[v6.1] INFO: rcu detected stall in fib6_run_gc
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syzbot
Nov 29, 2025, 1:36:27 PM (yesterday) Nov 29
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: f6e38ae624cf Linux 6.1.158
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=101afe92580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7eb38bd5021fec61
dashboard link: https://syzkaller.appspot.com/bug?extid=dcb974f152003e1beef2
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/0d8305ca1c94/disk-f6e38ae6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8bc85383c07b/vmlinux-f6e38ae6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d337081bce56/bzImage-f6e38ae6.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dcb974...@syzkaller.appspotmail.com
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { P6727 0-.... } 2632 jiffies s: 311833 root: 0x1/T
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6698 Comm: syz.0.9144 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:27 [inline]
RIP: 0010:static_key_false include/linux/jump_label.h:207 [inline]
RIP: 0010:native_write_msr arch/x86/include/asm/msr.h:147 [inline]
RIP: 0010:wrmsr arch/x86/include/asm/msr.h:254 [inline]
RIP: 0010:native_apic_msr_write+0x35/0x50 arch/x86/include/asm/apic.h:206
Code: 74 2a 83 ff 30 74 25 eb 10 81 ff d0 00 00 00 74 1b 81 ff e0 00 00 00 74 13 c1 ef 04 81 c7 00 08 00 00 89 f9 89 f0 31 d2 0f 30 <66> 90 c3 89 f6 31 d2 e9 1f ea f7 02 66 2e 0f 1f 84 00 00 00 00 00
RSP: 0018:ffffc90000007520 EFLAGS: 00000046
RAX: 000000000000007b RBX: 000000000000007b RCX: 0000000000000838
RDX: 0000000000000000 RSI: 000000000000007b RDI: 0000000000000838
RBP: 0000000000000000 R08: dffffc0000000000 R09: fffffbfff1c3ed56
R10: fffffbfff1c3ed56 R11: 1ffffffff1c3ed55 R12: dffffc0000000000
R13: 0000000010005fa1 R14: ffffffff8c5e4b40 R15: dffffc0000000000
FS: 00007f834a0af6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000027000 CR3: 0000000087f52000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
apic_write arch/x86/include/asm/apic.h:394 [inline]
lapic_next_event+0x5b/0x70 arch/x86/kernel/apic/apic.c:478
clockevents_program_event+0x1bc/0x310 kernel/time/clockevents.c:334
hrtimer_interrupt+0x59d/0x9c0 kernel/time/hrtimer.c:1886
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
__sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1118
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:fib6_clean_node+0x358/0x580 net/ipv6/ip6_fib.c:2196
Code: 00 00 00 00 fc ff df e8 36 e0 34 01 49 83 c5 08 4c 89 e8 48 c1 e8 03 42 80 3c 30 00 74 08 4c 89 ef e8 9c 0d ee f8 4d 8b 6d 00 <4d> 85 ed 0f 84 f3 00 00 00 e8 8a de 9d f8 43 80 3c 37 00 0f 85 a1
RSP: 0018:ffffc900000077a0 EFLAGS: 00000246
RAX: 1ffff11008004781 RBX: ffffc90000007a20 RCX: ffff88807d363b80
RDX: 0000000000000100 RSI: ffffffff8de4acc0 RDI: 0000000000000000
RBP: ffffc90000007880 R08: ffff88807d363b80 R09: 0000000000000003
R10: 00000000ffffffff R11: 0000000000000100 R12: ffffc90000007a10
R13: ffff88807ceeac00 R14: dffffc0000000000 R15: 1ffff92000000f42
fib6_walk_continue+0x640/0x8c0 net/ipv6/ip6_fib.c:2122
fib6_walk+0x149/0x290 net/ipv6/ip6_fib.c:2170
fib6_clean_tree net/ipv6/ip6_fib.c:2250 [inline]
__fib6_clean_all+0x231/0x370 net/ipv6/ip6_fib.c:2266
fib6_clean_all net/ipv6/ip6_fib.c:2277 [inline]
fib6_run_gc+0x114/0x290 net/ipv6/ip6_fib.c:2340
call_timer_fn+0x1a0/0x670 kernel/time/timer.c:1700
expire_timers kernel/time/timer.c:1751 [inline]
__run_timers+0x529/0x7d0 kernel/time/timer.c:2022
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2035
handle_softirqs+0x2a1/0x920 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x12f/0x220 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
sysvec_irq_work+0x9d/0xc0 arch/x86/kernel/irq_work.c:17
</IRQ>
