INFO: rcu detected stall in sock_close (2)

Status: upstream: reported syz repro on 2026/05/15 05:06
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+c4e22f103db026d879e6@syzkaller.appspotmail.com
First crash: 90d, last: 20d
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/05/31 upstream (ToT) e43ffb69e043 syz [report] INFO: rcu detected stall in security_file_open
▶ ▼ Similar bugs (16)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in sock_close (2) 1 1 932d 932d 0/3 auto-obsoleted due to no activity on 2024/05/03 14:38
upstream INFO: rcu detected stall in sock_close (4) net 1 2 1022d 1059d 0/29 auto-obsoleted due to no activity on 2024/01/24 15:51
linux-6.1 INFO: rcu detected stall in sock_close (3) 1 1 822d 822d 0/3 auto-obsoleted due to no activity on 2024/08/21 03:02
linux-6.1 INFO: rcu detected stall in sock_close origin:upstream 1 syz, C done 1 1130d 1130d 3/3 fixed on 2023/09/23 10:26
upstream INFO: rcu detected stall in sock_close cgroups mm 1 6 2444d 2445d 0/29 closed as invalid on 2019/12/04 14:04
linux-6.1 INFO: rcu detected stall in sock_close (2) 1 1 924d 924d 0/3 auto-obsoleted due to no activity on 2024/05/11 05:25
upstream INFO: rcu detected stall in sock_close (3) tipc 1 syz, C done done 5 1732d 2226d 0/29 closed as invalid on 2022/02/08 10:42
linux-5.15 INFO: rcu detected stall in sock_close 1 syz, C error 2 1110d 1164d 0/3 auto-obsoleted due to no activity on 2023/11/07 13:02
linux-5.15 INFO: rcu detected stall in sock_close (3) origin:upstream 1 syz, C error 17 65d 815d 0/3 upstream: reported C repro on 2024/05/20 00:06
upstream INFO: rcu detected stall in sock_close (2) cgroups mm 1 1 2409d 2409d 0/29 closed as invalid on 2020/01/09 08:13
upstream INFO: rcu detected stall in sock_close (5) prio:normal bpf sctp tipc 1 syz, C error 91 17d 393d 0/29 upstream: reported C repro on 2025/07/16 17:01
linux-6.1 BUG: soft lockup in sock_close origin:lts-only 1 syz, C inconclusive 8 53d 598d 0/3 upstream: reported C repro on 2024/12/23 18:51
linux-6.6 INFO: rcu detected stall in sock_close 1 syz error 2 270d 353d 0/2 auto-obsoleted due to no activity on 2026/02/24 12:42
android-5-10 BUG: soft lockup in sock_close 1 syz, C 192 12d 871d 0/2 upstream: reported C repro on 2024/03/25 07:28
android-5-15 BUG: soft lockup in sock_close origin:downstream 1 syz, C done 383 90d 869d 0/2 upstream: reported C repro on 2024/03/26 23:21
android-6-1 BUG: soft lockup in sock_close origin:downstream 1 syz, C error 16 15d 869d 0/2 upstream: reported C repro on 2024/03/27 04:09
▶ ▼ Fix bisection attempts (2)
Created Duration User Patch Repo Result
2026/07/24 09:44 2h30m bisect fix linux-6.6.y OK (0) job log log
2026/06/21 17:55 3h51m bisect fix linux-6.6.y OK (0) job log log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 GPs behind) idle=de9c/1/0x4000000000000000 softirq=12284/12285 fqs=3
rcu: 	(detected by 0, t=10502 jiffies, g=10797, q=134 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 5937 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:native_save_fl arch/x86/include/asm/irqflags.h:33 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:89 [inline]
RIP: 0010:arch_irqs_disabled arch/x86/include/asm/irqflags.h:131 [inline]
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xab/0x120 kernel/locking/spinlock.c:194
Code: e8 da 7f fd f6 48 b8 04 00 00 00 00 fc ff df 41 c6 04 07 00 48 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
RSP: 0018:ffffc900001f0ca0 EFLAGS: 00000046
RAX: dffffc0000000004 RBX: 0000000000000806 RCX: 0000000000000001
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffffffff97508fc0
RBP: ffffc900001f0d30 R08: ffffffff97508fc3 R09: 1ffffffff2ea11f8
R10: dffffc0000000000 R11: fffffbfff2ea11f9 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff97508fc0 R15: 1ffff9200003e194
