* [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
@ 2026-02-20 11:11 syzbot
2026-02-21 6:27 ` Forwarded: " syzbot
` (12 more replies)
0 siblings, 13 replies; 24+ messages in thread
From: syzbot @ 2026-02-20 11:11 UTC (permalink / raw)
To: anna-maria, frederic, linux-kernel, syzkaller-bugs, tglx
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+7ea2f5e9dfd468201817@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>
---
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 syzkaller@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 syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
If you want to overwrite report's subsystems, reply with:
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If the report is a duplicate of another one, reply with:
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If you want to undo deduplication, reply with:
#syz undup
^ permalink raw reply [flat|nested] 24+ messages in thread
* Forwarded: Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
@ 2026-02-21 6:27 ` syzbot
2026-02-23 13:40 ` Frederic Weisbecker
` (11 subsequent siblings)
12 siblings, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-21 6:27 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
Author: dingyihan@uniontech.com
#syz test
diff --git a/security/landlock/tsync.c b/security/landlock/tsync.c
index 0d2b9c646030..4a6b9d99e594 100644
--- a/security/landlock/tsync.c
+++ b/security/landlock/tsync.c
@@ -447,6 +447,19 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
shared_ctx.new_cred = new_cred;
shared_ctx.set_no_new_privs = task_no_new_privs(current);
+ /*
+ * We must serialize concurrent TSYNC requests within the same thread group.
+ * However, we cannot use a blocking mutex_lock() here. If Thread A holds
+ * the lock and queues task_work on Thread B, and Thread B calls TSYNC and
+ * blocks on the lock, Thread B will never return to user-mode to execute
+ * Thread A's task_work, resulting in a deadlock.
+ *
+ * Using mutex_trylock() allows us to fail gracefully, returning
+ * -ERESTARTNOINTR to process pending task_work and retry the syscall.
+ */
+ if (!mutex_trylock(¤t->signal->cred_guard_mutex))
+ return -ERESTARTNOINTR;
+
/*
* We schedule a pseudo-signal task_work for each of the calling task's
* sibling threads. In the task work, each thread:
@@ -557,5 +570,7 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
tsync_works_release(&works);
+ mutex_unlock(¤t->signal->cred_guard_mutex);
+
return atomic_read(&shared_ctx.preparation_error);
}
^ permalink raw reply related [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
2026-02-21 6:27 ` Forwarded: " syzbot
@ 2026-02-23 13:40 ` Frederic Weisbecker
2026-02-23 15:15 ` Günther Noack
2026-02-24 0:10 ` Hillf Danton
` (10 subsequent siblings)
12 siblings, 1 reply; 24+ messages in thread
From: Frederic Weisbecker @ 2026-02-23 13:40 UTC (permalink / raw)
To: syzbot, Mickaël Salaün, Günther Noack, Paul Moore,
James Morris, Serge E. Hallyn, linux-security-module
Cc: anna-maria, linux-kernel, syzkaller-bugs, tglx
Le Fri, Feb 20, 2026 at 03:11:21AM -0800, syzbot a écrit :
> 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+7ea2f5e9dfd468201817@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
Seems to be related to landlock security module.
Cc'ing maintainers for awareness.
Thanks.
> 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>
>
>
> ---
> 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 syzkaller@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 syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> 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
--
Frederic Weisbecker
SUSE Labs
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-23 13:40 ` Frederic Weisbecker
@ 2026-02-23 15:15 ` Günther Noack
0 siblings, 0 replies; 24+ messages in thread
From: Günther Noack @ 2026-02-23 15:15 UTC (permalink / raw)
To: Frederic Weisbecker
Cc: syzbot, Mickaël Salaün, Paul Moore, James Morris,
Serge E. Hallyn, linux-security-module, anna-maria, linux-kernel,
syzkaller-bugs, tglx
On Mon, Feb 23, 2026 at 02:40:15PM +0100, Frederic Weisbecker wrote:
> Le Fri, Feb 20, 2026 at 03:11:21AM -0800, syzbot a écrit :
> > 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
>
> Seems to be related to landlock security module.
> Cc'ing maintainers for awareness.
Thank you! That is correct. We are already discussing it in
https://lore.kernel.org/all/00A9E53EDC82309F+7b1dfc69-95f8-4ffc-a67c-967de0e2dfee@uniontech.com/
—Günther
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
2026-02-21 6:27 ` Forwarded: " syzbot
2026-02-23 13:40 ` Frederic Weisbecker
@ 2026-02-24 0:10 ` Hillf Danton
2026-02-24 3:05 ` syzbot
2026-02-24 10:00 ` Günther Noack
2026-02-24 3:17 ` Forwarded: " syzbot
` (9 subsequent siblings)
12 siblings, 2 replies; 24+ messages in thread
From: Hillf Danton @ 2026-02-24 0:10 UTC (permalink / raw)
To: syzbot; +Cc: linux-kernel, syzkaller-bugs
On Fri, Feb 20, 2026 at 03:11:21AM -0800
> 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
#syz test
--- x/security/landlock/tsync.c
+++ y/security/landlock/tsync.c
@@ -540,11 +540,8 @@ int landlock_restrict_sibling_threads(co
* of for_each_thread(). We can reset it on each loop iteration because
* all previous loop iterations are done with it already.
*
- * num_preparing is initialized to 1 so that the counter can not go to 0
- * and mark the completion as done before all task works are registered.
- * We decrement it at the end of the loop body.
*/
- atomic_set(&shared_ctx.num_preparing, 1);
+ atomic_set(&shared_ctx.num_preparing, 0);
reinit_completion(&shared_ctx.all_prepared);
/*
@@ -553,11 +550,7 @@ int landlock_restrict_sibling_threads(co
*/
found_more_threads = schedule_task_work(&works, &shared_ctx);
- /*
- * Decrement num_preparing for current, to undo that we initialized it
- * to 1 a few lines above.
- */
- if (atomic_dec_return(&shared_ctx.num_preparing) > 0) {
+ if (atomic_read(&shared_ctx.num_preparing) > 0) {
if (wait_for_completion_interruptible(
&shared_ctx.all_prepared)) {
/* In case of interruption, we need to retry the system call. */
--
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-24 0:10 ` Hillf Danton
@ 2026-02-24 3:05 ` syzbot
2026-02-24 10:00 ` Günther Noack
1 sibling, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-24 3:05 UTC (permalink / raw)
To: hdanton, linux-kernel, syzkaller-bugs
Hello,
syzbot tried to test the proposed patch but the build/boot failed:
batadv0: Interface activated: batadv_slave_0
[ 74.866770][ T5874] batman_adv: batadv0: Interface activated: batadv_slave_1
[ 74.884996][ T58] netdevsim netdevsim0 netdevsim0: set [1, 0] type 2 family 0 port 6081 - 0
[ 74.894310][ T58] netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
[ 74.905283][ T58] netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
[ 74.914746][ T58] netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
[ 75.043478][ T58] netdevsim netdevsim0 netdevsim3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[ 75.127104][ T58] netdevsim netdevsim0 netdevsim2 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[ 75.185369][ T58] netdevsim netdevsim0 netdevsim1 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[ 75.334360][ T58] netdevsim netdevsim0 netdevsim0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[ 75.469719][ T49] wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
[ 75.490337][ T49] wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50
[ 75.518222][ T49] wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
[ 75.526524][ T49] wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
2026/02/24 03:03:58 executed programs: 0
[ 76.930172][ T51] Bluetooth: hci0: unexpected cc 0x0c03 length: 249 > 1
[ 76.938217][ T51] Bluetooth: hci0: unexpected cc 0x1003 length: 249 > 9
[ 76.948739][ T51] Bluetooth: hci0: unexpected cc 0x1001 length: 249 > 9
[ 76.957301][ T51] Bluetooth: hci0: unexpected cc 0x0c23 length: 249 > 4
[ 76.965874][ T51] Bluetooth: hci0: unexpected cc 0x0c38 length: 249 > 2
[ 77.092846][ T5933] chnl_net:caif_netlink_parms(): no params data found
[ 77.162916][ T5933] bridge0: port 1(bridge_slave_0) entered blocking state
[ 77.170555][ T5933] bridge0: port 1(bridge_slave_0) entered disabled state
[ 77.178400][ T5933] bridge_slave_0: entered allmulticast mode
[ 77.187301][ T5933] bridge_slave_0: entered promiscuous mode
[ 77.195638][ T5933] bridge0: port 2(bridge_slave_1) entered blocking state
[ 77.202901][ T5933] bridge0: port 2(bridge_slave_1) entered disabled state
[ 77.210072][ T5933] bridge_slave_1: entered allmulticast mode
[ 77.217641][ T5933] bridge_slave_1: entered promiscuous mode
[ 77.246869][ T5933] bond0: (slave bond_slave_0): Enslaving as an active interface with an up link
[ 77.259177][ T5933] bond0: (slave bond_slave_1): Enslaving as an active interface with an up link
[ 77.296961][ T5933] team0: Port device team_slave_0 added
[ 77.305577][ T5933] team0: Port device team_slave_1 added
[ 77.330912][ T5933] batman_adv: batadv0: Adding interface: batadv_slave_0
[ 77.337915][ T5933] batman_adv: batadv0: The MTU of interface batadv_slave_0 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1532 would solve the problem.
[ 77.363986][ T5933] batman_adv: batadv0: Not using interface batadv_slave_0 (retrying later): interface not active
[ 77.376893][ T5933] batman_adv: batadv0: Adding interface: batadv_slave_1
[ 77.383931][ T5933] batman_adv: batadv0: The MTU of interface batadv_slave_1 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1532 would solve the problem.
[ 77.409943][ T5933] batman_adv: batadv0: Not using interface batadv_slave_1 (retrying later): interface not active
[ 77.455317][ T5933] hsr_slave_0: entered promiscuous mode
[ 77.463048][ T5933] hsr_slave_1: entered promiscuous mode
[ 77.469984][ T5933] debugfs: 'hsr0' already exists in 'hsr'
[ 77.475853][ T5933] Cannot create hsr debugfs directory
[ 77.989478][ T58] bridge_slave_1: left allmulticast mode
[ 77.997034][ T58] bridge_slave_1: left promiscuous mode
[ 78.003996][ T58] bridge0: port 2(bridge_slave_1) entered disabled state
[ 78.014607][ T58] bridge_slave_0: left allmulticast mode
[ 78.020289][ T58] bridge_slave_0: left promiscuous mode
[ 78.027158][ T58] bridge0: port 1(bridge_slave_0) entered disabled state
[ 78.170497][ T58] bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
[ 78.181273][ T58] bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
[ 78.191450][ T58] bond0 (unregistering): Released all slaves
[ 78.312349][ T58] hsr_slave_0: left promiscuous mode
[ 78.318549][ T58] hsr_slave_1: left promiscuous mode
[ 78.327463][ T58] batman_adv: batadv0: Interface deactivated: batadv_slave_0
[ 78.335002][ T58] batman_adv: batadv0: Removing interface: batadv_slave_0
[ 78.348743][ T58] batman_adv: batadv0: Interface deactivated: batadv_slave_1
[ 78.357270][ T58] batman_adv: batadv0: Removing interface: batadv_slave_1
[ 78.372232][ T58] veth1_macvtap: left promiscuous mode
[ 78.377993][ T58] veth0_macvtap: left promiscuous mode
[ 78.384521][ T58] veth1_vlan: left promiscuous mode
[ 78.390232][ T58] veth0_vlan: left promiscuous mode
[ 78.679788][ T58] team0 (unregistering): Port device team_slave_1 removed
[ 78.694967][ T58] team0 (unregistering): Port device team_slave_0 removed
[ 78.820049][ C0] list_del corruption, ffff88806e888490->next is NULL
[ 78.827266][ C0] ------------[ cut here ]------------
[ 78.832719][ C0] kernel BUG at lib/list_debug.c:53!