<TASK>
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:preempt_schedule_irq+0xac/0x150 kernel/sched/core.c:6873
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 0f 42 37 f7 e8 4a be 66 f7 fb bf 01 00 00 00 <e8> df b9 ff ff 48 c7 44 24 40 00 00 00 00 9c 8f 44 24 40 8b 44 24
RSP: 0018:ffffc9000c6379c0 EFLAGS: 00000282
RAX: 5879afb164684e00 RBX: 0000000000000000 RCX: 5879afb164684e00
RDX: dffffc0000000000 RSI: ffffffff8a8c0580 RDI: 0000000000000001
RBP: ffffc9000c637a60 R08: dffffc0000000000 R09: fffffbfff215c45e
R10: fffffbfff215c45e R11: 1ffffffff215c45d R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 1ffff920018c6f38
irqentry_exit+0x63/0x70 kernel/entry/common.c:439
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:pipe_write+0x892/0x1b00 fs/pipe.c:538
Code: 8b 7c 24 68 48 c7 07 00 00 00 00 ba 00 10 00 00 48 8b bc 24 c8 00 00 00 31 f6 48 8b 8c 24 c0 00 00 00 e8 a1 06 24 02 49 89 c4 <49> 63 dc bf 00 10 00 00 48 89 de e8 3e 9c 9f ff 48 81 fb 00 10 00
RSP: 0018:ffffc9000c637b20 EFLAGS: 00000283
RAX: 0000000000001000 RBX: ffff88809512f9d0 RCX: 0000000000080000
RDX: ffffc9000c6c9000 RSI: 000000000001f167 RDI: 000000000001f168
RBP: ffffc9000c637cf0 R08: dffffc0000000000 R09: ffffed1012a90200
R10: 0000000000000000 R11: 0000000000000200 R12: 0000000000001000
R13: dffffc0000000000 R14: 000000000000004b R15: 0000000000000001
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x44c/0x960 fs/read_write.c:584
ksys_write+0x143/0x240 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f834918f749
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:00007f834a0af038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f83493e5fa0 RCX: 00007f834918f749
RDX: 00000000fffffdef RSI: 00002000000001c0 RDI: 0000000000000000
RBP: 00007f8349213f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f83493e6038 R14: 00007f83493e5fa0 R15: 00007fffa8fc82e8
</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
syzbot found the following issue on:
HEAD commit: f6e38ae624cf Linux 6.1.158
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=101afe92580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7eb38bd5021fec61
dashboard link: https://syzkaller.appspot.com/bug?extid=dcb974f152003e1beef2
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/0d8305ca1c94/disk-f6e38ae6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8bc85383c07b/vmlinux-f6e38ae6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d337081bce56/bzImage-f6e38ae6.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dcb974...@syzkaller.appspotmail.com
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { P6727 0-.... } 2632 jiffies s: 311833 root: 0x1/T
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6698 Comm: syz.0.9144 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:27 [inline]
RIP: 0010:static_key_false include/linux/jump_label.h:207 [inline]
RIP: 0010:native_write_msr arch/x86/include/asm/msr.h:147 [inline]
RIP: 0010:wrmsr arch/x86/include/asm/msr.h:254 [inline]
RIP: 0010:native_apic_msr_write+0x35/0x50 arch/x86/include/asm/apic.h:206
Code: 74 2a 83 ff 30 74 25 eb 10 81 ff d0 00 00 00 74 1b 81 ff e0 00 00 00 74 13 c1 ef 04 81 c7 00 08 00 00 89 f9 89 f0 31 d2 0f 30 <66> 90 c3 89 f6 31 d2 e9 1f ea f7 02 66 2e 0f 1f 84 00 00 00 00 00
RSP: 0018:ffffc90000007520 EFLAGS: 00000046
RAX: 000000000000007b RBX: 000000000000007b RCX: 0000000000000838
RDX: 0000000000000000 RSI: 000000000000007b RDI: 0000000000000838
RBP: 0000000000000000 R08: dffffc0000000000 R09: fffffbfff1c3ed56
R10: fffffbfff1c3ed56 R11: 1ffffffff1c3ed55 R12: dffffc0000000000
R13: 0000000010005fa1 R14: ffffffff8c5e4b40 R15: dffffc0000000000
FS: 00007f834a0af6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000027000 CR3: 0000000087f52000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
