[syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 635c467cc14e Add linux-next specific files for 20260213
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1452f6e6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=61690c38d1398936
dashboard link: https://syzkaller.appspot.com/bug?extid=7ea2f5e9dfd468201817
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16e41c02580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15813652580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/78b3d15ca8e6/disk-635c467c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a95f3d108ef4/vmlinux-635c467c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e58086838b24/bzImage-635c467c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7ea2f5...@syzkaller.appspotmail.com

INFO: task syz.0.2812:14643 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.2812 state:D stack:25600 pid:14643 tgid:14643 ppid:13375 task_flags:0x400040 flags:0x00080002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5295 [inline]
__schedule+0x1585/0x5340 kernel/sched/core.c:6907
__schedule_loop kernel/sched/core.c:6989 [inline]
schedule+0x164/0x360 kernel/sched/core.c:7004
schedule_timeout+0xc3/0x2c0 kernel/time/sleep_timeout.c:75
do_wait_for_common kernel/sched/completion.c:100 [inline]
__wait_for_common kernel/sched/completion.c:121 [inline]
wait_for_common kernel/sched/completion.c:132 [inline]
wait_for_completion+0x2cc/0x5e0 kernel/sched/completion.c:153
restrict_one_thread security/landlock/tsync.c:128 [inline]
restrict_one_thread_callback+0x320/0x570 security/landlock/tsync.c:162
task_work_run+0x1d9/0x270 kernel/task_work.c:233
get_signal+0x11eb/0x1330 kernel/signal.c:2807
arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8d7f19bf79
RSP: 002b:00007ffe0b192a38 EFLAGS: 00000246 ORIG_RAX: 00000000000000db
RAX: fffffffffffffdfc RBX: 00000000000389f1 RCX: 00007f8d7f19bf79
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f8d7f41618c
RBP: 0000000000000032 R08: 3fffffffffffffff R09: 0000000000000000
R10: 00007ffe0b192b40 R11: 0000000000000246 R12: 00007ffe0b192b60
R13: 00007f8d7f41618c R14: 0000000000038a23 R15: 00007ffe0b192b40
</TASK>
INFO: task syz.0.2812:14644 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.2812 state:D stack:28216 pid:14644 tgid:14643 ppid:13375 task_flags:0x400040 flags:0x00080002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5295 [inline]
__schedule+0x1585/0x5340 kernel/sched/core.c:6907
__schedule_loop kernel/sched/core.c:6989 [inline]
schedule+0x164/0x360 kernel/sched/core.c:7004
schedule_timeout+0xc3/0x2c0 kernel/time/sleep_timeout.c:75
do_wait_for_common kernel/sched/completion.c:100 [inline]
__wait_for_common kernel/sched/completion.c:121 [inline]
wait_for_common kernel/sched/completion.c:132 [inline]
wait_for_completion+0x2cc/0x5e0 kernel/sched/completion.c:153
restrict_one_thread security/landlock/tsync.c:128 [inline]
restrict_one_thread_callback+0x320/0x570 security/landlock/tsync.c:162
task_work_run+0x1d9/0x270 kernel/task_work.c:233
get_signal+0x11eb/0x1330 kernel/signal.c:2807
arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8d7f19bf79
RSP: 002b:00007f8d8007c0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f8d7f415fa8 RCX: 00007f8d7f19bf79
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f8d7f415fa8
RBP: 00007f8d7f415fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8d7f416038 R14: 00007ffe0b1927f0 R15: 00007ffe0b1928d8
</TASK>
INFO: task syz.0.2812:14645 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.2812 state:D stack:28648 pid:14645 tgid:14643 ppid:13375 task_flags:0x400140 flags:0x00080006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5295 [inline]
__schedule+0x1585/0x5340 kernel/sched/core.c:6907
__schedule_loop kernel/sched/core.c:6989 [inline]
schedule+0x164/0x360 kernel/sched/core.c:7004
schedule_timeout+0xc3/0x2c0 kernel/time/sleep_timeout.c:75
do_wait_for_common kernel/sched/completion.c:100 [inline]
__wait_for_common kernel/sched/completion.c:121 [inline]
wait_for_common kernel/sched/completion.c:132 [inline]
wait_for_completion+0x2cc/0x5e0 kernel/sched/completion.c:153
landlock_restrict_sibling_threads+0xe9c/0x11f0 security/landlock/tsync.c:539
__do_sys_landlock_restrict_self security/landlock/syscalls.c:574 [inline]
__se_sys_landlock_restrict_self+0x540/0x810 security/landlock/syscalls.c:482
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8d7f19bf79
RSP: 002b:00007f8d8005b028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007f8d7f416090 RCX: 00007f8d7f19bf79
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000003
RBP: 00007f8d7f2327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8d7f416128 R14: 00007f8d7f416090 R15: 00007ffe0b1928d8
</TASK>
INFO: task syz.0.2812:14646 blocked for more than 144 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.2812 state:D stack:28832 pid:14646 tgid:14643 ppid:13375 task_flags:0x400140 flags:0x00080006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5295 [inline]
__schedule+0x1585/0x5340 kernel/sched/core.c:6907
__schedule_loop kernel/sched/core.c:6989 [inline]
schedule+0x164/0x360 kernel/sched/core.c:7004
schedule_timeout+0xc3/0x2c0 kernel/time/sleep_timeout.c:75
do_wait_for_common kernel/sched/completion.c:100 [inline]
__wait_for_common kernel/sched/completion.c:121 [inline]
wait_for_common kernel/sched/completion.c:132 [inline]
wait_for_completion+0x2cc/0x5e0 kernel/sched/completion.c:153
landlock_restrict_sibling_threads+0xe9c/0x11f0 security/landlock/tsync.c:539
__do_sys_landlock_restrict_self security/landlock/syscalls.c:574 [inline]
__se_sys_landlock_restrict_self+0x540/0x810 security/landlock/syscalls.c:482
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8d7f19bf79
RSP: 002b:00007f8d8003a028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007f8d7f416180 RCX: 00007f8d7f19bf79
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000003
RBP: 00007f8d7f2327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8d7f416218 R14: 00007f8d7f416180 R15: 00007ffe0b1928d8
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
#0: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
#0: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
#0: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
2 locks held by getty/5581:
#0: ffff8880328890a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000332b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45c/0x13c0 drivers/tty/n_tty.c:2211

