kernel/hung_task.c:379
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1

CPU: 1 PID: 2964 Comm: kworker/u4:9 Not tainted 6.6.100-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025

Workqueue: bat_events batadv_nc_worker
RIP: 0010:lockdep_hardirqs_on_prepare+0x187/0x760 kernel/locking/lockdep.c:4356
Code: 00 00 48 89 f8 48 c1 e8 03 80 3c 10 00 74 0f e8 5f 09 76 00 48 ba 00 00 00 00 00 fc ff df 48 8b 44 24 10 48 8b 98 d0 0a 00 00 <48> 8d b8 b8 0a 00 00 48 89 f8 48 c1 e8 03 80 3c 10 00 74 05 e8 d0
RSP: 0018:ffffc9000c36f960 EFLAGS: 00000046
RAX: ffff88802c6c1e00 RBX: 471835511319ffd4 RCX: ffffffff96eaa403
RDX: dffffc0000000000 RSI: ffffffff8afc66e0 RDI: ffff88802c6c28d0
RBP: ffffc9000c36fa08 R08: ffffffff8e4a7daf R09: 1ffffffff1c94fb5
R10: dffffc0000000000 R11: fffffbfff1c94fb6 R12: ffffffff8a35e2d1
R13: dffffc0000000000 R14: dffffc0000000000 R15: 1ffff9200186df44
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000001b2c95ffff CR3: 000000002cbef000 CR4: 00000000003506e0
Call Trace:
<TASK>
trace_hardirqs_on+0x28/0x40 kernel/trace/trace_preemptirq.c:61
__local_bh_enable_ip+0x12e/0x1c0 kernel/softirq.c:411
spin_unlock_bh include/linux/spinlock.h:396 [inline]
batadv_nc_purge_paths+0x311/0x3a0 net/batman-adv/network-coding.c:471
batadv_nc_worker+0x328/0x610 net/batman-adv/network-coding.c:720
process_one_work kernel/workqueue.c:2634 [inline]
process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792

kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>

---
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