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: 244d, last: 3d20h
▶ ▼ 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 553d 628d 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 506d 506d 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 221d 245d 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 2 16d 23d 0/2 upstream: reported on 2026/07/02 11:58
linux-6.6 INFO: rcu detected stall in __tun_chr_ioctl 1 1 124d 124d 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 5 34d 118d 0/3 upstream: reported on 2026/03/28 18:58

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-....: (5 ticks this GP) idle=ad7/1/0x4000000000000002 softirq=8251/8253 fqs=5247 
	(detected by 1, t=10502 jiffies, g=10189, q=1122)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4869 Comm: syz.2.229 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x60 kernel/kcov.c:202
Code: 2e 0f 1f 84 00 00 00 00 00 90 53 48 89 fb e8 17 00 00 00 48 8b 3d 80 fa 11 0c 48 89 de 5b e9 07 56 44 00 00 00 cc cc 00 00 cc <48> 8b 04 24 65 48 8b 0d 14 7d 89 7e 65 8b 15 15 7d 89 7e 81 e2 00
RSP: 0018:ffffc900000074b0 EFLAGS: 00000046
RAX: ffffffff814fa585 RBX: 0000000000000000 RCX: ffff88805f59bb80
RDX: 0000000000000100 RSI: ffffffff8a7a2a20 RDI: ffff88805f59bb80
RBP: 0000000000000001 R08: dffffc0000000000 R09: 1ffffffff203d218
R10: dffffc0000000000 R11: fffffbfff203d219 R12: dffffc0000000000
R13: ffff888065b8f3c0 R14: 0000000000000010 R15: ffff888065b8f4a8
FS:  00007f67b26426c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa0ad06cd58 CR3: 0000000022d63000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 rcu_lock_release+0xa/0x20 include/linux/rcupdate.h:318
 rcu_read_unlock include/linux/rcupdate.h:773 [inline]
 __task_pid_nr_ns+0x353/0x420 kernel/pid.c:501
 perf_event_pid_type kernel/events/core.c:1446 [inline]
 perf_event_pid kernel/events/core.c:1455 [inline]
 __perf_event_header__init_id+0x13c/0x4f0 kernel/events/core.c:7105
 perf_prepare_sample+0x158/0x1cb0 kernel/events/core.c:7624
 __perf_event_output kernel/events/core.c:7802 [inline]
 perf_event_output_forward+0x185/0x2e0 kernel/events/core.c:7822
 __perf_event_overflow+0x35f/0x550 kernel/events/core.c:9515
 perf_tp_event+0x324/0xbe0 kernel/events/core.c:10047
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10021
 perf_trace_preemptirq_template+0x2aa/0x360 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0x108/0x180 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 c2 22 9d 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007c60 EFLAGS: 00000206
RAX: bd9c8c14d3aafa00 RBX: 1ffff92000000f90 RCX: bd9c8c14d3aafa00
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a2a40
RBP: ffffc90000007d30 R08: ffffffff901e90cf R09: 1ffffffff203d219
R10: dffffc0000000000 R11: fffffbfff203d21a R12: ffffffff8c323400
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 rebalance_domains+0x88d/0x9b0 kernel/sched/fair.c:10660
 handle_softirqs+0x336/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 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:native_save_fl arch/x86/include/asm/irqflags.h:35 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:70 [inline]
RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:106 [inline]
RIP: 0010:lock_is_held_type+0x64/0x190 kernel/locking/lockdep.c:5662
Code: 00 00 00 65 48 8b 1d 9b 56 43 76 83 bb ec 0a 00 00 00 0f 85 df 00 00 00 41 89 f7 49 89 fe 48 c7 04 24 00 00 00 00 9c 8f 04 24 <4c> 8b 2c 24 fa 48 c7 c7 e0 39 2b 8a e8 4b 0e 00 00 65 ff 05 e4 5f
RSP: 0018:ffffc900031af1b8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff88805f59bb80 RCX: ffff88805f59bb80
RDX: 0000000000000010 RSI: 00000000ffffffff RDI: ffffffff8c31ef80
RBP: 00000000ffffffff R08: ffffc900031af36f R09: ffffc900031af360
R10: dffffc0000000000 R11: fffff52000635e6e R12: ffff8880b9000000
R13: ffffc900031af360 R14: ffffffff8c31ef80 R15: 00000000ffffffff
 lock_is_held include/linux/lockdep.h:287 [inline]
 schedule_debug kernel/sched/core.c:5621 [inline]
 __schedule+0x1e5/0x4350 kernel/sched/core.c:6286
 preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6799
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:put_cpu_partial+0x15e/0x190 mm/slub.c:2591
Code: 00 00 48 3b 44 24 08 75 4d 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 3f 72 01 08 41 f7 c5 00 02 00 00 74 c3 fb 4d 85 ff <75> c2 eb cb 48 c7 c7 30 24 3f 8c 4c 89 e6 e8 af 7e 4a 02 e9 e5 fe
RSP: 0018:ffffc900031af548 EFLAGS: 00000246
RAX: bd9c8c14d3aafa00 RBX: ffff888016c41500 RCX: bd9c8c14d3aafa00
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a2a40
RBP: 0000000000000001 R08: ffffffff901e90cf R09: 1ffffffff203d219
R10: dffffc0000000000 R11: fffffbfff203d21a R12: 0000000000000000
R13: 0000000000000286 R14: ffff8880b903dd30 R15: 0000000000000000
 qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xc0 mm/kasan/common.c:444
 kasan_slab_alloc include/linux/kasan.h:254 [inline]
 slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
 slab_alloc_node mm/slub.c:3225 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 __kmalloc_track_caller+0x187/0x330 mm/slub.c:4930
 kvasprintf+0xe3/0x1a0 lib/kasprintf.c:25
 kobject_set_name_vargs+0x5d/0x110 lib/kobject.c:297
 kobject_add_varg lib/kobject.c:392 [inline]
 kobject_init_and_add+0xeb/0x190 lib/kobject.c:481
 netdev_queue_add_kobject net/core/net-sysfs.c:1666 [inline]
 netdev_queue_update_kobjects+0x19c/0x3e0 net/core/net-sysfs.c:1711
 register_queue_kobjects net/core/net-sysfs.c:1772 [inline]
 netdev_register_kobject+0x273/0x320 net/core/net-sysfs.c:2018
 register_netdevice+0x10e8/0x1720 net/core/dev.c:10423
 tun_set_iff+0x847/0xdd0 drivers/net/tun.c:2805
 __tun_chr_ioctl+0x762/0x1f30 drivers/net/tun.c:3065
 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: 0033:0x7f67b43e9e99
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:00007f67b2642028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f67b4671fa0 RCX: 00007f67b43e9e99
RDX: 0000200000000180 RSI: 00000000400454ca RDI: 00000000000000c0
RBP: 00007f67b447feaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f67b4672038 R14: 00007f67b4671fa0 R15: 00007ffef5b3b0e8
 </TASK>

Crashes (14):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.