INFO: rcu detected stall in sys_recvmmsg (4)

Status: upstream: reported on 2026/04/22 14:30
Reported-by: syzbot+b089ec3c3cd5d4bbd763@syzkaller.appspotmail.com
First crash: 150d, last: 16d
▶ ▼ Similar bugs (11)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_recvmmsg (3) prio:low net 1 291 14d 1005d 0/29 upstream: reported on 2023/12/19 09:31
linux-6.1 INFO: rcu detected stall in sys_recvmmsg (3) 1 16 267d 663d 0/3 auto-obsoleted due to no activity on 2026/04/05 10:37
linux-4.19 INFO: rcu detected stall in sys_recvmmsg 1 syz, C error 1 1367d 1367d 0/1 upstream: reported C repro on 2022/12/23 04:58
linux-5.15 INFO: rcu detected stall in sys_recvmmsg missing-backport origin:upstream 1 syz, C done 82 53d 1263d 0/3 upstream: reported C repro on 2023/04/06 01:32
linux-6.6 INFO: rcu detected stall in sys_recvmmsg 1 8 201d 428d 0/2 auto-obsoleted due to no activity on 2026/06/11 04:39
linux-6.1 INFO: rcu detected stall in sys_recvmmsg (2) 1 5 766d 898d 0/3 auto-obsoleted due to no activity on 2024/11/22 11:58
upstream INFO: rcu detected stall in sys_recvmmsg mptcp 1 syz, C done 52 1692d 1824d 20/29 fixed on 2022/03/08 16:11
linux-6.6 INFO: rcu detected stall in sys_recvmmsg (2) 1 3 52d 77d 0/2 upstream: reported on 2026/07/04 16:20
linux-6.1 INFO: rcu detected stall in sys_recvmmsg 1 5 1144d 1275d 0/3 auto-obsoleted due to no activity on 2023/11/11 06:06
upstream INFO: rcu detected stall in sys_recvmmsg (2) net 1 4 1453d 1483d 0/29 auto-obsoleted due to no activity on 2023/01/03 09:53
android-5-15 BUG: soft lockup in sys_recvmmsg 1 5 786d 879d 0/2 auto-obsoleted due to no activity on 2024/10/23 09:30

