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: 293d, last: 2d14h
▶ ▼ 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 602d 677d 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 555d 555d 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 270d 294d 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 65d 72d 0/2 upstream: reported on 2026/07/02 11:58
linux-6.6 INFO: rcu detected stall in __tun_chr_ioctl 1 1 173d 173d 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 7 19d 168d 0/3 upstream: reported on 2026/03/28 18:58

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-....: (1 GPs behind) idle=f1d/1/0x4000000000000002 softirq=12688/12689 fqs=2099 
	(detected by 1, t=10502 jiffies, g=16253, q=1152)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6158 Comm: syz.6.387 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:perf_swevent_event+0x6b/0x540 kernel/events/core.c:-1
Code: 00 00 00 48 89 d8 48 c1 e8 03 80 3c 08 00 74 08 48 89 df e8 07 b6 25 00 48 8b 1b 31 ff 48 89 de e8 0a 8c e0 ff 48 85 db 74 5b <48> 8b 04 24 48 8d 98 f0 00 00 00 48 89 d8 48 c1 e8 03 48 b9 00 00
RSP: 0000:ffffc900000075e8 EFLAGS: 00000006
RAX: ffffffff81988776 RBX: 0000000000000005 RCX: ffff88801ec55940
RDX: 0000000000000100 RSI: 0000000000000005 RDI: 0000000000000000
RBP: ffffc900000076c0 R08: ffffffff8d8b122f R09: 1ffffffff1b16245
R10: dffffc0000000000 R11: fffffbfff1b16246 R12: 0000000000000001
R13: ffff8880b90351c8 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f05ae4d06c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffa4 CR3: 000000005b1bd000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 perf_tp_event+0x324/0xbe0 kernel/events/core.c:10057
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10031
 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 f2 0f 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: 0000:ffffc90000007b00 EFLAGS: 00000206
RAX: 460fd893ae605c00 RBX: 1ffff92000000f64 RCX: 460fd893ae605c00
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a4540
RBP: ffffc90000007bd8 R08: ffffffff901ef0cf R09: 1ffffffff203de19
R10: dffffc0000000000 R11: fffffbfff203de1a 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]
 ieee80211_iterate_active_interfaces_atomic+0x132/0x140 net/mac80211/util.c:831
 mac80211_hwsim_beacon+0x9b/0x180 drivers/net/wireless/mac80211_hwsim.c:1865
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4ea/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_run_softirq+0x176/0x240 kernel/time/hrtimer.c:1766
 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:device_add_attrs+0x85/0x690 drivers/base/core.c:2640
Code: 74 40 4d 8d 66 18 4c 89 e0 48 c1 e8 03 80 3c 28 00 74 08 4c 89 e7 e8 7a 0c e5 fc 49 8b 34 24 48 89 df e8 7e e0 14 fd 41 89 c5 <31> ff 89 c6 e8 f2 e1 9f fc 45 85 ed 74 5d e8 88 de 9f fc e9 e3 04
RSP: 0000:ffffc90002e9fae8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff888061234608 RCX: 0000000000080000
RDX: ffffc90015cb2000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: dffffc0000000000 R08: ffff88801a1849fb R09: 1ffff1100343093f
R10: dffffc0000000000 R11: ffffed1003430940 R12: ffffffff8be46eb8
R13: 0000000000000000 R14: ffffffff8be46ea0 R15: 0000000000000000
 device_add+0x677/0x1050 drivers/base/core.c:3363
 netdev_register_kobject+0x184/0x320 net/core/net-sysfs.c:2014
 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: 0033:0x7f05b0278159
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:00007f05ae4d0028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f05b04fffa0 RCX: 00007f05b0278159
RDX: 0000200000000080 RSI: 00000000400454ca RDI: 0000000000000004
RBP: 00007f05b030f03b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f05b0500038 R14: 00007f05b04fffa0 R15: 00007ffe205dabe8
 </TASK>

Crashes (18):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.