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: 262d, last: 9d00h
▶ ▼ 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 571d 646d 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 524d 524d 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 239d 263d 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 34d 41d 0/2 upstream: reported on 2026/07/02 11:58
linux-6.6 INFO: rcu detected stall in __tun_chr_ioctl 1 1 143d 143d 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 52d 137d 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=edb/1/0x4000000000000002 softirq=54848/54849 fqs=2100 
	(detected by 1, t=10505 jiffies, g=78721, q=267)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 19267 Comm: syz.3.5518 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:__perf_event_overflow+0x424/0x550 kernel/events/core.c:9523
Code: 00 48 81 c3 38 04 00 00 48 89 df e8 a6 83 ec ff eb 10 e8 bf ab e0 ff 4c 8b 34 24 eb 05 e8 b4 ab e0 ff 44 89 f0 48 83 c4 20 5b <41> 5c 41 5d 41 5e 41 5f 5d c3 e8 9d ab e0 ff 45 31 f6 eb e4 89 c1
RSP: 0018:ffffc90000007150 EFLAGS: 00000086
RAX: 0000000000000000 RBX: ffff8880b9035250 RCX: ffff888025398000
RDX: 0000000000000100 RSI: ffffffff8a2b3e80 RDI: ffff88805a74fa40
RBP: ffff88805a74fbd0 R08: ffffffff8d8b0def R09: 1ffffffff1b161bd
R10: dffffc0000000000 R11: fffffbfff1b161be R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88805a74fb78
FS:  00007fa7cc8ff6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1583bf1000 CR3: 000000004a609000 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: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 02 20 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:ffffc90000007640 EFLAGS: 00000206
RAX: e98731c28d245300 RBX: 1ffff92000000ecc RCX: e98731c28d245300
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a4200
RBP: ffffc90000007710 R08: ffffffff901ee15f R09: 1ffffffff203dc2b
R10: dffffc0000000000 R11: fffffbfff203dc2c 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]
 ip6_route_output_flags+0x1e9/0x300 net/ipv6/route.c:2648
 ip6_route_output include/net/ip6_route.h:98 [inline]
 icmpv6_rt_has_prefsrc+0x4f/0x390 net/ipv6/icmp.c:246
 icmp6_send+0xcbc/0x19a0 net/ipv6/icmp.c:562
 __icmpv6_send include/linux/icmpv6.h:28 [inline]
 icmpv6_send include/linux/icmpv6.h:49 [inline]
 ip6_link_failure+0x35/0x490 net/ipv6/route.c:2789
 dst_link_failure include/net/dst.h:422 [inline]
 ndisc_error_report+0x10e/0x150 net/ipv6/ndisc.c:717
 neigh_invalidate+0x23b/0x460 net/core/neighbour.c:1001
 neigh_timer_handler+0x90d/0xff0 net/core/neighbour.c:1088
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x56c/0x810 kernel/time/timer.c:1970
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
 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:memset+0x2b/0x40 mm/kasan/shadow.c:47
Code: 41 56 53 48 89 d3 89 f5 49 89 fe 48 8b 4c 24 18 48 89 d6 ba 01 00 00 00 e8 12 ef ff ff 84 c0 74 11 4c 89 f7 89 ee 48 89 da 5b <41> 5e 5d e9 0d ad 50 02 31 c0 5b 41 5e 5d c3 66 0f 1f 44 00 00 41
RSP: 0018:ffffc900022a77c8 EFLAGS: 00000202
RAX: f2f2f2f8f1f1f101 RBX: ffff88806215d490 RCX: ffffffff815cb728
RDX: 0000000000000010 RSI: 0000000000000000 RDI: ffff88806215d498
RBP: 0000000000000000 R08: ffff88806215d4a7 R09: 1ffff1100c42ba94
R10: dffffc0000000000 R11: ffffed100c42ba95 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff88806215d498 R15: ffffffff8d459db8
 lockdep_init_map_type+0x98/0x900 kernel/locking/lockdep.c:4767
 lockdep_init_map_waits include/linux/lockdep.h:195 [inline]
 lockdep_init_map_wait include/linux/lockdep.h:202 [inline]
 lockdep_init_map include/linux/lockdep.h:208 [inline]
 __kernfs_create_file+0x10a/0x2e0 fs/kernfs/file.c:997
 sysfs_add_file_mode_ns+0x2d2/0x390 fs/sysfs/file.c:321
 create_files fs/sysfs/group.c:64 [inline]
 internal_create_group+0x492/0xd00 fs/sysfs/group.c:149
 internal_create_groups fs/sysfs/group.c:189 [inline]
 sysfs_create_groups+0x55/0x120 fs/sysfs/group.c:215
 device_add_groups drivers/base/core.c:2491 [inline]
 device_add_attrs+0x12f/0x690 drivers/base/core.c:2650
 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: 0033:0x7fa7ce6a7019
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:00007fa7cc8ff028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa7ce92efa0 RCX: 00007fa7ce6a7019
RDX: 00002000000000c0 RSI: 00000000400454ca RDI: 0000000000000006
RBP: 00007fa7ce73e00c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa7ce92f038 R14: 00007fa7ce92efa0 R15: 00007ffeb4c9dcb8
 </TASK>

Crashes (16):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.