[v6.1] INFO: rcu detected stall in task_work_run

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f89b6e15694c Linux 6.1.149
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11c2ea42580000
kernel config: https://syzkaller.appspot.com/x/.config?x=115cdcc5760d448b
dashboard link: https://syzkaller.appspot.com/bug?extid=bd458038ebcbde78a479
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1732a312580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d50897075012/disk-f89b6e15.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/be1ee22a32ec/vmlinux-f89b6e15.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f434e015cacd/bzImage-f89b6e15.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bd4580...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 2641 jiffies s: 7881 root: 0x1/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 8254 Comm: syz.1.3594 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:85 [inline]
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:102 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:128 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:159 [inline]
RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline]
RIP: 0010:kasan_check_range+0x7b/0x290 mm/kasan/generic.c:189
Code: 5c 37 ff 48 c1 eb 03 4e 8d 14 3b 4d 89 d6 4d 29 ce 49 83 fe 10 7f 26 4d 85 f6 0f 84 39 01 00 00 48 f7 d3 4c 01 db 41 80 39 00 <0f> 85 c1 01 00 00 49 ff c1 48 ff c3 75 ee e9 1c 01 00 00 44 89 cb
RSP: 0018:ffffc90000006be0 EFLAGS: 00000046
RAX: 0000000000000001 RBX: ffffffffffffffff RCX: ffffffff8163002b
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90ae1240
RBP: ffffc90000006e50 R08: dffffc0000000000 R09: fffffbfff215c248
R10: fffffbfff215c249 R11: 1ffffffff215c248 R12: ffff88807da528e8
R13: ffff88807da52802 R14: 0000000000000001 R15: dffffc0000000001
FS: 000055558fb7e500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b33f63fff CR3: 000000002713e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
instrument_atomic_read include/linux/instrumented.h:72 [inline]
_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
hlock_class kernel/locking/lockdep.c:228 [inline]
check_wait_context kernel/locking/lockdep.c:4748 [inline]
__lock_acquire+0x92b/0x7c50 kernel/locking/lockdep.c:4999
lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
rcu_read_lock include/linux/rcupdate.h:791 [inline]
__perf_output_begin kernel/events/ring_buffer.c:163 [inline]
perf_output_begin_forward+0xb5/0xa80 kernel/events/ring_buffer.c:272
__perf_event_output kernel/events/core.c:7732 [inline]
perf_event_output_forward+0x179/0x2a0 kernel/events/core.c:7750
__perf_event_overflow+0x448/0x610 kernel/events/core.c:9496
perf_swevent_overflow kernel/events/core.c:9572 [inline]
perf_swevent_event+0x4ad/0x530 kernel/events/core.c:9610
perf_tp_event+0x335/0xb60 kernel/events/core.c:10029
perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10002
perf_trace_preemptirq_template+0x287/0x330 include/trace/events/preemptirq.h:14
trace_irq_enable_rcuidle+0xd3/0x140 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x84/0x500 kernel/rcu/tree_plugin.h:685
Code: f1 f1 f1 00 f2 f2 f2 4a 89 04 2b 66 42 c7 44 2b 09 f3 f3 42 c6 44 2b 0b f3 65 44 8b 35 5d 97 96 7e 41 f7 c6 00 00 f0 00 74 45 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 66 42 c7 44 2b
RSP: 0018:ffffc90000007760 EFLAGS: 00000206
RAX: 260ef2e77e0f0a00 RBX: 1ffff92000000ef4 RCX: 260ef2e77e0f0a00
RDX: dffffc0000000000 RSI: ffffffff8a8c0300 RDI: ffffffff8adefae0
RBP: ffffc90000007860 R08: dffffc0000000000 R09: fffffbfff215c26a
R10: fffffbfff215c26a R11: 1ffffffff215c269 R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8e3b900 R15: 0000000000000001
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
ndisc_send_skb+0xda7/0x1510 net/ipv6/ndisc.c:521
addrconf_rs_timer+0x2b8/0x600 net/ipv6/addrconf.c:3979
call_timer_fn+0x1a0/0x670 kernel/time/timer.c:1504
expire_timers kernel/time/timer.c:1549 [inline]
__run_timers+0x525/0x7c0 kernel/time/timer.c:1820
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1833
handle_softirqs+0x2a1/0x920 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x12f/0x220 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa5/0x100 kernel/locking/spinlock.c:194
Code: 74 05 e8 fe d1 65 f7 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> c6 5b 36 f7 65 8b 05 e7 14 e1 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc9000d007bc0 EFLAGS: 00000206
RAX: 260ef2e77e0f0a00 RBX: 0000000000000a06 RCX: 260ef2e77e0f0a00
RDX: dffffc0000000000 RSI: ffffffff8a8c0300 RDI: 0000000000000001
RBP: ffffc9000d007c58 R08: dffffc0000000000 R09: ffffed10171c6af6
R10: ffffed10171c6af6 R11: 1ffff110171c6af5 R12: dffffc0000000000
R13: 0000000000000001 R14: ffffffff96e0e9f0 R15: 1ffff92001a00f78
debug_object_activate+0x2d7/0x490 lib/debugobjects.c:716
debug_rcu_head_queue kernel/rcu/rcu.h:190 [inline]
call_rcu+0xa7/0x980 kernel/rcu/tree.c:2834
task_work_run+0x1ca/0x250 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fdaf4d8ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdd9396858 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 000000000003493b RCX: 00007fdaf4d8ebe9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000001 R09: 00000001d9396b4f
R10: 0000001b33320000 R11: 0000000000000246 R12: 00007fdaf4fc5fac
R13: 00007fdaf4fc5fa0 R14: ffffffffffffffff R15: 0000000000000005
</TASK>


