[v5.15] WARNING in dst_release

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 91d48252ad4b Linux 5.15.202
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10477360580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=3d1454ccef42e43b13f8
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/74e75dfcb812/disk-91d48252.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bfa72aab00f2/vmlinux-91d48252.xz
kernel image: https://storage.googleapis.com/syzbot-assets/47ea72d1c7dc/bzImage-91d48252.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3d1454...@syzkaller.appspotmail.com

batman_adv: Cannot find parent device
------------[ cut here ]------------
dst_release underflow
WARNING: CPU: 0 PID: 12765 at net/core/dst.c:172 dst_release+0x15a/0x180 net/core/dst.c:172
Modules linked in:
CPU: 0 PID: 12765 Comm: syz.3.18675 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:dst_release+0x15a/0x180 net/core/dst.c:172
Code: 8b 48 89 da 44 89 f1 5b 41 5e 41 5f 5d e9 1e 15 cb 01 e8 59 74 92 f9 c6 05 30 91 8f 05 01 48 c7 c7 a0 5b 1f 8b e8 96 cc ca 01 <0f> 0b e9 0b ff ff ff 44 89 f1 80 e1 07 fe c1 38 c1 0f 8c 41 ff ff
RSP: 0018:ffffc9000454edb8 EFLAGS: 00010246
RAX: 368615de3c571e00 RBX: ffff888060d8bb40 RCX: 0000000000080000
RDX: ffffc900053c9000 RSI: 000000000000916e RDI: 000000000000916f
RBP: 000000000000002c R08: ffff8880b902795b R09: 1ffff11017204f2b
R10: dffffc0000000000 R11: ffffed1017204f2c R12: ffff88804c4460d6
R13: 0000000000000001 R14: 00000000ffffffff R15: 1ffff11009888d95
FS: 00007f60d476c6c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff84ab52158 CR3: 000000006307a000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
ip6gre_tnl_link_config net/ipv6/ip6_gre.c:1199 [inline]
ip6gre_newlink+0x3c6/0x530 net/ipv6/ip6_gre.c:2045
__rtnl_newlink net/core/rtnetlink.c:3526 [inline]
rtnl_newlink+0x1359/0x1a50 net/core/rtnetlink.c:3574
rtnetlink_rcv_msg+0x844/0xf30 net/core/rtnetlink.c:5684
netlink_rcv_skb+0x1f5/0x440 net/netlink/af_netlink.c:2507
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x774/0x920 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
____sys_sendmsg+0x5b7/0x8f0 net/socket.c:2445
___sys_sendmsg+0x236/0x2e0 net/socket.c:2499
__sys_sendmsg net/socket.c:2528 [inline]
__do_sys_sendmsg net/socket.c:2537 [inline]
__se_sys_sendmsg+0x1af/0x290 net/socket.c:2535
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f60d6512819
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:00007f60d476c028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f60d678bfa0 RCX: 00007f60d6512819
RDX: 0000000000040800 RSI: 0000200000000000 RDI: 0000000000000003
RBP: 00007f60d65a8c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f60d678c038 R14: 00007f60d678bfa0 R15: 00007ffd4fe836b8
</TASK>


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