[ 78.838048][ C0] Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
[ 78.844303][ C0] CPU: 0 UID: 0 PID: 5487 Comm: dhcpcd Not tainted syzkaller #0 PREEMPT(full)
[ 78.853223][ C0] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
[ 78.863256][ C0] RIP: 0010:__list_del_entry_valid_or_report+0xdf/0x190
[ 78.870177][ C0] Code: 49 39 1f 0f 85 9e 00 00 00 b0 01 5b 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc cc 48 c7 c7 40 c1 29 8c 48 89 de e8 c2 29 65 fc 90 <0f> 0b 48 c7 c7 a0 c1 29 8c 48 89 de e8 b0 29 65 fc 90 0f 0b 4c 89
[ 78.889849][ C0] RSP: 0018:ffffc90000007d58 EFLAGS: 00010046
[ 78.895995][ C0] RAX: 0000000000000033 RBX: ffff88806e888490 RCX: f63d3b529a1a7600
[ 78.903953][ C0] RDX: 0000000000000100 RSI: 0000000080000102 RDI: 0000000000000000
[ 78.911915][ C0] RBP: 0000000000000203 R08: ffffc90000007ae7 R09: 1ffff92000000f5c
[ 78.919872][ C0] R10: dffffc0000000000 R11: fffff52000000f5d R12: 1ffff1100dd11092
[ 78.927827][ C0] R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
[ 78.935780][ C0] FS: 00007f45c61e0740(0000) GS:ffff888125009000(0000) knlGS:0000000000000000
[ 78.944695][ C0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 78.951264][ C0] CR2: 0000561094e94138 CR3: 000000003472a000 CR4: 00000000003526f0
[ 78.959224][ C0] Call Trace:
[ 78.962488][ C0] <IRQ>
[ 78.965324][ C0] dst_destroy+0x202/0x5a0
[ 78.969728][ C0] ? _raw_spin_unlock_irqrestore+0x30/0x80
[ 78.975693][ C0] ? rcu_core+0x751/0x1070
[ 78.980104][ C0] ? __pfx_dst_destroy_rcu+0x10/0x10
[ 78.985381][ C0] rcu_core+0x7cd/0x1070
[ 78.989615][ C0] ? __pfx_rcu_core+0x10/0x10
[ 78.994277][ C0] ? _raw_spin_unlock_irqrestore+0x4c/0x80
[ 79.000075][ C0] handle_softirqs+0x22a/0x870
[ 79.004841][ C0] ? do_softirq+0x76/0xd0
[ 79.009165][ C0] ? inet6_fill_ifla6_attrs+0x1150/0x25e0
[ 79.014877][ C0] do_softirq+0x76/0xd0
[ 79.019025][ C0] </IRQ>
[ 79.021949][ C0] <TASK>
[ 79.024871][ C0] __local_bh_enable_ip+0xf8/0x130
[ 79.029987][ C0] inet6_fill_ifla6_attrs+0x1150/0x25e0
[ 79.035523][ C0] ? __pfx_inet6_fill_ifla6_attrs+0x10/0x10
[ 79.041400][ C0] ? nla_put+0xd0/0x150
[ 79.045548][ C0] inet6_fill_link_af+0x9b/0x120
[ 79.050473][ C0] rtnl_fill_link_af+0x1c8/0x440
[ 79.055405][ C0] rtnl_fill_ifinfo+0x1e08/0x20f0
[ 79.060421][ C0] ? __pfx_rtnl_fill_ifinfo+0x10/0x10
[ 79.065866][ C0] ? __asan_memset+0x22/0x50
[ 79.070449][ C0] ? __nla_validate_parse+0x2480/0x2dc0
[ 79.076021][ C0] ? update_load_avg+0x1b0/0x1ec0
[ 79.081042][ C0] ? __lock_acquire+0x6b5/0x2cf0
[ 79.085985][ C0] ? xas_load+0x593/0x5b0
[ 79.090308][ C0] ? xa_find+0x25b/0x2b0
[ 79.094537][ C0] ? xa_find+0x8c/0x2b0
[ 79.098679][ C0] rtnl_dump_ifinfo+0xbb1/0x1180
[ 79.103609][ C0] ? __pfx_rtnl_dump_ifinfo+0x10/0x10
[ 79.109062][ C0] ? __lock_acquire+0x6b5/0x2cf0
[ 79.114005][ C0] ? trace_kmalloc+0x2a/0x110
[ 79.118667][ C0] ? __kmalloc_node_track_caller_noprof+0x4f9/0x7b0
[ 79.125243][ C0] ? __pfx_rtnl_dump_ifinfo+0x10/0x10
[ 79.130598][ C0] rtnl_dumpit+0xa2/0x200
[ 79.134926][ C0] netlink_dump+0x722/0xe80
[ 79.139430][ C0] ? __pfx_netlink_dump+0x10/0x10
[ 79.144446][ C0] ? __netlink_lookup+0x7e4/0x8b0
[ 79.149544][ C0] ? netlink_lookup+0x30/0x200
[ 79.154297][ C0] ? netlink_lookup+0x30/0x200
[ 79.159049][ C0] ? netlink_lookup+0x30/0x200
[ 79.163803][ C0] __netlink_dump_start+0x5cb/0x7e0
[ 79.168994][ C0] rtnetlink_rcv_msg+0xa3a/0xbe0
[ 79.173914][ C0] ? __pfx_rtnl_dump_ifinfo+0x10/0x10
[ 79.179273][ C0] ? rtnetlink_rcv_msg+0x1b9/0xbe0
[ 79.184367][ C0] ? __pfx_rtnetlink_rcv_msg+0x10/0x10
[ 79.189808][ C0] ? __pfx_rtnl_dumpit+0x10/0x10
[ 79.194727][ C0] ? __pfx_rtnl_dump_ifinfo+0x10/0x10
[ 79.200098][ C0] netlink_rcv_skb+0x232/0x4b0
[ 79.204854][ C0] ? __pfx_rtnetlink_rcv_msg+0x10/0x10
[ 79.210320][ C0] ? __pfx_netlink_rcv_skb+0x10/0x10
[ 79.215638][ C0] ? netlink_deliver_tap+0x2e/0x1b0
[ 79.220896][ C0] netlink_unicast+0x80f/0x9b0
[ 79.225675][ C0] ? __pfx_netlink_unicast+0x10/0x10
[ 79.230970][ C0] ? netlink_sendmsg+0x650/0xb40
[ 79.235916][ C0] ? skb_put+0x11b/0x210
[ 79.240161][ C0] netlink_sendmsg+0x813/0xb40
[ 79.244919][ C0] ? __pfx_netlink_sendmsg+0x10/0x10
[ 79.250190][ C0] ? tomoyo_socket_sendmsg_permission+0x1e0/0x300
[ 79.256599][ C0] ? __pfx_netlink_sendmsg+0x10/0x10
[ 79.261870][ C0] sock_sendmsg_nosec+0x18f/0x1d0
[ 79.266890][ C0] __sys_sendto+0x3ff/0x590
[ 79.271378][ C0] ? __pfx___sys_sendto+0x10/0x10
[ 79.276392][ C0] ? rcu_is_watching+0x15/0xb0
[ 79.281149][ C0] __x64_sys_sendto+0xde/0x100
[ 79.285900][ C0] do_syscall_64+0x14d/0xf80
[ 79.290478][ C0] ? trace_irq_disable+0x3b/0x150
[ 79.295493][ C0] ? entry_SYSCALL_64_after_hwframe+0x77/0x7f
[ 79.301544][ C0] ? clear_bhb_loop+0x40/0x90
[ 79.306206][ C0] entry_SYSCALL_64_after_hwframe+0x77/0x7f
[ 79.312116][ C0] RIP: 0033:0x7f45c626a407
[ 79.316533][ C0] 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
[ 79.336123][ C0] RSP: 002b:00007fff5ef7c930 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
[ 79.344524][ C0] RAX: ffffffffffffffda RBX: 00007f45c61e0740 RCX: 00007f45c626a407
[ 79.352489][ C0] RDX: 0000000000000014 RSI: 00007fff5ef7c9c0 RDI: 0000000000000016
[ 79.360448][ C0] RBP: 00007fff5ef7c9a4 R08: 00007fff5ef7c9a4 R09: 000000000000000c
[ 79.368403][ C0] R10: 0000000000000000 R11: 0000000000000202 R12: 00007fff5ef9d2b0
[ 79.376357][ C0] R13: 00007f45c61e06c8 R14: 00007fff5ef7caa0 R15: 00007fff5ef8d080
[ 79.384327][ C0] </TASK>
[ 79.387327][ C0] Modules linked in:
[ 79.391216][ C0] ---[ end trace 0000000000000000 ]---
[ 79.396657][ C0] RIP: 0010:__list_del_entry_valid_or_report+0xdf/0x190
[ 79.403589][ C0] Code: 49 39 1f 0f 85 9e 00 00 00 b0 01 5b 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc cc 48 c7 c7 40 c1 29 8c 48 89 de e8 c2 29 65 fc 90 <0f> 0b 48 c7 c7 a0 c1 29 8c 48 89 de e8 b0 29 65 fc 90 0f 0b 4c 89
[ 79.423200][ C0] RSP: 0018:ffffc90000007d58 EFLAGS: 00010046
[ 79.429261][ C0] RAX: 0000000000000033 RBX: ffff88806e888490 RCX: f63d3b529a1a7600
[ 79.437219][ C0] RDX: 0000000000000100 RSI: 0000000080000102 RDI: 0000000000000000
[ 79.445172][ C0] RBP: 0000000000000203 R08: ffffc90000007ae7 R09: 1ffff92000000f5c
[ 79.453132][ C0] R10: dffffc0000000000 R11: fffff52000000f5d R12: 1ffff1100dd11092
[ 79.461084][ C0] R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
[ 79.469035][ C0] FS: 00007f45c61e0740(0000) GS:ffff888125009000(0000) knlGS:0000000000000000
[ 79.477943][ C0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 79.484508][ C0] CR2: 0000561094e94138 CR3: 000000003472a000 CR4: 00000000003526f0
[ 79.492468][ C0] Kernel panic - not syncing: Fatal exception in interrupt
[ 79.500018][ C0] Kernel Offset: disabled
[ 79.504325][ C0] Rebooting in 86400 seconds..
syzkaller build log:
go env (err=<nil>)
AR='ar'
CC='gcc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='g++'
GCCGO='gccgo'
GO111MODULE='auto'
GOAMD64='v1'
GOARCH='amd64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/syzkaller/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/syzkaller/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build1172046918=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/syzkaller/jobs/linux/gopath/src/github.com/google/syzkaller/go.mod'
GOMODCACHE='/syzkaller/jobs/linux/gopath/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/syzkaller/jobs/linux/gopath'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/syzkaller/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.24.4'
GOWORK=''
PKG_CONFIG='pkg-config'
git status (err=<nil>)
HEAD detached at 1e62d198252
nothing to commit, working tree clean
tput: No value for $TERM and no -T specified
tput: No value for $TERM and no -T specified
Makefile:31: run command via tools/syz-env for best compatibility, see:
Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
go list -f '{{.Stale}}' -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336" ./sys/syz-sysgen | grep -q false || go install -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336" ./sys/syz-sysgen
make .descriptions
tput: No value for $TERM and no -T specified
tput: No value for $TERM and no -T specified
Makefile:31: run command via tools/syz-env for best compatibility, see:
Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
bin/syz-sysgen
touch .descriptions
GOOS=linux GOARCH=amd64 go build -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336" -o ./bin/linux_amd64/syz-execprog github.com/google/syzkaller/tools/syz-execprog
mkdir -p ./bin/linux_amd64
g++ -o ./bin/linux_amd64/syz-executor executor/executor.cc \
-m64 -O2 -pthread -Wall -Werror -Wparentheses -Wunused-const-variable -Wframe-larger-than=16384 -Wno-stringop-overflow -Wno-array-bounds -Wno-format-overflow -Wno-unused-but-set-variable -Wno-unused-command-line-argument -static-pie -std=c++17 -I. -Iexecutor/_include -DGOOS_linux=1 -DGOARCH_amd64=1 \
-DHOSTGOOS_linux=1 -DGIT_REVISION=\"1e62d1982527c3b4e18df04d61f2560fa1f434cc\"
/usr/bin/ld: /tmp/ccL3cRx2.o: in function `Connection::Connect(char const*, char const*)':
executor.cc:(.text._ZN10Connection7ConnectEPKcS1_[_ZN10Connection7ConnectEPKcS1_]+0x386): warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
./tools/check-syzos.sh 2>/dev/null
Error text is too large and was truncated, full error text is at:
https://syzkaller.appspot.com/x/error.txt?x=11bac006580000
Tested on:
commit: 779cae95 Add linux-next specific files for 20260223
git tree: linux-next
kernel config: https://syzkaller.appspot.com/x/.config?x=ee920513e4deca5f
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
patch: https://syzkaller.appspot.com/x/patch.diff?x=15d8e55a580000
^ permalink raw reply [flat|nested] 24+ messages in thread
* Forwarded: Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
` (2 preceding siblings ...)
2026-02-24 0:10 ` Hillf Danton
@ 2026-02-24 3:17 ` syzbot
2026-02-24 4:25 ` syzbot
` (8 subsequent siblings)
12 siblings, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-24 3:17 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
Author: dingyihan@uniontech.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
--- a/security/landlock/tsync.c
+++ b/security/landlock/tsync.c
@@ -447,6 +447,12 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
shared_ctx.new_cred = new_cred;
shared_ctx.set_no_new_privs = task_no_new_privs(current);
+ /*
+ * Serialize concurrent TSYNC operations to prevent deadlocks
+ * when multiple threads call landlock_restrict_self() simultaneously.
+ */
+ down_write(¤t->signal->exec_update_lock);
+
/*
* We schedule a pseudo-signal task_work for each of the calling task's
* sibling threads. In the task work, each thread:
@@ -527,14 +533,17 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
-ERESTARTNOINTR);
/*
- * Cancel task works for tasks that did not start running yet,
- * and decrement all_prepared and num_unfinished accordingly.
+ * Opportunistic improvement: try to cancel task works
+ * for tasks that did not start running yet. We do not
+ * have a guarantee that it cancels any of the enqueued
+ * task works (because task_work_run() might already have
+ * dequeued them).
*/
cancel_tsync_works(&works, &shared_ctx);
/*
- * The remaining task works have started running, so waiting for
- * their completion will finish.
+ * We must wait for the remaining task works to finish to
+ * prevent a use-after-free of the local shared_ctx.