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 8ce36b2849ef Linux 6.1.163
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11b6ec02580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=bd458038ebcbde78a479
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=12cb915a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11b12ffa580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6cee9de046d6/disk-8ce36b28.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e0455cf6949c/vmlinux-8ce36b28.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fb16f4beed74/bzImage-8ce36b28.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bd4580...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 2634 jiffies s: 3197 root: 0x1/.

rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0

CPU: 0 PID: 4498 Comm: syz.0.27 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:rcu_lockdep_current_cpu_online+0xf4/0x120 kernel/rcu/tree.c:780
Code: 48 c7 c7 80 34 b3 8c be 04 00 00 00 e8 c5 ec 66 00 83 3d 2e c0 46 0b 00 74 11 b0 01 65 ff 0d eb fa 95 7e 74 0a 5b 41 5e 41 5f <c3> 31 c0 eb ed e8 4a 0f 94 ff eb ef 48 c7 c7 80 26 b3 8c 48 89 de
RSP: 0018:ffffc90000007328 EFLAGS: 00000002
RAX: 1ffffffff1966501 RBX: 0000000000000000 RCX: 9dae53cd2246c500
RDX: ffff888079c81dc0 RSI: ffffffff8adf0d00 RDI: ffff8880b8e3b9e0
RBP: ffffc90000007470 R08: ffffc900000073f7 R09: ffffc900000073e0
R10: dffffc0000000000 R11: fffff52000000e7f R12: 1ffff92000000e78
R13: ffffc900000074c0 R14: 0000000000000030 R15: ffff888017773c00
FS: 000055557465b500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000

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

CR2: 0000001b31963fff CR3: 000000002368d000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>

rcu_read_lock_held_common kernel/rcu/update.c:112 [inline]
rcu_read_lock_held+0x1a/0x40 kernel/rcu/update.c:309
__perf_output_begin kernel/events/ring_buffer.c:170 [inline]
perf_output_begin_forward+0x1d1/0xa80 kernel/events/ring_buffer.c:272
__perf_event_output kernel/events/core.c:7732 [inline]
perf_event_output_forward+0x1ad/0x2f0 kernel/events/core.c:7750
__perf_event_overflow+0x448/0x610 kernel/events/core.c:9496
perf_tp_event+0x38c/0xc00 kernel/events/core.c:10029
perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10002
perf_trace_preemptirq_template+0x268/0x320 include/trace/events/preemptirq.h:14

trace_irq_enable_rcuidle+0xd3/0x140 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728

RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 92 31 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007aa0 EFLAGS: 00000206
RAX: 9dae53cd2246c500 RBX: 1ffff92000000f5c RCX: 9dae53cd2246c500
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0d20
RBP: ffffc90000007b90 R08: ffff8880b8e3580b R09: 1ffff110171c6b01
R10: dffffc0000000000 R11: ffffed10171c6b02 R12: 0000000000000246

R13: dffffc0000000000 R14: ffff8880b8e3b900 R15: 0000000000000001
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]

ieee80211_iterate_active_interfaces_atomic+0x156/0x170 net/mac80211/util.c:826
mac80211_hwsim_beacon+0xb7/0x1b0 drivers/net/wireless/mac80211_hwsim.c:2147
__run_hrtimer kernel/time/hrtimer.c:1747 [inline]
__hrtimer_run_queues+0x560/0xd70 kernel/time/hrtimer.c:1811
hrtimer_run_softirq+0x183/0x2a0 kernel/time/hrtimer.c:1828
handle_softirqs+0x2a1/0x930 kernel/softirq.c:596

__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]

__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679

irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691

RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:202
Code: 00 00 00 66 90 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 9e 12 2e f7 48 89 df e8 e6 da 2e f7 e8 c1 2d 52 f7 fb bf 01 00 00 00 <e8> 86 3b 22 f7 65 8b 05 47 c0 cb 75 85 c0 74 02 5b c3 e8 94 d4 c9
RSP: 0018:ffffc900033c7df0 EFLAGS: 00000286
RAX: 9dae53cd2246c500 RBX: ffff888079c827c0 RCX: 9dae53cd2246c500
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: 0000000000000001
RBP: ffffc900033c7ec0 R08: ffff8880b8e3580b R09: 1ffff110171c6b01
R10: dffffc0000000000 R11: ffffed10171c6b02 R12: dffffc0000000000
R13: ffff888079ff6500 R14: ffff888079c827c0 R15: ffff888079c82728
task_work_run+0x193/0x260 kernel/task_work.c:199

resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177

exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210

__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303

do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f3b7dd9bf79
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffbbab6d48 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fffbbab6e30 RCX: 00007f3b7dd9bf79

RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003

RBP: 000000000007fc4f R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b30d20000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3b7e015fac R14: 00007f3b7e015fa8 R15: 00007f3b7e015fa0
</TASK>


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