[syzbot] [net?] kernel BUG in pn_socket_sendmsg

[syzbot <syzbot+706f5eb79044e686c794@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    97e797263a5e Add linux-next specific files for 20260420
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=111f5702580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=354b135d724a721f
dashboard link: https://syzkaller.appspot.com/bug?extid=706f5eb79044e686c794
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14bbf4ce580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=152051ba580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bfe08255b02b/disk-97e79726.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/70874e341331/vmlinux-97e79726.xz
kernel image: https://storage.googleapis.com/syzbot-assets/68352f7fca94/bzImage-97e79726.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+706f5eb79044e686c794@syzkaller.appspotmail.com

netlink: 'syz.0.17': attribute type 2 has an invalid length.
------------[ cut here ]------------
kernel BUG at net/phonet/socket.c:213!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 6014 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:pn_socket_autobind net/phonet/socket.c:213 [inline]
RIP: 0010:pn_socket_sendmsg+0x240/0x250 net/phonet/socket.c:421
Code: cc cc cc e8 c2 0c d2 00 89 d9 80 e1 07 fe c1 38 c1 0f 8c 04 ff ff ff 48 89 df e8 bb d3 be f7 e9 f7 fe ff ff e8 c1 5a 55 f7 90 <0f> 0b 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90
RSP: 0018:ffffc900050d7ba0 EFLAGS: 00010293
RAX: ffffffff8a6fa75f RBX: 0000000000000000 RCX: ffff888031b91ec0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900050d7c58 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f9e8df R12: dffffc0000000000
R13: ffff88805c7b5ec0 R14: ffff888034fecec0 R15: 1ffff92000a1af78
FS:  00007f347ac666c0(0000) GS:ffff888125a62000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f347b5f7680 CR3: 000000003d362000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 sock_sendmsg_nosec+0x112/0x150 net/socket.c:797
 __sock_sendmsg net/socket.c:812 [inline]
 __sys_sendto+0x402/0x590 net/socket.c:2280
 __do_sys_sendto net/socket.c:2287 [inline]
 __se_sys_sendto net/socket.c:2283 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2283
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f347b5cd04e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007f347ac64e88 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f347ac666c0 RCX: 00007f347b5cd04e
RDX: 0000000000000020 RSI: 00007f347ac65000 RDI: 0000000000000006
RBP: 0000000000000000 R08: 00007f347ac64f04 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000006
R13: 00007f347ac64f58 R14: 00007f347ac65000 R15: 0000000000000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:pn_socket_autobind net/phonet/socket.c:213 [inline]
RIP: 0010:pn_socket_sendmsg+0x240/0x250 net/phonet/socket.c:421
Code: cc cc cc e8 c2 0c d2 00 89 d9 80 e1 07 fe c1 38 c1 0f 8c 04 ff ff ff 48 89 df e8 bb d3 be f7 e9 f7 fe ff ff e8 c1 5a 55 f7 90 <0f> 0b 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90
RSP: 0018:ffffc900050d7ba0 EFLAGS: 00010293
RAX: ffffffff8a6fa75f RBX: 0000000000000000 RCX: ffff888031b91ec0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900050d7c58 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f9e8df R12: dffffc0000000000
R13: ffff88805c7b5ec0 R14: ffff888034fecec0 R15: 1ffff92000a1af78
FS:  00007f347ac666c0(0000) GS:ffff888125a62000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f347b5f7680 CR3: 000000003d362000 CR4: 00000000003526f0


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