*/
wait_for_completion(&shared_ctx.all_prepared);
}
@@ -557,5 +566,7 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
tsync_works_release(&works);
+ up_write(¤t->signal->exec_update_lock);
+
return atomic_read(&shared_ctx.preparation_error);
}
在 2026/2/24 11:03, syzbot 写道:
>> Hi Günther,
>>
>> Thank you for the detailed analysis! I completely agree that serializing the TSYNC
>> operations is the right way to prevent this deadlock. I have drafted a patch using
>> `exec_update_lock` (similar to how seccomp uses `cred_guard_mutex`).
>>
>> Regarding your proposal to split this into two patches (one for the cleanup
>> path and one for the lock): Maybe combining them into a single patch is a better choice. Here is why:
>>
>> We actually *cannot* remove `wait_for_completion(&shared_ctx.all_prepared)`
>> in the interrupt recovery path. Since `shared_ctx` is allocated on the local
>> stack of the caller, removing the wait would cause a severe Use-After-Free (UAF) if the
>> thread returns to userspace while sibling task_works are still executing and dereferencing `ctx`.
>>
>> By adding the lock, we inherently resolve the deadlock, meaning the sibling task_works
>> will never get stuck. Thus, `wait_for_completion` becomes perfectly safe to keep,
>> and it remains strictly necessary to protect the stack memory. Therefore, the "fix" for the
>> cleanup path is simply updating the comments to reflect this reality, which is tightly coupled with the locking fix.
>> It felt more cohesive as a single patch.
>>
>> I have test the patch on my laptop,and it will not trigger the issue.Let's have syzbot test this combined logic:
>>
>> #syz test:
>
> "---" does not look like a valid git repo address.
>
^ permalink raw reply [flat|nested] 24+ messages in thread
* Forwarded: Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
` (3 preceding siblings ...)
2026-02-24 3:17 ` Forwarded: " syzbot
@ 2026-02-24 4:25 ` syzbot
2026-02-24 14:43 ` syzbot
` (7 subsequent siblings)
12 siblings, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-24 4:25 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
Author: dingyihan@uniontech.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 635c467cc14e
--- a/security/landlock/tsync.c
+++ b/security/landlock/tsync.c
@@ -447,6 +447,12 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
shared_ctx.new_cred = new_cred;
shared_ctx.set_no_new_privs = task_no_new_privs(current);
+ /*
+ * Serialize concurrent TSYNC operations to prevent deadlocks
+ * when multiple threads call landlock_restrict_self() simultaneously.
+ */
+ down_write(¤t->signal->exec_update_lock);
+
/*
* We schedule a pseudo-signal task_work for each of the calling task's
* sibling threads. In the task work, each thread:
@@ -527,14 +533,17 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
-ERESTARTNOINTR);
/*
- * Cancel task works for tasks that did not start running yet,
- * and decrement all_prepared and num_unfinished accordingly.
+ * Opportunistic improvement: try to cancel task works
+ * for tasks that did not start running yet. We do not
+ * have a guarantee that it cancels any of the enqueued
+ * task works (because task_work_run() might already have
+ * dequeued them).
*/
cancel_tsync_works(&works, &shared_ctx);
/*
- * The remaining task works have started running, so waiting for
- * their completion will finish.
+ * We must wait for the remaining task works to finish to
+ * prevent a use-after-free of the local shared_ctx.
*/
wait_for_completion(&shared_ctx.all_prepared);
}
@@ -557,5 +566,7 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
tsync_works_release(&works);
+ up_write(¤t->signal->exec_update_lock);
+
return atomic_read(&shared_ctx.preparation_error);
}
在 2026/2/24 12:08, syzbot 写道:
> Hello,
>
> syzbot tried to test the proposed patch but the build/boot failed:
>
> team0: Port device team_slave_1 added
> [ 77.956359][ T5910] batman_adv: batadv0: Adding interface: batadv_slave_0
> [ 77.963600][ T5910] batman_adv: batadv0: The MTU of interface batadv_slave_0 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1532 would solve the problem.
> [ 77.989888][ T5910] batman_adv: batadv0: Not using interface batadv_slave_0 (retrying later): interface not active
> [ 78.004522][ T5910] batman_adv: batadv0: Adding interface: batadv_slave_1
> [ 78.011605][ T5910] batman_adv: batadv0: The MTU of interface batadv_slave_1 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1532 would solve the problem.
> [ 78.038002][ T5910] batman_adv: batadv0: Not using interface batadv_slave_1 (retrying later): interface not active
> [ 78.080982][ T5910] hsr_slave_0: entered promiscuous mode
> [ 78.087753][ T5910] hsr_slave_1: entered promiscuous mode
> [ 78.233618][ T5910] netdevsim netdevsim0 netdevsim0: renamed from eth0
> [ 78.246125][ T5910] netdevsim netdevsim0 netdevsim1: renamed from eth1
> [ 78.256883][ T5910] netdevsim netdevsim0 netdevsim2: renamed from eth2
> [ 78.267118][ T5910] netdevsim netdevsim0 netdevsim3: renamed from eth3
> [ 78.297441][ T5910] bridge0: port 2(bridge_slave_1) entered blocking state
> [ 78.304646][ T5910] bridge0: port 2(bridge_slave_1) entered forwarding state
> [ 78.312595][ T5910] bridge0: port 1(bridge_slave_0) entered blocking state
> [ 78.319734][ T5910] bridge0: port 1(bridge_slave_0) entered forwarding state
> [ 78.384207][ T5910] 8021q: adding VLAN 0 to HW filter on device bond0
> [ 78.404563][ T1004] bridge0: port 1(bridge_slave_0) entered disabled state
> [ 78.413314][ T1004] bridge0: port 2(bridge_slave_1) entered disabled state
> [ 78.428785][ T5910] 8021q: adding VLAN 0 to HW filter on device team0
> [ 78.443104][ T65] bridge0: port 1(bridge_slave_0) entered blocking state
> [ 78.450377][ T65] bridge0: port 1(bridge_slave_0) entered forwarding state
> [ 78.464952][ T12] bridge0: port 2(bridge_slave_1) entered blocking state
> [ 78.472313][ T12] bridge0: port 2(bridge_slave_1) entered forwarding state
> [ 78.645479][ T5910] 8021q: adding VLAN 0 to HW filter on device batadv0
> [ 78.696816][ T5910] veth0_vlan: entered promiscuous mode
> [ 78.709183][ T5910] veth1_vlan: entered promiscuous mode
> [ 78.745020][ T5910] veth0_macvtap: entered promiscuous mode
> [ 78.756102][ T5910] veth1_macvtap: entered promiscuous mode
> [ 78.779292][ T5910] batman_adv: batadv0: Interface activated: batadv_slave_0
> [ 78.795080][ T5910] batman_adv: batadv0: Interface activated: batadv_slave_1
> [ 78.812914][ T12] netdevsim netdevsim0 netdevsim0: set [1, 0] type 2 family 0 port 6081 - 0
> [ 78.824397][ T12] netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
> [ 78.840142][ T12] netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
> [ 78.850096][ T12] netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
> [ 78.975137][ T13] netdevsim netdevsim0 netdevsim3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
> [ 79.080924][ T13] netdevsim netdevsim0 netdevsim2 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
> [ 79.141701][ T13] netdevsim netdevsim0 netdevsim1 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
> [ 79.219381][ T13] netdevsim netdevsim0 netdevsim0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
> 2026/02/24 04:06:47 executed programs: 0
> [ 79.336447][ T5143] Bluetooth: hci0: unexpected cc 0x0c03 length: 249 > 1
> [ 79.347436][ T5143] Bluetooth: hci0: unexpected cc 0x1003 length: 249 > 9
> [ 79.355112][ T5143] Bluetooth: hci0: unexpected cc 0x1001 length: 249 > 9
> [ 79.363931][ T5143] Bluetooth: hci0: unexpected cc 0x0c23 length: 249 > 4
> [ 79.372285][ T5143] Bluetooth: hci0: unexpected cc 0x0c38 length: 249 > 2
> [ 79.509332][ T5936] chnl_net:caif_netlink_parms(): no params data found
> [ 79.580835][ T5936] bridge0: port 1(bridge_slave_0) entered blocking state
> [ 79.588539][ T5936] bridge0: port 1(bridge_slave_0) entered disabled state
> [ 79.596107][ T5936] bridge_slave_0: entered allmulticast mode
> [ 79.603587][ T5936] bridge_slave_0: entered promiscuous mode
> [ 79.613548][ T5936] bridge0: port 2(bridge_slave_1) entered blocking state
> [ 79.620886][ T5936] bridge0: port 2(bridge_slave_1) entered disabled state
> [ 79.628076][ T5936] bridge_slave_1: entered allmulticast mode
> [ 79.635811][ T5936] bridge_slave_1: entered promiscuous mode
> [ 79.673346][ T5936] bond0: (slave bond_slave_0): Enslaving as an active interface with an up link
> [ 79.687123][ T5936] bond0: (slave bond_slave_1): Enslaving as an active interface with an up link
> [ 79.721491][ T5936] team0: Port device team_slave_0 added
> [ 79.729676][ T5936] team0: Port device team_slave_1 added
> [ 79.759645][ T5936] batman_adv: batadv0: Adding interface: batadv_slave_0
> [ 79.766762][ T5936] batman_adv: batadv0: The MTU of interface batadv_slave_0 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1532 would solve the problem.
> [ 79.793316][ T5936] batman_adv: batadv0: Not using interface batadv_slave_0 (retrying later): interface not active
> [ 79.806250][ T5936] batman_adv: batadv0: Adding interface: batadv_slave_1
> [ 79.816021][ T5936] batman_adv: batadv0: The MTU of interface batadv_slave_1 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1532 would solve the problem.
> [ 79.842146][ T5936] batman_adv: batadv0: Not using interface batadv_slave_1 (retrying later): interface not active
> [ 79.891341][ T5936] hsr_slave_0: entered promiscuous mode
> [ 79.898314][ T5936] hsr_slave_1: entered promiscuous mode
> [ 79.906509][ T5936] debugfs: 'hsr0' already exists in 'hsr'
> [ 79.913302][ T5936] Cannot create hsr debugfs directory
> [ 81.411273][ T51] Bluetooth: hci0: command tx timeout
> [ 81.652909][ T42] cfg80211: failed to load regulatory.db
> [ 81.863344][ T13] bridge_slave_1: left allmulticast mode
> [ 81.869093][ T13] bridge_slave_1: left promiscuous mode
> [ 81.875947][ T13] bridge0: port 2(bridge_slave_1) entered disabled state
> [ 81.886804][ T13] bridge_slave_0: left allmulticast mode
> [ 81.895320][ T13] bridge_slave_0: left promiscuous mode
> [ 81.902418][ T13] bridge0: port 1(bridge_slave_0) entered disabled state
> [ 82.056915][ T13] bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
> [ 82.067689][ T13] bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
> [ 82.077661][ T13] bond0 (unregistering): Released all slaves
> [ 82.165586][ T13] hsr_slave_0: left promiscuous mode
> [ 82.171808][ T13] hsr_slave_1: left promiscuous mode
> [ 82.177965][ T13] batman_adv: batadv0: Interface deactivated: batadv_slave_0
> [ 82.188972][ T13] batman_adv: batadv0: Removing interface: batadv_slave_0
> [ 82.201305][ T13] batman_adv: batadv0: Interface deactivated: batadv_slave_1
> [ 82.208712][ T13] batman_adv: batadv0: Removing interface: batadv_slave_1
> [ 82.224168][ T13] veth1_macvtap: left promiscuous mode
> [ 82.229800][ T13] veth0_macvtap: left promiscuous mode
> [ 82.235949][ T13] veth1_vlan: left promiscuous mode
> [ 82.243307][ T13] veth0_vlan: left promiscuous mode
> [ 82.524939][ T13] team0 (unregistering): Port device team_slave_1 removed
> [ 82.542673][ T13] team0 (unregistering): Port device team_slave_0 removed
> [ 82.750272][ C1] list_del corruption, ffff88802a450890->next is NULL
> [ 82.757771][ C1] ------------[ cut here ]------------
> [ 82.763241][ C1] kernel BUG at lib/list_debug.c:53!
