INFO: rcu detected stall in __tun_chr_ioctl (2)

Status: upstream: reported on 2025/11/23 13:35
Reported-by: syzbot+e51b463bd916f2ba7b55@syzkaller.appspotmail.com
First crash: 307d, last: 3d03h
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in __tun_chr_ioctl mm 1 4 617d 692d 0/29 auto-obsoleted due to no activity on 2025/04/18 05:25
linux-5.15 INFO: rcu detected stall in __tun_chr_ioctl 1 1 569d 569d 0/3 auto-obsoleted due to no activity on 2025/06/14 12:09
linux-6.1 INFO: rcu detected stall in __tun_chr_ioctl 1 3 284d 309d 0/3 auto-obsoleted due to no activity on 2026/03/26 13:49
linux-6.6 INFO: rcu detected stall in __tun_chr_ioctl (2) 1 3 6d05h 86d 0/2 upstream: reported on 2026/07/02 11:58
linux-6.6 INFO: rcu detected stall in __tun_chr_ioctl 1 1 188d 188d 0/2 auto-obsoleted due to no activity on 2026/07/01 00:03
linux-6.1 INFO: rcu detected stall in __tun_chr_ioctl (2) 1 8 11d 182d 0/3 upstream: reported on 2026/03/28 18:58

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-....: (1 GPs behind) idle=21f/1/0x4000000000000000 softirq=12121/12124 fqs=5237 
	(t=10502 jiffies g=13669 q=1801)
NMI backtrace for cpu 0
CPU: 0 PID: 6176 Comm: syz.2.584 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
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:finish_lock_switch+0x12f/0x290 kernel/sched/core.c:4804
Code: 83 c7 18 be ff ff ff ff e8 8e da 6c 08 85 c0 74 46 4d 85 ff 75 62 0f 1f 44 00 00 48 89 df e8 78 4a 76 08 e8 93 e3 2a 00 fb 5b <41> 5c 41 5d 41 5e 41 5f 5d c3 48 89 df e8 2f 0e fe ff 43 80 3c 2c
RSP: 0018:ffffc9000414f918 EFLAGS: 00000282
RAX: e87491697c24a000 RBX: ffff888024038000 RCX: e87491697c24a000
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a48c0
RBP: 1ffff11017207613 R08: ffffffff901f10cf R09: 1ffffffff203e219
R10: dffffc0000000000 R11: fffffbfff203e21a R12: 1ffff110172075c1
R13: dffffc0000000000 R14: ffff8880b903ae08 R15: 0000000000000000
 finish_task_switch+0x12f/0x650 kernel/sched/core.c:4921
 context_switch kernel/sched/core.c:5052 [inline]
 __schedule+0x11cb/0x4350 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
 __mutex_lock_common+0xdf5/0x2400 kernel/locking/mutex.c:669
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 __tun_chr_ioctl+0x3f3/0x1f30 drivers/net/tun.c:3066
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 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: 0033:0x7f80c1a0b159
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:00007f80bfc63028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f80c1c92fa0 RCX: 00007f80c1a0b159
RDX: 00002000000000c0 RSI: 00000000400454ca RDI: 0000000000000007
RBP: 00007f80c1aa206b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f80c1c93038 R14: 00007f80c1c92fa0 R15: 00007ffc3050f068
 </TASK>

Crashes (20):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/24 08:40 linux-5.15.y 0248c33e835e 0281b448 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/09/17 22:20 linux-5.15.y 0248c33e835e 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/09/10 05:38 linux-5.15.y 0996e0926f6b 4e8b1cc6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/09/01 06:45 linux-5.15.y 28c35638ec51 316d9396 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/08/04 01:42 linux-5.15.y 6e2fd6534337 9451e17e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/07/28 15:57 linux-5.15.y 674f684f7c61 edc8a875 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/07/21 18:03 linux-5.15.y c86c4726e7f0 7c5de9c3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/07/15 04:09 linux-5.15.y c86c4726e7f0 2130f682 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/07/03 16:18 linux-5.15.y eceeec79dbc6 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/06/08 02:32 linux-5.15.y dc027a595035 cc095639 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/04/28 13:56 linux-5.15.y b9d57c40a767 ce741359 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/03/31 01:41 linux-5.15.y 91d48252ad4b d0af506e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/03/04 06:20 linux-5.15.y 3330a8d33e08 4180d919 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/02/27 03:15 linux-5.15.y 3330a8d33e08 a2f13f71 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/02/11 19:24 linux-5.15.y e45d5d41c134 75707236 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/01/14 18:27 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/01/08 05:24 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/01/03 01:26 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2025/12/30 15:16 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2025/11/23 13:35 linux-5.15.y cc5ec8769306 4fb8ef37 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
* Struck through repros no longer work on HEAD.