[v6.1] INFO: rcu detected stall in __tun_chr_ioctl

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f6e38ae624cf Linux 6.1.158
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1547d97c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7eb38bd5021fec61
dashboard link: https://syzkaller.appspot.com/bug?extid=9880bfcee0c54e33bf3b
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0d8305ca1c94/disk-f6e38ae6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8bc85383c07b/vmlinux-f6e38ae6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d337081bce56/bzImage-f6e38ae6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9880bf...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 2675 jiffies s: 300457 root: 0x1/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6117 Comm: syz.3.10976 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:check_kcov_mode kernel/kcov.c:182 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:245 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp8+0x13/0x80 kernel/kcov.c:320
Code: 11 08 05 00 00 00 48 89 7c 11 10 48 89 74 11 18 48 89 44 11 20 c3 90 48 8b 04 24 65 48 8b 0d f4 94 81 7e 65 8b 15 f5 94 81 7e <81> e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 57 83 b9 1c 16 00 00
RSP: 0018:ffffc90000006fe8 EFLAGS: 00000046
RAX: ffffffff81a2db92 RBX: 0000000000000000 RCX: ffff88802f2fbb80
RDX: 0000000000000102 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000007340 R08: dffffc0000000000 R09: ffffc90000007180
R10: fffff52000000e37 R11: 1ffff92000000e30 R12: ffffc900000071e6
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff888065f98c00
FS: 00007fb2a03416c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555869a4808 CR3: 0000000053741000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000200000000300 DR2: 0000200000000300
DR3: 0000200000000300 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
__perf_event_header__init_id+0x3b2/0x530 kernel/events/core.c:7025
perf_prepare_sample+0x18b/0x2040 kernel/events/core.c:7536
__perf_event_output kernel/events/core.c:7730 [inline]
perf_event_output_forward+0x163/0x2a0 kernel/events/core.c:7750
__perf_event_overflow+0x448/0x610 kernel/events/core.c:9496
perf_tp_event+0x335/0xb60 kernel/events/core.c:10029
perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10002
perf_trace_preemptirq_template+0x287/0x330 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+0x84/0x500 kernel/rcu/tree_plugin.h:685
Code: f1 f1 f1 00 f2 f2 f2 4a 89 04 2b 66 42 c7 44 2b 09 f3 f3 42 c6 44 2b 0b f3 65 44 8b 35 ed 90 96 7e 41 f7 c6 00 00 f0 00 74 45 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 66 42 c7 44 2b
RSP: 0018:ffffc90000007760 EFLAGS: 00000206
RAX: 50ac0c7265ef5b00 RBX: 1ffff92000000ef4 RCX: 50ac0c7265ef5b00
RDX: dffffc0000000000 RSI: ffffffff8a8c0580 RDI: ffffffff8adef760
RBP: ffffc90000007860 R08: dffffc0000000000 R09: fffffbfff215c467
R10: fffffbfff215c467 R11: 1ffffffff215c466 R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8e3b900 R15: 0000000000000001
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
ndisc_send_skb+0xda7/0x1510 net/ipv6/ndisc.c:521
addrconf_rs_timer+0x2b8/0x600 net/ipv6/addrconf.c:3979
call_timer_fn+0x1a0/0x670 kernel/time/timer.c:1700
expire_timers kernel/time/timer.c:1751 [inline]
__run_timers+0x529/0x7d0 kernel/time/timer.c:2022
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2035
handle_softirqs+0x2a1/0x920 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x12f/0x220 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:unwind_next_frame+0x688/0x20b0 arch/x86/kernel/unwind_orc.c:475
Code: 49 0f bf 04 24 48 01 c5 e9 fa 00 00 00 4c 8d 7b 40 4c 89 f8 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 ff e8 2b 9a 98 00 49 8b 17 <4d> 8d 7c 24 01 4c 89 e0 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 cc
RSP: 0018:ffffc90004226fb0 EFLAGS: 00000246
RAX: 1ffff92000844e19 RBX: ffffc90004227088 RCX: ffffffff8e7f92c0
RDX: ffffc90004227d00 RSI: ffffffff8e7f92bc RDI: ffffffff8138655f
RBP: ffffffff8f1797c0 R08: 0000000000000001 R09: 0000000000000014
R10: fffff52000844e1d R11: 1ffff92000844e1b R12: ffffffff8f1797bc
R13: dffffc0000000000 R14: ffffffff8e7f92bc R15: ffffc900042270c8
arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0x98/0xe0 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
kasan_save_free_info+0x2d/0x50 mm/kasan/generic.c:516
____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1729 [inline]
slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1755
slab_free mm/slub.c:3687 [inline]
__kmem_cache_free+0xb6/0x1f0 mm/slub.c:3700
memcg_free_slab_cgroups mm/slab.h:456 [inline]
unaccount_slab mm/slab.h:645 [inline]
__free_slab+0xcb/0x300 mm/slub.c:2020
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:305
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook+0x4b/0x480 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+0x123/0x2f0 mm/slub.c:3383
kmem_cache_zalloc include/linux/slab.h:689 [inline]
__kernfs_new_node+0xd4/0x7d0 fs/kernfs/dir.c:614
kernfs_new_node+0x148/0x250 fs/kernfs/dir.c:690
__kernfs_create_file+0x47/0x2e0 fs/kernfs/file.c:1068
sysfs_add_file_mode_ns+0x234/0x2f0 fs/sysfs/file.c:294
create_files fs/sysfs/group.c:64 [inline]
internal_create_group+0x487/0xce0 fs/sysfs/group.c:148
internal_create_groups fs/sysfs/group.c:188 [inline]
sysfs_create_groups+0x55/0x120 fs/sysfs/group.c:214
device_add_groups drivers/base/core.c:2752 [inline]
device_add_attrs+0x1ae/0x800 drivers/base/core.c:2911
device_add+0x64b/0xfb0 drivers/base/core.c:3648
netdev_register_kobject+0x176/0x310 net/core/net-sysfs.c:2013
register_netdevice+0x12b9/0x1aa0 net/core/dev.c:10204
tun_set_iff+0x848/0xed0 drivers/net/tun.c:2851
__tun_chr_ioctl+0x730/0x1e10 drivers/net/tun.c:3114
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:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb29f58f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb2a0341038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fb29f7e5fa0 RCX: 00007fb29f58f749
RDX: 00002000000000c0 RSI: 00000000400454ca RDI: 000000000000000a
RBP: 00007fb29f613f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb29f7e6038 R14: 00007fb29f7e5fa0 R15: 00007ffc74c19fd8
</TASK>


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