syzbot


INFO: rcu detected stall in sys_futex (2)

Status: upstream: reported syz repro on 2024/06/05 16:49
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+6ceb9abf06f08ceec1d2@syzkaller.appspotmail.com
First crash: 470d, last: 4h54m
Bug presence (2)
Date Name Commit Repro Result
2025/09/05 linux-5.15.y (ToT) 7a6c2d093c45 syz [report] INFO: rcu detected stall in sock_write_iter
2025/09/05 upstream (ToT) d69eb204c255 syz Didn't crash
Similar bugs (11)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_futex (7) kernel 1 syz error 90 3d15h 451d 0/29 upstream: reported syz repro on 2024/06/24 16:48
upstream INFO: rcu detected stall in sys_futex (3) mm 1 959 2080d 2129d 0/29 auto-closed as invalid on 2020/03/08 12:44
upstream INFO: rcu detected stall in sys_futex (2) kernel 1 6 2248d 2392d 0/29 auto-closed as invalid on 2019/10/25 14:11
upstream INFO: rcu detected stall in sys_futex (4) kernel 1 1 1329d 1329d 0/29 closed as invalid on 2022/02/08 10:00
upstream INFO: rcu detected stall in sys_futex kernel 1 1 2454d 2454d 0/29 closed as invalid on 2018/12/31 04:10
linux-6.6 INFO: rcu detected stall in futex origin:lts-only 1 C 6 22d 39d 0/2 upstream: reported C repro on 2025/08/10 09:30
linux-5.15 INFO: rcu detected stall in sys_futex 1 4 626d 800d 0/3 auto-obsoleted due to no activity on 2024/04/10 17:08
linux-6.1 INFO: rcu detected stall in sys_futex origin:lts-only 1 syz done 20 37m 806d 0/3 upstream: reported syz repro on 2023/07/05 11:35
upstream INFO: rcu detected stall in sys_futex (5) kernel 1 12 1060d 1305d 0/29 auto-obsoleted due to no activity on 2023/02/12 18:33
upstream INFO: rcu detected stall in sys_futex (6) kernel 1 10 629d 864d 0/29 auto-obsoleted due to no activity on 2024/03/29 00:57
upstream INFO: rcu detected stall in futex kvm 1 1 1705d 1705d 0/29 auto-closed as invalid on 2021/04/17 19:46
Last patch testing requests (1)
Created Duration User Patch Repo Result
2025/03/16 10:05 15m retest repro linux-5.15.y OK log
Fix bisection attempts (2)
Created Duration User Patch Repo Result
2025/03/05 06:47 16m fix candidate upstream error job log
2025/01/18 16:59 22m fix candidate upstream error job log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-....: (0 ticks this GP) idle=a37/1/0x4000000000000002 softirq=19359/19362 fqs=5222 
	(detected by 1, t=10502 jiffies, g=22925, q=165793)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 10641 Comm: syz.3.2907 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:kasan_check_range+0x1ab/0x290 mm/kasan/generic.c:-1
Code: 4d 89 d6 4d 8d 56 07 4d 85 f6 4d 0f 49 d6 49 83 e2 f8 4d 29 d6 74 12 41 80 39 00 0f 85 a0 00 00 00 49 ff c1 49 ff ce 75 ee 5b <41> 5e 41 5f c3 84 db 75 61 f7 c3 00 ff 00 00 75 5e f7 c3 00 00 ff
RSP: 0018:ffffc900000079f0 EFLAGS: 00000056
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff812a4f09
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8d698de8
RBP: 0000000000000000 R08: dffffc0000000000 R09: fffffbfff1ad31be
R10: fffffbfff1ad31be R11: 1ffffffff1ad31bd R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: dffffc0000000001
FS:  000055558d8bf500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055556f00d808 CR3: 0000000059f61000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 instrument_atomic_read include/linux/instrumented.h:71 [inline]
 test_bit include/asm-generic/bitops/instrumented-non-atomic.h:134 [inline]
 cpumask_test_cpu include/linux/cpumask.h:344 [inline]
 cpu_online include/linux/cpumask.h:895 [inline]
 trace_irq_work_entry arch/x86/include/asm/trace/irq_vectors.h:64 [inline]
 __sysvec_irq_work+0x79/0x240 arch/x86/kernel/irq_work.c:20
 instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
 sysvec_irq_work+0x4a/0xc0 arch/x86/kernel/irq_work.c:17
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x84/0x480 kernel/rcu/tree_plugin.h:674
Code: f1 f1 f1 00 f2 f2 f2 4a 89 04 2b 66 42 c7 44 2b 09 f3 f3 42 c6 44 2b 0b f3 65 44 8b 35 dd 13 9e 7e 41 f7 c6 00 00 f0 00 74 45 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 66 42 c7 44 2b
RSP: 0018:ffffc90000007ae0 EFLAGS: 00000206
RAX: 6c2d1079a006a600 RBX: 1ffff92000000f60 RCX: 6c2d1079a006a600
RDX: dffffc0000000000 RSI: ffffffff8a0b1620 RDI: ffffffff8a59a240
RBP: ffffc90000007bb8 R08: dffffc0000000000 R09: ffffed101720765a
R10: ffffed101720765a R11: 1ffff11017207659 R12: ffffffff8c120900
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:771 [inline]
 ieee80211_iterate_active_interfaces_atomic+0x132/0x140 net/mac80211/util.c:831
 mac80211_hwsim_beacon+0x9b/0x180 drivers/net/wireless/mac80211_hwsim.c:1865
 __run_hrtimer kernel/time/hrtimer.c:1690 [inline]
 __hrtimer_run_queues+0x53d/0xc40 kernel/time/hrtimer.c:1754
 hrtimer_run_softirq+0x176/0x240 kernel/time/hrtimer.c:1771
 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 ec 7c 55 08 85 c0 74 4a 4d 85 ff 75 66 0f 1f 44 00 00 48 89 df e8 46 e7 5e 08 e8 71 75 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:ffffc9000380f7c8 EFLAGS: 00000282
RAX: 6c2d1079a006a600 RBX: ffff8880b903a300 RCX: 6c2d1079a006a600
RDX: dffffc0000000000 RSI: ffffffff8a0b1620 RDI: ffffffff8a59a240
RBP: 1ffff1101720760b R08: dffffc0000000000 R09: ffffed101720765a
R10: ffffed101720765a R11: 1ffff11017207659 R12: 1ffff110172075b9
R13: dffffc0000000000 R14: ffff8880b903adc8 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
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 freezable_schedule include/linux/freezer.h:172 [inline]
 futex_wait_queue_me+0x22d/0x440 kernel/futex/core.c:2863
 futex_wait+0x202/0x5c0 kernel/futex/core.c:2964
 do_futex+0xd1c/0x1240 kernel/futex/core.c:3982
 __do_sys_futex kernel/futex/core.c:4059 [inline]
 __se_sys_futex+0x3a3/0x430 kernel/futex/core.c:4040
 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: 0033:0x7f213929bbe9
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:00007ffeee351a08 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 000000000004a478 RCX: 00007f213929bbe9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f21394d2fac
RBP: 0000000000000032 R08: 000dcec441570d18 R09: 00000001ee351cff
R10: 00007ffeee351b00 R11: 0000000000000246 R12: 00007f21394d2fac
R13: 00007ffeee351b00 R14: 000000000004a4aa R15: 00007ffeee351b20
 </TASK>

