syzbot


INFO: rcu detected stall in tcp_write_timer (3)

Status: upstream: reported on 2025/09/29 07:41
Reported-by: syzbot+17b5e26c2a6a7eedcb8c@syzkaller.appspotmail.com
First crash: 11d, last: 11d
Similar bugs (20)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in tcp_write_timer (2) bpf 1 2 1711d 1767d 0/29 auto-closed as invalid on 2021/05/03 11:59
upstream INFO: rcu detected stall in tcp_write_timer (4) net 1 1 452d 452d 0/29 auto-obsoleted due to no activity on 2024/10/13 08:46
linux-5.15 INFO: rcu detected stall in tcp_write_timer 1 4 361d 414d 0/3 auto-obsoleted due to no activity on 2025/01/22 08:13
upstream INFO: rcu detected stall in tcp_write_timer net 1 3 2260d 2255d 0/29 auto-closed as invalid on 2019/10/25 14:11
linux-5.15 INFO: rcu detected stall in tcp_write_timer (2) 1 2 147d 231d 0/3 auto-obsoleted due to no activity on 2025/08/25 02:13
upstream INFO: rcu detected stall in tcp_write_timer (3) net 1 1 1578d 1578d 0/29 auto-closed as invalid on 2021/09/13 13:17
linux-6.1 INFO: rcu detected stall in tcp_write_timer 1 16 247d 477d 0/3 auto-obsoleted due to no activity on 2025/05/16 12:07
upstream BUG: soft lockup in tcp_write_timer (4) mm 1 4 462d 486d 26/29 fixed on 2024/07/09 19:14
linux-4.14 INFO: rcu detected stall in tcp_write_timer 1 4 1862d 2105d 0/1 auto-closed as invalid on 2021/01/02 05:45
linux-4.19 INFO: rcu detected stall in tcp_write_timer 1 2 1991d 2045d 0/1 auto-closed as invalid on 2020/08/26 06:46
linux-4.19 BUG: soft lockup in tcp_write_timer (3) 1 2 1015d 1028d 0/1 upstream: reported on 2022/12/17 21:41
linux-4.19 BUG: soft lockup in tcp_write_timer (2) 1 2 1424d 1488d 0/1 auto-closed as invalid on 2022/03/16 10:56
android-54 BUG: soft lockup in tcp_write_timer 1 1 160d 160d 0/2 auto-obsoleted due to no activity on 2025/08/01 21:51
linux-4.19 BUG: soft lockup in tcp_write_timer 1 1 1653d 1653d 0/1 auto-closed as invalid on 2021/07/30 14:52
upstream BUG: soft lockup in tcp_write_timer (2) kvm 1 1 1264d 1264d 0/29 auto-closed as invalid on 2022/06/24 22:31
upstream BUG: soft lockup in tcp_write_timer (3) net 1 6 641d 748d 0/29 closed as invalid on 2024/03/18 17:07
upstream BUG: soft lockup in tcp_write_timer (7) net 1 1 27d 27d 0/29 closed as invalid on 2025/09/29 07:16
upstream BUG: soft lockup in tcp_write_timer (6) bpf 1 1 74d 74d 0/29 closed as invalid on 2025/09/01 08:24
upstream BUG: soft lockup in tcp_write_timer (5) net mm 1 8 130d 192d 0/29 closed as invalid on 2025/07/11 15:27
android-5-15 BUG: soft lockup in tcp_write_timer 1 11 424d 537d 0/2 auto-obsoleted due to no activity on 2024/11/10 05:27

