INFO: rcu detected stall in __tun_chr_ioctl (2)

Status: upstream: reported on 2026/03/28 18:58
Reported-by: syzbot+d77d02a11256ce87187c@syzkaller.appspotmail.com
First crash: 156d, last: 7d05h
▶ ▼ 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 590d 665d 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 543d 543d 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 258d 282d 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 53d 60d 0/2 upstream: reported on 2026/07/02 11:58
linux-6.6 INFO: rcu detected stall in __tun_chr_ioctl 1 1 161d 161d 0/2 auto-obsoleted due to no activity on 2026/07/01 00:03
linux-5.15 INFO: rcu detected stall in __tun_chr_ioctl (2) 1 16 27d 281d 0/3 upstream: reported on 2025/11/23 13:35

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2627 jiffies s: 465501 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 21145 Comm: syz.3.16094 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:perf_prepare_sample+0x871/0x2020 kernel/events/core.c:7590
Code: 8b 06 8d 04 40 8d 1c c3 4c 8b 74 24 10 48 8b 44 24 28 42 0f b6 04 20 84 c0 0f 85 93 12 00 00 48 8b 44 24 08 66 01 18 4c 89 f6 <48> 81 e6 00 30 00 00 31 ff e8 d1 78 dd ff 4c 89 f0 48 25 00 30 00
RSP: 0018:ffffc900001dfd40 EFLAGS: 00000046
RAX: ffffffff81a4bbae RBX: ffffc900001dfee0 RCX: ffff88806508da00
RDX: 0000000000000100 RSI: 0000000000000004 RDI: 0000000000000000
RBP: ffffc900001dfe30 R08: ffffffff8fa27048 R09: ffffffff8fa27058
R10: ffffffff8fa27050 R11: ffffffff8fa27043 R12: dffffc0000000000
R13: 0000000000000004 R14: 0000000000000004 R15: ffffc900001e0180
FS:  00007f70e131e6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f53eedeb7c0 CR3: 000000007c3d6000 CR4: 00000000003506e0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 __perf_event_output kernel/events/core.c:7730 [inline]
 perf_event_output_forward+0x197/0x2f0 kernel/events/core.c:7750
 __perf_event_overflow+0x457/0x630 kernel/events/core.c:9496
 perf_swevent_overflow+0x19b/0x230 kernel/events/core.c:9579
 perf_swevent_event+0x458/0x570 kernel/events/core.c:-1
 perf_tp_event+0x36b/0xc10 kernel/events/core.c:10064
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10032
 perf_trace_preemptirq_template+0x268/0x320 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0xd3/0x140 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
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 12 7c 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc900001e05a0 EFLAGS: 00000206
RAX: 58241eebbd57e200 RBX: 1ffff9200003c0bc RCX: 58241eebbd57e200
RDX: dffffc0000000000 RSI: ffffffff8a8c1820 RDI: ffffffff8adf6120
RBP: ffffc900001e0690 R08: ffffffff90b1224f R09: 1ffffffff2162449
R10: dffffc0000000000 R11: fffffbfff216244a R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8f3bb00 R15: 0000000000000002
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 is_bpf_text_address+0x27a/0x2a0 kernel/bpf/core.c:738
 kernel_text_address+0x9c/0xd0 kernel/extable.c:125
 __kernel_text_address+0x9/0x30 kernel/extable.c:79
 unwind_get_return_address+0x49/0x80 arch/x86/kernel/unwind_orc.c:323
 arch_stack_walk+0xf2/0x140 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 kmem_cache_free+0xf7/0x2a0 mm/slub.c:3709
 rcu_do_batch kernel/rcu/tree.c:2297 [inline]
 rcu_core+0x9a3/0x1740 kernel/rcu/tree.c:2557
 handle_softirqs+0x291/0x910 kernel/softirq.c:596
 __do_softirq kernel/softirq.c:630 [inline]
 invoke_softirq kernel/softirq.c:470 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:put_cpu_partial+0x1b0/0x250 mm/slub.c:2666
Code: 3b 44 24 18 0f 85 b4 00 00 00 48 83 c4 20 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 dc 06 5e 08 f7 c5 00 02 00 00 74 c0 fb 4d 85 e4 <75> bf eb c8 e8 87 d0 3f 02 85 c0 0f 84 e9 fe ff ff 83 3d 60 54 4e
RSP: 0018:ffffc90005baf758 EFLAGS: 00000246
RAX: 58241eebbd57e200 RBX: ffff888017442140 RCX: 58241eebbd57e200
RDX: dffffc0000000000 RSI: ffffffff8a8c1820 RDI: ffffffff8adf6120
RBP: 0000000000000282 R08: ffffffff90b1224f R09: 1ffffffff2162449
R10: dffffc0000000000 R11: fffffbfff216244a R12: 0000000000000000
R13: 0000000000000001 R14: ffff88806508da00 R15: ffff8880b8f3ea80
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x490 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 slab_alloc mm/slub.c:3367 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3374 [inline]
 kmem_cache_alloc+0x18b/0x2f0 mm/slub.c:3383
 kmem_cache_zalloc include/linux/slab.h:689 [inline]
 __kernfs_new_node+0xe1/0x7f0 fs/kernfs/dir.c:614
 kernfs_new_node+0x148/0x250 fs/kernfs/dir.c:690
 kernfs_create_link+0xa3/0x200 fs/kernfs/symlink.c:39
 sysfs_do_create_link_sd+0x83/0x110 fs/sysfs/symlink.c:44
 device_add_class_symlinks drivers/base/core.c:3419 [inline]
 device_add+0x641/0x1050 drivers/base/core.c:3645
 netdev_register_kobject+0x184/0x320 net/core/net-sysfs.c:2013
 register_netdevice+0x133a/0x1b80 net/core/dev.c:10243
 tun_set_iff+0x82b/0xea0 drivers/net/tun.c:2854
 __tun_chr_ioctl+0x770/0x1ed0 drivers/net/tun.c:3117
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f70e039e0d9
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:00007f70e131e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f70e0625fa0 RCX: 00007f70e039e0d9
RDX: 0000200000000080 RSI: 00000000400454ca RDI: 0000000000000066
RBP: 00007f70e0435024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f70e0626038 R14: 00007f70e0625fa0 R15: 00007ffe35a6a258
 </TASK>

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/24 15:21 linux-6.1.y 05208478041c b55bd4c3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/08/22 06:40 linux-6.1.y 7e6e67054721 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/06/21 03:24 linux-6.1.y fdb6fcb41cc7 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/06/13 06:25 linux-6.1.y 228da13e907e 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/05/13 16:16 linux-6.1.y ad16b162f21d fec2a7ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/04/18 21:34 linux-6.1.y 7c87defbd336 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2026/03/28 18:58 linux-6.1.y 1989cd3d56e2 b5ceaad2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
* Struck through repros no longer work on HEAD.