syzbot


INFO: rcu detected stall in syscall_enter_from_user_mode (2)

Status: upstream: reported C repro on 2026/06/28 07:45
Reported-by: syzbot+e75ee9208fc01cbc1013@syzkaller.appspotmail.com
First crash: 18d, last: 18d
Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in syscall_enter_from_user_mode (2) 1 1 710d 710d 0/3 auto-obsoleted due to no activity on 2024/11/13 07:03
linux-6.1 INFO: rcu detected stall in syscall_enter_from_user_mode 1 1 1107d 1107d 0/3 auto-obsoleted due to no activity on 2023/10/13 06:46
upstream INFO: rcu detected stall in syscall_enter_from_user_mode (2) kernel 1 11 1282d 1572d 0/29 auto-obsoleted due to no activity on 2023/04/22 11:15
linux-6.1 INFO: rcu detected stall in syscall_enter_from_user_mode (3) origin:lts-only 1 C done 16 24d 504d 0/3 upstream: reported C repro on 2025/02/27 13:22
upstream INFO: rcu detected stall in syscall_enter_from_user_mode (3) kernel 1 5 947d 1112d 0/29 auto-obsoleted due to no activity on 2024/03/11 14:48
linux-5.15 INFO: rcu detected stall in syscall_enter_from_user_mode missing-backport origin:upstream 1 C done 171 17d 946d 0/3 upstream: reported C repro on 2023/12/13 03:22
linux-6.6 INFO: rcu detected stall in syscall_enter_from_user_mode 1 1 246d 246d 0/2 auto-obsoleted due to no activity on 2026/02/19 17:17
upstream INFO: rcu detected stall in syscall_enter_from_user_mode kernel 1 2 1629d 1643d 0/29 closed as invalid on 2022/02/08 10:10
android-5-15 BUG: soft lockup in syscall_enter_from_user_mode 1 1 791d 791d 0/2 auto-obsoleted due to no activity on 2024/08/14 14:14

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P23/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=9585, q=175 ncpus=2)
task:kworker/1:0     state:R  running task     stack:27120 pid:23    ppid:2      flags:0x00004000
Workqueue: events_power_efficient gc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:692
RIP: 0010:seqcount_lockdep_reader_access+0x19a/0x1d0 include/linux/seqlock.h:105
Code: f8 4d 85 e4 75 16 e8 c5 fd cb f8 eb 15 e8 be fd cb f8 e8 a9 f0 c8 01 4d 85 e4 74 ea e8 af fd cb f8 fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 3e 00 00 00 00 43 c7 44 3e 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc900001d79a0 EFLAGS: 00000293
RAX: ffffffff88bae7a1 RBX: 0000000000000000 RCX: ffff88801be75a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900001d7a50 R08: ffffffff911bc597 R09: 1ffffffff22378b2
R10: dffffc0000000000 R11: fffffbfff22378b3 R12: 0000000000000200
R13: dffffc0000000000 R14: 1ffff9200003af34 R15: dffffc0000000000
 nf_conntrack_get_ht include/net/netfilter/nf_conntrack.h:350 [inline]
 gc_worker+0x314/0x14a0 net/netfilter/nf_conntrack_core.c:1504
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730
 worker_thread+0xa5e/0xfe0 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 10409 jiffies! g9585 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:27848 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 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
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0x111/0x120 kernel/locking/spinlock.c:194
 debug_object_free+0x2c2/0x470 lib/debugobjects.c:866
 destroy_timer_on_stack kernel/time/timer.c:812 [inline]
 schedule_timeout+0x1a1/0x2d0 kernel/time/timer.c:2172
 rcu_gp_fqs_loop+0x30d/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:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 6096 Comm: syz-executor140 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:27 [inline]
RIP: 0010:static_key_false include/linux/jump_label.h:207 [inline]
RIP: 0010:native_write_msr arch/x86/include/asm/msr.h:147 [inline]
RIP: 0010:wrmsrl arch/x86/include/asm/msr.h:262 [inline]
RIP: 0010:lapic_next_deadline+0x25/0x40 arch/x86/kernel/apic/apic.c:461
Code: 00 00 00 00 00 f3 0f 1e fa 0f ae f0 0f ae e8 0f 31 48 c1 e2 20 48 09 c2 48 8d 04 fa 48 89 c2 48 c1 ea 20 b9 e0 06 00 00 0f 30 <66> 90 31 c0 c3 bf e0 06 00 00 48 89 c6 31 d2 e8 c7 6e 24 03 31 c0
RSP: 0018:ffffc900001f0e88 EFLAGS: 00000003
RAX: 00000086de0eef5e RBX: ffff8880b8f282c0 RCX: 00000000000006e0
RDX: 0000000000000086 RSI: ffff8880b8f282c0 RDI: 0000000000229e2d
RBP: 0000000000000000 R08: ffffffff8e8ae5ef R09: 1ffffffff1d15cbd
R10: dffffc0000000000 R11: fffffbfff1d15cbe R12: dffffc0000000000
R13: 00000000008cccc4 R14: 0000000000229e2d R15: 0000000000000019
FS:  00007f977d54f6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f977d5ec036 CR3: 0000000025125000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 clockevents_program_event+0x1c0/0x310 kernel/time/clockevents.c:334
 hrtimer_interrupt+0x565/0x980 kernel/time/hrtimer.c:1893
 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:__syscall_enter_from_user_work kernel/entry/common.c:97 [inline]
RIP: 0010:syscall_enter_from_user_mode+0x2e/0x80 kernel/entry/common.c:118
Code: 41 56 53 48 89 f3 49 89 fe 48 8b 7c 24 10 e8 e9 fa ff ff 66 90 66 90 e8 70 75 09 f7 e8 2b 75 09 f7 fb 65 48 8b 05 52 d9 7f 75 <48> 8b 70 08 40 f6 c6 3f 74 0b 4c 89 f7 5b 41 5e e9 cd c0 ef f6 48
RSP: 0018:ffffc90004c47f08 EFLAGS: 00000286
RAX: ffff888024c55a00 RBX: 000000000000000f RCX: 63a761d2e2bb9200
RDX: dffffc0000000000 RSI: ffffffff8acacb60 RDI: ffffffff8b1c7be0
RBP: ffffc90004c47f48 R08: ffffffff8e8ae5ef R09: 1ffffffff1d15cbd
R10: dffffc0000000000 R11: fffffbfff1d15cbe R12: 0000000000000000
R13: 0000000000000000 R14: ffffc90004c47f58 R15: 0000000000000000
 do_syscall_64+0x28/0xb0 arch/x86/entry/common.c:72
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f977d55dc49
Code: df 01 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 c7 c0 0f 00 00 00 0f 05 <0f> 1f 80 00 00 00 00 48 81 ec 48 01 00 00 49 89 d0 64 48 8b 0c 25
RSP: 002b:00007f977d54ebc0 EFLAGS: 00000202 ORIG_RAX: 000000000000000f
RAX: ffffffffffffffda RBX: 00007f977d621b68 RCX: 00007f977d55dc49
RDX: 00007f977d54ebc0 RSI: 00007f977d54ecf0 RDI: 0000000000000021
RBP: 00007f977d621b60 R08: 00007f977d54fcdc R09: 0000000000000000
R10: 00007f977d54fcdc R11: 0000000000000202 R12: 00007f977d621b6c
R13: 0000000000000016 R14: 00007ffd4ab206e0 R15: 00007ffd4ab207c8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/28 07:45 linux-6.6.y d1cfde2d5d15 fb92f11c .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in syscall_enter_from_user_mode
* Struck through repros no longer work on HEAD.