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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cc5ec8769306 Linux 5.15.196
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=159424b4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=20c97ad9ef8e059612a0
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ed7568bc5bb4/disk-cc5ec876.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e343e0aaac77/vmlinux-cc5ec876.xz
kernel image: https://storage.googleapis.com/syzbot-assets/089870f2a980/bzImage-cc5ec876.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+20c97a...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 0-....: (1 GPs behind) idle=349/1/0x4000000000000000 softirq=22061/22064 fqs=2077
(t=10500 jiffies g=30165 q=2178)
NMI backtrace for cpu 0
CPU: 0 PID: 8790 Comm: syz.7.1103 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
<IRQ>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_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+0x6d8/0x1110 kernel/rcu/tree.c:2619
update_process_times+0x193/0x200 kernel/time/timer.c:1818
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+0x4fe/0xc40 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:lock_acquire+0x1f2/0x3f0 kernel/locking/lockdep.c:5627
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f6 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 66 43 c7 44 3d 09 00 00 43 c6 44 3d 0b
RSP: 0018:ffffc90000007960 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ce6bed8a23c4ee00
RDX: 0000000000000000 RSI: ffffffff8a0b2f00 RDI: ffffffff8a59e580
RBP: ffffc90000007a80 R08: dffffc0000000000 R09: fffffbfff1ff7c19
R10: fffffbfff1ff7c19 R11: 1ffffffff1ff7c18 R12: ffffffff8c11c760
R13: 1ffff92000000f38 R14: 0000000000000246 R15: dffffc0000000000
rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:313
rcu_read_lock include/linux/rcupdate.h:740 [inline]
__rhashtable_remove_fast include/linux/rhashtable.h:1074 [inline]
rhashtable_remove_fast include/linux/rhashtable.h:1112 [inline]
inet_frag_kill+0x2e2/0xfd0 net/ipv4/inet_fragment.c:244
ipq_kill net/ipv4/ip_fragment.c:118 [inline]
ip_expire+0x16e/0x720 net/ipv4/ip_fragment.c:156
call_timer_fn+0x16c/0x530 kernel/time/timer.c:1451
expire_timers kernel/time/timer.c:1496 [inline]
__run_timers+0x525/0x7c0 kernel/time/timer.c:1767
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1780
handle_softirqs+0x328/0x820 kernel/softirq.c:576
__do_softirq kernel/softirq.c:610 [inline]
invoke_softirq kernel/softirq.c:450 [inline]
__irq_exit_rcu+0x12f/0x220 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:preempt_schedule_irq+0xac/0x150 kernel/sched/core.c:6799
Code: 44 24 20 f6 44 24 21 02 74 0b 0f 0b 48 f7 03 08 00 00 00 74 70 bf 01 00 00 00 e8 cf b7 9f f7 e8 1a 31 cc f7 fb bf 01 00 00 00 <e8> ef b5 ff ff 48 c7 44 24 40 00 00 00 00 9c 8f 44 24 40 8b 44 24
RSP: 0018:ffffc900030bfaa0 EFLAGS: 00000286
RAX: ce6bed8a23c4ee00 RBX: 0000000000000000 RCX: ce6bed8a23c4ee00
RDX: dffffc0000000000 RSI: ffffffff8a0b1c60 RDI: 0000000000000001
RBP: ffffc900030bfb50 R08: dffffc0000000000 R09: fffffbfff1ff7c1f
R10: fffffbfff1ff7c1f R11: 1ffffffff1ff7c1e R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 1ffff92000617f54
irqentry_exit+0x63/0x70 kernel/entry/common.c:432
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:up_read+0x0/0x20 kernel/locking/rwsem.c:1592
Code: c7 c1 c8 d0 69 8d 80 e1 07 80 c1 03 38 c1 0f 8c 96 fe ff ff 48 c7 c7 c8 d0 69 8d e8 1a e7 60 00 e9 85 fe ff ff 0f 1f 44 00 00 <53> 48 89 fb 48 83 c7 70 48 8b 74 24 08 e8 5e 2e 01 00 48 89 df 5b
RSP: 0018:ffffc900030bfc10 EFLAGS: 00000286
RAX: ffffffff81350ace RBX: 0000000000000000 RCX: ffff888029660000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88807e39a3b8
RBP: 0000000000000000 R08: dffffc0000000000 R09: ffffed100fc73478
R10: ffffed100fc73478 R11: 1ffff1100fc73477 R12: ffff88807e39a3b8
R13: 0000000000000000 R14: 0000000000000000 R15: ffffc900030bfc78
mmap_read_unlock include/linux/mmap_lock.h:144 [inline]
__bad_area arch/x86/mm/fault.c:827 [inline]
bad_area+0x5d/0x90 arch/x86/mm/fault.c:835
handle_page_fault arch/x86/mm/fault.c:1445 [inline]
exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1501
asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0010:do_strncpy_from_user lib/strncpy_from_user.c:72 [inline]
RIP: 0010:strncpy_from_user+0x271/0x360 lib/strncpy_from_user.c:139
Code: e9 93 00 00 00 e8 bf 87 7d fd 49 83 c5 08 4d 89 f4 4c 8b 74 24 08 4c 8b 3c 24 31 ff 4c 89 e6 e8 85 8b 7d fd 49 83 ec 01 72 44 <43> 8a 2c 2f 4a 8d 3c 2b 48 89 f8 48 c1 e8 03 48 b9 00 00 00 00 00
RSP: 0018:ffffc900030bfd28 EFLAGS: 00050212
RAX: ffffffff83fa446b RBX: ffff888074598020 RCX: ffff888029660000
RDX: 0000000000000000 RSI: 0000000000000fe0 RDI: 0000000000000000
RBP: ffff888074598020 R08: 0000000000000fe0 R09: 0000000000000020
R10: fffff940003a2cc1 R11: 1ffffd40003a2cc0 R12: 0000000000000fdf
R13: 0000000000000000 R14: 0000000000000fe0 R15: 0000000000000000
getname_flags+0xef/0x500 fs/namei.c:149
do_sys_openat2+0xcf/0x4a0 fs/open.c:1247
do_sys_open fs/open.c:1269 [inline]
__do_sys_openat fs/open.c:1285 [inline]
__se_sys_openat fs/open.c:1280 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1280
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: 0033:0x7fc7514f5749
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:00007fc74f75c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fc75174bfa0 RCX: 00007fc7514f5749
RDX: 00000000001c1341 RSI: 0000000000000000 RDI: ffffffffffffff9c
RBP: 00007fc751579f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc75174c038 R14: 00007fc75174bfa0 R15: 00007ffd484d6fe8
</TASK>


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