Crashes (33):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/05 08:55 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in futex
2025/04/08 15:43 linux-5.15.y 0c935c049b5c a775275d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_futex
2025/03/19 14:24 linux-5.15.y 0c935c049b5c 8d0a2921 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_futex
2025/01/02 00:57 linux-5.15.y 91786f140358 d3ccff63 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in sys_futex
2025/01/01 17:38 linux-5.15.y 91786f140358 d3ccff63 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in sys_futex
2024/12/14 04:24 linux-5.15.y 0a51d2d4527b 7cbfbb3a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_futex
2024/11/13 09:14 linux-5.15.y 3c17fc483905 62026c85 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_futex
2024/10/12 08:25 linux-5.15.y 3a5928702e71 084d8178 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_futex
2024/10/06 13:38 linux-5.15.y 3a5928702e71 d7906eff .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in sys_futex
2024/09/23 11:34 linux-5.15.y 3a5928702e71 89298aad .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_futex
2024/08/13 03:25 linux-5.15.y 7e89efd3ae1c 7b0f4b46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_futex
2024/08/03 03:41 linux-5.15.y 7e89efd3ae1c 1786a2a8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_futex
2024/06/12 14:06 linux-5.15.y c61bd26ae81a f815599d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_futex
2024/06/05 16:49 linux-5.15.y c61bd26ae81a 5aa1a7c9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_futex
2024/08/22 15:56 linux-5.15.y fa93fa65db6e ca02180f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 INFO: rcu detected stall in sys_futex
2025/09/18 21:17 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in futex
2025/09/15 11:47 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in futex
2025/09/14 01:07 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in futex
2025/09/11 15:25 linux-5.15.y de9476bb4f1b fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in futex
2025/09/05 01:01 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in futex
2025/09/05 00:42 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in futex
2025/09/05 00:10 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in futex
2025/09/02 11:39 linux-5.15.y 01879f56bdde 807a3b61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in futex
2025/08/31 03:29 linux-5.15.y 01879f56bdde 807a3b61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in futex
2025/08/27 15:43 linux-5.15.y c79648372d02 e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in futex
2025/08/24 14:54 linux-5.15.y c79648372d02 bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in futex
2025/08/22 23:50 linux-5.15.y c79648372d02 bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in futex
2025/08/16 12:49 linux-5.15.y c79648372d02 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in futex
2025/08/06 05:55 linux-5.15.y c79648372d02 ffe1dd46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in futex
2025/07/06 20:02 linux-5.15.y 3dea0e7f549e 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in futex
2025/05/17 10:42 linux-5.15.y 3b8db0e4f263 f41472b0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in futex
2025/05/14 20:58 linux-5.15.y 3b8db0e4f263 a4fa04ef .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in futex
2025/04/16 06:19 linux-5.15.y f7347f400572 a95239b1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in futex
* Struck through repros no longer work on HEAD.