syzbot


INFO: rcu detected stall in sys_getpid

Status: upstream: reported C repro on 2025/09/06 16:11
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+35993bdd136c7a8427a4@syzkaller.appspotmail.com
First crash: 110d, last: 31d
Bug presence (2)
Date Name Commit Repro Result
2025/09/08 linux-6.6.y (ToT) 355bd0b51d2f C [report] INFO: rcu detected stall in corrupted
2025/09/08 upstream (ToT) 76eeb9b8de98 C Didn't crash
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in sys_getpid 1 1 547d 547d 0/3 auto-obsoleted due to no activity on 2024/10/04 19:18
linux-6.1 INFO: rcu detected stall in sys_getpid 1 1 244d 244d 0/3 auto-obsoleted due to no activity on 2025/08/03 12:49
linux-6.1 INFO: rcu detected stall in sys_getpid (2) 1 1 23d 23d 0/3 upstream: reported on 2025/12/02 23:35
linux-5.15 INFO: rcu detected stall in sys_getpid (2) origin:lts-only 1 C error 13 13d 390d 0/3 upstream: reported C repro on 2024/11/30 21:19
Fix bisection attempts (1)
Created Duration User Patch Repo Result
2025/09/28 16:26 2h06m fix candidate upstream OK (0) job log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P969/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=8469, q=73 ncpus=2)
task:kworker/1:2     state:R  running task     stack:25832 pid:969   ppid:2      flags:0x00004000
Workqueue: events_power_efficient gc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7009
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:692
RIP: 0010:check_kcov_mode kernel/kcov.c:182 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x17/0x60 kernel/kcov.c:216
Code: 48 8b 3d 0c 00 c5 0c 48 89 de 5b e9 a3 8a 56 00 cc cc cc f3 0f 1e fa 48 8b 04 24 65 48 8b 0d 20 28 7e 7e 65 8b 15 21 28 7e 7e <81> e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 1c 16 00 00
RSP: 0018:ffffc90004467a58 EFLAGS: 00000202
RAX: ffffffff88ace1d9 RBX: 000000000002926c RCX: ffff88802249da00
RDX: 0000000080000000 RSI: ffffffff8afc6ae0 RDI: ffffffff8afc6aa0
RBP: ffffc90004467bb0 R08: ffffffff90da8597 R09: 1ffffffff21b50b2
R10: dffffc0000000000 R11: fffffbfff21b50b3 R12: ffff88802249da00
R13: dffffc0000000000 R14: 0000000000000001 R15: 00000000000524d9
 rcu_read_unlock include/linux/rcupdate.h:815 [inline]
 gc_worker+0xcc9/0x14b0 net/netfilter/nf_conntrack_core.c:1579
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 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 10526 jiffies! g8469 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:27088 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 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: 5795 Comm: syz-executor267 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:lapic_next_event+0x11/0x20 arch/x86/kernel/apic/apic.c:449
Code: 90 06 c6 05 00 c1 90 0e 01 0f b6 05 d9 aa 90 0e c3 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 48 89 fe bf 80 03 00 00 e8 1f 1b 01 00 <31> c0 c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 f3 0f 1e fa 53 48 83
RSP: 0018:ffffc900001f0e60 EFLAGS: 00000046
RAX: 0000000000074d2a RBX: ffff8880b8f28280 RCX: 0000000000000838
RDX: 0000000000000000 RSI: 0000000000074d2a RDI: 0000000000000838
RBP: 0000000000000000 R08: ffffffff8e4a8d6f R09: 1ffffffff1c951ad
R10: dffffc0000000000 R11: fffffbfff1c951ae R12: dffffc0000000000
R13: 0000000010005df3 R14: 0000000000074d2a R15: 0000000000000020
FS:  00007fc9e0fc46c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000058 CR3: 0000000072260000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 clockevents_program_event+0x1c0/0x310 kernel/time/clockevents.c:334
 hrtimer_interrupt+0x5a1/0x9c0 kernel/time/hrtimer.c:1889
 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:task_pid_ptr kernel/pid.c:326 [inline]
RIP: 0010:__task_pid_nr_ns+0x165/0x470 kernel/pid.c:503
Code: f0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 f7 e8 51 8e 84 00 4d 8b 36 eb 08 e8 f7 32 2d 00 45 31 f6 31 ff 89 ee e8 9b 36 2d 00 <85> ed 74 48 49 81 c7 10 09 00 00 4c 89 f8 48 c1 e8 03 42 80 3c 28
RSP: 0018:ffffc9000454fed8 EFLAGS: 00000293
RAX: ffffffff81585ca5 RBX: ffff888027ce1b40 RCX: 0000000000000000
RDX: ffff888028dfbc00 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: dffffc0000000000 R09: 1ffffffff21b50a0
R10: dffffc0000000000 R11: fffffbfff21b50a1 R12: 0000000000000001
R13: dffffc0000000000 R14: ffffffff8cbdf480 R15: ffff888028dfbc00
 task_tgid_vnr include/linux/sched.h:1642 [inline]
 __ia32_sys_getpid+0x1d/0x20 kernel/sys.c:960
 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: 0033:0x7fc9e100a4f7
Code: 0b e9 68 fe ff ff 48 83 c4 18 48 8d 3d 62 9f 08 00 5b 5d 41 5c 41 5d 41 5e 41 5f e9 53 b9 fd ff 0f 1f 00 b8 27 00 00 00 0f 05 <c3> 0f 1f 84 00 00 00 00 00 31 f6 31 ff e9 c7 11 03 00 0f 1f 80 00
RSP: 002b:00007fc9e0fc3b88 EFLAGS: 00000206 ORIG_RAX: 0000000000000027
RAX: ffffffffffffffda RBX: 00007fc9e0fc3cf0 RCX: 00007fc9e100a4f7
RDX: 00007fc9e0fc3bc0 RSI: 00007fc9e0fc3cf0 RDI: 0000000000000021
RBP: 0000000000000000 R08: 00007fc9e0fc46c0 R09: 00007fc9e0fc46c0
R10: 0000000000000000 R11: 0000000000000206 R12: 00007fc9e108e30c
R13: 0000000000000000 R14: 00007ffd126fecb0 R15: 00007ffd126fed98
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/14 11:01 linux-6.6.y 0a805b6ea8cd 07e030de .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2025/09/06 16:10 linux-6.6.y 355bd0b51d2f d291dd2d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2025/11/25 06:21 linux-6.6.y 1e89a1be4fe9 64219f15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2025/09/10 07:55 linux-6.6.y fe9731e10004 fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
* Struck through repros no longer work on HEAD.