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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b9d57c40a767 Linux 5.15.203
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=165be896580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=7d56c691ce261944ee2a
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/1b2ee9aebbe3/disk-b9d57c40.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e5742bf875d7/vmlinux-b9d57c40.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5175fafcf12a/bzImage-b9d57c40.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7d56c6...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 1-....: (10500 ticks this GP) idle=74f/1/0x4000000000000000 softirq=83579/83579 fqs=5215
(t=10502 jiffies g=112721 q=81204)
NMI backtrace for cpu 1
CPU: 1 PID: 28111 Comm: syz.6.4726 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:deref_stack_reg+0xdf/0x120 arch/x86/kernel/unwind_orc.c:360
Code: 4c 89 f7 4c 89 fa e8 b0 46 f5 ff 85 c0 74 04 31 c0 eb 26 4c 89 f7 e8 90 07 00 00 49 89 c6 48 89 d8 48 c1 e8 03 42 80 3c 20 00 <74> 08 48 89 df e8 e7 18 89 00 4c 89 33 b0 01 5b 41 5c 41 5d 41 5e
RSP: 0018:ffffc90000dd04d0 EFLAGS: 00000246
RAX: 1ffff920001ba0cd RBX: ffffc90000dd0668 RCX: 0000000000000001
RDX: ffffc90000dd0668 RSI: ffffc90000dd06b0 RDI: ffffc90000dd06b0
RBP: ffffc90000dd1000 R08: ffffc90000dd0687 R09: ffffc90000dd0678
R10: dffffc0000000000 R11: fffff520001ba0d1 R12: dffffc0000000000
R13: ffffc90000dc9000 R14: ffffc90000dd0760 R15: ffffc90000dd0628
unwind_next_frame+0x115d/0x1d90 arch/x86/kernel/unwind_orc.c:-1
__unwind_start+0x5bb/0x740 arch/x86/kernel/unwind_orc.c:704
unwind_start arch/x86/include/asm/unwind.h:60 [inline]
arch_stack_walk+0xda/0x140 arch/x86/kernel/stacktrace.c:24
stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
kasan_slab_free include/linux/kasan.h:230 [inline]
slab_free_hook mm/slub.c:1710 [inline]
slab_free_freelist_hook+0xea/0x170 mm/slub.c:1736
slab_free mm/slub.c:3504 [inline]
kfree+0xef/0x2a0 mm/slub.c:4564
skb_free_head net/core/skbuff.c:655 [inline]
skb_release_data+0x6b8/0x800 net/core/skbuff.c:677
skb_release_all net/core/skbuff.c:742 [inline]
__kfree_skb net/core/skbuff.c:756 [inline]
kfree_skb_reason+0xaf/0x110 net/core/skbuff.c:776
kfree_skb include/linux/skbuff.h:1118 [inline]
inet_frag_rbtree_purge net/ipv4/inet_fragment.c:280 [inline]
inet_frag_destroy+0x13a/0x230 net/ipv4/inet_fragment.c:300
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:finish_lock_switch+0x134/0x280 kernel/sched/core.c:4804
Code: be ff ff ff ff e8 3c 62 68 08 85 c0 74 4a 4d 85 ff 75 66 0f 1f 44 00 00 48 89 df e8 e6 cd 71 08 e8 61 e6 2a 00 fb 48 83 c4 08 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 48 89 df e8 c9 09 fe ff 43 80 3c
RSP: 0018:ffffc9000319f7c8 EFLAGS: 00000282
RAX: d0bb297b0fc77e00 RBX: ffff8880b913a340 RCX: d0bb297b0fc77e00
RDX: dffffc0000000000 RSI: ffffffff8a2b2800 RDI: ffffffff8a79fe40
RBP: 1ffff11017227613 R08: ffffffff901d51cf R09: 1ffffffff203aa39
R10: dffffc0000000000 R11: fffffbfff203aa3a R12: 1ffff110172275c1
R13: dffffc0000000000 R14: ffff8880b913ae08 R15: 0000000000000000
finish_task_switch+0x12f/0x640 kernel/sched/core.c:4921
context_switch kernel/sched/core.c:5052 [inline]
__schedule+0x11f7/0x43c0 kernel/sched/core.c:6395
preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6571
preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6596
preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
smp_call_function_single+0x42b/0x4c0 kernel/smp.c:760
task_function_call kernel/events/core.c:120 [inline]
perf_install_in_context+0x5c7/0x920 kernel/events/core.c:3016
__do_sys_perf_event_open kernel/events/core.c:12793 [inline]
__se_sys_perf_event_open+0x12b3/0x1bb0 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: 0033:0x7f7f7ac72dd9
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:00007f7f78e8a028 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00007f7f7aeec180 RCX: 00007f7f7ac72dd9
RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 0000200000000000
RBP: 00007f7f7ad08d69 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7f7aeec218 R14: 00007f7f7aeec180 R15: 00007ffd45471848
</TASK>
ODEBUG: Out of memory. ODEBUG disabled


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