[v5.15] INFO: task hung in fuse_simple_request (4)
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syzbot
Oct 25, 2025, 4:54:26 PM (2 days ago) Oct 25
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: ac56c046adf4 Linux 5.15.195
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14f3c258580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=cd83f334cffc0e28ef31
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c11ec9487150/disk-ac56c046.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f1130a72d3a0/vmlinux-ac56c046.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7608cb6a3be5/bzImage-ac56c046.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cd83f3...@syzkaller.appspotmail.com
INFO: task syz.1.431:5682 blocked for more than 144 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.431 state:D stack:27648 pid: 5682 ppid: 4189 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x10e7/0x19c0 fs/fuse/dev.c:515
fuse_flush+0x522/0x720 fs/fuse/file.c:517
filp_close+0xac/0x150 fs/open.c:1363
__range_close fs/file.c:692 [inline]
__close_range+0x208/0x4d0 fs/file.c:747
__do_sys_close_range fs/open.c:1408 [inline]
__se_sys_close_range fs/open.c:1405 [inline]
__x64_sys_close_range+0x76/0x80 fs/open.c:1405
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f30d4580fc9
RSP: 002b:00007ffd08f683b8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: ffffffffffffffda RBX: 00007f30d47d9da0 RCX: 00007f30d4580fc9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f30d47d9da0 R08: 00000000000000e0 R09: 0000000d08f686af
R10: 00007f30d47d9cb0 R11: 0000000000000246 R12: 000000000002907c
R13: 00007f30d47d8090 R14: ffffffffffffffff R15: 00007ffd08f684d0
</TASK>
Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8c11c720 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
1 lock held by udevd/3562:
2 locks held by getty/3947:
#0: ffff88814cd9e098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc900026562e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
3 locks held by kworker/u5:4/4195:
#0: ffff88802a938138 ((wq_completion)hci6){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc900033dfd00 ((work_completion)(&hdev->power_on)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffff8880741ccff0 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_open+0xa4/0x1270 net/bluetooth/hci_core.c:1446
2 locks held by kworker/u4:8/4357:
#0: ffff888016879138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc90003117d00 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
2 locks held by udevd/4411:
3 locks held by kworker/1:12/5844:
#0: ffff888016870938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc90003347d00 ((work_completion)(&pwq->unbound_release_work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffffffff8c1211a8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
#2: ffffffff8c1211a8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x347/0x6b0 kernel/rcu/tree_exp.h:845
3 locks held by kworker/0:19/7154:
#0: ffff8881425e6538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc900032b7d00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffff888148366220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:764 [inline]
#2: ffff888148366220 (&dev->mutex){....}-{3:3}, at: hub_event+0x1a7/0x5560 drivers/usb/core/hub.c:5827
2 locks held by syz.5.866/7422:
#0: ffff888076bbc098 (&tty->ldisc_sem){++++}-{0:0}, at: __tty_ldisc_lock drivers/tty/tty_ldisc.c:300 [inline]
#0: ffff888076bbc098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_lock_pair_timeout drivers/tty/tty_ldisc.c:346 [inline]
#0: ffff888076bbc098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_lock_pair drivers/tty/tty_ldisc.c:377 [inline]
#0: ffff888076bbc098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_release+0x58/0x200 drivers/tty/tty_ldisc.c:802
#1: ffff888076bbe098 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: __tty_ldisc_lock_nested drivers/tty/tty_ldisc.c:306 [inline]
#1: ffff888076bbe098 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: tty_ldisc_lock_pair_timeout drivers/tty/tty_ldisc.c:348 [inline]
#1: ffff888076bbe098 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: tty_ldisc_lock_pair drivers/tty/tty_ldisc.c:377 [inline]
#1: ffff888076bbe098 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: tty_ldisc_release+0x7c/0x200 drivers/tty/tty_ldisc.c:802
=============================================
NMI backtrace for cpu 1
CPU: 1 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
watchdog+0xe0f/0xe50 kernel/hung_task.c:369
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4357 Comm: kworker/u4:8 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: bat_events batadv_nc_worker
RIP: 0010:__lock_acquire+0x41d/0x7c60 kernel/locking/lockdep.c:-1
Code: 10 49 8d 5f 18 48 89 d8 48 c1 e8 03 48 89 44 24 20 42 80 3c 00 00 74 12 48 89 df e8 2d 31 60 00 49 b8 00 00 00 00 00 fc ff df <48> 89 9c 24 a8 00 00 00 48 8b 45 10 48 89 03 65 8b 05 a1 74 a6 7e
RSP: 0018:ffffc90003117820 EFLAGS: 00000046
RAX: 1ffff1100f670523 RBX: ffff88807b382918 RCX: 1ffff1100f670524
RDX: 0000000000000015 RSI: 0000000000000000 RDI: ffff88807b382910
RBP: ffffc90003117a70 R08: dffffc0000000000 R09: 0000000000000000
R10: fffffbfff1ad334e R11: 1ffffffff1ad334d R12: ffff88807b382900
R13: 0000000000000000 R14: 0000000000000015 R15: ffff88807b382900
FS: 0000000000000000(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6665fa3dac CR3: 00000000540be000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:313
rcu_read_lock include/linux/rcupdate.h:740 [inline]
batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:412 [inline]
batadv_nc_worker+0xc9/0x5c0 net/batman-adv/network-coding.c:723
process_one_work+0x863/0x1000 kernel/workqueue.c:2310
worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
syzbot found the following issue on:
HEAD commit: ac56c046adf4 Linux 5.15.195
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14f3c258580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=cd83f334cffc0e28ef31
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c11ec9487150/disk-ac56c046.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f1130a72d3a0/vmlinux-ac56c046.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7608cb6a3be5/bzImage-ac56c046.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cd83f3...@syzkaller.appspotmail.com
INFO: task syz.1.431:5682 blocked for more than 144 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.431 state:D stack:27648 pid: 5682 ppid: 4189 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x10e7/0x19c0 fs/fuse/dev.c:515
fuse_flush+0x522/0x720 fs/fuse/file.c:517
filp_close+0xac/0x150 fs/open.c:1363
__range_close fs/file.c:692 [inline]
__close_range+0x208/0x4d0 fs/file.c:747
__do_sys_close_range fs/open.c:1408 [inline]
__se_sys_close_range fs/open.c:1405 [inline]
__x64_sys_close_range+0x76/0x80 fs/open.c:1405
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f30d4580fc9
RSP: 002b:00007ffd08f683b8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: ffffffffffffffda RBX: 00007f30d47d9da0 RCX: 00007f30d4580fc9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f30d47d9da0 R08: 00000000000000e0 R09: 0000000d08f686af
R10: 00007f30d47d9cb0 R11: 0000000000000246 R12: 000000000002907c
R13: 00007f30d47d8090 R14: ffffffffffffffff R15: 00007ffd08f684d0
</TASK>
Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8c11c720 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
1 lock held by udevd/3562:
2 locks held by getty/3947:
#0: ffff88814cd9e098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc900026562e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
3 locks held by kworker/u5:4/4195:
#0: ffff88802a938138 ((wq_completion)hci6){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc900033dfd00 ((work_completion)(&hdev->power_on)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffff8880741ccff0 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_open+0xa4/0x1270 net/bluetooth/hci_core.c:1446
2 locks held by kworker/u4:8/4357:
#0: ffff888016879138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc90003117d00 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
2 locks held by udevd/4411:
3 locks held by kworker/1:12/5844:
#0: ffff888016870938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc90003347d00 ((work_completion)(&pwq->unbound_release_work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffffffff8c1211a8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
#2: ffffffff8c1211a8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x347/0x6b0 kernel/rcu/tree_exp.h:845
3 locks held by kworker/0:19/7154:
#0: ffff8881425e6538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc900032b7d00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffff888148366220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:764 [inline]
#2: ffff888148366220 (&dev->mutex){....}-{3:3}, at: hub_event+0x1a7/0x5560 drivers/usb/core/hub.c:5827
2 locks held by syz.5.866/7422:
#0: ffff888076bbc098 (&tty->ldisc_sem){++++}-{0:0}, at: __tty_ldisc_lock drivers/tty/tty_ldisc.c:300 [inline]
#0: ffff888076bbc098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_lock_pair_timeout drivers/tty/tty_ldisc.c:346 [inline]
#0: ffff888076bbc098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_lock_pair drivers/tty/tty_ldisc.c:377 [inline]
#0: ffff888076bbc098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_release+0x58/0x200 drivers/tty/tty_ldisc.c:802
#1: ffff888076bbe098 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: __tty_ldisc_lock_nested drivers/tty/tty_ldisc.c:306 [inline]
#1: ffff888076bbe098 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: tty_ldisc_lock_pair_timeout drivers/tty/tty_ldisc.c:348 [inline]
#1: ffff888076bbe098 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: tty_ldisc_lock_pair drivers/tty/tty_ldisc.c:377 [inline]
#1: ffff888076bbe098 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: tty_ldisc_release+0x7c/0x200 drivers/tty/tty_ldisc.c:802
=============================================
NMI backtrace for cpu 1
CPU: 1 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
watchdog+0xe0f/0xe50 kernel/hung_task.c:369
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4357 Comm: kworker/u4:8 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: bat_events batadv_nc_worker
RIP: 0010:__lock_acquire+0x41d/0x7c60 kernel/locking/lockdep.c:-1
Code: 10 49 8d 5f 18 48 89 d8 48 c1 e8 03 48 89 44 24 20 42 80 3c 00 00 74 12 48 89 df e8 2d 31 60 00 49 b8 00 00 00 00 00 fc ff df <48> 89 9c 24 a8 00 00 00 48 8b 45 10 48 89 03 65 8b 05 a1 74 a6 7e
RSP: 0018:ffffc90003117820 EFLAGS: 00000046
RAX: 1ffff1100f670523 RBX: ffff88807b382918 RCX: 1ffff1100f670524
RDX: 0000000000000015 RSI: 0000000000000000 RDI: ffff88807b382910
RBP: ffffc90003117a70 R08: dffffc0000000000 R09: 0000000000000000
R10: fffffbfff1ad334e R11: 1ffffffff1ad334d R12: ffff88807b382900
R13: 0000000000000000 R14: 0000000000000015 R15: ffff88807b382900
FS: 0000000000000000(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6665fa3dac CR3: 00000000540be000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:313
rcu_read_lock include/linux/rcupdate.h:740 [inline]
batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:412 [inline]
batadv_nc_worker+0xc9/0x5c0 net/batman-adv/network-coding.c:723
process_one_work+0x863/0x1000 kernel/workqueue.c:2310
worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
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