[v5.15] BUG: soft lockup in rtnetlink_rcv_msg

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c79648372d02 Linux 5.15.189
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=178332a2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9e47345638b85bd0
dashboard link: https://syzkaller.appspot.com/bug?extid=688a40542bb6692b42fe
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11c2c2a2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7ab49562317a/disk-c7964837.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e847ec1e38d3/vmlinux-c7964837.xz
kernel image: https://storage.googleapis.com/syzbot-assets/263158c6371c/Image-c7964837.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+688a40...@syzkaller.appspotmail.com

watchdog: BUG: soft lockup - CPU#0 stuck for 24s! [syz-executor:4166]
Modules linked in:
irq event stamp: 123296
hardirqs last enabled at (123295): [<ffff80000819dc64>] __local_bh_enable_ip+0x1f8/0x380 kernel/softirq.c:406
hardirqs last disabled at (123296): [<ffff8000111baf54>] enter_el1_irq_or_nmi+0x10/0x1c arch/arm64/kernel/entry-common.c:227
softirqs last enabled at (123294): [<ffff80000f706c28>] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:31
softirqs last disabled at (123288): [<ffff80000f706bf4>] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:18
CPU: 0 PID: 4166 Comm: syz-executor Not tainted 5.15.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : mutex_spin_on_owner+0x144/0x33c kernel/locking/mutex.c:364
lr : instrument_atomic_read include/linux/instrumented.h:71 [inline]
lr : atomic_long_read include/linux/atomic/atomic-instrumented.h:1183 [inline]
lr : __mutex_owner kernel/locking/mutex.c:78 [inline]
lr : mutex_spin_on_owner+0x264/0x33c kernel/locking/mutex.c:352
sp : ffff80001f117230
x29: ffff80001f117280 x28: ffff0000c761d1c0 x27: 1fffe0001814f370
x26: ffff0000c0a79b80 x25: ffff0000c0a79b6c x24: dfff800000000000
x23: 1ffff00002c53830 x22: ffff80001629c180 x21: ffff0000c0a79b40
x20: 1fffe00018ec3a38 x19: 1fffe0001814f36d x18: 0000000000000200
x17: 0000000000000000 x16: ffff8000111bc798 x15: 0000000000000001
x14: 00000000ffff8000 x13: 1ffff0000282e06b x12: 0000000000000001
x11: 1ffff00002c53830 x10: 0000000000000000 x9 : 0000000000000007
x8 : 0000000000000001 x7 : ffff8000082b6d34 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff8000082b6c50
x2 : 0000000000000000 x1 : 0000000000000008 x0 : 0000000000000001
Call trace:
mutex_spin_on_owner+0x144/0x33c kernel/locking/mutex.c:364
mutex_optimistic_spin+0x4c/0x2b0 kernel/locking/mutex.c:469
__mutex_lock_common+0x1b4/0x1edc kernel/locking/mutex.c:599
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
rtnl_lock net/core/rtnetlink.c:72 [inline]
rtnetlink_rcv_msg+0x98c/0xd04 net/core/rtnetlink.c:5647
netlink_rcv_skb+0x208/0x3c4 net/netlink/af_netlink.c:2507
rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:5668
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x624/0x8b0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x6e8/0x9cc net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
__sys_sendto+0x2e8/0x3d8 net/socket.c:2063
__do_sys_sendto net/socket.c:2075 [inline]
__se_sys_sendto net/socket.c:2071 [inline]
__arm64_sys_sendto+0xd8/0xf8 net/socket.c:2071
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584


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