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-....: (1 GPs behind) idle=c3d/1/0x4000000000000000 softirq=63936/63942 fqs=4564 
	(t=10500 jiffies g=84397 q=2208)
NMI backtrace for cpu 0
CPU: 0 PID: 20131 Comm: syz.0.4500 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <IRQ>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x397/0x3d0 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+0x6d8/0x1110 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:1690 [inline]
 __hrtimer_run_queues+0x4fe/0xc40 kernel/time/hrtimer.c:1754
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1816
 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:seqcount_lockdep_reader_access+0x17b/0x1c0 include/linux/seqlock.h:106
Code: 00 4d 85 e4 75 16 e8 54 cc 0f 00 eb 15 e8 4d cc 0f 00 e8 88 ef 40 08 4d 85 e4 74 ea e8 3e cc 0f 00 fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 3e 00 00 00 00 66 43 c7 44 3e 09 00 00 43 c6 44 3e 0b 00
RSP: 0018:ffffc90000006ce0 EFLAGS: 00000246
RAX: ffffffff8167fee2 RBX: 0000000000000000 RCX: ffff88807ab95940
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000006d80 R08: dffffc0000000000 R09: fffffbfff1ff7832
R10: fffffbfff1ff7832 R11: 1ffffffff1ff7831 R12: 0000000000000200
R13: 000001fb63109b96 R14: 1ffff92000000d9c R15: dffffc0000000000
 ktime_get_with_offset+0x90/0x320 kernel/time/timekeeping.c:872
 ktime_get_real include/linux/timekeeping.h:79 [inline]
 __net_timestamp include/linux/skbuff.h:3970 [inline]
 net_timestamp_set net/core/dev.c:2195 [inline]
 dev_queue_xmit_nit+0x83c/0xb00 net/core/dev.c:2345
 xmit_one net/core/dev.c:3644 [inline]
 dev_hard_start_xmit+0x13e/0x7e0 net/core/dev.c:3665
 sch_direct_xmit+0x24e/0x4a0 net/sched/sch_generic.c:342
 __dev_xmit_skb net/core/dev.c:3884 [inline]
 __dev_queue_xmit+0x170e/0x2ed0 net/core/dev.c:4253
 NF_HOOK+0x2d4/0x360 include/linux/netfilter.h:302
 arp_xmit+0x142/0x230 net/ipv4/arp.c:642
 arp_solicit+0xc1b/0xe60 net/ipv4/arp.c:391
 neigh_probe net/core/neighbour.c:1017 [inline]
 __neigh_event_send+0xf12/0x14e0 net/core/neighbour.c:1178
 neigh_event_send include/net/neighbour.h:438 [inline]
 neigh_resolve_output+0x1b3/0x6a0 net/core/neighbour.c:1488
 neigh_output include/net/neighbour.h:509 [inline]
 ip_finish_output2+0xca1/0x1080 net/ipv4/ip_output.c:228
 dst_output include/net/dst.h:452 [inline]
 ip_local_out net/ipv4/ip_output.c:126 [inline]
 __ip_queue_xmit+0x11c3/0x1c00 net/ipv4/ip_output.c:532
 __tcp_transmit_skb+0x1ced/0x31c0 net/ipv4/tcp_output.c:1404
 tcp_transmit_skb net/ipv4/tcp_output.c:1422 [inline]
 __tcp_retransmit_skb+0x92c/0x1290 net/ipv4/tcp_output.c:3267
 tcp_retransmit_skb+0x2e/0x350 net/ipv4/tcp_output.c:3290
 tcp_retransmit_timer+0x144b/0x2540 net/ipv4/tcp_timer.c:570
 tcp_write_timer_handler+0x205/0x9a0 net/ipv4/tcp_timer.c:655
 tcp_write_timer+0x126/0x280 net/ipv4/tcp_timer.c:675
 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:on_stack arch/x86/include/asm/stacktrace.h:60 [inline]
RIP: 0010:stack_access_ok arch/x86/kernel/unwind_orc.c:347 [inline]
RIP: 0010:deref_stack_reg+0x8c/0x120 arch/x86/kernel/unwind_orc.c:357
Code: 85 92 00 00 00 41 83 3f 00 0f 95 c0 4d 39 f5 0f 96 c1 20 c1 4c 39 f5 0f 97 c0 20 c8 3c 01 75 14 49 8d 46 08 4c 39 e8 0f 97 c1 <48> 39 e8 0f 96 c0 84 c1 75 32 49 8d 7f 28 48 89 f8 48 c1 e8 03 42
RSP: 0018:ffffc9000331f870 EFLAGS: 00000202
RAX: ffffc9000331fea8 RBX: ffffc9000331f9a8 RCX: 0000000000000001
RDX: ffffc9000331f9a8 RSI: ffffc9000331fea0 RDI: ffffc9000331f978
RBP: ffffc90003320000 R08: dffffc0000000000 R09: ffffc9000331f9b8
R10: fffff52000663f39 R11: 1ffff92000663f37 R12: dffffc0000000000
R13: ffffc90003318000 R14: ffffc9000331fea0 R15: ffffc9000331f968
 unwind_next_frame+0x115d/0x1d90 arch/x86/kernel/unwind_orc.c:-1
 arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x98/0xe0 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]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x100/0x290 mm/slub.c:3238
 kmem_cache_zalloc include/linux/slab.h:725 [inline]
 lsm_inode_alloc security/security.c:595 [inline]
 security_inode_alloc+0x30/0x110 security/security.c:1033
 inode_init_always+0x8f4/0xcb0 fs/inode.c:232
 alloc_inode fs/inode.c:268 [inline]
 new_inode_pseudo+0x8e/0x210 fs/inode.c:1001
 sock_alloc net/socket.c:626 [inline]
 __sock_create+0x129/0x900 net/socket.c:1450
 sock_create net/socket.c:1542 [inline]
 __sys_socket+0xe2/0x170 net/socket.c:1584
 __do_sys_socket net/socket.c:1593 [inline]
 __se_sys_socket net/socket.c:1591 [inline]
 __x64_sys_socket+0x76/0x80 net/socket.c:1591
 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: 0033:0x7fc1fea76ec9
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:00007fc1fccbd038 EFLAGS: 00000246 ORIG_RAX: 0000000000000029
RAX: ffffffffffffffda RBX: 00007fc1fecce090 RCX: 00007fc1fea76ec9
RDX: 0000000000000073 RSI: 0000000000000002 RDI: 000000000000000a
RBP: 00007fc1feaf9f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc1fecce128 R14: 00007fc1fecce090 R15: 00007ffe0d11caa8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/29 07:40 linux-5.15.y 43bb85222e53 001c9061 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in tcp_write_timer
* Struck through repros no longer work on HEAD.