FS:  000055555c86a500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000012c0 CR3: 0000000076357000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 debug_hrtimer_deactivate kernel/time/hrtimer.c:455 [inline]
 __run_hrtimer kernel/time/hrtimer.c:1718 [inline]
 __hrtimer_run_queues+0x2cb/0xc40 kernel/time/hrtimer.c:1814
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x9f/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:nft_rcv_nl_event+0x4/0x5c0 net/netfilter/nf_tables_api.c:11458
Code: 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 48 89 df e8 70 61 11 f9 48 8b 3b 5b e9 87 a3 f4 f8 0f 1f 80 00 00 00 00 f3 0f 1e fa <55> 48 89 e5 41 57 41 56 41 55 41 54 53 48 83 e4 e0 48 81 ec 00 01
RSP: 0018:ffffc900034d7b20 EFLAGS: 00000246
RAX: ffffffff815ab388 RBX: 0000000000000000 RCX: ffff888028fd1e00
RDX: ffffc900034d7ca0 RSI: 0000000000000001 RDI: ffffffff8e44a6a0
RBP: 00000000fffffffa R08: ffffffff8e8b19af R09: 1ffffffff1d16335
R10: dffffc0000000000 R11: fffffbfff1d16336 R12: ffffffff8e44a6a0
R13: 0000000000000000 R14: dffffc0000000000 R15: 1ffffffff1c894d4
 notifier_call_chain+0x197/0x380 kernel/notifier.c:93
 blocking_notifier_call_chain+0x6a/0x90 kernel/notifier.c:388
 netlink_release+0x1279/0x1ad0 net/netlink/af_netlink.c:767
 __sock_release net/socket.c:659 [inline]
 sock_close+0xbd/0x230 net/socket.c:1420
 __fput+0x234/0x970 fs/file_table.c:384
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 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:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f931d39ce59
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:00007ffcb9becc58 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffcb9becd40 RCX: 00007f931d39ce59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000016a3f R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2c420000 R11: 0000000000000246 R12: 00007ffcb9becd80
R13: 00007f931d615fac R14: 0000000000016aa2 R15: 00007f931d615fa0
 </TASK>
rcu: rcu_preempt kthread starved for 10496 jiffies! g10797 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:27656 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: 0 PID: 59 Comm: kworker/u4:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:rep_nop arch/x86/include/asm/vdso/processor.h:13 [inline]
RIP: 0010:cpu_relax arch/x86/include/asm/vdso/processor.h:18 [inline]
RIP: 0010:csd_lock_wait kernel/smp.c:311 [inline]
RIP: 0010:smp_call_function_many_cond+0xdfc/0x1140 kernel/smp.c:855
Code: 75 7b 45 8b 2c 24 44 89 ee 83 e6 01 31 ff e8 cb f5 0a 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 06 f2 0a 00 eb 38 <f3> 90 42 0f b6 04 2b 84 c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8
RSP: 0018:ffffc900015b7780 EFLAGS: 00000293
RAX: ffffffff817c3016 RBX: 1ffff110171e826d RCX: ffff88801ee81e00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900015b7900 R08: ffffffff911c6507 R09: 1ffffffff2238ca0
R10: dffffc0000000000 R11: fffffbfff2238ca1 R12: ffff8880b8f41368
R13: dffffc0000000000 R14: ffff8880b8e3d148 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f17d58c0e9c CR3: 000000000cf32000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1022
 on_each_cpu include/linux/smp.h:71 [inline]
 text_poke_sync arch/x86/kernel/alternative.c:2222 [inline]
 text_poke_bp_batch+0x31e/0x990 arch/x86/kernel/alternative.c:2432
 text_poke_flush arch/x86/kernel/alternative.c:2623 [inline]
 text_poke_finish+0x30/0x50 arch/x86/kernel/alternative.c:2630
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 static_key_enable_cpuslocked+0x123/0x240 kernel/jump_label.c:207
 static_key_enable+0x1a/0x20 kernel/jump_label.c:220
 toggle_allocation_gate+0xa8/0x260 mm/kfence/core.c:847
 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>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/15 05:05 linux-6.6.y 3b9f64db0496 6ccb967e .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sock_close
* Struck through repros no longer work on HEAD.