[v5.15] INFO: rcu detected stall in ip6_frag_expire

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 241d66fa280c Linux 5.15.208
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10d10673980000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=4c13ae1dc374920a9b79
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/aa5371307962/disk-241d66fa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/df72e55b8c3c/vmlinux-241d66fa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/96a6e7e64a47/bzImage-241d66fa.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4c13ae...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 0-....: (1 GPs behind) idle=511/1/0x4000000000000000 softirq=12554/12556 fqs=4043
(t=10500 jiffies g=14977 q=1531)
NMI backtrace for cpu 0
CPU: 0 PID: 5935 Comm: syz.2.455 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
<IRQ>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
rcu_dump_cpu_stacks+0x22f/0x380 kernel/rcu/tree_stall.h:349
print_cpu_stall+0x31d/0x5f0 kernel/rcu/tree_stall.h:633
check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
rcu_pending kernel/rcu/tree.c:3936 [inline]
rcu_sched_clock_irq+0x6ea/0x1120 kernel/rcu/tree.c:2619
update_process_times+0x193/0x200 kernel/time/timer.c:2021
tick_sched_handle kernel/time/tick-sched.c:254 [inline]
tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x4b4/0xb70 kernel/time/hrtimer.c:1749
hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1811
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
__sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1108
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:queue_work_on+0x1a0/0x1f0 kernel/workqueue.c:1564
Code: 4d 85 e4 75 16 e8 80 36 2b 00 eb 15 e8 79 36 2b 00 e8 14 da 6e 08 4d 85 e4 74 ea e8 6a 36 2b 00 fb 48 c7 44 24 20 0e 36 e0 45 <48> b8 00 00 00 00 00 fc ff df 49 c7 44 05 00 00 00 00 00 41 c7 44
RSP: 0018:ffffc900000079c0 EFLAGS: 00000246
RAX: ffffffff814dffa6 RBX: 0000000000000000 RCX: ffff88802bfb1dc0
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000007a88 R08: ffffffff901d61cf R09: 1ffffffff203ac39
R10: dffffc0000000000 R11: fffffbfff203ac3a R12: 0000000000000200
R13: 1ffff92000000f3c R14: 0000000000000000 R15: ffff888078e4c801
queue_work include/linux/workqueue.h:512 [inline]
schedule_work include/linux/workqueue.h:573 [inline]
__rhashtable_remove_fast_one include/linux/rhashtable.h:1059 [inline]
__rhashtable_remove_fast include/linux/rhashtable.h:1083 [inline]
rhashtable_remove_fast include/linux/rhashtable.h:1112 [inline]
inet_frag_kill+0xde0/0xf00 net/ipv4/inet_fragment.c:244
ip6frag_expire_frag_queue include/net/ipv6_frag.h:78 [inline]
ip6_frag_expire+0x131/0x6d0 net/ipv6/reassembly.c:80
call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
expire_timers kernel/time/timer.c:1699 [inline]
__run_timers+0x53e/0x800 kernel/time/timer.c:1970
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
handle_softirqs+0x339/0x830 kernel/softirq.c:576
__do_softirq kernel/softirq.c:610 [inline]
invoke_softirq kernel/softirq.c:450 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> bf 2a 8c f7 65 8b 05 f0 26 3c 76 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900032cfd00 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a06 RCX: a8dd8de78f509000
RDX: dffffc0000000000 RSI: ffffffff8a2b3100 RDI: 0000000000000001
RBP: ffffc900032cfd90 R08: ffffffff901d61cf R09: 1ffffffff203ac39
R10: dffffc0000000000 R11: fffffbfff203ac3a R12: dffffc0000000000
R13: 0000000000000000 R14: ffff88805fe82408 R15: 1ffff92000659fa0
__do_sys_perf_event_open kernel/events/core.c:12794 [inline]
__se_sys_perf_event_open+0x12bb/0x1bb0 kernel/events/core.c:12387
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fc220547e59
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:00007fc21e780028 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00007fc2207c1090 RCX: 00007fc220547e59
RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 0000200000000300
RBP: 00007fc2205ddd6f R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc2207c1128 R14: 00007fc2207c1090 R15: 00007ffc64e70148
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

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