syzbot


INFO: rcu detected stall in sendmsg

Status: upstream: reported on 2025/07/31 17:16
Reported-by: syzbot+e8d3f56cde2a4d5e38ae@syzkaller.appspotmail.com
First crash: 288d, last: 7d05h
Similar bugs (21)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in sendmsg (5) 1 C 30 6d22h 327d 0/3 upstream: reported C repro on 2025/06/23 07:43
linux-6.1 INFO: rcu detected stall in sendmsg (3) 1 4 591d 658d 0/3 auto-obsoleted due to no activity on 2025/01/09 18:13
upstream INFO: rcu detected stall in sendmsg net 1 1 1683d 1683d 0/29 auto-closed as invalid on 2022/01/03 17:11
linux-6.1 INFO: rcu detected stall in sendmsg (4) 1 2 431d 442d 0/3 auto-obsoleted due to no activity on 2025/06/19 03:57
linux-6.1 INFO: rcu detected stall in sendmsg (2) 1 1 781d 781d 0/3 auto-obsoleted due to no activity on 2024/07/04 03:49
upstream INFO: rcu detected stall in sendmsg (2) batman 1 1 1553d 1553d 0/29 auto-closed as invalid on 2022/05/13 12:25
upstream INFO: rcu detected stall in sendmsg (4) mm 1 C error error 64 14d 722d 0/29 upstream: reported C repro on 2024/05/24 06:18
upstream INFO: rcu detected stall in sendmsg (3) net 1 4 830d 914d 0/29 auto-obsoleted due to no activity on 2024/05/05 18:15
linux-5.15 INFO: rcu detected stall in sys_sendmsg origin:upstream 1 C error 48 2d14h 787d 0/3 upstream: reported C repro on 2024/03/19 21:37
linux-6.1 INFO: rcu detected stall in sendmsg 1 1 1015d 1015d 0/3 auto-obsoleted due to no activity on 2023/11/12 19:28
upstream BUG: soft lockup in sys_sendmsg (2) block 1 C error error 46 1d16h 345d 0/29 upstream: reported C repro on 2025/06/05 02:15
upstream INFO: rcu detected stall in sys_sendmsg (2) cgroups mm 1 5 2354d 2356d 0/29 closed as invalid on 2019/12/04 14:14
upstream INFO: rcu detected stall in sys_sendmsg (3) kernel 1 1 2320d 2320d 0/29 closed as invalid on 2020/01/08 05:33
linux-6.1 INFO: rcu detected stall in sys_sendmsg 1 6 594d 681d 0/3 auto-obsoleted due to no activity on 2025/01/06 11:24
upstream INFO: rcu detected stall in sys_sendmsg net 1 C done 2 2436d 2436d 13/29 fixed on 2019/10/09 10:54
android-6-1 BUG: soft lockup in sys_sendmsg origin:upstream 1 C 3 739d 767d 0/2 upstream: reported C repro on 2024/04/09 06:46
linux-6.1 BUG: soft lockup in sys_sendmsg 1 2 1068d 1074d 0/3 auto-obsoleted due to no activity on 2023/09/20 17:26
android-5-10 BUG: soft lockup in sys_sendmsg 1 C error 64 20d 784d 0/2 upstream: reported C repro on 2024/03/22 10:41
upstream BUG: soft lockup in sys_sendmsg tipc batman 1 C 3 782d 823d 25/29 fixed on 2024/05/22 23:36
android-5-15 BUG: soft lockup in sys_sendmsg origin:upstream 1 C error 13 611d 784d 0/2 upstream: reported C repro on 2024/03/22 10:44
linux-6.1 BUG: soft lockup in sys_sendmsg (2) origin:upstream 1 C done 1 769d 769d 3/3 fixed on 2024/05/15 09:17

