[v6.6] INFO: rcu detected stall in kcm_ioctl

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3a8ababb8b6a Linux 6.6.101
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=102375a2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a2bd95b6de4839b7
dashboard link: https://syzkaller.appspot.com/bug?extid=f28e1c7468794afe771e
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ae2055ece513/disk-3a8ababb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/72f91e4de841/vmlinux-3a8ababb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3dae292c190e/bzImage-3a8ababb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f28e1c...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-....: (5 ticks this GP) idle=ea24/1/0x4000000000000000 softirq=12153/12153 fqs=2100
rcu: hardirqs softirqs csw/system
rcu: number: 8825008 0 0
rcu: cputime: 5492 47024 0 ==> 52500(ms)
rcu: (detected by 1, t=10502 jiffies, g=10161, q=2343 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6297 Comm: syz.2.137 Not tainted 6.6.101-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:check_preemption_disabled+0x42/0x110 lib/smp_processor_id.c:55
Code: 65 8b 05 2d 8c 96 75 65 8b 0d 22 8c 96 75 f7 c1 ff ff ff 7f 74 1f 65 48 8b 0c 25 28 00 00 00 48 3b 4c 24 08 0f 85 c4 00 00 00 <48> 83 c4 10 5b 41 5e 41 5f 5d c3 48 c7 04 24 00 00 00 00 9c 8f 04
RSP: 0018:ffffc900000072c8 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 58cce5e7c8d5ebdc RCX: db75b7ecc7de8c00
RDX: 0000000000000001 RSI: ffffffff8aaacbc0 RDI: ffffffff8afc6780
RBP: ffffc90000007410 R08: ffffffff8e4a84ef R09: 1ffffffff1c9509d
R10: dffffc0000000000 R11: fffffbfff1c9509e R12: ffff88801e7f0b08
R13: dffffc0000000000 R14: ffff88801e7f0ad0 R15: 1ffff92000000e6c
FS: 00007fd1251f66c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd1251d5d58 CR3: 000000005a055000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000200000000300 DR2: 0000200000000300
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
lockdep_recursion_finish kernel/locking/lockdep.c:467 [inline]
lock_release+0x538/0x8b0 kernel/locking/lockdep.c:5776
rcu_lock_release include/linux/rcupdate.h:344 [inline]
rcu_read_unlock include/linux/rcupdate.h:819 [inline]
__perf_event_output kernel/events/core.c:7969 [inline]
perf_event_output_forward+0x2f7/0x3a0 kernel/events/core.c:7978
__perf_event_overflow+0x447/0x630 kernel/events/core.c:9703
perf_swevent_overflow kernel/events/core.c:9779 [inline]
perf_swevent_event+0x2f5/0x5c0 kernel/events/core.c:-1
perf_tp_event+0x4f9/0x13a0 kernel/events/core.c:10329
perf_trace_run_bpf_submit+0xf4/0x1c0 kernel/events/core.c:10253
perf_trace_preemptirq_template+0x281/0x340 include/trace/events/preemptirq.h:14
trace_irq_enable+0xbf/0xe0 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x18/0x40 kernel/trace/trace_preemptirq.c:56
asm_sysvec_irq_work+0x1a/0x20 arch/x86/include/asm/idtentry.h:723
RIP: 0010:rcu_read_unlock_special+0x88/0x4c0 kernel/rcu/tree_plugin.h:682
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 a9 4e 93 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:ffffc90000007b00 EFLAGS: 00000206
RAX: db75b7ecc7de8c00 RBX: 1ffff92000000f68 RCX: db75b7ecc7de8c00
RDX: dffffc0000000000 RSI: ffffffff8aaaba40 RDI: ffffffff8afc6780
RBP: ffffc90000007c00 R08: ffffffff8e4a84ef R09: 1ffffffff1c9509d
R10: dffffc0000000000 R11: fffffbfff1c9509e R12: ffffffff8cd35400
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
__rcu_read_unlock+0x7c/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:818 [inline]
ieee80211_rx_napi+0x21d/0x3c0 net/mac80211/rx.c:5430
ieee80211_rx include/net/mac80211.h:4969 [inline]
ieee80211_handle_queued_frames+0x106/0x1a0 net/mac80211/main.c:319
tasklet_action_common+0x2eb/0x4c0 kernel/softirq.c:809
handle_softirqs+0x280/0x820 kernel/softirq.c:578
__do_softirq kernel/softirq.c:612 [inline]
invoke_softirq kernel/softirq.c:452 [inline]
__irq_exit_rcu+0xc7/0x190 kernel/softirq.c:661
irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:finish_task_switch+0x26a/0x920 kernel/sched/core.c:5255
Code: 0f 84 37 01 00 00 48 85 db 0f 85 56 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 40 6b 1a 09 e8 fb a3 2f 00 fb 4c 8b 65 c0 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc9000c2e7358 EFLAGS: 00000282
RAX: db75b7ecc7de8c00 RBX: 0000000000000000 RCX: db75b7ecc7de8c00
RDX: dffffc0000000000 RSI: ffffffff8aaaba40 RDI: ffffffff8afc6780
RBP: ffffc9000c2e73b0 R08: ffffffff8e4a84ef R09: 1ffffffff1c9509d
R10: dffffc0000000000 R11: fffffbfff1c9509e R12: ffff88801e7f0000
R13: dffffc0000000000 R14: ffff888022ae3c00 R15: ffff8880b8e3cf08
context_switch kernel/sched/core.c:5384 [inline]
__schedule+0x14da/0x44d0 kernel/sched/core.c:6700
preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867
preempt_schedule+0xab/0xc0 kernel/sched/core.c:6891
preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
_raw_spin_unlock_irqrestore+0xfa/0x110 kernel/locking/spinlock.c:194
__stack_depot_save+0x560/0x630 lib/stackdepot.c:439
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x5f/0x70 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:374 [inline]
__kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:383
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:721 [inline]
ref_tracker_alloc+0x134/0x460 lib/ref_tracker.c:203
__netns_tracker_alloc include/net/net_namespace.h:334 [inline]
netns_tracker_alloc include/net/net_namespace.h:343 [inline]
get_net_track include/net/net_namespace.h:360 [inline]
sk_alloc+0x1b3/0x360 net/core/sock.c:2159
kcm_clone net/kcm/kcmsock.c:1518 [inline]
kcm_ioctl+0x215/0xff0 net/kcm/kcmsock.c:1563
sock_do_ioctl+0xd7/0x2f0 net/socket.c:1222
sock_ioctl+0x623/0x7a0 net/socket.c:1341
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd126f8ebe9
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:00007fd1251f6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd1271b5fa0 RCX: 00007fd126f8ebe9
RDX: 0000000000000000 RSI: 00000000000089e2 RDI: 0000000000000010
RBP: 00007fd127011e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd1271b6038 R14: 00007fd1271b5fa0 R15: 00007ffcf83ed018
</TASK>


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.