> [ 82.768569][ C1] Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
> [ 82.774843][ C1] CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full)
> [ 82.783771][ C1] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
> [ 82.793910][ C1] RIP: 0010:__list_del_entry_valid_or_report+0xdf/0x190
> [ 82.800835][ C1] Code: 49 39 1f 0f 85 9e 00 00 00 b0 01 5b 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc cc 48 c7 c7 40 c1 29 8c 48 89 de e8 42 29 65 fc 90 <0f> 0b 48 c7 c7 a0 c1 29 8c 48 89 de e8 30 29 65 fc 90 0f 0b 4c 89
> [ 82.820420][ C1] RSP: 0018:ffffc90000a08d58 EFLAGS: 00010046
> [ 82.826480][ C1] RAX: 0000000000000033 RBX: ffff88802a450890 RCX: e58e7f17a2332a00
> [ 82.834525][ C1] RDX: 0000000000000100 RSI: 0000000000000102 RDI: 0000000000000000
> [ 82.842485][ C1] RBP: 0000000000000203 R08: ffffc90000a08ae7 R09: 1ffff9200014115c
> [ 82.850447][ C1] R10: dffffc0000000000 R11: fffff5200014115d R12: 1ffff1100548a112
> [ 82.858428][ C1] R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
> [ 82.866388][ C1] FS: 0000000000000000(0000) GS:ffff888125109000(0000) knlGS:0000000000000000
> [ 82.875311][ C1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 82.881921][ C1] CR2: 00007f396a9de368 CR3: 000000000e74c000 CR4: 00000000003526f0
> [ 82.889883][ C1] Call Trace:
> [ 82.893147][ C1] <IRQ>
> [ 82.896012][ C1] dst_destroy+0x202/0x5a0
> [ 82.900422][ C1] ? _raw_spin_unlock_irqrestore+0x30/0x80
> [ 82.906213][ C1] ? rcu_core+0x751/0x1070
> [ 82.910617][ C1] ? __pfx_dst_destroy_rcu+0x10/0x10
> [ 82.915891][ C1] rcu_core+0x7cd/0x1070
> [ 82.920126][ C1] ? __pfx_rcu_core+0x10/0x10
> [ 82.924791][ C1] ? sched_balance_domains+0x13a/0x950
> [ 82.930242][ C1] handle_softirqs+0x22a/0x870
> [ 82.935088][ C1] ? __irq_exit_rcu+0x5f/0x150
> [ 82.939842][ C1] __irq_exit_rcu+0x5f/0x150
> [ 82.944421][ C1] irq_exit_rcu+0x9/0x30
> [ 82.948653][ C1] sysvec_apic_timer_interrupt+0xa6/0xc0
> [ 82.954279][ C1] </IRQ>
> [ 82.957194][ C1] <TASK>
> [ 82.960106][ C1] asm_sysvec_apic_timer_interrupt+0x1a/0x20
> [ 82.966079][ C1] RIP: 0010:pv_native_safe_halt+0xf/0x20
> [ 82.971695][ C1] Code: ee 73 02 c3 cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 43 5d 10 00 fb f4 <e9> 7c ea 02 00 cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
> [ 82.991282][ C1] RSP: 0018:ffffc90000197e20 EFLAGS: 00000242
> [ 82.997334][ C1] RAX: 0000000000045cc1 RBX: ffffffff819ad30d RCX: 0000000080000001
> [ 83.005293][ C1] RDX: 0000000000000001 RSI: ffffffff8e013334 RDI: ffffffff8c29be00
> [ 83.013439][ C1] RBP: ffffc90000197f10 R08: ffff8880b853395b R09: 1ffff110170a672b
> [ 83.021511][ C1] R10: dffffc0000000000 R11: ffffed10170a672c R12: ffffffff9033b6b0
> [ 83.029470][ C1] R13: 1ffff11003b5e000 R14: 0000000000000001 R15: 0000000000000001
> [ 83.037433][ C1] ? do_idle+0x1bd/0x500
> [ 83.041683][ C1] default_idle+0x9/0x20
> [ 83.045914][ C1] default_idle_call+0x72/0xb0
> [ 83.050753][ C1] do_idle+0x1bd/0x500
> [ 83.054807][ C1] ? _raw_spin_unlock_irqrestore+0x4c/0x80
> [ 83.060598][ C1] ? __pfx_do_idle+0x10/0x10
> [ 83.065174][ C1] ? _raw_spin_unlock_irqrestore+0x30/0x80
> [ 83.071057][ C1] cpu_startup_entry+0x43/0x60
> [ 83.075812][ C1] start_secondary+0x101/0x110
> [ 83.080648][ C1] common_startup_64+0x13e/0x147
> [ 83.085576][ C1] </TASK>
> [ 83.088575][ C1] Modules linked in:
> [ 83.092472][ C1] ---[ end trace 0000000000000000 ]---
> [ 83.097909][ C1] RIP: 0010:__list_del_entry_valid_or_report+0xdf/0x190
> [ 83.104866][ C1] Code: 49 39 1f 0f 85 9e 00 00 00 b0 01 5b 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc cc 48 c7 c7 40 c1 29 8c 48 89 de e8 42 29 65 fc 90 <0f> 0b 48 c7 c7 a0 c1 29 8c 48 89 de e8 30 29 65 fc 90 0f 0b 4c 89
> [ 83.124458][ C1] RSP: 0018:ffffc90000a08d58 EFLAGS: 00010046
> [ 83.130525][ C1] RAX: 0000000000000033 RBX: ffff88802a450890 RCX: e58e7f17a2332a00
> [ 83.138482][ C1] RDX: 0000000000000100 RSI: 0000000000000102 RDI: 0000000000000000
> [ 83.146435][ C1] RBP: 0000000000000203 R08: ffffc90000a08ae7 R09: 1ffff9200014115c
> [ 83.154477][ C1] R10: dffffc0000000000 R11: fffff5200014115d R12: 1ffff1100548a112
> [ 83.162435][ C1] R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
> [ 83.170390][ C1] FS: 0000000000000000(0000) GS:ffff888125109000(0000) knlGS:0000000000000000
> [ 83.179304][ C1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 83.185872][ C1] CR2: 00007f396a9de368 CR3: 000000000e74c000 CR4: 00000000003526f0
> [ 83.193840][ C1] Kernel panic - not syncing: Fatal exception in interrupt
> [ 83.201135][ C1] Kernel Offset: disabled
> [ 83.205437][ C1] Rebooting in 86400 seconds..
>
>
> syzkaller build log:
> go env (err=<nil>)
> AR='ar'
> CC='gcc'
> CGO_CFLAGS='-O2 -g'
> CGO_CPPFLAGS=''
> CGO_CXXFLAGS='-O2 -g'
> CGO_ENABLED='1'
> CGO_FFLAGS='-O2 -g'
> CGO_LDFLAGS='-O2 -g'
> CXX='g++'
> GCCGO='gccgo'
> GO111MODULE='auto'
> GOAMD64='v1'
> GOARCH='amd64'
> GOAUTH='netrc'
> GOBIN=''
> GOCACHE='/syzkaller/.cache/go-build'
> GOCACHEPROG=''
> GODEBUG=''
> GOENV='/syzkaller/.config/go/env'
> GOEXE=''
> GOEXPERIMENT=''
> GOFIPS140='off'
> GOFLAGS=''
> GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build3187194119=/tmp/go-build -gno-record-gcc-switches'
> GOHOSTARCH='amd64'
> GOHOSTOS='linux'
> GOINSECURE=''
> GOMOD='/syzkaller/jobs-2/linux/gopath/src/github.com/google/syzkaller/go.mod'
> GOMODCACHE='/syzkaller/jobs-2/linux/gopath/pkg/mod'
> GONOPROXY=''
> GONOSUMDB=''
> GOOS='linux'
> GOPATH='/syzkaller/jobs-2/linux/gopath'
> GOPRIVATE=''
> GOPROXY='https://proxy.golang.org,direct'
> GOROOT='/usr/local/go'
> GOSUMDB='sum.golang.org'
> GOTELEMETRY='local'
> GOTELEMETRYDIR='/syzkaller/.config/go/telemetry'
> GOTMPDIR=''
> GOTOOLCHAIN='auto'
> GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'
> GOVCS=''
> GOVERSION='go1.24.4'
> GOWORK=''
> PKG_CONFIG='pkg-config'
>
> git status (err=<nil>)
> HEAD detached at 1e62d19825
> nothing to commit, working tree clean
>
>
> tput: No value for $TERM and no -T specified
> tput: No value for $TERM and no -T specified
> Makefile:31: run command via tools/syz-env for best compatibility, see:
> Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
> go list -f '{{.Stale}}' -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336" ./sys/syz-sysgen | grep -q false || go install -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336" ./sys/syz-sysgen
> make .descriptions
> tput: No value for $TERM and no -T specified
> tput: No value for $TERM and no -T specified
> Makefile:31: run command via tools/syz-env for best compatibility, see:
> Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
> bin/syz-sysgen
> touch .descriptions
> GOOS=linux GOARCH=amd64 go build -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336" -o ./bin/linux_amd64/syz-execprog github.com/google/syzkaller/tools/syz-execprog
> mkdir -p ./bin/linux_amd64
> g++ -o ./bin/linux_amd64/syz-executor executor/executor.cc \
> -m64 -O2 -pthread -Wall -Werror -Wparentheses -Wunused-const-variable -Wframe-larger-than=16384 -Wno-stringop-overflow -Wno-array-bounds -Wno-format-overflow -Wno-unused-but-set-variable -Wno-unused-command-line-argument -static-pie -std=c++17 -I. -Iexecutor/_include -DGOOS_linux=1 -DGOARCH_amd64=1 \
> -DHOSTGOOS_linux=1 -DGIT_REVISION=\"1e62d1982527c3b4e18df04d61f2560fa1f434cc\"
> /usr/bin/ld: /tmp/ccAQ1hzd.o: in function `Connection::Connect(char const*, char const*)':
> executor.cc:(.text._ZN10Connection7ConnectEPKcS1_[_ZN10Connection7ConnectEPKcS1_]+0x386): warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
> ./tools/check-syzos.sh 2>/dev/null
>
>
> Error text is too large and was truncated, full error text is at:
> https://syzkaller.appspot.com/x/error.txt?x=11c2155a580000
>
>
> Tested on:
>
> commit: 779cae95 Add linux-next specific files for 20260223
> git tree: linux-next
> kernel config: https://syzkaller.appspot.com/x/.config?x=ee920513e4deca5f
> 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
> patch: https://syzkaller.appspot.com/x/patch.diff?x=1782455a580000
>
>
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-24 0:10 ` Hillf Danton
2026-02-24 3:05 ` syzbot
@ 2026-02-24 10:00 ` Günther Noack
1 sibling, 0 replies; 24+ messages in thread
From: Günther Noack @ 2026-02-24 10:00 UTC (permalink / raw)
To: Hillf Danton; +Cc: syzbot, linux-kernel, syzkaller-bugs
On Tue, Feb 24, 2026 at 08:10:30AM +0800, Hillf Danton wrote:
> On Fri, Feb 20, 2026 at 03:11:21AM -0800
> > 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
>
> #syz test
>
> --- x/security/landlock/tsync.c
> +++ y/security/landlock/tsync.c
> @@ -540,11 +540,8 @@ int landlock_restrict_sibling_threads(co
> * of for_each_thread(). We can reset it on each loop iteration because
> * all previous loop iterations are done with it already.
> *
> - * num_preparing is initialized to 1 so that the counter can not go to 0
> - * and mark the completion as done before all task works are registered.
> - * We decrement it at the end of the loop body.
> */
> - atomic_set(&shared_ctx.num_preparing, 1);
> + atomic_set(&shared_ctx.num_preparing, 0);
> reinit_completion(&shared_ctx.all_prepared);
>
> /*
> @@ -553,11 +550,7 @@ int landlock_restrict_sibling_threads(co
> */
> found_more_threads = schedule_task_work(&works, &shared_ctx);
>
> - /*
> - * Decrement num_preparing for current, to undo that we initialized it
> - * to 1 a few lines above.
> - */
> - if (atomic_dec_return(&shared_ctx.num_preparing) > 0) {
> + if (atomic_read(&shared_ctx.num_preparing) > 0) {
> if (wait_for_completion_interruptible(
> &shared_ctx.all_prepared)) {
> /* In case of interruption, we need to retry the system call. */
> --
Hello Hillf!
Thanks for your contribution;
We have already analyzed the bug on an adjacent mail thread and have a
tentative patch of which we know it'll fix the issue:
https://lore.kernel.org/all/20260224062729.2908692-1-dingyihan@uniontech.com/
–Günther
^ permalink raw reply [flat|nested] 24+ messages in thread
* Forwarded: Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
` (4 preceding siblings ...)
2026-02-24 4:25 ` syzbot
@ 2026-02-24 14:43 ` syzbot
2026-02-25 5:10 ` Hillf Danton
` (6 subsequent siblings)
12 siblings, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-24 14:43 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
Author: gnoack@google.com
#syz set subsystems: lsm, kernel
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
` (5 preceding siblings ...)
2026-02-24 14:43 ` syzbot
@ 2026-02-25 5:10 ` Hillf Danton
2026-02-25 5:48 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-25 10:22 ` [syzbot] [kernel?] " Hillf Danton
` (5 subsequent siblings)
12 siblings, 1 reply; 24+ messages in thread
From: Hillf Danton @ 2026-02-25 5:10 UTC (permalink / raw)
To: syzbot; +Cc: linux-kernel, syzkaller-bugs
On Fri, Feb 20, 2026 at 03:11:21AM -0800
> 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
#syz test
--- x/security/landlock/tsync.c
+++ y/security/landlock/tsync.c
@@ -540,11 +540,8 @@ int landlock_restrict_sibling_threads(co
* of for_each_thread(). We can reset it on each loop iteration because
* all previous loop iterations are done with it already.
*
- * num_preparing is initialized to 1 so that the counter can not go to 0
- * and mark the completion as done before all task works are registered.
- * We decrement it at the end of the loop body.
*/
- atomic_set(&shared_ctx.num_preparing, 1);
+ atomic_set(&shared_ctx.num_preparing, 0);
reinit_completion(&shared_ctx.all_prepared);
/*
@@ -553,11 +550,7 @@ int landlock_restrict_sibling_threads(co
*/
found_more_threads = schedule_task_work(&works, &shared_ctx);
- /*
- * Decrement num_preparing for current, to undo that we initialized it
- * to 1 a few lines above.
