[v6.1] BUG: soft lockup in tipc_disc_timeout

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3369c6df2fae Linux 6.1.146
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14ab37d4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=aafe227a6f76c0c3
dashboard link: https://syzkaller.appspot.com/bug?extid=c2f8826cba2c5fd3c982
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c6c6f55858e8/disk-3369c6df.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a99117bdae3d/vmlinux-3369c6df.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9ca71d7a5035/Image-3369c6df.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c2f882...@syzkaller.appspotmail.com

watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [ksoftirqd/1:21]
Modules linked in:
irq event stamp: 1290461
hardirqs last enabled at (1290460): [<ffff8000083b94f4>] seqcount_lockdep_reader_access include/linux/seqlock.h:104 [inline]
hardirqs last enabled at (1290460): [<ffff8000083b94f4>] timekeeping_get_delta kernel/time/timekeeping.c:254 [inline]
hardirqs last enabled at (1290460): [<ffff8000083b94f4>] timekeeping_get_ns+0x124/0x3b8 kernel/time/timekeeping.c:388
hardirqs last disabled at (1290461): [<ffff800011944e78>] __el1_irq arch/arm64/kernel/entry-common.c:468 [inline]
hardirqs last disabled at (1290461): [<ffff800011944e78>] el1_interrupt+0x24/0x54 arch/arm64/kernel/entry-common.c:486
softirqs last enabled at (898206): [<ffff8000081a9670>] softirq_handle_end kernel/softirq.c:439 [inline]
softirqs last enabled at (898206): [<ffff8000081a9670>] handle_softirqs+0xaf8/0xc6c kernel/softirq.c:624
softirqs last disabled at (898211): [<ffff8000081abf10>] run_ksoftirqd+0x7c/0x2a0 kernel/softirq.c:963
CPU: 1 PID: 21 Comm: ksoftirqd/1 Not tainted 6.1.146-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : check_kcov_mode kernel/kcov.c:182 [inline]
pc : __sanitizer_cov_trace_pc+0x54/0x94 kernel/kcov.c:216
lr : cake_drop net/sched/sch_cake.c:1574 [inline]
lr : cake_enqueue+0x3344/0x6880 net/sched/sch_cake.c:1945
sp : ffff80001c926df0
x29: ffff80001c927260 x28: 1fffe0001b4ac85b x27: ffff000100300000
x26: 00000000000179a8 x25: ffff0000da5642d8 x24: ffff0000da5602d0
x23: ffff80001c9273c0 x22: dfff800000000000 x21: ffff0000da5602c0
x20: 0000000000000000 x19: 00000000000004e3 x18: 0000000031db878b
x17: ffff8000181e7000 x16: ffff8000082d2400 x15: ffff800017cc7fc0
x14: ffff0000c0a52658 x13: 1ffff00002a160b1 x12: 0000000000ff0100
x11: ff0080000ffa688c x10: 0000000000000301 x9 : ffff80000ffa688c
x8 : ffff0000c0a51bc0 x7 : ffff8000083b9900 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : 0000000000000002 x1 : 00000000000004e3 x0 : 00000000000004e3
Call trace:
check_kcov_mode kernel/kcov.c:182 [inline]
__sanitizer_cov_trace_pc+0x54/0x94 kernel/kcov.c:216
qdisc_enqueue include/net/sch_generic.h:816 [inline]
netem_dequeue+0xa74/0x107c net/sched/sch_netem.c:737
dequeue_skb net/sched/sch_generic.c:292 [inline]
qdisc_restart net/sched/sch_generic.c:397 [inline]
__qdisc_run+0x1c4/0x1368 net/sched/sch_generic.c:415
__dev_xmit_skb net/core/dev.c:3958 [inline]
__dev_queue_xmit+0xc18/0x309c net/core/dev.c:4300
dev_queue_xmit include/linux/netdevice.h:3051 [inline]
tipc_l2_send_msg+0x29c/0x35c net/tipc/bearer.c:518
tipc_bearer_xmit_skb+0x244/0x384 net/tipc/bearer.c:577
tipc_disc_timeout+0x4c8/0x608 net/tipc/discover.c:338
call_timer_fn+0x1b8/0x964 kernel/time/timer.c:1504
expire_timers kernel/time/timer.c:1549 [inline]
__run_timers+0x460/0x6bc kernel/time/timer.c:1820
run_timer_softirq+0x7c/0x114 kernel/time/timer.c:1833
handle_softirqs+0x318/0xc6c kernel/softirq.c:596
run_ksoftirqd+0x7c/0x2a0 kernel/softirq.c:963
smpboot_thread_fn+0x4b0/0x964 kernel/smpboot.c:164
kthread+0x250/0x2d8 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:849


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[syzbot]

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