[v6.6] INFO: task hung in ip_tunnel_init_net

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8b73de7da85f Linux 6.6.156
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1651baf9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7be9809cedd6b69c
dashboard link: https://syzkaller.appspot.com/bug?extid=666b424bdc01e7afd243
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d7e87682fef0/disk-8b73de7d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/096830afc063/vmlinux-8b73de7d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/89c175e4560d/bzImage-8b73de7d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+666b42...@syzkaller.appspotmail.com

INFO: task syz-executor:26922 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor state:D stack:25000 pid:26922 ppid:1 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5382 [inline]
__schedule+0x15ae/0x4660 kernel/sched/core.c:6701
schedule+0xbd/0x170 kernel/sched/core.c:6775
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6834
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
ip_tunnel_init_net+0x2d2/0x7c0 net/ipv4/ip_tunnel.c:1103
ops_init+0x391/0x640 net/core/net_namespace.c:139
setup_net+0x3b6/0xa20 net/core/net_namespace.c:343
copy_net_ns+0x35e/0x5d0 net/core/net_namespace.c:520
create_new_namespaces+0x3ce/0x700 kernel/nsproxy.c:110
unshare_nsproxy_namespaces+0x11a/0x160 kernel/nsproxy.c:228
ksys_unshare+0x4fa/0x8f0 kernel/fork.c:3444
__do_sys_unshare kernel/fork.c:3518 [inline]
__se_sys_unshare kernel/fork.c:3516 [inline]
__x64_sys_unshare+0x38/0x40 kernel/fork.c:3516
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f4fca39f427
RSP: 002b:00007ffc1dee3c38 EFLAGS: 00000202 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007f4fca625f40 RCX: 00007f4fca39f427
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 00007f4fca6267b8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000008
R13: 0000000000000003 R14: 00007ffc1dee3e78 R15: 0000000000000000
</TASK>
INFO: task syz-executor:26985 blocked for more than 150 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor state:D stack:25384 pid:26985 ppid:1 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5382 [inline]
__schedule+0x15ae/0x4660 kernel/sched/core.c:6701
schedule+0xbd/0x170 kernel/sched/core.c:6775
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6834
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
rtnl_lock net/core/rtnetlink.c:78 [inline]
rtnetlink_rcv_msg+0x7ed/0xf90 net/core/rtnetlink.c:6481
netlink_rcv_skb+0x235/0x4c0 net/netlink/af_netlink.c:2550
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x7b1/0x930 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
__sys_sendto+0x4a9/0x6b0 net/socket.c:2201


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