- */
- if (atomic_dec_return(&shared_ctx.num_preparing) > 0) {
+ if (atomic_read(&shared_ctx.num_preparing) > 0) {
if (wait_for_completion_interruptible(
&shared_ctx.all_prepared)) {
/* In case of interruption, we need to retry the system call. */
--
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [lsm] [kernel] INFO: task hung in restrict_one_thread_callback
2026-02-25 5:10 ` Hillf Danton
@ 2026-02-25 5:48 ` syzbot
0 siblings, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-25 5:48 UTC (permalink / raw)
To: hdanton, linux-kernel, syzkaller-bugs
Hello,
syzbot tried to test the proposed patch but the build/boot failed:
solve the problem.
[ 78.743458][ T5851] batman_adv: batadv0: Not using interface batadv_slave_0 (retrying later): interface not active
[ 78.756837][ T5851] batman_adv: batadv0: Adding interface: batadv_slave_1
[ 78.763834][ T5851] batman_adv: batadv0: The MTU of interface batadv_slave_1 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1532 would solve the problem.
[ 78.790221][ T5851] batman_adv: batadv0: Not using interface batadv_slave_1 (retrying later): interface not active
[ 78.842842][ T5851] hsr_slave_0: entered promiscuous mode
[ 78.849518][ T5851] hsr_slave_1: entered promiscuous mode
[ 79.004198][ T5851] netdevsim netdevsim0 netdevsim0: renamed from eth0
[ 79.016554][ T5851] netdevsim netdevsim0 netdevsim1: renamed from eth1
[ 79.026423][ T5851] netdevsim netdevsim0 netdevsim2: renamed from eth2
[ 79.037255][ T5851] netdevsim netdevsim0 netdevsim3: renamed from eth3
[ 79.067028][ T5851] bridge0: port 2(bridge_slave_1) entered blocking state
[ 79.074261][ T5851] bridge0: port 2(bridge_slave_1) entered forwarding state
[ 79.082267][ T5851] bridge0: port 1(bridge_slave_0) entered blocking state
[ 79.089420][ T5851] bridge0: port 1(bridge_slave_0) entered forwarding state
[ 79.155204][ T5851] 8021q: adding VLAN 0 to HW filter on device bond0
[ 79.175970][ T13] bridge0: port 1(bridge_slave_0) entered disabled state
[ 79.184850][ T13] bridge0: port 2(bridge_slave_1) entered disabled state
[ 79.199897][ T5851] 8021q: adding VLAN 0 to HW filter on device team0
[ 79.214615][ T34] bridge0: port 1(bridge_slave_0) entered blocking state
[ 79.221833][ T34] bridge0: port 1(bridge_slave_0) entered forwarding state
[ 79.236712][ T13] bridge0: port 2(bridge_slave_1) entered blocking state
[ 79.243903][ T13] bridge0: port 2(bridge_slave_1) entered forwarding state
[ 79.408928][ T5851] 8021q: adding VLAN 0 to HW filter on device batadv0
[ 79.463023][ T5851] veth0_vlan: entered promiscuous mode
[ 79.477117][ T5851] veth1_vlan: entered promiscuous mode
[ 79.509142][ T5851] veth0_macvtap: entered promiscuous mode
[ 79.522317][ T5851] veth1_macvtap: entered promiscuous mode
[ 79.548452][ T5851] batman_adv: batadv0: Interface activated: batadv_slave_0
[ 79.564433][ T5851] batman_adv: batadv0: Interface activated: batadv_slave_1
[ 79.582613][ T13] netdevsim netdevsim0 netdevsim0: set [1, 0] type 2 family 0 port 6081 - 0
[ 79.592417][ T13] netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
[ 79.603800][ T13] netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
[ 79.613486][ T13] netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
[ 79.739047][ T13] netdevsim netdevsim0 netdevsim3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[ 79.812788][ T13] netdevsim netdevsim0 netdevsim2 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[ 79.872039][ T13] netdevsim netdevsim0 netdevsim1 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[ 79.942563][ T13] netdevsim netdevsim0 netdevsim0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[ 81.433446][ T5916] Bluetooth: hci0: unexpected cc 0x0c03 length: 249 > 1
[ 81.441927][ T5916] Bluetooth: hci0: unexpected cc 0x1003 length: 249 > 9
[ 81.449463][ T5916] Bluetooth: hci0: unexpected cc 0x1001 length: 249 > 9
[ 81.458889][ T5916] Bluetooth: hci0: unexpected cc 0x0c23 length: 249 > 4
[ 81.469111][ T5916] Bluetooth: hci0: unexpected cc 0x0c38 length: 249 > 2
[ 81.788635][ T60] wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
[ 81.800542][ T60] wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50
[ 81.841775][ T49] wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
[ 81.849630][ T49] wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
2026/02/25 05:46:55 executed programs: 0
[ 82.312058][ T5916] Bluetooth: hci0: unexpected cc 0x0c03 length: 249 > 1
[ 82.319910][ T5916] Bluetooth: hci0: unexpected cc 0x1003 length: 249 > 9
[ 82.328471][ T5916] Bluetooth: hci0: unexpected cc 0x1001 length: 249 > 9
[ 82.336971][ T5916] Bluetooth: hci0: unexpected cc 0x0c23 length: 249 > 4
[ 82.345829][ T5916] Bluetooth: hci0: unexpected cc 0x0c38 length: 249 > 2
[ 82.519074][ T13] bridge_slave_1: left allmulticast mode
[ 82.526263][ T13] bridge_slave_1: left promiscuous mode
[ 82.533594][ T13] bridge0: port 2(bridge_slave_1) entered disabled state
[ 82.548805][ T13] bridge_slave_0: left allmulticast mode
[ 82.556325][ T13] bridge_slave_0: left promiscuous mode
[ 82.562340][ T13] bridge0: port 1(bridge_slave_0) entered disabled state
[ 82.717269][ T13] bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
[ 82.728345][ T13] bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
[ 82.738943][ T13] bond0 (unregistering): Released all slaves
[ 82.757301][ T5931] chnl_net:caif_netlink_parms(): no params data found
[ 82.833828][ T13] hsr_slave_0: left promiscuous mode
[ 82.839749][ T13] hsr_slave_1: left promiscuous mode
[ 82.846290][ T13] batman_adv: batadv0: Interface deactivated: batadv_slave_0
[ 82.853749][ T13] batman_adv: batadv0: Removing interface: batadv_slave_0
[ 82.861904][ T13] batman_adv: batadv0: Interface deactivated: batadv_slave_1
[ 82.869392][ T13] batman_adv: batadv0: Removing interface: batadv_slave_1
[ 82.882539][ T13] veth1_macvtap: left promiscuous mode
[ 82.888098][ T13] veth0_macvtap: left promiscuous mode
[ 82.894054][ T13] veth1_vlan: left promiscuous mode
[ 82.899337][ T13] veth0_vlan: left promiscuous mode
[ 83.067570][ T13] team0 (unregistering): Port device team_slave_1 removed
[ 83.082020][ T13] team0 (unregistering): Port device team_slave_0 removed
[ 83.200290][ C0] list_del corruption, ffff88807a010490->next is NULL
[ 83.205002][ T5931] bridge0: port 1(bridge_slave_0) entered blocking state
[ 83.207990][ C0] ------------[ cut here ]------------
[ 83.219658][ T5931] bridge0: port 1(bridge_slave_0) entered disabled state
[ 83.219918][ C0] kernel BUG at lib/list_debug.c:53!
[ 83.227607][ T5931] bridge_slave_0: entered allmulticast mode
[ 83.232418][ C0] Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
[ 83.240210][ T5931] bridge_slave_0: entered promiscuous mode
[ 83.244623][ C0] CPU: 0 UID: 0 PID: 13 Comm: kworker/u8:1 Not tainted syzkaller #0 PREEMPT(full)
[ 83.244647][ C0] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
[ 83.244659][ C0] Workqueue: netns cleanup_net
[ 83.244695][ C0] RIP: 0010:__list_del_entry_valid_or_report+0xdf/0x190
[ 83.244725][ C0] Code: 49 39 1f 0f 85 9e 00 00 00 b0 01 5b 41 5c 41 5d 41 5e 41 5f e9 92 35 f9 06 cc 48 c7 c7 40 e6 29 8c 48 89 de e8 92 7e 64 fc 90 <0f> 0b 48 c7 c7 a0 e6 29 8c 48 89 de e8 80 7e 64 fc 90 0f 0b 4c 89
[ 83.244738][ C0] RSP: 0018:ffffc90000007d58 EFLAGS: 00010046
[ 83.244755][ C0] RAX: 0000000000000033 RBX: ffff88807a010490 RCX: 3a9e0b388ac91000
[ 83.244768][ C0] RDX: 0000000000000100 RSI: 0000000000000102 RDI: 0000000000000000
[ 83.244779][ C0] RBP: 0000000000000203 R08: ffffc90000007ae7 R09: 1ffff92000000f5c
[ 83.244793][ C0] R10: dffffc0000000000 R11: fffff52000000f5d R12: 1ffff1100f402092
[ 83.244806][ C0] R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
[ 83.244817][ C0] FS: 0000000000000000(0000) GS:ffff888125003000(0000) knlGS:0000000000000000
[ 83.244831][ C0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 83.261190][ T5931] bridge0: port 2(bridge_slave_1) entered blocking state
[ 83.269927][ C0] CR2: 00007f0271347e20 CR3: 000000007b4e0000 CR4: 00000000003526f0
[ 83.290308][ T5931] bridge0: port 2(bridge_slave_1) entered disabled state
[ 83.301203][ C0] Call Trace:
[ 83.301227][ C0] <IRQ>
[ 83.301235][ C0] dst_destroy+0x202/0x5a0
[ 83.394956][ C0] ? _raw_spin_unlock_irqrestore+0x30/0x80
[ 83.400766][ C0] ? rcu_core+0x751/0x1070
[ 83.405169][ C0] ? __pfx_dst_destroy_rcu+0x10/0x10
[ 83.410442][ C0] rcu_core+0x7cd/0x1070
[ 83.414766][ C0] ? __pfx_rcu_core+0x10/0x10
[ 83.419429][ C0] ? sched_clock_cpu+0x74/0x440
[ 83.424271][ C0] handle_softirqs+0x22a/0x870
[ 83.429025][ C0] ? __irq_exit_rcu+0x5f/0x150
[ 83.433795][ C0] __irq_exit_rcu+0x5f/0x150
[ 83.438376][ C0] irq_exit_rcu+0x9/0x30
[ 83.442780][ C0] sysvec_apic_timer_interrupt+0xa6/0xc0
[ 83.448407][ C0] </IRQ>
[ 83.451324][ C0] <TASK>
[ 83.454244][ C0] asm_sysvec_apic_timer_interrupt+0x1a/0x20
[ 83.460226][ C0] RIP: 0010:_raw_spin_unlock_irqrestore+0x47/0x80
[ 83.466634][ C0] Code: f7 e8 fd 50 e6 f5 f7 c3 00 02 00 00 74 05 e8 70 aa 11 f6 9c 58 a9 00 02 00 00 75 27 f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> f4 13 d8 f5 65 8b 05 7d a3 85 07 85 c0 74 18 5b 41 5e c3 cc cc
[ 83.486347][ C0] RSP: 0018:ffffc90000127568 EFLAGS: 00000206
[ 83.492412][ C0] RAX: 0000000000000006 RBX: 0000000000000286 RCX: 0000000080000001
[ 83.500369][ C0] RDX: 0000000000000007 RSI: ffffffff8e017d97 RDI: 0000000000000001
[ 83.508328][ C0] RBP: ffffc90000127688 R08: ffffffff9033d9b7 R09: 1ffffffff2067b36
[ 83.516286][ C0] R10: dffffc0000000000 R11: fffffbfff2067b37 R12: ffff88807cb00690
[ 83.524422][ C0] R13: ffff88807cb00680 R14: ffff88807cb00630 R15: 1ffff11004c521b8
[ 83.532473][ C0] ref_tracker_dir_exit+0x4e6/0x660
[ 83.537725][ C0] ? __pfx_ref_tracker_dir_exit+0x10/0x10
[ 83.543442][ C0] ? lockdep_hardirqs_on+0x7a/0x110
[ 83.548624][ C0] ? kfree+0x1c1/0x630
[ 83.552871][ C0] ? dev_addr_flush+0x18f/0x210
[ 83.557723][ C0] free_netdev+0x459/0x8e0
[ 83.562123][ C0] ? kfree+0x1c1/0x630
[ 83.566274][ C0] ? _raw_spin_unlock_irqrestore+0x30/0x80
[ 83.572073][ C0] netdev_run_todo+0xf8d/0x1130
[ 83.576911][ C0] ? __pfx_netdev_run_todo+0x10/0x10
[ 83.582265][ C0] ? unregister_netdevice_queue+0x19b/0x360
[ 83.588142][ C0] ? __pfx_unregister_netdevice_queue+0x10/0x10
[ 83.594371][ C0] ? batadv_meshif_destroy_netlink+0x1b0/0x250
[ 83.600525][ C0] default_device_exit_batch+0x986/0xa00
[ 83.606167][ C0] ? __pfx_default_device_exit_batch+0x10/0x10
[ 83.612331][ C0] ? __pfx_default_device_exit_batch+0x10/0x10
[ 83.618507][ C0] ops_undo_list+0x52b/0x940
[ 83.623122][ C0] ? __pfx_ops_undo_list+0x10/0x10
[ 83.628322][ C0] ? idr_destroy+0x218/0x290
[ 83.633006][ C0] ? do_raw_spin_unlock+0xf5/0x210
[ 83.638124][ C0] cleanup_net+0x56b/0x800
[ 83.642541][ C0] ? __pfx_cleanup_net+0x10/0x10
[ 83.647472][ C0] ? process_one_work+0x87c/0x1650
[ 83.652595][ C0] process_one_work+0x949/0x1650
[ 83.657528][ C0] ? __pfx_process_one_work+0x10/0x10
[ 83.662904][ C0] ? do_raw_spin_lock+0x12b/0x2f0
[ 83.667935][ C0] worker_thread+0xb46/0x1140
[ 83.672618][ C0] kthread+0x388/0x470
[ 83.676774][ C0] ? __pfx_worker_thread+0x10/0x10
[ 83.681899][ C0] ? __pfx_kthread+0x10/0x10
[ 83.686471][ C0] ret_from_fork+0x51e/0xb90
[ 83.691059][ C0] ? __pfx_ret_from_fork+0x10/0x10
[ 83.696159][ C0] ? __switch_to+0xc7d/0x1450
[ 83.700824][ C0] ? __pfx_kthread+0x10/0x10
[ 83.705417][ C0] ret_from_fork_asm+0x1a/0x30
[ 83.710181][ C0] </TASK>
[ 83.713185][ C0] Modules linked in:
[ 83.717162][ C0] ---[ end trace 0000000000000000 ]---
[ 83.722734][ C0] RIP: 0010:__list_del_entry_valid_or_report+0xdf/0x190
[ 83.729761][ C0] Code: 49 39 1f 0f 85 9e 00 00 00 b0 01 5b 41 5c 41 5d 41 5e 41 5f e9 92 35 f9 06 cc 48 c7 c7 40 e6 29 8c 48 89 de e8 92 7e 64 fc 90 <0f> 0b 48 c7 c7 a0 e6 29 8c 48 89 de e8 80 7e 64 fc 90 0f 0b 4c 89
[ 83.749417][ C0] RSP: 0018:ffffc90000007d58 EFLAGS: 00010046
[ 83.755559][ C0] RAX: 0000000000000033 RBX: ffff88807a010490 RCX: 3a9e0b388ac91000
[ 83.763516][ C0] RDX: 0000000000000100 RSI: 0000000000000102 RDI: 0000000000000000
[ 83.771476][ C0] RBP: 0000000000000203 R08: ffffc90000007ae7 R09: 1ffff92000000f5c
[ 83.779453][ C0] R10: dffffc0000000000 R11: fffff52000000f5d R12: 1ffff1100f402092
[ 83.787413][ C0] R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
[ 83.795457][ C0] FS: 0000000000000000(0000) GS:ffff888125003000(0000) knlGS:0000000000000000
[ 83.804372][ C0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 83.810937][ C0] CR2: 00007f0271347e20 CR3: 000000007b4e0000 CR4: 00000000003526f0
[ 83.818904][ C0] Kernel panic - not syncing: Fatal exception in interrupt
[ 83.826454][ C0] Kernel Offset: disabled
[ 83.830787][ C0] Rebooting in 86400 seconds..
