INFO: rcu detected stall in proc_sys_call_handler

Status: upstream: reported on 2026/10/15 07:19
Reported-by: syzbot+35b3caa272f06831029a@syzkaller.appspotmail.com
First crash: 7h44m, last: 7h44m
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in proc_sys_call_handler (2) fs 1 4 558d 761d 0/29 auto-obsoleted due to no activity on 2025/07/04 12:08
upstream INFO: rcu detected stall in proc_sys_call_handler kernel 1 1 1586d 1586d 0/29 auto-closed as invalid on 2022/09/09 16:54
linux-4.19 BUG: soft lockup in proc_sys_call_handler 1 1 1363d 1363d 0/1 upstream: reported on 2023/01/21 03:02

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10500 ticks this GP) idle=821/1/0x4000000000000000 softirq=28362/28362 fqs=0 
	(t=10500 jiffies g=39973 q=62)
rcu: rcu_preempt kthread timer wakeup didn't happen for 10499 jiffies! g39973 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=21026
rcu: rcu_preempt kthread starved for 10500 jiffies! g39973 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:26448 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11c3/0x4350 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2117
 rcu_gp_fqs_loop+0x2be/0x11f0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x9a/0x370 kernel/rcu/tree.c:2145
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
NMI backtrace for cpu 0
CPU: 0 PID: 11047 Comm: syz.3.1784 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_check_gp_kthread_starvation+0x1cd/0x250 kernel/rcu/tree_stall.h:487
 print_cpu_stall+0x31a/0x5f0 kernel/rcu/tree_stall.h:631
 check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x6ec/0x1120 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:2021
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4b0/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x397/0x8b0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/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:lock_release+0x5a4/0x8a0 kernel/locking/lockdep.c:5761
Code: 80 00 00 00 f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 2c 04 f8 75 6f 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 2c 00 00 00 00 43 c7 44 2c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc900035d7a00 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 00e5d55ccbc13571 RCX: 1a1dcccaf9235000
RDX: 0000000000000003 RSI: ffffffff8a2b3e80 RDI: ffffffff8a7a4c00
RBP: ffffc900035d7b08 R08: ffffffff8e6b282f R09: 1ffffffff1cd6505
R10: dffffc0000000000 R11: fffffbfff1cd6506 R12: 1ffff920006baf4c
R13: dffffc0000000000 R14: ffff88801e55c660 R15: 0000000000000246
 might_alloc include/linux/sched/mm.h:206 [inline]
 slab_pre_alloc_hook+0x20/0xc0 mm/slab.h:492
 slab_alloc_node mm/slub.c:3139 [inline]
 __kmalloc_node+0x6d/0x3a0 mm/slub.c:4456
 kmalloc_node include/linux/slab.h:630 [inline]
 kvmalloc_node+0x84/0x130 mm/util.c:619
 kvmalloc include/linux/mm.h:816 [inline]
 kvzalloc include/linux/mm.h:824 [inline]
 proc_sys_call_handler+0x366/0x6c0 fs/proc/proc_sysctl.c:571
 call_write_iter include/linux/fs.h:2179 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x748/0xd70 fs/read_write.c:594
 ksys_write+0x153/0x260 fs/read_write.c:647
 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: 0033:0x7fc699c67559
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:00007fc697e9e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc699eef090 RCX: 00007fc699c67559
RDX: 0000000000000001 RSI: 0000200000000180 RDI: 000000000000000a
RBP: 00007fc699cfe8b0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc699eef128 R14: 00007fc699eef090 R15: 00007ffc83f10eb8
 </TASK>
NMI backtrace for cpu 0
CPU: 0 PID: 11047 Comm: syz.3.1784 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_dump_cpu_stacks+0x22d/0x380 kernel/rcu/tree_stall.h:349
 print_cpu_stall+0x31f/0x5f0 kernel/rcu/tree_stall.h:633
 check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x6ec/0x1120 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:2021
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4b0/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x397/0x8b0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/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:lock_release+0x5a4/0x8a0 kernel/locking/lockdep.c:5761
Code: 80 00 00 00 f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 2c 04 f8 75 6f 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 2c 00 00 00 00 43 c7 44 2c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc900035d7a00 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 00e5d55ccbc13571 RCX: 1a1dcccaf9235000
RDX: 0000000000000003 RSI: ffffffff8a2b3e80 RDI: ffffffff8a7a4c00
RBP: ffffc900035d7b08 R08: ffffffff8e6b282f R09: 1ffffffff1cd6505
R10: dffffc0000000000 R11: fffffbfff1cd6506 R12: 1ffff920006baf4c
R13: dffffc0000000000 R14: ffff88801e55c660 R15: 0000000000000246
 might_alloc include/linux/sched/mm.h:206 [inline]
 slab_pre_alloc_hook+0x20/0xc0 mm/slab.h:492
 slab_alloc_node mm/slub.c:3139 [inline]
 __kmalloc_node+0x6d/0x3a0 mm/slub.c:4456
 kmalloc_node include/linux/slab.h:630 [inline]
 kvmalloc_node+0x84/0x130 mm/util.c:619
 kvmalloc include/linux/mm.h:816 [inline]
 kvzalloc include/linux/mm.h:824 [inline]
 proc_sys_call_handler+0x366/0x6c0 fs/proc/proc_sysctl.c:571
 call_write_iter include/linux/fs.h:2179 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x748/0xd70 fs/read_write.c:594
 ksys_write+0x153/0x260 fs/read_write.c:647
 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: 0033:0x7fc699c67559
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:00007fc697e9e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc699eef090 RCX: 00007fc699c67559
RDX: 0000000000000001 RSI: 0000200000000180 RDI: 000000000000000a
RBP: 00007fc699cfe8b0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc699eef128 R14: 00007fc699eef090 R15: 00007ffc83f10eb8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/15 07:18 linux-5.15.y a051a4bf909f 8fb0ae89 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in proc_sys_call_handler
* Struck through repros no longer work on HEAD.