syzbot


INFO: rcu detected stall in lapb_t1timer_expiry

Status: upstream: reported on 2025/11/17 07:08
Reported-by: syzbot+72e9568c3431cf1fb5e6@syzkaller.appspotmail.com
First crash: 22d, last: 12d
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in lapb_t1timer_expiry kvm 1 1 1324d 1324d 0/29 auto-closed as invalid on 2022/06/25 00:02
upstream INFO: rcu detected stall in lapb_t1timer_expiry (2) usb x25 1 C error error 21 6d13h 508d 0/29 upstream: reported C repro on 2024/07/20 04:25

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5161
	(detected by 0, t=10502 jiffies, g=8953, q=1971)
task:syz.0.261       state:R  running task     stack:25408 pid: 5161 ppid:  4183 flags:0x0000400c
Call Trace:
 <IRQ>
 sched_show_task+0x444/0x570 kernel/sched/core.c:8659
 rcu_print_detail_task_stall_rnp kernel/rcu/tree_stall.h:233 [inline]
 print_other_cpu_stall+0xe73/0x1220 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+0x831/0x1110 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:1818
 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+0x4fe/0xc40 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:lock_acquire+0x1f2/0x3f0 kernel/locking/lockdep.c:5627
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f6 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 66 43 c7 44 3d 09 00 00 43 c6 44 3d 0b
RSP: 0018:ffffc900000077a0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 24859b08a3e9b800
RDX: 0000000000000000 RSI: ffffffff8a0b2f00 RDI: ffffffff8a59e580
RBP: ffffc900000078b8 R08: dffffc0000000000 R09: fffffbfff1ff7c26
R10: fffffbfff1ff7c26 R11: 1ffffffff1ff7c25 R12: ffffffff8d277c48
R13: 1ffff92000000f00 R14: 0000000000000246 R15: dffffc0000000000
 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:364 [inline]
 __dev_xmit_skb net/core/dev.c:3911 [inline]
 __dev_queue_xmit+0xb8a/0x2ed0 net/core/dev.c:4253
 lapb_data_transmit+0x86/0xa0 net/lapb/lapb_iface.c:447
 lapb_transmit_buffer+0x15f/0x1f0 net/lapb/lapb_out.c:149
 lapb_t1timer_expiry+0x652/0xa70 net/lapb/lapb_timer.c:-1
 call_timer_fn+0x16c/0x530 kernel/time/timer.c:1451
 expire_timers kernel/time/timer.c:1496 [inline]
 __run_timers+0x525/0x7c0 kernel/time/timer.c:1767
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1780
 handle_softirqs+0x328/0x820 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x12f/0x220 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 7c fc 55 08 85 c0 74 4a 4d 85 ff 75 66 0f 1f 44 00 00 48 89 df e8 76 67 5f 08 e8 11 76 2a 00 fb 48 83 c4 08 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 48 89 df e8 d9 0f fe ff 43 80 3c
RSP: 0018:ffffc9000333f6a8 EFLAGS: 00000282
RAX: 24859b08a3e9b800 RBX: ffff8880b903a340 RCX: 24859b08a3e9b800
RDX: dffffc0000000000 RSI: ffffffff8a0b1c60 RDI: ffffffff8a59e580
RBP: 1ffff11017207613 R08: dffffc0000000000 R09: ffffed1017207662
R10: ffffed1017207662 R11: 1ffff11017207661 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+0x11c3/0x4390 kernel/sched/core.c:6395
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6799
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:check_kcov_mode kernel/kcov.c:172 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:227 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x13/0x80 kernel/kcov.c:293
Code: 4a 89 7c 02 10 4a 89 74 02 18 4a 89 44 02 20 48 ff c1 48 89 0a c3 90 48 8b 04 24 65 48 8b 0d 44 a0 8a 7e 65 8b 15 45 a0 8a 7e <81> e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 5b 83 b9 34 16 00 00
RSP: 0018:ffffc9000333fa98 EFLAGS: 00000286
RAX: ffffffff8810aa3d RBX: 0000000000000000 RCX: ffff888027310000
RDX: 0000000080000000 RSI: 0000000000000000 RDI: 0000000000000008
RBP: ffffc9000333fc30 R08: dffffc0000000000 R09: ffffed1004e62001
R10: ffffed1004e62001 R11: 1ffff11004e62000 R12: 0000000000000000
R13: ffffc900011cb030 R14: dffffc0000000000 R15: 0000000000000001
 bpf_prog_run_xdp include/linux/filter.h:803 [inline]
 bpf_test_run+0x1ed/0x7d0 net/bpf/test_run.c:117
 bpf_prog_test_run_xdp+0x3fc/0x920 net/bpf/test_run.c:812
 bpf_prog_test_run+0x31e/0x390 kernel/bpf/syscall.c:3374
 __sys_bpf+0x535/0x670 kernel/bpf/syscall.c:4675
 __do_sys_bpf kernel/bpf/syscall.c:4761 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:4759 [inline]
 __x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4759
 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: 0033:0x7efda9b1c749
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:00007efda7d83038 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007efda9d72fa0 RCX: 00007efda9b1c749
RDX: 0000000000000050 RSI: 0000200000000840 RDI: 000000000000000a
RBP: 00007efda9ba0f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007efda9d73038 R14: 00007efda9d72fa0 R15: 00007fffa546da78
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/27 17:19 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in lapb_t1timer_expiry
2025/11/17 07:07 linux-5.15.y cc5ec8769306 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in lapb_t1timer_expiry
* Struck through repros no longer work on HEAD.