syzkaller build log:
go env (err=<nil>)
AR='ar'
CC='gcc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='g++'
GCCGO='gccgo'
GO111MODULE='auto'
GOAMD64='v1'
GOARCH='amd64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/syzkaller/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/syzkaller/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build3026588339=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/syzkaller/jobs/linux/gopath/src/github.com/google/syzkaller/go.mod'
GOMODCACHE='/syzkaller/jobs/linux/gopath/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/syzkaller/jobs/linux/gopath'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/syzkaller/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.24.4'
GOWORK=''
PKG_CONFIG='pkg-config'
git status (err=<nil>)
HEAD detached at 1e62d198252
nothing to commit, working tree clean
tput: No value for $TERM and no -T specified
tput: No value for $TERM and no -T specified
Makefile:31: run command via tools/syz-env for best compatibility, see:
Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
go list -f '{{.Stale}}' -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336" ./sys/syz-sysgen | grep -q false || go install -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336" ./sys/syz-sysgen
make .descriptions
tput: No value for $TERM and no -T specified
tput: No value for $TERM and no -T specified
Makefile:31: run command via tools/syz-env for best compatibility, see:
Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
bin/syz-sysgen
touch .descriptions
GOOS=linux GOARCH=amd64 go build -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336" -o ./bin/linux_amd64/syz-execprog github.com/google/syzkaller/tools/syz-execprog
mkdir -p ./bin/linux_amd64
g++ -o ./bin/linux_amd64/syz-executor executor/executor.cc \
-m64 -O2 -pthread -Wall -Werror -Wparentheses -Wunused-const-variable -Wframe-larger-than=16384 -Wno-stringop-overflow -Wno-array-bounds -Wno-format-overflow -Wno-unused-but-set-variable -Wno-unused-command-line-argument -static-pie -std=c++17 -I. -Iexecutor/_include -DGOOS_linux=1 -DGOARCH_amd64=1 \
-DHOSTGOOS_linux=1 -DGIT_REVISION=\"1e62d1982527c3b4e18df04d61f2560fa1f434cc\"
/usr/bin/ld: /tmp/ccL6rzBw.o: in function `Connection::Connect(char const*, char const*)':
executor.cc:(.text._ZN10Connection7ConnectEPKcS1_[_ZN10Connection7ConnectEPKcS1_]+0x386): warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
./tools/check-syzos.sh 2>/dev/null
Error text is too large and was truncated, full error text is at:
https://syzkaller.appspot.com/x/error.txt?x=13712006580000
Tested on:
commit: 3ef088b0 Add linux-next specific files for 20260224
git tree: linux-next
kernel config: https://syzkaller.appspot.com/x/.config?x=d7e77f46c8f0a58
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
patch: https://syzkaller.appspot.com/x/patch.diff?x=15112006580000
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
` (6 preceding siblings ...)
2026-02-25 5:10 ` Hillf Danton
@ 2026-02-25 10:22 ` Hillf Danton
2026-02-25 10:51 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-25 12:21 ` [syzbot] [kernel?] " Hillf Danton
` (4 subsequent siblings)
12 siblings, 1 reply; 24+ messages in thread
From: Hillf Danton @ 2026-02-25 10:22 UTC (permalink / raw)
To: syzbot; +Cc: linux-kernel, syzkaller-bugs
On Fri, Feb 20, 2026 at 03:11:21AM -0800
> 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
#syz test upstream master
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [lsm] [kernel] INFO: task hung in restrict_one_thread_callback
2026-02-25 10:22 ` [syzbot] [kernel?] " Hillf Danton
@ 2026-02-25 10:51 ` syzbot
0 siblings, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-25 10:51 UTC (permalink / raw)
To: hdanton, linux-kernel, syzkaller-bugs
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in restrict_one_thread_callback
INFO: task syz.0.140:6853 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.140 state:D stack:25600 pid:6853 tgid:6853 ppid:6361 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: 0033:0x7f2c1c79bf79
RSP: 002b:00007ffccde0b128 EFLAGS: 00000246 ORIG_RAX: 00000000000000db
RAX: fffffffffffffdfc RBX: 000000000001f230 RCX: 00007f2c1c79bf79
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f2c1ca1618c
RBP: 0000000000000032 R08: 3fffffffffffffff R09: 0000000000000000
R10: 00007ffccde0b230 R11: 0000000000000246 R12: 00007ffccde0b250
R13: 00007f2c1ca1618c R14: 000000000001f262 R15: 00007ffccde0b230
</TASK>
INFO: task syz.0.140:6854 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.140 state:D stack:28264 pid:6854 tgid:6853 ppid:6361 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: 0033:0x7f2c1c79bf79
RSP: 002b:00007f2c1d6710e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f2c1ca15fa8 RCX: 00007f2c1c79bf79
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f2c1ca15fa8
RBP: 00007f2c1ca15fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2c1ca16038 R14: 00007ffccde0aee0 R15: 00007ffccde0afc8
</TASK>
INFO: task syz.0.140:6855 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.140 state:D stack:28216 pid:6855 tgid:6853 ppid:6361 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: 0033:0x7f2c1c79bf79
RSP: 002b:00007f2c1d650028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007f2c1ca16090 RCX: 00007f2c1c79bf79
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000003
RBP: 00007f2c1c8327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2c1ca16128 R14: 00007f2c1ca16090 R15: 00007ffccde0afc8
</TASK>
INFO: task syz.0.140:6856 blocked for more than 144 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.140 state:D stack:28368 pid:6856 tgid:6853 ppid:6361 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: 0033:0x7f2c1c79bf79
RSP: 002b:00007f2c1d62f028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007f2c1ca16180 RCX: 00007f2c1c79bf79
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000003
RBP: 00007f2c1c8327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2c1ca16218 R14: 00007f2c1ca16180 R15: 00007ffccde0afc8
</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
5 locks held by kworker/u8:10/1152:
#0: ffff8880b873ade0 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x31/0x150 kernel/sched/core.c:647
#1: ffff8880b8724588 (psi_seq){-.-.}-{0:0}, at: psi_task_switch+0x53/0x880 kernel/sched/psi.c:933
#2: ffff888053c88788 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: class_wiphy_constructor include/net/cfg80211.h:6441 [inline]
#2: ffff888053c88788 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: cfg80211_wiphy_work+0xb4/0x4a0 net/wireless/core.c:426
#3: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
#3: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
#3: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: ieee80211_sta_active_ibss+0xc3/0x330 net/mac80211/ibss.c:635
#4: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
#4: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
#4: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: class_rcu_constructor include/linux/rcupdate.h:1193 [inline]
#4: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: unwind_next_frame+0xa5/0x23c0 arch/x86/kernel/unwind_orc.c:495
2 locks held by getty/5584:
#0: ffff888037fb00a0 (&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: 13992 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:rcu_read_unlock include/linux/rcupdate.h:879 [inline]
RIP: 0010:xa_load+0x16a/0x210 lib/xarray.c:1621
Code: 06 04 00 00 75 07 e8 f5 4e 0f f6 eb c3 e8 6e bb 01 00 89 c5 31 ff 89 c6 e8 23 53 0f f6 85 ed 74 10 e8 9a 68 f4 f5 84 c0 74 0e <e8> d1 4e 0f f6 eb 56 e8 ca 4e 0f f6 eb 4f e8 43 bb 01 00 89 c5 31
RSP: 0018:ffffc90003497230 EFLAGS: 00000202
RAX: 0000000000000001 RBX: ffffffff8bb68ba0 RCX: 0000000080000001
RDX: ffff8880584c3c80 RSI: ffffffff8c29ba60 RDI: ffffffff8c29ba20
RBP: 0000000000000001 R08: ffff8880584c3c80 R09: 0000000000000002
R10: 0000000000000406 R11: 0000000000000000 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff88803369ca00 R15: ffffc90003497230
FS: 000055558749a500(0000) GS:ffff888125311000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f92f6facc00 CR3: 0000000074826000 CR4: 00000000003526f0
Call Trace:
<TASK>
memcg_list_lru_allocated mm/list_lru.c:510 [inline]
memcg_list_lru_alloc+0x14c/0x800 mm/list_lru.c:521
__memcg_slab_post_alloc_hook+0x312/0xa80 mm/memcontrol.c:3220
memcg_slab_post_alloc_hook mm/slub.c:2459 [inline]
slab_post_alloc_hook mm/slub.c:4512 [inline]
slab_alloc_node mm/slub.c:4830 [inline]
kmem_cache_alloc_lru_noprof+0x346/0x640 mm/slub.c:4849
__d_alloc+0x37/0x6f0 fs/dcache.c:1740
d_alloc_parallel+0xe6/0x1610 fs/dcache.c:2604
__lookup_slow+0x137/0x410 fs/namei.c:1901
lookup_slow+0x53/0x70 fs/namei.c:1933
walk_component fs/namei.c:2279 [inline]
link_path_walk+0x1273/0x18d0 fs/namei.c:2644
path_openat+0x2c3/0x3860 fs/namei.c:4826
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 fs/open.c:1366
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1383
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: 0033:0x7f92f6f5c84e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007ffcaf09ae38 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 000055558749a500 RCX: 00007f92f6f5c84e
RDX: 0000000000080001 RSI: 00007f92f703376c RDI: ffffffffffffff9c
RBP: 00007f92f703376c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
R13: 00007ffcaf09af10 R14: 0000000000043e78 R15: 00007ffcaf09b480
</TASK>
Tested on:
commit: 7dff99b3 Remove WARN_ALL_UNSEEDED_RANDOM kernel config..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16d4f152580000
kernel config: https://syzkaller.appspot.com/x/.config?x=56c0294cb1688557
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
Note: no patches were applied.
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
` (7 preceding siblings ...)