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 GPs behind) idle=40fc/1/0x4000000000000000 softirq=18903/18906 fqs=1
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4374/1:b..l P6804/1:b..l
	(detected by 0, t=10502 jiffies, g=26101, q=174 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 6884 Comm: syz.0.618 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:__run_hrtimer kernel/time/hrtimer.c:1749 [inline]
RIP: 0010:__hrtimer_run_queues+0x50c/0xc90 kernel/time/hrtimer.c:1815
Code: ef ff 54 24 50 41 89 c4 eb 4d e8 3f 11 10 00 65 4c 8b 35 e7 3e 90 7e 49 81 c6 c8 0a 00 00 4c 89 f3 48 c1 eb 03 42 0f b6 04 3b <84> c0 0f 85 72 03 00 00 41 c7 06 01 00 00 00 4c 89 ef ff 54 24 50
RSP: 0018:ffffc900001e0d60 EFLAGS: 00000802
RAX: 0000000000000000 RBX: 1ffff11004d50519 RCX: ffff888026a81e00
RDX: 0000000000010000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900001e0eb0 R08: ffffffff8e2116af R09: 1ffffffff1c422d5
R10: dffffc0000000000 R11: fffffbfff1c422d6 R12: 0000000000000002
R13: ffff888055887340 R14: ffff888026a828c8 R15: dffffc0000000000
FS:  00007fb3716066c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055faac0d4fe1 CR3: 000000007d959000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 hrtimer_interrupt+0x399/0x980 kernel/time/hrtimer.c:1877
 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+0x9b/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:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> df 69 1d f7 65 8b 05 e0 0a c7 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900035475c0 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a06 RCX: 2442d186c08ae400
RDX: dffffc0000000000 RSI: ffffffff8a8c18a0 RDI: 0000000000000001
RBP: ffffc90003547650 R08: ffffffff90b132ef R09: 1ffffffff216265d
R10: dffffc0000000000 R11: fffffbfff216265e R12: dffffc0000000000
R13: 0000000000000000 R14: ffff88805436a6c0 R15: 1ffff920006a8eb8
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 __wake_up_common_lock kernel/sched/wait.c:140 [inline]
 __wake_up_sync_key+0x128/0x190 kernel/sched/wait.c:208
 __unix_dgram_recvmsg+0x4b7/0xda0 net/unix/af_unix.c:2480
 ____sys_recvmsg+0x2c8/0x5b0 net/socket.c:-1
 ___sys_recvmsg+0x210/0x590 net/socket.c:2780
 do_recvmmsg+0x370/0x810 net/socket.c:2874
 __sys_recvmmsg net/socket.c:2953 [inline]
 __do_sys_recvmmsg net/socket.c:2976 [inline]
 __se_sys_recvmmsg net/socket.c:2969 [inline]
 __x64_sys_recvmmsg+0x195/0x250 net/socket.c:2969
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb37079e159
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:00007fb371606028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007fb370a26090 RCX: 00007fb37079e159
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000006
RBP: 00007fb370835024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb370a26128 R14: 00007fb370a26090 R15: 00007ffda69c2b88
 </TASK>
task:dhcpcd-run-hook state:R  running task     stack:23472 pid:6804  ppid:3935   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5246 [inline]
 __schedule+0x107f/0x4030 kernel/sched/core.c:6563
 preempt_schedule_notrace+0xd9/0x120 kernel/sched/core.c:6825
 preempt_schedule_notrace_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
 rcu_is_watching+0x76/0xa0 kernel/rcu/tree.c:722
 rcu_read_unlock include/linux/rcupdate.h:820 [inline]
 is_bpf_text_address+0x200/0x2a0 kernel/bpf/core.c:738
 kernel_text_address+0x9c/0xd0 kernel/extable.c:125
 __kernel_text_address+0x9/0x30 kernel/extable.c:79
 unwind_get_return_address+0x49/0x80 arch/x86/kernel/unwind_orc.c:323
 arch_stack_walk+0xf2/0x140 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 __kasan_slab_alloc+0x6b/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x490 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 slab_alloc mm/slub.c:3367 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3374 [inline]
 kmem_cache_alloc+0x18b/0x2f0 mm/slub.c:3383
 dup_fd+0x52/0xa20 fs/file.c:316
 copy_files+0x72/0xe0 kernel/fork.c:1647
 copy_process+0x180e/0x4070 kernel/fork.c:2346
 kernel_clone+0x24b/0x900 kernel/fork.c:2765
 __do_sys_clone kernel/fork.c:2906 [inline]
 __se_sys_clone kernel/fork.c:2890 [inline]
 __x64_sys_clone+0x1a7/0x220 kernel/fork.c:2890
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0a2a579636
RSP: 002b:00007ffe3508cb10 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffe3508cb18 RCX: 00007f0a2a579636
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 000055faac0c8e60 R08: 0000000000000000 R09: 3c00000040001201
R10: 00007f0a2a3dff50 R11: 0000000000000246 R12: 000055faac0d5800
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
task:kworker/u4:8    state:R  running task     stack:23824 pid:4374  ppid:2      flags:0x00004000
Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5246 [inline]
 __schedule+0x107f/0x4030 kernel/sched/core.c:6563
 preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6875
 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:lock_acquire+0x225/0x4a0 kernel/locking/lockdep.c:5680
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3d 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 44 3d 00 00 00 00 00 43 c7 44 3d 08 00 00 00 00 65 48 8b 04
RSP: 0018:ffffc900048f7920 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 7f1cec236e347500
RDX: 0000000000000000 RSI: ffffffff8a8c2a20 RDI: ffffffff8adf6420
RBP: ffffc900048f7a28 R08: dffffc0000000000 R09: 1ffffffff2162648
R10: dffffc0000000000 R11: fffffbfff2162649 R12: 0000000000000000
R13: 1ffff9200091ef30 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 batadv_iv_ogm_slide_own_bcast_window net/batman-adv/bat_iv_ogm.c:769 [inline]
 batadv_iv_ogm_schedule_buff net/batman-adv/bat_iv_ogm.c:849 [inline]
 batadv_iv_ogm_schedule+0x458/0x1080 net/batman-adv/bat_iv_ogm.c:908
 batadv_iv_send_outstanding_bat_ogm_packet+0x6e9/0x800 net/batman-adv/bat_iv_ogm.c:1805
 process_one_work+0x8ab/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaf5/0x12a0 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: rcu_preempt kthread starved for 10457 jiffies! g26101 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:26800 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5246 [inline]
 __schedule+0x107f/0x4030 kernel/sched/core.c:6563
 schedule+0xb9/0x180 kernel/sched/core.c:6639
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x303/0x1350 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 PID: 4831 Comm: kworker/u4:13 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:424 [inline]
RIP: 0010:smp_call_function_many_cond+0x1148/0x1250 kernel/smp.c:998
Code: 41 8b 1f 89 de 83 e6 01 31 ff e8 23 02 0b 00 83 e3 01 48 bb 00 00 00 00 00 fc ff df 75 0a e8 af fe 0a 00 e9 34 ff ff ff f3 90 <41> 0f b6 04 1c 84 c0 75 14 41 f7 07 01 00 00 00 0f 84 17 ff ff ff
RSP: 0018:ffffc900034e7800 EFLAGS: 00000293
RAX: ffffffff81774303 RBX: dffffc0000000000 RCX: ffff88802db63c00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900034e7960 R08: ffffffff90b13247 R09: 1ffffffff2162648
R10: dffffc0000000000 R11: fffffbfff2162649 R12: 1ffff110171e820d
R13: ffff8880b8e3bd80 R14: 0000000000000001 R15: ffff8880b8f41068
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007eff361eb840 CR3: 000000000c88e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3b/0x80 kernel/smp.c:1165
 on_each_cpu include/linux/smp.h:71 [inline]
 text_poke_sync arch/x86/kernel/alternative.c:1574 [inline]
 text_poke_bp_batch+0x2b7/0x850 arch/x86/kernel/alternative.c:1774
 text_poke_flush arch/x86/kernel/alternative.c:1965 [inline]
 text_poke_finish+0x16/0x30 arch/x86/kernel/alternative.c:1972
 arch_jump_label_transform_apply+0x13/0x20 arch/x86/kernel/jump_label.c:146
 static_key_enable_cpuslocked+0x11f/0x240 kernel/jump_label.c:207
 static_key_enable+0x16/0x20 kernel/jump_label.c:220
 toggle_allocation_gate+0xba/0x470 mm/kfence/core.c:821
 process_one_work+0x8ab/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaf5/0x12a0 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
vkms_vblank_simulate: vblank timer overrun

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/03 15:03 linux-6.1.y cf82dcca9634 6a988719 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_recvmmsg
2026/08/18 11:06 linux-6.1.y e4f7d8be268e 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_recvmmsg
2026/07/25 12:16 linux-6.1.y dc5c83b7f5f8 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_recvmmsg
2026/06/13 18:53 linux-6.1.y 228da13e907e 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_recvmmsg
2026/04/22 14:29 linux-6.1.y 7c87defbd336 4595e353 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_recvmmsg
* Struck through repros no longer work on HEAD.