INFO: rcu detected stall in ip_expire

Status: upstream: reported on 2026/09/20 15:33
Reported-by: syzbot+55ac70112784c8c5d044@syzkaller.appspotmail.com
First crash: 22d, last: 13h12m
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in ip_expire (2) 1 1 127d 127d 0/3 auto-obsoleted due to no activity on 2026/09/15 02:40
linux-5.15 INFO: rcu detected stall in ip_expire (2) 1 2 6d10h 7d16h 0/3 upstream: reported on 2026/10/05 00:10
upstream INFO: rcu detected stall in ip_expire (2) net 1 1 2102d 2102d 0/29 auto-closed as invalid on 2021/04/09 11:48
linux-6.1 INFO: rcu detected stall in ip_expire 1 1 751d 751d 0/3 auto-obsoleted due to no activity on 2024/12/30 13:44
linux-5.15 INFO: rcu detected stall in ip_expire 1 1 318d 318d 0/3 auto-obsoleted due to no activity on 2026/03/08 05:26
upstream INFO: rcu detected stall in ip_expire net 1 1 2232d 2232d 0/29 auto-closed as invalid on 2020/11/30 05:39
upstream BUG: soft lockup in ip_expire net 1 1 385d 385d 0/29 closed as invalid on 2025/11/14 20:35

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 1, t=10502 jiffies, g=9797, q=3821 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10480 (4294958381-4294947901), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10481 jiffies! g9797 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:27848 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x30d/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6038 Comm: syz.0.64 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:find_held_lock kernel/locking/lockdep.c:-1 [inline]
RIP: 0010:__lock_release kernel/locking/lockdep.c:5465 [inline]
RIP: 0010:lock_release+0x207/0x8c0 kernel/locking/lockdep.c:5810
Code: 89 44 24 30 83 f8 32 0f 83 d3 04 00 00 4b 8d 04 b6 4c 8d 24 c3 48 89 c3 4c 89 e7 48 8b 74 24 18 e8 3e 91 29 09 44 89 7c 24 3c <44> 89 fa 85 c0 0f 84 d7 01 00 00 4d 85 e4 0f 84 01 03 00 00 4d 8d
RSP: 0018:ffffc90000007120 EFLAGS: 00000046
RAX: 0000000000000001 RBX: 0000000000000014 RCX: 9d48c6afd793ff00
RDX: 1ffff11004e91c9c RSI: ffffffff8d14bc88 RDI: ffff88802748e588
RBP: ffffc90000007230 R08: ffffffff8e8c626f R09: 1ffffffff1d18c4d
R10: dffffc0000000000 R11: fffffbfff1d18c4e R12: ffff88802748e588
R13: dffffc0000000000 R14: 0000000000000004 R15: 0000000000000004
FS:  00007f9a033d56c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000100000000 CR3: 000000002da50000 CR4: 00000000003506f0
DR0: 0000000000000008 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 seqcount_lockdep_reader_access+0xe4/0x1d0 include/linux/seqlock.h:103
 timekeeping_get_delta kernel/time/timekeeping.c:254 [inline]
 timekeeping_get_ns kernel/time/timekeeping.c:388 [inline]
 ktime_get+0x7f/0x280 kernel/time/timekeeping.c:848
 hrtimer_forward_now include/linux/hrtimer.h:509 [inline]
 perf_swevent_hrtimer+0x4ae/0x610 kernel/events/core.c:11235
 __run_hrtimer kernel/time/hrtimer.c:1754 [inline]
 __hrtimer_run_queues+0x4e8/0xc10 kernel/time/hrtimer.c:1818
 hrtimer_interrupt+0x39d/0x980 kernel/time/hrtimer.c:1880
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x51/0xc0 arch/x86/kernel/apic/apic.c:1088
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xc0/0x120 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> ab 96 c0 f6 65 8b 05 1c 54 67 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc90000007900 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: 9d48c6afd793ff00
RDX: dffffc0000000000 RSI: ffffffff8acacce0 RDI: 0000000000000001
RBP: ffffc90000007980 R08: ffffffff911f0617 R09: 1ffffffff223e0c2
R10: dffffc0000000000 R11: fffffbfff223e0c3 R12: dffffc0000000000
R13: ffff88805c1c9f50 R14: ffffffff974b5dd8 R15: 1ffff92000000f20
 debug_object_assert_init+0x1f1/0x300 lib/debugobjects.c:946
 debug_timer_assert_init kernel/time/timer.c:792 [inline]
 debug_assert_init kernel/time/timer.c:837 [inline]
 __timer_delete+0x3f/0x290 kernel/time/timer.c:1321
 del_timer include/linux/timer.h:213 [inline]
 inet_frag_destroy+0x7b/0x290 net/ipv4/inet_fragment.c:354
 inet_frag_putn include/net/inet_frag.h:139 [inline]
 ip_expire+0x55b/0x850 net/ipv4/ip_fragment.c:192
 call_timer_fn+0x189/0x540 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x570/0x810 kernel/time/timer.c:2023
 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x27d/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:deref_stack_reg+0x0/0x230 arch/x86/kernel/unwind_orc.c:402
Code: e2 07 80 c2 03 38 c2 0f 8c d5 fe ff ff 48 89 4c 24 18 e8 33 58 a4 00 48 8b 4c 24 18 e9 c1 fe ff ff 66 0f 1f 84 00 00 00 00 00 <55> 41 57 41 56 41 55 41 54 53 48 83 ec 18 48 89 54 24 10 48 89 34
RSP: 0018:ffffc9000b6af530 EFLAGS: 00000283
RAX: fffffffffffffff0 RBX: ffffffff8f1bb40d RCX: 0000000000000003
RDX: ffffc9000b6af648 RSI: ffffc9000b6afa70 RDI: ffffc9000b6af608
RBP: ffffc9000b6af658 R08: ffff88802748da00 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000002 R12: ffffc9000b6afa58
R13: ffffc9000b6af608 R14: ffffffff8f1bb40c R15: dffffc0000000000
 unwind_next_frame+0x1781/0x2990 arch/x86/kernel/unwind_orc.c:648
 arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
 save_stack+0x125/0x230 mm/page_owner.c:128
 __reset_page_owner+0x4e/0x190 mm/page_owner.c:149
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 __slab_free+0x35a/0x400 mm/slub.c:3736
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:770
 slab_alloc_node mm/slub.c:3495 [inline]
 __kmem_cache_alloc_node+0x194/0x250 mm/slub.c:3534
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc+0xa7/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 tomoyo_realpath_from_path+0xe6/0x5c0 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_number_perm+0x248/0x5e0 security/tomoyo/file.c:723
 security_file_ioctl+0x70/0xa0 security/security.c:2735
 __do_sys_ioctl fs/ioctl.c:865 [inline]
 __se_sys_ioctl+0x48/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9a0519e199
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:00007f9a033d5028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9a05426090 RCX: 00007f9a0519e199
RDX: 0000200000000000 RSI: 00000000400454ca RDI: 000000000000000b
RBP: 00007f9a052358e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9a05426128 R14: 00007f9a05426090 R15: 00007fff9c0a4318
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/06 07:37 linux-6.6.y a91a6aa9253c f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in ip_expire
2026/09/20 15:32 linux-6.6.y 79643295eba1 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in ip_expire
2026/10/12 03:45 linux-6.6.y a91a6aa9253c 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf BUG: soft lockup in ip_expire
* Struck through repros no longer work on HEAD.