2026-02-25 10:22 ` [syzbot] [kernel?] " Hillf Danton
@ 2026-02-25 12:21 ` Hillf Danton
2026-02-25 14:15 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-25 22:32 ` [syzbot] [kernel?] " Hillf Danton
` (3 subsequent siblings)
12 siblings, 1 reply; 24+ messages in thread
From: Hillf Danton @ 2026-02-25 12:21 UTC (permalink / raw)
To: syzbot; +Cc: linux-kernel, syzkaller-bugs
On Fri, Feb 20, 2026 at 03:11:21AM -0800
> 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
#syz test upstream master
--- x/security/landlock/tsync.c
+++ y/security/landlock/tsync.c
@@ -502,11 +502,8 @@ int landlock_restrict_sibling_threads(co
* of for_each_thread(). We can reset it on each loop iteration because
* all previous loop iterations are done with it already.
*
- * num_preparing is initialized to 1 so that the counter can not go to 0
- * and mark the completion as done before all task works are registered.
- * We decrement it at the end of the loop body.
*/
- atomic_set(&shared_ctx.num_preparing, 1);
+ atomic_set(&shared_ctx.num_preparing, 0);
reinit_completion(&shared_ctx.all_prepared);
/*
@@ -515,11 +512,7 @@ int landlock_restrict_sibling_threads(co
*/
found_more_threads = schedule_task_work(&works, &shared_ctx);
- /*
- * Decrement num_preparing for current, to undo that we initialized it
- * to 1 a few lines above.
- */
- if (atomic_dec_return(&shared_ctx.num_preparing) > 0) {
+ if (atomic_read(&shared_ctx.num_preparing) > 0) {
if (wait_for_completion_interruptible(
&shared_ctx.all_prepared)) {
/* In case of interruption, we need to retry the system call. */
--
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [lsm] [kernel] INFO: task hung in restrict_one_thread_callback
2026-02-25 12:21 ` [syzbot] [kernel?] " Hillf Danton
@ 2026-02-25 14:15 ` syzbot
0 siblings, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-25 14:15 UTC (permalink / raw)
To: hdanton, linux-kernel, syzkaller-bugs
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in landlock_restrict_sibling_threads
INFO: task syz.0.146:6909 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.146 state:D stack:28832 pid:6909 tgid:6908 ppid:6445 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+0xf3d/0x11f0 security/landlock/tsync.c:549
__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: 0033:0x7f81f479bf79
RSP: 002b:00007f81f559d028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007f81f4a15fa0 RCX: 00007f81f479bf79
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000003
RBP: 00007f81f48327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f81f4a16038 R14: 00007f81f4a15fa0 R15: 00007ffd3d3acd98
</TASK>
INFO: task syz.0.146:6910 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.146 state:D stack:28616 pid:6910 tgid:6908 ppid:6445 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+0xf3d/0x11f0 security/landlock/tsync.c:549
__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: 0033:0x7f81f479bf79
RSP: 002b:00007f81f557c028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007f81f4a16090 RCX: 00007f81f479bf79
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000003
RBP: 00007f81f48327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f81f4a16128 R14: 00007f81f4a16090 R15: 00007ffd3d3acd98
</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
5 locks held by kworker/u8:6/411:
2 locks held by getty/5575:
#0: ffff888036de80a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc900033332f0 (&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: 411 Comm: kworker/u8:6 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: 0x0 (events_unbound)
RIP: 0010:lockdep_recursion_finish kernel/locking/lockdep.c:470 [inline]
RIP: 0010:lock_is_held_type+0xda/0x150 kernel/locking/lockdep.c:5941
Code: f9 eb cb 31 db eb 1c 83 fd ff 74 12 31 c0 f6 43 22 03 0f 95 c0 31 db 39 c5 0f 94 c3 eb 05 bb 01 00 00 00 48 c7 c7 0f 1d 28 8e <e8> 21 18 00 00 b8 ff ff ff ff 65 0f c1 05 04 f0 88 07 83 f8 01 75
RSP: 0018:ffffc900034afa88 EFLAGS: 00000046
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000080000001
RDX: 0000000000000000 RSI: ffffffff8e028949 RDI: ffffffff8e281d0f
RBP: 00000000ffffffff R08: ffffffff903384b7 R09: 1ffffffff2067096
R10: dffffc0000000000 R11: fffffbfff2067097 R12: 0000000000000246
R13: ffff888024c8dac0 R14: ffffffff8e9603a0 R15: 1ffff110170e75b3
FS: 0000000000000000(0000) GS:ffff888125311000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055558fd504e8 CR3: 000000000e74c000 CR4: 00000000003526f0
Call Trace:
<TASK>
lock_is_held include/linux/lockdep.h:249 [inline]
schedule_debug kernel/sched/core.c:5874 [inline]
__schedule+0x262/0x5340 kernel/sched/core.c:6783
__schedule_loop kernel/sched/core.c:6989 [inline]
schedule+0x164/0x360 kernel/sched/core.c:7004
worker_thread+0xc1e/0xfc0 kernel/workqueue.c:3454
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>
Tested on:
commit: 7dff99b3 Remove WARN_ALL_UNSEEDED_RANDOM kernel config..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11e97c4a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=56c0294cb1688557
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
patch: https://syzkaller.appspot.com/x/patch.diff?x=13c17c4a580000
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
` (8 preceding siblings ...)
2026-02-25 12:21 ` [syzbot] [kernel?] " Hillf Danton
@ 2026-02-25 22:32 ` Hillf Danton
2026-02-26 0:13 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-26 2:19 ` [syzbot] [kernel?] " Hillf Danton
` (2 subsequent siblings)
12 siblings, 1 reply; 24+ messages in thread
From: Hillf Danton @ 2026-02-25 22:32 UTC (permalink / raw)
To: syzbot; +Cc: linux-kernel, syzkaller-bugs
On Fri, Feb 20, 2026 at 03:11:21AM -0800
> 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
#syz test upstream master
--- x/security/landlock/tsync.c
+++ y/security/landlock/tsync.c
@@ -441,7 +441,7 @@ int landlock_restrict_sibling_threads(co
atomic_set(&shared_ctx.preparation_error, 0);
init_completion(&shared_ctx.all_prepared);
init_completion(&shared_ctx.ready_to_commit);
- atomic_set(&shared_ctx.num_unfinished, 1);
+ atomic_set(&shared_ctx.num_unfinished, 0);
init_completion(&shared_ctx.all_finished);
shared_ctx.old_cred = old_cred;
shared_ctx.new_cred = new_cred;
@@ -502,11 +502,8 @@ int landlock_restrict_sibling_threads(co
* of for_each_thread(). We can reset it on each loop iteration because
* all previous loop iterations are done with it already.
*
- * num_preparing is initialized to 1 so that the counter can not go to 0
- * and mark the completion as done before all task works are registered.
- * We decrement it at the end of the loop body.
*/
- atomic_set(&shared_ctx.num_preparing, 1);
+ atomic_set(&shared_ctx.num_preparing, 0);
reinit_completion(&shared_ctx.all_prepared);
/*
@@ -515,11 +512,7 @@ int landlock_restrict_sibling_threads(co
*/
found_more_threads = schedule_task_work(&works, &shared_ctx);
- /*
- * Decrement num_preparing for current, to undo that we initialized it
- * to 1 a few lines above.
- */
- if (atomic_dec_return(&shared_ctx.num_preparing) > 0) {
+ if (atomic_read(&shared_ctx.num_preparing) > 0) {
if (wait_for_completion_interruptible(
&shared_ctx.all_prepared)) {
/* In case of interruption, we need to retry the system call. */
@@ -548,11 +541,7 @@ int landlock_restrict_sibling_threads(co
*/
complete_all(&shared_ctx.ready_to_commit);
- /*
- * Decrement num_unfinished for current, to undo that we initialized it to 1
- * at the beginning.
- */
- if (atomic_dec_return(&shared_ctx.num_unfinished) > 0)
+ if (atomic_read(&shared_ctx.num_unfinished) > 0)
wait_for_completion(&shared_ctx.all_finished);
tsync_works_release(&works);
--
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [lsm] [kernel] INFO: task hung in restrict_one_thread_callback
2026-02-25 22:32 ` [syzbot] [kernel?] " Hillf Danton
@ 2026-02-26 0:13 ` syzbot
0 siblings, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-26 0:13 UTC (permalink / raw)
To: hdanton, linux-kernel, syzkaller-bugs
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in landlock_restrict_sibling_threads
INFO: task syz.0.301:7302 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.301 state:D stack:28800 pid:7302 tgid:7301 ppid:6339 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+0xf34/0x11e0 security/landlock/tsync.c:545
__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: 0033:0x7f349af9bf79
RSP: 002b:00007f349be5c028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007f349b215fa0 RCX: 00007f349af9bf79
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000003
RBP: 00007f349b0327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f349b216038 R14: 00007f349b215fa0 R15: 00007fffd651db08
</TASK>
INFO: task syz.0.301:7303 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.301 state:D stack:27968 pid:7303 tgid:7301 ppid:6339 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+0xf34/0x11e0 security/landlock/tsync.c:545
__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: 0033:0x7f349af9bf79
RSP: 002b:00007f349be3b028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007f349b216090 RCX: 00007f349af9bf79
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000003
RBP: 00007f349b0327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f349b216128 R14: 00007f349b216090 R15: 00007fffd651db08
</TASK>
Showing all locks held in the system:
1 lock held by khungtaskd/30:
#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 klogd/5181:
#0: ffff8880b873ade0 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x31/0x150 kernel/sched/core.c:647
#1: ffff8880b8724588 (psi_seq){-.-.}-{0:0}, at: psi_task_switch+0x53/0x880 kernel/sched/psi.c:933
2 locks held by getty/5575:
#0: ffff888032b4e0a0 (&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: 30 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: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:63
Code: 4e 74 02 c3 cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 43 0d 11 00 fb f4 <e9> 7c ea 02 00 cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffc90000197e20 EFLAGS: 00000246
RAX: 00000000001af755 RBX: ffffffff819ad0dd RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8e00f3b4 RDI: ffffffff8c29bc00
RBP: ffffc90000197f10 R08: ffff8880b873395b R09: 1ffff110170e672b
R10: dffffc0000000000 R11: ffffed10170e672c R12: ffffffff903388b0
R13: 1ffff11003bd3000 R14: 0000000000000001 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff88812530f000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055559296f4e8 CR3: 00000000372e2000 CR4: 00000000003526f0
Call Trace:
<TASK>
arch_safe_halt arch/x86/kernel/process.c:766 [inline]
default_idle+0x9/0x20 arch/x86/kernel/process.c:767
default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:191 [inline]
do_idle+0x1bd/0x500 kernel/sched/idle.c:332
cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:430
start_secondary+0x101/0x110 arch/x86/kernel/smpboot.c:312
common_startup_64+0x13e/0x147
</TASK>
Tested on:
commit: d9d32e5b Merge tag 'ata-7.0-rc2' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12a328d6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=56c0294cb1688557
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
patch: https://syzkaller.appspot.com/x/patch.diff?x=1155b55a580000
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
` (9 preceding siblings ...)
2026-02-25 22:32 ` [syzbot] [kernel?] " Hillf Danton
@ 2026-02-26 2:19 ` Hillf Danton
2026-02-26 2:44 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-26 10:04 ` [syzbot] [kernel?] " Hillf Danton
2026-02-27 0:03 ` [syzbot] [kernel?] " Hillf Danton
12 siblings, 1 reply; 24+ messages in thread
From: Hillf Danton @ 2026-02-26 2:19 UTC (permalink / raw)
To: syzbot; +Cc: linux-kernel, syzkaller-bugs
On Fri, Feb 20, 2026 at 03:11:21AM -0800
> 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
#syz test upstream master
--- x/security/landlock/tsync.c
+++ y/security/landlock/tsync.c
@@ -391,7 +391,8 @@ static bool schedule_task_work(struct ts
ctx->task = NULL;
atomic_dec(&shared_ctx->num_preparing);
- atomic_dec(&shared_ctx->num_unfinished);
+ if (atomic_dec_return(&shared_ctx->num_unfinished) == 0)
+ complete_all(&shared_ctx->all_finished);
}
}
@@ -441,7 +442,7 @@ int landlock_restrict_sibling_threads(co
atomic_set(&shared_ctx.preparation_error, 0);
init_completion(&shared_ctx.all_prepared);
init_completion(&shared_ctx.ready_to_commit);
- atomic_set(&shared_ctx.num_unfinished, 1);
+ atomic_set(&shared_ctx.num_unfinished, 0);
init_completion(&shared_ctx.all_finished);
shared_ctx.old_cred = old_cred;
shared_ctx.new_cred = new_cred;
@@ -502,11 +503,8 @@ int landlock_restrict_sibling_threads(co
* of for_each_thread(). We can reset it on each loop iteration because
* all previous loop iterations are done with it already.
*
- * num_preparing is initialized to 1 so that the counter can not go to 0
- * and mark the completion as done before all task works are registered.
- * We decrement it at the end of the loop body.
*/
- atomic_set(&shared_ctx.num_preparing, 1);
+ atomic_set(&shared_ctx.num_preparing, 0);
reinit_completion(&shared_ctx.all_prepared);
/*
@@ -515,11 +513,7 @@ int landlock_restrict_sibling_threads(co
*/
found_more_threads = schedule_task_work(&works, &shared_ctx);
- /*
- * Decrement num_preparing for current, to undo that we initialized it
- * to 1 a few lines above.
