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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cbb31f77b879 Linux 6.6.121
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1638a05a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2a950bf7c0bff9f9
dashboard link: https://syzkaller.appspot.com/bug?extid=e1911ff1021583c0e9b0
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/487f8544b25c/disk-cbb31f77.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/129a28b457e8/vmlinux-cbb31f77.xz
kernel image: https://storage.googleapis.com/syzbot-assets/47e034f9408f/bzImage-cbb31f77.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e1911f...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 1-....: (1 GPs behind) idle=9bac/1/0x4000000000000000 softirq=77692/77693 fqs=4298
rcu: hardirqs softirqs csw/system
rcu: number: 1193496 0 0
rcu: cputime: 20722 31767 73 ==> 52490(ms)
rcu: (t=10500 jiffies g=107269 q=1425 ncpus=2)
CPU: 1 PID: 19149 Comm: syz.1.4671 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:lock_acquire+0x208/0x420 kernel/locking/lockdep.c:5758
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3c 04 f8 0f 85 f0 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 43 c7 44 3c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc900001f0760 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 9430fd082032cc00
RDX: 0000000000000000 RSI: ffffffff8acada80 RDI: ffffffff8b1c80e0
RBP: ffffc900001f0880 R08: dffffc0000000000 R09: 1ffffffff2237cb8
R10: dffffc0000000000 R11: fffffbfff2237cb9 R12: 1ffff9200003e0f8
R13: ffff8880b8f3da98 R14: 0000000000000246 R15: dffffc0000000000
FS: 00007fb65ed406c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007feda9c1c440 CR3: 0000000039226000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
rt6_uncached_list_add net/ipv6/route.c:145 [inline]
icmp6_dst_alloc+0x2a2/0x400 net/ipv6/route.c:3334
ndisc_send_skb+0x44e/0x14f0 net/ipv6/ndisc.c:493
addrconf_rs_timer+0x2d5/0x630 net/ipv6/addrconf.c:4024
call_timer_fn+0x189/0x540 kernel/time/timer.c:1701
expire_timers kernel/time/timer.c:1752 [inline]
__run_timers+0x542/0x800 kernel/time/timer.c:2023
run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2036
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+0xd3/0x190 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/0x8f0 kernel/sched/core.c:5255
Code: 0f 84 33 01 00 00 48 85 db 0f 85 52 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 50 52 30 09 e8 0b 21 30 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:ffffc90003336ed8 EFLAGS: 00000286
RAX: 9430fd082032cc00 RBX: 0000000000000000 RCX: 9430fd082032cc00
RDX: dffffc0000000000 RSI: ffffffff8acac900 RDI: ffffffff8b1c80e0
RBP: ffffc90003336f30 R08: ffffffff911be50f R09: 1ffffffff2237ca1
R10: dffffc0000000000 R11: fffffbfff2237ca2 R12: ffff888028738000
R13: dffffc0000000000 R14: ffff888055dd5a00 R15: ffff8880b8f3cac8
context_switch kernel/sched/core.c:5384 [inline]
__schedule+0x155b/0x45a0 kernel/sched/core.c:6700
schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6833
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x6a9/0xcc0 kernel/locking/mutex.c:747
rtnl_lock net/core/rtnetlink.c:78 [inline]
rtnetlink_rcv_msg+0x811/0xfa0 net/core/rtnetlink.c:6469
netlink_rcv_skb+0x241/0x4d0 net/netlink/af_netlink.c:2545
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x751/0x8d0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x5ba/0x960 net/socket.c:2594
___sys_sendmsg+0x2a6/0x360 net/socket.c:2648
__sys_sendmsg net/socket.c:2677 [inline]
__do_sys_sendmsg net/socket.c:2686 [inline]
__se_sys_sendmsg+0x1c2/0x2b0 net/socket.c:2684
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb65dd9aeb9
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:00007fb65ed40028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fb65e015fa0 RCX: 00007fb65dd9aeb9
RDX: 0000000000000880 RSI: 0000200000000940 RDI: 0000000000000006
RBP: 00007fb65de08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb65e016038 R14: 00007fb65e015fa0 R15: 00007fffa6366138
</TASK>


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