apic_write arch/x86/include/asm/apic.h:394 [inline]
lapic_next_event+0x5b/0x70 arch/x86/kernel/apic/apic.c:478
clockevents_program_event+0x1bc/0x310 kernel/time/clockevents.c:334
hrtimer_interrupt+0x59d/0x9c0 kernel/time/hrtimer.c:1886
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
__sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1118
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:fib6_clean_node+0x358/0x580 net/ipv6/ip6_fib.c:2196
Code: 00 00 00 00 fc ff df e8 36 e0 34 01 49 83 c5 08 4c 89 e8 48 c1 e8 03 42 80 3c 30 00 74 08 4c 89 ef e8 9c 0d ee f8 4d 8b 6d 00 <4d> 85 ed 0f 84 f3 00 00 00 e8 8a de 9d f8 43 80 3c 37 00 0f 85 a1
RSP: 0018:ffffc900000077a0 EFLAGS: 00000246
RAX: 1ffff11008004781 RBX: ffffc90000007a20 RCX: ffff88807d363b80
RDX: 0000000000000100 RSI: ffffffff8de4acc0 RDI: 0000000000000000
RBP: ffffc90000007880 R08: ffff88807d363b80 R09: 0000000000000003
R10: 00000000ffffffff R11: 0000000000000100 R12: ffffc90000007a10
R13: ffff88807ceeac00 R14: dffffc0000000000 R15: 1ffff92000000f42
fib6_walk_continue+0x640/0x8c0 net/ipv6/ip6_fib.c:2122
fib6_walk+0x149/0x290 net/ipv6/ip6_fib.c:2170
fib6_clean_tree net/ipv6/ip6_fib.c:2250 [inline]
__fib6_clean_all+0x231/0x370 net/ipv6/ip6_fib.c:2266
fib6_clean_all net/ipv6/ip6_fib.c:2277 [inline]
fib6_run_gc+0x114/0x290 net/ipv6/ip6_fib.c:2340
call_timer_fn+0x1a0/0x670 kernel/time/timer.c:1700
expire_timers kernel/time/timer.c:1751 [inline]
__run_timers+0x529/0x7d0 kernel/time/timer.c:2022
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2035
handle_softirqs+0x2a1/0x920 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x12f/0x220 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
sysvec_irq_work+0x9d/0xc0 arch/x86/kernel/irq_work.c:17
</IRQ>
<TASK>
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:preempt_schedule_irq+0xac/0x150 kernel/sched/core.c:6873
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 0f 42 37 f7 e8 4a be 66 f7 fb bf 01 00 00 00 <e8> df b9 ff ff 48 c7 44 24 40 00 00 00 00 9c 8f 44 24 40 8b 44 24
RSP: 0018:ffffc9000c6379c0 EFLAGS: 00000282
RAX: 5879afb164684e00 RBX: 0000000000000000 RCX: 5879afb164684e00
RDX: dffffc0000000000 RSI: ffffffff8a8c0580 RDI: 0000000000000001
RBP: ffffc9000c637a60 R08: dffffc0000000000 R09: fffffbfff215c45e
R10: fffffbfff215c45e R11: 1ffffffff215c45d R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 1ffff920018c6f38
irqentry_exit+0x63/0x70 kernel/entry/common.c:439
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:pipe_write+0x892/0x1b00 fs/pipe.c:538
Code: 8b 7c 24 68 48 c7 07 00 00 00 00 ba 00 10 00 00 48 8b bc 24 c8 00 00 00 31 f6 48 8b 8c 24 c0 00 00 00 e8 a1 06 24 02 49 89 c4 <49> 63 dc bf 00 10 00 00 48 89 de e8 3e 9c 9f ff 48 81 fb 00 10 00
RSP: 0018:ffffc9000c637b20 EFLAGS: 00000283
RAX: 0000000000001000 RBX: ffff88809512f9d0 RCX: 0000000000080000
RDX: ffffc9000c6c9000 RSI: 000000000001f167 RDI: 000000000001f168
RBP: ffffc9000c637cf0 R08: dffffc0000000000 R09: ffffed1012a90200
R10: 0000000000000000 R11: 0000000000000200 R12: 0000000000001000
R13: dffffc0000000000 R14: 000000000000004b R15: 0000000000000001
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x44c/0x960 fs/read_write.c:584
ksys_write+0x143/0x240 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f834918f749
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:00007f834a0af038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f83493e5fa0 RCX: 00007f834918f749
RDX: 00000000fffffdef RSI: 00002000000001c0 RDI: 0000000000000000
RBP: 00007f8349213f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f83493e6038 R14: 00007f83493e5fa0 R15: 00007fffa8fc82e8
</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
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