[v6.1] INFO: rcu detected stall in ppp_release
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syzbot
Feb 8, 2026, 12:49:41 AM (2 days ago) Feb 8
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: 0182cb5b74ee Linux 6.1.162
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15426b22580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=4f10c36460cda5d1824c
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/8b6fc106fd9c/disk-0182cb5b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f9ed1286c8af/vmlinux-0182cb5b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/10c7fc900d05/bzImage-0182cb5b.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4f10c3...@syzkaller.appspotmail.com
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2657 jiffies s: 1329 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4476 Comm: syz.4.32 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:__wrmsr arch/x86/include/asm/msr.h:94 [inline]
RIP: 0010:native_apic_msr_eoi_write+0x0/0x10 arch/x86/include/asm/apic.h:211
Code: 74 08 4c 89 f7 e8 f0 4b 9b 00 49 8b 06 bf f0 03 00 00 89 de 5b 41 5e 41 5f ff e0 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 <b9> 0b 08 00 00 31 c0 31 d2 0f 30 c3 0f 1f 40 00 81 ff cf 00 00 00
RSP: 0018:ffffc900001e09b8 EFLAGS: 00000046
RAX: 1ffffffff18c9f66 RBX: ffffffff8c64fb30 RCX: 7ff2d9632412e100
RDX: 1ffffffff1f41208 RSI: 0000000000000000 RDI: 00000000000000b0
RBP: 0000000000000000 R08: ffffffff8fa09048 R09: ffffffff8fa09058
R10: ffffffff8fa09050 R11: ffffffff8fa09043 R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000
FS: 00007f9a10d2b6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbb02617dac CR3: 0000000058d5e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
apic_eoi arch/x86/include/asm/apic.h:399 [inline]
ack_APIC_irq arch/x86/include/asm/apic.h:445 [inline]
__sysvec_irq_work+0x53/0x350 arch/x86/kernel/irq_work.c:19
instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
sysvec_irq_work+0x4a/0xc0 arch/x86/kernel/irq_work.c:17
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 92 31 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc900001e0aa0 EFLAGS: 00000206
RAX: 7ff2d9632412e100 RBX: 1ffff9200003c15c RCX: 7ff2d9632412e100
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0d20
RBP: ffffc900001e0b90 R08: ffffffff90af424f R09: 1ffffffff215e849
R10: dffffc0000000000 R11: fffffbfff215e84a R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8f3b900 R15: 0000000000000002
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
ieee80211_iterate_active_interfaces_atomic+0x156/0x170 net/mac80211/util.c:826
mac80211_hwsim_beacon+0xb7/0x1b0 drivers/net/wireless/mac80211_hwsim.c:2147
__run_hrtimer kernel/time/hrtimer.c:1747 [inline]
__hrtimer_run_queues+0x560/0xd70 kernel/time/hrtimer.c:1811
hrtimer_run_softirq+0x183/0x2a0 kernel/time/hrtimer.c:1828
handle_softirqs+0x2a1/0x930 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:finish_task_switch+0x26a/0x8f0 kernel/sched/core.c:5124
Code: 0f 84 3b 01 00 00 48 85 db 0f 85 5a 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 d0 fd dc 08 e8 eb 2c 2f 00 fb 4c 8b 65 c0 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc90004a2f6d8 EFLAGS: 00000286
RAX: 7ff2d9632412e100 RBX: 0000000000000000 RCX: 7ff2d9632412e100
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0d20
RBP: ffffc90004a2f730 R08: ffffffff90af424f R09: 1ffffffff215e849
R10: dffffc0000000000 R11: fffffbfff215e84a R12: ffff8880302b1dc0
R13: dffffc0000000000 R14: ffff888026770000 R15: ffff8880b8f3b5d0
context_switch kernel/sched/core.c:5248 [inline]
__schedule+0x11d9/0x40e0 kernel/sched/core.c:6562
preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6874
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:fib_netdev_event+0x5e/0x470 net/ipv4/fib_frontend.c:1487
Code: 0b f9 49 8b 1f 4c 8d b3 50 06 00 00 e8 4b 29 65 01 4c 89 f0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 f7 e8 35 ed 0b f9 4d 8b 36 <bf> 06 00 00 00 4c 89 e6 e8 55 05 bb f8 49 83 fc 06 75 24 e8 6a 01
RSP: 0018:ffffc90004a2fa50 EFLAGS: 00000246
RAX: 1ffff11004cf0cca RBX: ffff888026786000 RCX: ffff8880302b1dc0
RDX: ffffc9000f4fa000 RSI: 000000000001ad9c RDI: 000000000001ad9d
RBP: 0000000000000000 R08: ffffffff90af424f R09: 1ffffffff215e849
R10: dffffc0000000000 R11: fffffbfff215e84a R12: 0000000000000006
R13: dffffc0000000000 R14: ffff888059ca3880 R15: ffffc90004a2fb80
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
call_netdevice_notifiers_extack net/core/dev.c:2052 [inline]
call_netdevice_notifiers net/core/dev.c:2066 [inline]
unregister_netdevice_many+0x1086/0x1930 net/core/dev.c:11003
unregister_netdevice_queue+0x324/0x370 net/core/dev.c:10934
unregister_netdevice include/linux/netdevice.h:3075 [inline]
ppp_release+0xec/0x1f0 drivers/net/ppp/ppp_generic.c:420
__fput+0x22c/0x920 fs/file_table.c:320
task_work_run+0x1d0/0x260 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9a0fd9aeb9
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:00007f9a10d2b028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: fffffffffffffff2 RBX: 00007f9a10016090 RCX: 00007f9a0fd9aeb9
RDX: 000000110c230041 RSI: 00000000c004743e RDI: 0000000000000008
RBP: 00007f9a0fe08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9a10016128 R14: 00007f9a10016090 R15: 00007ffc90354e78