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:161 [inline]
__sys_info lib/sys_info.c:157 [inline]
sys_info+0x135/0x170 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
watchdog+0xfd9/0x1030 kernel/hung_task.c:515
kthread+0x388/0x470 kernel/kthread.c:467
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 86 Comm: kworker/u8:5 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:native_save_fl arch/x86/include/asm/irqflags.h:26 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:109 [inline]
RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:127 [inline]
RIP: 0010:lock_acquire+0xab/0x2e0 kernel/locking/lockdep.c:5864
Code: 84 c1 00 00 00 65 8b 05 73 b8 9f 11 85 c0 0f 85 b2 00 00 00 65 48 8b 05 bb 72 9f 11 83 b8 14 0b 00 00 00 0f 85 9d 00 00 00 9c <5b> fa 48 c7 c7 8f a1 02 8e e8 57 40 17 0a 65 ff 05 40 b8 9f 11 45
RSP: 0018:ffffc9000260f498 EFLAGS: 00000246
RAX: ffff88801df81e40 RBX: ffffffff818f9166 RCX: 0000000080000002
RDX: 0000000000000000 RSI: ffffffff8176da62 RDI: 1ffffffff1d2c05c
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: ffffc9000260f638 R11: ffffffff81b11580 R12: 0000000000000002
R13: ffffffff8e9602e0 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff88812510b000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe09b2c1ff8 CR3: 000000000e74c000 CR4: 00000000003526f0
Call Trace:
<TASK>
rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
rcu_read_lock include/linux/rcupdate.h:850 [inline]
class_rcu_constructor include/linux/rcupdate.h:1193 [inline]
unwind_next_frame+0xc2/0x23c0 arch/x86/kernel/unwind_orc.c:495
arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
unpoison_slab_object mm/kasan/common.c:340 [inline]
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4501 [inline]
slab_alloc_node mm/slub.c:4830 [inline]
kmem_cache_alloc_node_noprof+0x384/0x690 mm/slub.c:4882
__alloc_skb+0x1d0/0x7d0 net/core/skbuff.c:702
alloc_skb include/linux/skbuff.h:1383 [inline]
nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:819 [inline]
nsim_dev_trap_report drivers/net/netdevsim/dev.c:876 [inline]
nsim_dev_trap_report_work+0x29a/0xb80 drivers/net/netdevsim/dev.c:922
process_one_work+0x949/0x1650 kernel/workqueue.c:3279
process_scheduled_works kernel/workqueue.c:3362 [inline]
worker_thread+0xb46/0x1140 kernel/workqueue.c:3443
kthread+0x388/0x470 kernel/kthread.c:467
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>


---
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