syzbot


INFO: rcu detected stall in futex (2)

Status: upstream: reported C repro on 2025/10/31 01:02
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+aa74f9a1d1d8b3371105@syzkaller.appspotmail.com
First crash: 54d, last: 2d05h
Bug presence (2)
Date Name Commit Repro Result
2025/12/14 linux-6.6.y (ToT) 5fa4793a2d2d C [report] INFO: task hung in perf_event_release_kernel
2025/12/14 upstream (ToT) 8f0b4cce4481 C Didn't crash
Similar bugs (12)
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 100 15d 547d 0/29 upstream: reported syz repro on 2024/06/24 16:48
linux-5.15 INFO: rcu detected stall in sys_futex (2) origin:lts-only 1 syz error 50 1h04m 566d 0/3 upstream: reported syz repro on 2024/06/05 16:49
linux-6.6 INFO: rcu detected stall in futex origin:lts-only 1 C done 6 118d 136d 2/2 fixed on 2025/10/06 10:09
upstream INFO: rcu detected stall in futex kvm 1 1 1801d 1801d 0/29 auto-closed as invalid on 2021/04/17 19:46
linux-6.1 INFO: rcu detected stall in sys_futex origin:lts-only 1 syz done 27 28d 903d 0/3 upstream: reported syz repro on 2023/07/05 11:35
upstream INFO: rcu detected stall in sys_futex (3) mm 1 959 2176d 2225d 0/29 auto-closed as invalid on 2020/03/08 12:44
upstream INFO: rcu detected stall in sys_futex (2) kernel 1 6 2344d 2489d 0/29 auto-closed as invalid on 2019/10/25 14:11
upstream INFO: rcu detected stall in sys_futex (4) kernel 1 1 1426d 1426d 0/29 closed as invalid on 2022/02/08 10:00
upstream INFO: rcu detected stall in sys_futex kernel 1 1 2550d 2550d 0/29 closed as invalid on 2018/12/31 04:10
linux-5.15 INFO: rcu detected stall in sys_futex 1 4 722d 897d 0/3 auto-obsoleted due to no activity on 2024/04/10 17:08
upstream INFO: rcu detected stall in sys_futex (5) kernel 1 12 1156d 1401d 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 725d 961d 0/29 auto-obsoleted due to no activity on 2024/03/29 00:57