</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: 0182cb5b74ee Linux 6.1.162
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15426b22580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=4f10c36460cda5d1824c
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/8b6fc106fd9c/disk-0182cb5b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f9ed1286c8af/vmlinux-0182cb5b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/10c7fc900d05/bzImage-0182cb5b.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4f10c3...@syzkaller.appspotmail.com
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2657 jiffies s: 1329 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4476 Comm: syz.4.32 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:__wrmsr arch/x86/include/asm/msr.h:94 [inline]
RIP: 0010:native_apic_msr_eoi_write+0x0/0x10 arch/x86/include/asm/apic.h:211
Code: 74 08 4c 89 f7 e8 f0 4b 9b 00 49 8b 06 bf f0 03 00 00 89 de 5b 41 5e 41 5f ff e0 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 <b9> 0b 08 00 00 31 c0 31 d2 0f 30 c3 0f 1f 40 00 81 ff cf 00 00 00
RSP: 0018:ffffc900001e09b8 EFLAGS: 00000046
RAX: 1ffffffff18c9f66 RBX: ffffffff8c64fb30 RCX: 7ff2d9632412e100
RDX: 1ffffffff1f41208 RSI: 0000000000000000 RDI: 00000000000000b0
RBP: 0000000000000000 R08: ffffffff8fa09048 R09: ffffffff8fa09058
R10: ffffffff8fa09050 R11: ffffffff8fa09043 R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000
FS: 00007f9a10d2b6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbb02617dac CR3: 0000000058d5e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
apic_eoi arch/x86/include/asm/apic.h:399 [inline]
ack_APIC_irq arch/x86/include/asm/apic.h:445 [inline]
__sysvec_irq_work+0x53/0x350 arch/x86/kernel/irq_work.c:19
instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
sysvec_irq_work+0x4a/0xc0 arch/x86/kernel/irq_work.c:17
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 92 31 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc900001e0aa0 EFLAGS: 00000206
RAX: 7ff2d9632412e100 RBX: 1ffff9200003c15c RCX: 7ff2d9632412e100
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0d20
RBP: ffffc900001e0b90 R08: ffffffff90af424f R09: 1ffffffff215e849
R10: dffffc0000000000 R11: fffffbfff215e84a R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8f3b900 R15: 0000000000000002
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
ieee80211_iterate_active_interfaces_atomic+0x156/0x170 net/mac80211/util.c:826
mac80211_hwsim_beacon+0xb7/0x1b0 drivers/net/wireless/mac80211_hwsim.c:2147
__run_hrtimer kernel/time/hrtimer.c:1747 [inline]
__hrtimer_run_queues+0x560/0xd70 kernel/time/hrtimer.c:1811
hrtimer_run_softirq+0x183/0x2a0 kernel/time/hrtimer.c:1828
handle_softirqs+0x2a1/0x930 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:finish_task_switch+0x26a/0x8f0 kernel/sched/core.c:5124
Code: 0f 84 3b 01 00 00 48 85 db 0f 85 5a 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 d0 fd dc 08 e8 eb 2c 2f 00 fb 4c 8b 65 c0 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc90004a2f6d8 EFLAGS: 00000286
RAX: 7ff2d9632412e100 RBX: 0000000000000000 RCX: 7ff2d9632412e100
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0d20
RBP: ffffc90004a2f730 R08: ffffffff90af424f R09: 1ffffffff215e849
R10: dffffc0000000000 R11: fffffbfff215e84a R12: ffff8880302b1dc0
R13: dffffc0000000000 R14: ffff888026770000 R15: ffff8880b8f3b5d0
context_switch kernel/sched/core.c:5248 [inline]
__schedule+0x11d9/0x40e0 kernel/sched/core.c:6562
preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6874
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:fib_netdev_event+0x5e/0x470 net/ipv4/fib_frontend.c:1487
Code: 0b f9 49 8b 1f 4c 8d b3 50 06 00 00 e8 4b 29 65 01 4c 89 f0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 f7 e8 35 ed 0b f9 4d 8b 36 <bf> 06 00 00 00 4c 89 e6 e8 55 05 bb f8 49 83 fc 06 75 24 e8 6a 01
RSP: 0018:ffffc90004a2fa50 EFLAGS: 00000246
RAX: 1ffff11004cf0cca RBX: ffff888026786000 RCX: ffff8880302b1dc0
RDX: ffffc9000f4fa000 RSI: 000000000001ad9c RDI: 000000000001ad9d
RBP: 0000000000000000 R08: ffffffff90af424f R09: 1ffffffff215e849
R10: dffffc0000000000 R11: fffffbfff215e84a R12: 0000000000000006
R13: dffffc0000000000 R14: ffff888059ca3880 R15: ffffc90004a2fb80
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
call_netdevice_notifiers_extack net/core/dev.c:2052 [inline]
call_netdevice_notifiers net/core/dev.c:2066 [inline]
unregister_netdevice_many+0x1086/0x1930 net/core/dev.c:11003
unregister_netdevice_queue+0x324/0x370 net/core/dev.c:10934
unregister_netdevice include/linux/netdevice.h:3075 [inline]
ppp_release+0xec/0x1f0 drivers/net/ppp/ppp_generic.c:420
__fput+0x22c/0x920 fs/file_table.c:320
task_work_run+0x1d0/0x260 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9a0fd9aeb9
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:00007f9a10d2b028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: fffffffffffffff2 RBX: 00007f9a10016090 RCX: 00007f9a0fd9aeb9
RDX: 000000110c230041 RSI: 00000000c004743e RDI: 0000000000000008
RBP: 00007f9a0fe08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9a10016128 R14: 00007f9a10016090 R15: 00007ffc90354e78
</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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