Sample crash report:
bridge0: received packet on veth0_to_bridge with own address as source address (addr:62:39:da:c1:a1:45, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P788/2:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=87513, q=156 ncpus=2)
task:kworker/1:2     state:R  running task     stack:23592 pid:788   ppid:2      flags:0x00004000
Workqueue: mld mld_ifc_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6891
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 __local_bh_enable_ip+0x14b/0x1c0 kernel/softirq.c:413
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:856 [inline]
 __dev_queue_xmit+0x1b2c/0x3660 net/core/dev.c:4490
 neigh_output include/net/neighbour.h:543 [inline]
 ip6_finish_output2+0xe3d/0x1630 net/ipv6/ip6_output.c:141
 dst_output include/net/dst.h:467 [inline]
 NF_HOOK+0x167/0x4a0 include/linux/netfilter.h:304
 mld_sendpack+0x7f5/0xd50 net/ipv6/mcast.c:1823
 mld_send_cr net/ipv6/mcast.c:2124 [inline]
 mld_ifc_work+0x835/0xb40 net/ipv6/mcast.c:2654
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: rcu_preempt kthread starved for 2152 jiffies! g87513 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:26952 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 16345 Comm: syz.3.3045 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:lock_acquire+0x208/0x420 kernel/locking/lockdep.c:5758
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3c 04 f8 0f 85 f0 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 43 c7 44 3c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc900001f05e0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0dece9e8530c2d00
RDX: 0000000000000000 RSI: ffffffff8acadb60 RDI: ffffffff8b1c8fa0
RBP: ffffc900001f06f0 R08: dffffc0000000000 R09: 1ffffffff2238ca0
R10: dffffc0000000000 R11: fffffbfff2238ca1 R12: 1ffff9200003e0c8
R13: ffffffff8d1320e0 R14: 0000000000000246 R15: dffffc0000000000
FS:  00007fdb902cd6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2dd0aff8 CR3: 000000007d73f000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 net_generic+0x3a/0x240 include/net/netns/generic.h:45
 br_nf_pre_routing+0x1b8/0x1420 net/bridge/br_netfilter_hooks.c:518
 nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:277 [inline]
 br_handle_frame+0x1245/0x14d0 net/bridge/br_input.c:424
 __netif_receive_skb_core+0xfab/0x3af0 net/core/dev.c:5540
 __netif_receive_skb_one_core net/core/dev.c:5644 [inline]
 __netif_receive_skb+0x74/0x290 net/core/dev.c:5760
 process_backlog+0x391/0x6f0 net/core/dev.c:6088
 __napi_poll+0xc0/0x460 net/core/dev.c:6650
 napi_poll net/core/dev.c:6717 [inline]
 net_rx_action+0x616/0xc40 net/core/dev.c:6853
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:finish_task_switch+0x26a/0x8f0 kernel/sched/core.c:5255
Code: 0f 84 33 01 00 00 48 85 db 0f 85 52 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 00 a9 32 09 e8 9b 29 30 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:ffffc90003387138 EFLAGS: 00000282
RAX: 0dece9e8530c2d00 RBX: 0000000000000000 RCX: 0dece9e8530c2d00
RDX: dffffc0000000000 RSI: ffffffff8acac9e0 RDI: ffffffff8b1c8fa0
RBP: ffffc90003387190 R08: ffffffff8e8b19af R09: 1ffffffff1d16335
R10: dffffc0000000000 R11: fffffbfff1d16336 R12: ffff88801f3f3c00
R13: dffffc0000000000 R14: ffff88801ca41e00 R15: ffff8880b8f3cac8
 context_switch kernel/sched/core.c:5384 [inline]
 __schedule+0x155b/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0xc1/0x2d0 kernel/time/timer.c:2144
 sctp_wait_for_connect+0x399/0x690 net/sctp/socket.c:9363
 sctp_sendmsg_to_asoc+0x13e9/0x1830 net/sctp/socket.c:1883
 sctp_sendmsg+0x1b83/0x28c0 net/sctp/socket.c:2029
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x5ba/0x960 net/socket.c:2594
 ___sys_sendmsg+0x2a6/0x360 net/socket.c:2648
 __sys_sendmsg net/socket.c:2677 [inline]
 __do_sys_sendmsg net/socket.c:2686 [inline]
 __se_sys_sendmsg+0x1c2/0x2b0 net/socket.c:2684
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fdb8f39cdd9
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:00007fdb902cd028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fdb8f615fa0 RCX: 00007fdb8f39cdd9
RDX: 0000000000000010 RSI: 0000200000000ac0 RDI: 0000000000000008
RBP: 00007fdb8f432d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdb8f616038 R14: 00007fdb8f615fa0 R15: 00007fff33a42398
 </TASK>
bridge0: received packet on veth0_to_bridge with own address as source address (addr:62:39:da:c1:a1:45, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:62:39:da:c1:a1:45, vlan:0)

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/09 03:51 linux-6.6.y 3b9f64db0496 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sendmsg
2026/04/22 01:01 linux-6.6.y 9760bf04666d 0b6ab7ec .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sendmsg
2026/04/19 08:30 linux-6.6.y 9760bf04666d 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sendmsg
2026/04/06 18:30 linux-6.6.y 80de0a958133 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sendmsg
2026/03/22 20:57 linux-6.6.y 4fc00fe35d46 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sendmsg
2026/03/04 08:13 linux-6.6.y 7a137e9bfa0e 4180d919 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sendmsg
2026/02/03 20:45 linux-6.6.y 2cf6f68313dc 6df4c87a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sendmsg
2025/12/14 05:51 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sendmsg
2025/11/19 17:46 linux-6.6.y 0a805b6ea8cd 26ee5237 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sendmsg
2025/08/22 19:57 linux-6.6.y bb9c90ab9c5a bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sendmsg
2025/07/31 17:15 linux-6.6.y dbcb8d8e4163 0c075d67 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sendmsg
* Struck through repros no longer work on HEAD.