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (10500 ticks this GP) idle=acec/1/0x4000000000000000 softirq=12175/12176 fqs=4745
rcu: 	         hardirqs   softirqs   csw/system
rcu: 	 number:  1467867          0            0
rcu: 	cputime:    15696      36792           41   ==> 52520(ms)
rcu: 	(t=10504 jiffies g=11233 q=1161 ncpus=2)
CPU: 1 PID: 5927 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:lock_acquire+0x21f/0x410 kernel/locking/lockdep.c:5758
Code: 3c 00 00 00 00 66 43 c7 44 3c 09 00 00 43 c6 44 3c 0b 00 65 48 8b 04 25 28 00 00 00 48 3b 84 24 c0 00 00 00 0f 85 f9 00 00 00 <48> 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 0f 0b e9 6f fe ff ff
RSP: 0018:ffffc900001f0480 EFLAGS: 00000246
RAX: 7b4ffda3f2efe800 RBX: 0000000000000000 RCX: 7b4ffda3f2efe800
RDX: 0000000000000000 RSI: ffffffff8aaace60 RDI: ffffffff8afc6f80
RBP: ffffc900001f0590 R08: dffffc0000000000 R09: 1ffffffff21b28a0
R10: dffffc0000000000 R11: fffffbfff21b28a1 R12: 1ffff9200003e09c
R13: ffffffff8cd2ff20 R14: 0000000000000246 R15: dffffc0000000000
FS:  000055556b1c3500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000007a44c000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 is_bpf_text_address+0x47/0x2a0 kernel/bpf/core.c:741
 kernel_text_address+0xa0/0xd0 kernel/extable.c:125
 __kernel_text_address+0xd/0x30 kernel/extable.c:79
 unwind_get_return_address+0x5d/0xc0 arch/x86/kernel/unwind_orc.c:369
 arch_stack_walk+0x11d/0x190 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 kmem_cache_alloc_node+0x150/0x330 mm/slub.c:3540
 __alloc_skb+0x108/0x2c0 net/core/skbuff.c:643
 alloc_skb include/linux/skbuff.h:1284 [inline]
 lapb_send_control+0x38/0x3e0 net/lapb/lapb_subr.c:227
 lapb_t1timer_expiry+0x699/0xab0 net/lapb/lapb_timer.c:-1
 call_timer_fn+0x16e/0x530 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x52d/0x7d0 kernel/time/timer.c:2023
 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2036
 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+0xc7/0x190 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:preempt_schedule_irq+0xb0/0x140 kernel/sched/core.c:7009
Code: 44 24 20 f6 44 24 21 02 74 0b 0f 0b 48 f7 03 08 00 00 00 74 63 bf 01 00 00 00 e8 8b b3 eb f6 e8 26 3a 1c f7 fb bf 01 00 00 00 <e8> db b5 ff ff 48 c7 44 24 40 00 00 00 00 9c 8f 44 24 40 8b 44 24
RSP: 0018:ffffc900032f79c0 EFLAGS: 00000282
RAX: 7b4ffda3f2efe800 RBX: 0000000000000000 RCX: 7b4ffda3f2efe800
RDX: dffffc0000000000 RSI: ffffffff8aaabce0 RDI: 0000000000000001
RBP: ffffc900032f7a60 R08: ffffffff8e4a212f R09: 1ffffffff1c94425
R10: dffffc0000000000 R11: fffffbfff1c94426 R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 1ffff9200065ef38
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:692
RIP: 0010:get_futex_key+0xb95/0x1020 kernel/futex/core.c:405
Code: ad 8a e8 7e f5 ed ff e8 69 ae f6 ff 48 c7 c7 20 ff d2 8c 4c 89 e6 e8 1a c4 ed ff 31 db 48 8b bc 24 80 00 00 00 e8 4b 08 00 00 <48> c7 44 24 60 0e 36 e0 45 48 8b 44 24 58 4a c7 04 28 00 00 00 00
RSP: 0018:ffffc900032f7b20 EFLAGS: 00000246
RAX: 1ffff9200065ef91 RBX: 0000000000000000 RCX: ffff88802d075a00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff8cd52ea0
RBP: ffffc900032f7c10 R08: ffffc900032f7c97 R09: 0000000000000000
R10: ffffc900032f7c80 R11: fffff5200065ef93 R12: 0000000000000000
R13: dffffc0000000000 R14: 0000000000000fac R15: 00007f00d01e5000
 futex_wake+0x10b/0x4b0 kernel/futex/waitwake.c:154
 do_futex+0x35d/0x3e0 kernel/futex/syscalls.c:139
 __do_sys_futex kernel/futex/syscalls.c:211 [inline]
 __se_sys_futex+0x36f/0x3f0 kernel/futex/syscalls.c:192
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f00cff8f749
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:00007ffec37a0e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007f00d01e5fa8 RCX: 00007f00cff8f749
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007f00d01e5fac
RBP: 0000000000000000 R08: 0000000000745d1e R09: 00000002c37a114f
R10: 0000000000000004 R11: 0000000000000246 R12: 00007f00d01e5fac
R13: 00007f00d01e5fa0 R14: 0000000000001300 R15: 0000000000000005
 </TASK>

Crashes (13):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/14 02:06 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/22 06:01 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 futex
2025/12/21 17:46 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 futex
2025/12/21 16:52 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 futex
2025/12/13 23:17 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 futex
2025/12/10 02:10 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 futex
2025/12/05 11:56 linux-6.6.y 4791134e4aeb d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/03 21:22 linux-6.6.y 4791134e4aeb d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/11/29 16:12 linux-6.6.y 1e89a1be4fe9 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/11/16 13:42 linux-6.6.y 0a805b6ea8cd f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/11/11 08:38 linux-6.6.y 0a805b6ea8cd 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/11/04 02:45 linux-6.6.y 0a805b6ea8cd 686bf657 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in futex
2025/10/31 01:02 linux-6.6.y e5bbb12db2c7 2c50b6a9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in futex
* Struck through repros no longer work on HEAD.