[v6.1] INFO: rcu detected stall in inet6_ioctl

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 779f9571ac3e Linux 6.1.164
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=102c3794580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=8d034ddbd850b337f6c9
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d8bc7a0c33a8/disk-779f9571.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/870b0bf266c7/vmlinux-779f9571.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ce1e3301c41d/bzImage-779f9571.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8d034d...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2691 jiffies s: 265917 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: 9918 Comm: syz.4.10184 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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_cmp4+0x23/0x80 kernel/kcov.c:313
Code: 48 89 44 11 20 c3 90 48 8b 04 24 65 48 8b 15 b4 f6 7f 7e 65 8b 0d b5 f6 7f 7e 81 e1 00 01 ff 00 74 11 81 f9 00 01 00 00 75 5b <83> ba 1c 16 00 00 00 74 52 8b 8a f8 15 00 00 83 f9 03 75 47 48 8b
RSP: 0018:ffffc900001e0878 EFLAGS: 00000046
RAX: ffffffff818a8ca6 RBX: 0000000000000014 RCX: 0000000000000100
RDX: ffff888044d19dc0 RSI: 0000000000000001 RDI: 0000000000000008
RBP: 0000000000000001 R08: ffffffff8e1fcd2f R09: 1ffffffff1c3f9a5
R10: dffffc0000000000 R11: fffffbfff1c3f9a6 R12: 0000000000000001
R13: 0000000000000001 R14: ffffc900001e0900 R15: 00000000000000a8
FS: 00007fdd97ca66c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6cb4f456b8 CR3: 000000006779c000 CR4: 00000000003506e0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000200000000300
DR3: 0000200000000300 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
perf_trace_buf_alloc+0xc6/0x300 kernel/trace/trace_event_perf.c:419
perf_trace_preemptirq_template+0x143/0x320 include/trace/events/preemptirq.h:14
trace_irq_disable include/trace/events/preemptirq.h:36 [inline]
trace_hardirqs_off_finish+0x13f/0x180 kernel/trace/trace_preemptirq.c:67
irqentry_enter+0x33/0x50 kernel/entry/common.c:382
sysvec_irq_work+0xa/0xc0 arch/x86/kernel/irq_work.c:17
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 92 31 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:ffffc900001e0aa0 EFLAGS: 00000206
RAX: 0ea7ecb1164bdd00 RBX: 1ffff9200003c15c RCX: 0ea7ecb1164bdd00
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0de0
RBP: ffffc900001e0b90 R08: ffffffff90af524f R09: 1ffffffff215ea49
R10: dffffc0000000000 R11: fffffbfff215ea4a R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8f3b900 R15: 0000000000000002
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
ieee80211_iterate_active_interfaces_atomic+0x156/0x170 net/mac80211/util.c:826
mac80211_hwsim_beacon+0xb7/0x1b0 drivers/net/wireless/mac80211_hwsim.c:2147
__run_hrtimer kernel/time/hrtimer.c:1747 [inline]
__hrtimer_run_queues+0x560/0xd70 kernel/time/hrtimer.c:1811
hrtimer_run_softirq+0x183/0x2a0 kernel/time/hrtimer.c:1828
handle_softirqs+0x2a1/0x930 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:__raw_callee_save___kvm_vcpu_is_preempted+0xf/0x20
Code: be 03 00 00 00 e8 11 c5 00 03 bf 21 10 01 c0 be 0e 00 00 00 e9 02 c5 00 03 00 00 48 8b 04 fd 80 f9 64 8c 80 b8 50 74 02 00 00 <0f> 95 c0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 55 48 89 e5 41
RSP: 0018:ffffc90003b2f800 EFLAGS: 00000246
RAX: ffff8880b8e00000 RBX: 0000000000000000 RCX: ffffffff8163a0db
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000000
RBP: 1ffffffff1ba8c78 R08: ffffffff8dd463c7 R09: 1ffffffff1ba8c78
R10: dffffc0000000000 R11: fffffbfff1ba8c79 R12: ffffffff8dd463c0
R13: ffffffff8dd46410 R14: dffffc0000000000 R15: ffff888081b68000
pv_vcpu_is_preempted arch/x86/include/asm/paravirt.h:613 [inline]
vcpu_is_preempted arch/x86/include/asm/qspinlock.h:63 [inline]
owner_on_cpu include/linux/sched.h:2291 [inline]
mutex_spin_on_owner+0x196/0x350 kernel/locking/mutex.c:373
mutex_optimistic_spin kernel/locking/mutex.c:476 [inline]
__mutex_lock_common kernel/locking/mutex.c:607 [inline]
__mutex_lock+0x187/0xaf0 kernel/locking/mutex.c:747
ipv6_route_ioctl+0x31e/0x500 net/ipv6/route.c:4511
inet6_ioctl+0x207/0x280 net/ipv6/af_inet6.c:586
sock_do_ioctl+0xfb/0x320 net/socket.c:1201
sock_ioctl+0x4d2/0x710 net/socket.c:1320
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: 0033:0x7fdd96d9c799
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:00007fdd97ca6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fdd97015fa0 RCX: 00007fdd96d9c799
RDX: 0000200000000000 RSI: 000000000000890b RDI: 000000000000000e
RBP: 00007fdd96e32bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdd97016038 R14: 00007fdd97015fa0 R15: 00007fffafd627c8
</TASK>


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