- */
- if (atomic_dec_return(&shared_ctx.num_preparing) > 0) {
+ if (atomic_read(&shared_ctx.num_preparing) > 0) {
if (wait_for_completion_interruptible(
&shared_ctx.all_prepared)) {
/* In case of interruption, we need to retry the system call. */
@@ -548,11 +542,7 @@ int landlock_restrict_sibling_threads(co
*/
complete_all(&shared_ctx.ready_to_commit);
- /*
- * Decrement num_unfinished for current, to undo that we initialized it to 1
- * at the beginning.
- */
- if (atomic_dec_return(&shared_ctx.num_unfinished) > 0)
+ if (atomic_read(&shared_ctx.num_unfinished) > 0)
wait_for_completion(&shared_ctx.all_finished);
tsync_works_release(&works);
--
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [lsm] [kernel] INFO: task hung in restrict_one_thread_callback
2026-02-26 2:19 ` [syzbot] [kernel?] " Hillf Danton
@ 2026-02-26 2:44 ` syzbot
0 siblings, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-26 2:44 UTC (permalink / raw)
To: hdanton, linux-kernel, syzkaller-bugs
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in landlock_restrict_sibling_threads
INFO: task syz.0.918:9226 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.918 state:D stack:28832 pid:9226 tgid:9225 ppid:8262 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+0xf64/0x1220 security/landlock/tsync.c:546
__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: 0033:0x7f6aa979bf79
RSP: 002b:00007f6aaa59a028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007f6aa9a15fa0 RCX: 00007f6aa979bf79
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000003
RBP: 00007f6aa98327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6aa9a16038 R14: 00007f6aa9a15fa0 R15: 00007ffc551bff08
</TASK>
INFO: task syz.0.918:9227 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.918 state:D stack:28104 pid:9227 tgid:9225 ppid:8262 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+0xf64/0x1220 security/landlock/tsync.c:546
__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: 0033:0x7f6aa979bf79
RSP: 002b:00007f6aaa579028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007f6aa9a16090 RCX: 00007f6aa979bf79
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000003
RBP: 00007f6aa98327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6aa9a16128 R14: 00007f6aa9a16090 R15: 00007ffc551bff08
</TASK>
Showing all locks held in the system:
1 lock held by khungtaskd/30:
#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
5 locks held by kworker/u8:2/35:
#0: ffff8880b863ade0 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x31/0x150 kernel/sched/core.c:647
#1: ffffc90000ab7c40 ((work_completion)(&(&forw_packet_aggr->delayed_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3251 [inline]
#1: ffffc90000ab7c40 ((work_completion)(&(&forw_packet_aggr->delayed_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa25/0x1830 kernel/workqueue.c:3358
#2: ffff8880b8626118 (&base->lock){-.-.}-{2:2}, at: lock_timer_base kernel/time/timer.c:1004 [inline]
#2: ffff8880b8626118 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x1ae/0xf30 kernel/time/timer.c:1085
#3: ffffffff9a6dcd08 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_object_activate+0x83/0x580 lib/debugobjects.c:818
#4: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
#4: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
#4: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: class_rcu_constructor include/linux/rcupdate.h:1193 [inline]
#4: ffffffff8e9602e0 (rcu_read_lock){....}-{1:3}, at: unwind_next_frame+0xa5/0x23c0 arch/x86/kernel/unwind_orc.c:495
2 locks held by getty/5586:
#0: ffff888036bd30a0 (&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 1
CPU: 1 UID: 0 PID: 30 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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:63
Code: 4e 74 02 c3 cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 43 0d 11 00 fb f4 <e9> 7c ea 02 00 cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffffff8e607dc0 EFLAGS: 00000242
RAX: 000000000022ab89 RBX: ffffffff819ad0dd RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8e00f3b4 RDI: ffffffff8c29bc00
RBP: ffffffff8e607eb0 R08: ffff8880b863395b R09: 1ffff110170c672b
R10: dffffc0000000000 R11: ffffed10170c672c R12: ffffffff903388b0
R13: 1ffffffff1cd29d8 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff88812520f000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055558c7f44e8 CR3: 000000000e74c000 CR4: 00000000003526f0
Call Trace:
<TASK>
arch_safe_halt arch/x86/kernel/process.c:766 [inline]
default_idle+0x9/0x20 arch/x86/kernel/process.c:767
default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:191 [inline]
do_idle+0x1bd/0x500 kernel/sched/idle.c:332
cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:430
rest_init+0x2de/0x300 init/main.c:760
start_kernel+0x385/0x3d0 init/main.c:1210
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x147
</TASK>
Tested on:
commit: d9d32e5b Merge tag 'ata-7.0-rc2' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15d4a006580000
kernel config: https://syzkaller.appspot.com/x/.config?x=56c0294cb1688557
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
patch: https://syzkaller.appspot.com/x/patch.diff?x=139e4d5a580000
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
` (10 preceding siblings ...)
2026-02-26 2:19 ` [syzbot] [kernel?] " Hillf Danton
@ 2026-02-26 10:04 ` Hillf Danton
2026-02-26 10:50 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-27 0:03 ` [syzbot] [kernel?] " Hillf Danton
12 siblings, 1 reply; 24+ messages in thread
From: Hillf Danton @ 2026-02-26 10:04 UTC (permalink / raw)
To: syzbot; +Cc: linux-kernel, syzkaller-bugs
On Fri, Feb 20, 2026 at 03:11:21AM -0800
> 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
#syz test upstream master
--- x/security/landlock/tsync.c
+++ y/security/landlock/tsync.c
@@ -391,7 +391,8 @@ static bool schedule_task_work(struct ts
ctx->task = NULL;
atomic_dec(&shared_ctx->num_preparing);
- atomic_dec(&shared_ctx->num_unfinished);
+ if (atomic_dec_return(&shared_ctx->num_unfinished) == 0)
+ complete_all(&shared_ctx->all_finished);
}
}
@@ -432,16 +433,21 @@ static void cancel_tsync_works(struct ts
int landlock_restrict_sibling_threads(const struct cred *old_cred,
const struct cred *new_cred)
{
+ static int concur = 0;
int err;
struct tsync_shared_context shared_ctx;
struct tsync_works works = {};
size_t newly_discovered_threads;
bool found_more_threads;
+ if (concur++) {
+ concur--;
+ return -EBUSY;
+ }
atomic_set(&shared_ctx.preparation_error, 0);
init_completion(&shared_ctx.all_prepared);
init_completion(&shared_ctx.ready_to_commit);
- atomic_set(&shared_ctx.num_unfinished, 1);
+ atomic_set(&shared_ctx.num_unfinished, 0);
init_completion(&shared_ctx.all_finished);
shared_ctx.old_cred = old_cred;
shared_ctx.new_cred = new_cred;
@@ -502,11 +508,8 @@ int landlock_restrict_sibling_threads(co
* of for_each_thread(). We can reset it on each loop iteration because
* all previous loop iterations are done with it already.
*
- * num_preparing is initialized to 1 so that the counter can not go to 0
- * and mark the completion as done before all task works are registered.
- * We decrement it at the end of the loop body.
*/
- atomic_set(&shared_ctx.num_preparing, 1);
+ atomic_set(&shared_ctx.num_preparing, 0);
reinit_completion(&shared_ctx.all_prepared);
/*
@@ -515,11 +518,7 @@ int landlock_restrict_sibling_threads(co
*/
found_more_threads = schedule_task_work(&works, &shared_ctx);
- /*
- * Decrement num_preparing for current, to undo that we initialized it
- * to 1 a few lines above.
- */
- if (atomic_dec_return(&shared_ctx.num_preparing) > 0) {
+ if (atomic_read(&shared_ctx.num_preparing) > 0) {
if (wait_for_completion_interruptible(
&shared_ctx.all_prepared)) {
/* In case of interruption, we need to retry the system call. */
@@ -548,14 +547,11 @@ int landlock_restrict_sibling_threads(co
*/
complete_all(&shared_ctx.ready_to_commit);
- /*
- * Decrement num_unfinished for current, to undo that we initialized it to 1
- * at the beginning.
- */
- if (atomic_dec_return(&shared_ctx.num_unfinished) > 0)
+ if (atomic_read(&shared_ctx.num_unfinished) > 0)
wait_for_completion(&shared_ctx.all_finished);
tsync_works_release(&works);
+ concur--;
return atomic_read(&shared_ctx.preparation_error);
}
--
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [lsm] [kernel] INFO: task hung in restrict_one_thread_callback
2026-02-26 10:04 ` [syzbot] [kernel?] " Hillf Danton
@ 2026-02-26 10:50 ` syzbot
0 siblings, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-26 10:50 UTC (permalink / raw)
To: hdanton, linux-kernel, syzkaller-bugs
Hello,
syzbot has tested the proposed patch and the reproducer did not trigger any issue:
Reported-by: syzbot+7ea2f5e9dfd468201817@syzkaller.appspotmail.com
Tested-by: syzbot+7ea2f5e9dfd468201817@syzkaller.appspotmail.com
Tested on:
commit: f4d0ec0a Merge tag 'erofs-for-7.0-rc2-fixes' of git://..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17891b94580000
kernel config: https://syzkaller.appspot.com/x/.config?x=56c0294cb1688557
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
patch: https://syzkaller.appspot.com/x/patch.diff?x=136050ba580000
Note: testing is done by a robot and is best-effort only.
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
` (11 preceding siblings ...)
2026-02-26 10:04 ` [syzbot] [kernel?] " Hillf Danton
@ 2026-02-27 0:03 ` Hillf Danton
2026-02-27 1:49 ` [syzbot] [lsm] [kernel] " syzbot
12 siblings, 1 reply; 24+ messages in thread
From: Hillf Danton @ 2026-02-27 0:03 UTC (permalink / raw)
To: syzbot; +Cc: linux-kernel, syzkaller-bugs
On Fri, Feb 20, 2026 at 03:11:21AM -0800
> 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
#syz test upstream master
--- x/security/landlock/tsync.c
+++ y/security/landlock/tsync.c
@@ -432,12 +432,17 @@ static void cancel_tsync_works(struct ts
int landlock_restrict_sibling_threads(const struct cred *old_cred,
const struct cred *new_cred)
{
+ static int concur = 0;
int err;
struct tsync_shared_context shared_ctx;
struct tsync_works works = {};
size_t newly_discovered_threads;
bool found_more_threads;
+ if (concur++) {
+ concur--;
+ return -EBUSY;
+ }
atomic_set(&shared_ctx.preparation_error, 0);
init_completion(&shared_ctx.all_prepared);
init_completion(&shared_ctx.ready_to_commit);
@@ -556,6 +561,7 @@ int landlock_restrict_sibling_threads(co
wait_for_completion(&shared_ctx.all_finished);
tsync_works_release(&works);
+ concur--;
return atomic_read(&shared_ctx.preparation_error);
}
--
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [syzbot] [lsm] [kernel] INFO: task hung in restrict_one_thread_callback
2026-02-27 0:03 ` [syzbot] [kernel?] " Hillf Danton
@ 2026-02-27 1:49 ` syzbot
0 siblings, 0 replies; 24+ messages in thread
From: syzbot @ 2026-02-27 1:49 UTC (permalink / raw)
To: hdanton, linux-kernel, syzkaller-bugs
Hello,
syzbot has tested the proposed patch and the reproducer did not trigger any issue:
Reported-by: syzbot+7ea2f5e9dfd468201817@syzkaller.appspotmail.com
Tested-by: syzbot+7ea2f5e9dfd468201817@syzkaller.appspotmail.com
Tested on:
commit: 3f4a08e6 Merge tag 'kmalloc_obj-v7.0-rc2' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=145a555a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=56c0294cb1688557
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
patch: https://syzkaller.appspot.com/x/patch.diff?x=166ae072580000
Note: testing is done by a robot and is best-effort only.
^ permalink raw reply [flat|nested] 24+ messages in thread
end of thread, other threads:[~2026-02-27 1:49 UTC | newest]
Thread overview: 24+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-02-20 11:11 [syzbot] [kernel?] INFO: task hung in restrict_one_thread_callback syzbot
2026-02-21 6:27 ` Forwarded: " syzbot
2026-02-23 13:40 ` Frederic Weisbecker
2026-02-23 15:15 ` Günther Noack
2026-02-24 0:10 ` Hillf Danton
2026-02-24 3:05 ` syzbot
2026-02-24 10:00 ` Günther Noack
2026-02-24 3:17 ` Forwarded: " syzbot
2026-02-24 4:25 ` syzbot
2026-02-24 14:43 ` syzbot
2026-02-25 5:10 ` Hillf Danton
2026-02-25 5:48 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-25 10:22 ` [syzbot] [kernel?] " Hillf Danton
2026-02-25 10:51 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-25 12:21 ` [syzbot] [kernel?] " Hillf Danton
2026-02-25 14:15 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-25 22:32 ` [syzbot] [kernel?] " Hillf Danton
2026-02-26 0:13 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-26 2:19 ` [syzbot] [kernel?] " Hillf Danton
2026-02-26 2:44 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-26 10:04 ` [syzbot] [kernel?] " Hillf Danton
2026-02-26 10:50 ` [syzbot] [lsm] [kernel] " syzbot
2026-02-27 0:03 ` [syzbot] [kernel?] " Hillf Danton
2026-02-27 1:49 ` [syzbot] [lsm] [kernel] " syzbot
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