[v5.15] INFO: rcu detected stall in fib6_run_gc

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dc027a595035 Linux 5.15.209
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=175cd76a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=07af271ec64d668c8982
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/3d51783ddbbf/disk-dc027a59.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b6879bfcdc05/vmlinux-dc027a59.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e4755824edc0/bzImage-dc027a59.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+07af27...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P12510
(detected by 0, t=10502 jiffies, g=46469, q=2218)
task:syz.3.2048 state:R running task stack:24688 pid:12510 ppid: 4195 flags:0x0000400c
Call Trace:
<IRQ>
sched_show_task+0x459/0x580 kernel/sched/core.c:8659
rcu_print_detail_task_stall_rnp kernel/rcu/tree_stall.h:233 [inline]
print_other_cpu_stall+0xec5/0x1270 kernel/rcu/tree_stall.h:573
check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
rcu_pending kernel/rcu/tree.c:3936 [inline]
rcu_sched_clock_irq+0x843/0x1120 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:fib6_clean_node+0x0/0x540 net/ipv6/ip6_fib.c:2170
Code: 84 00 00 00 00 00 0f 1f 40 00 53 48 89 fb e8 e7 33 d6 f8 48 83 c3 c8 48 8b 3d 7c a8 e8 04 48 89 de 5b e9 23 84 1a f9 0f 1f 00 <55> 48 89 e5 41 57 41 56 41 55 41 54 53 48 83 e4 e0 48 81 ec c0 00
RSP: 0018:ffffc90000007888 EFLAGS: 00000246
RAX: 1ffff92000000f43 RBX: 0000000000000000 RCX: ffff88804fcf0000
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffffc900000079e0
RBP: ffffc90000007a00 R08: ffff88804fcf0000 R09: 0000000000000005
R10: 0000000000000004 R11: 0000000000000100 R12: ffff88801f4ed200
R13: 1ffff92000000f41 R14: dffffc0000000000 R15: ffffc90000007a10
fib6_walk_continue+0x640/0x8c0 net/ipv6/ip6_fib.c:2115
fib6_walk+0x149/0x290 net/ipv6/ip6_fib.c:2163
fib6_clean_tree net/ipv6/ip6_fib.c:2243 [inline]
__fib6_clean_all+0x25f/0x3c0 net/ipv6/ip6_fib.c:2259
fib6_clean_all net/ipv6/ip6_fib.c:2270 [inline]
fib6_run_gc+0x11a/0x2a0 net/ipv6/ip6_fib.c:2333
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 4c ee 68 08 85 c0 74 4a 4d 85 ff 75 66 0f 1f 44 00 00 48 89 df e8 f6 59 72 08 e8 f1 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:ffffc90003bfef88 EFLAGS: 00000286
RAX: 3b0a6865dabf2900 RBX: ffff8880b903a340 RCX: 3b0a6865dabf2900
RDX: dffffc0000000000 RSI: ffffffff8a2b3180 RDI: ffffffff8a7a09c0
RBP: 1ffff11017207613 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: 1ffff110172075c1
R13: dffffc0000000000 R14: ffff8880b903ae08 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_notrace+0xd9/0x120 kernel/sched/core.c:6650
preempt_schedule_notrace_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
rcu_is_watching+0x72/0xa0 kernel/rcu/tree.c:1124
trace_lock_acquire include/trace/events/lock.h:13 [inline]
lock_acquire+0xc8/0x400 kernel/locking/lockdep.c:5594
rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:313
rcu_read_lock include/linux/rcupdate.h:740 [inline]
is_bpf_text_address+0x1d/0x270 kernel/bpf/core.c:725
kernel_text_address kernel/extable.c:151 [inline]
__kernel_text_address+0x9a/0x100 kernel/extable.c:105
unwind_get_return_address+0x49/0x80 arch/x86/kernel/unwind_orc.c:323
arch_stack_walk+0xf2/0x140 arch/x86/kernel/stacktrace.c:26
stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
__kasan_slab_alloc+0x9c/0xd0 mm/kasan/common.c:467
kasan_slab_alloc include/linux/kasan.h:254 [inline]
slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
slab_alloc_node mm/slub.c:3225 [inline]
kmem_cache_alloc_node+0x12d/0x2d0 mm/slub.c:3261
__alloc_skb+0xf4/0x750 net/core/skbuff.c:415
alloc_skb include/linux/skbuff.h:1162 [inline]
netlink_to_full_skb net/netlink/af_netlink.c:171 [inline]
__netlink_deliver_tap_skb net/netlink/af_netlink.c:296 [inline]
__netlink_deliver_tap+0x2f2/0x7c0 net/netlink/af_netlink.c:323
netlink_deliver_tap+0x16c/0x180 net/netlink/af_netlink.c:336
netlink_deliver_tap_kernel net/netlink/af_netlink.c:345 [inline]
netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
netlink_unicast+0x74f/0x920 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
sock_write_iter+0x2a6/0x3a0 net/socket.c:1089
call_write_iter include/linux/fs.h:2173 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x745/0xd60 fs/read_write.c:594
ksys_write+0x152/0x260 fs/read_write.c:647
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: 0033:0x7f4a9e7f9e59
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:00007f4a9ca32028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f4a9ea73090 RCX: 00007f4a9e7f9e59
RDX: 000000000000fe33 RSI: 0000200000000040 RDI: 0000000000000009
RBP: 00007f4a9e88fd6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4a9ea73128 R14: 00007f4a9ea73090 R15: 00007ffdc7545368
</TASK>


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