[v6.1] kernel BUG in pn_socket_sendmsg

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7c87defbd336 Linux 6.1.169
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=173b1702580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=52724de20f69d3257938
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cf55a056d548/disk-7c87defb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/af13139876bb/vmlinux-7c87defb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/02c231cd5348/Image-7c87defb.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+52724d...@syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at net/phonet/socket.c:213!
Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 4431 Comm: syz.0.11 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : pn_socket_autobind net/phonet/socket.c:213 [inline]
pc : pn_socket_sendmsg+0x210/0x214 net/phonet/socket.c:422
lr : pn_socket_autobind net/phonet/socket.c:213 [inline]
lr : pn_socket_sendmsg+0x210/0x214 net/phonet/socket.c:422
sp : ffff800021347a40
x29: ffff800021347aa0 x28: ffff700004268f64 x27: 1fffe0001ebc4d83
x26: dfff800000000000 x25: ffff700004268f48 x24: ffff800021347a60
x23: ffff0000f5e26c18 x22: 0000000000000000 x21: ffff0000c4bd0c80
x20: ffff800021347be0 x19: 0000000000000020 x18: 0000000000000000
x17: 0000000000000000 x16: ffff8000082d92bc x15: 0000000000000002
x14: 0000000000000001 x13: 1fffe0001897a1a3 x12: 0000000000080000
x11: 0000000000000bf6 x10: ffff80002192a000 x9 : ffff800010f16a70
x8 : 0000000000000bf7 x7 : ffff80000fd55fa0 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
x2 : ffff800021347860 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
pn_socket_autobind net/phonet/socket.c:213 [inline]
pn_socket_sendmsg+0x210/0x214 net/phonet/socket.c:422
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
__sys_sendto+0x324/0x440 net/socket.c:2152
__do_sys_sendto net/socket.c:2164 [inline]
__se_sys_sendto net/socket.c:2160 [inline]
__arm64_sys_sendto+0xd8/0xf8 net/socket.c:2160
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: aa1603e0 97c37ac7 17ffffc1 97c37a4e (d4210000)
---[ end trace 0000000000000000 ]---


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 7c87defbd336 Linux 6.1.169
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=15d221ba580000

kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=52724de20f69d3257938
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=172effca580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11429906580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cf55a056d548/disk-7c87defb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/af13139876bb/vmlinux-7c87defb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/02c231cd5348/Image-7c87defb.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+52724d...@syzkaller.appspotmail.com

netlink: 'syz.0.17': attribute type 2 has an invalid length.

------------[ cut here ]------------
kernel BUG at net/phonet/socket.c:213!
Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in:

CPU: 1 PID: 4503 Comm: syz.0.17 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : pn_socket_autobind net/phonet/socket.c:213 [inline]
pc : pn_socket_sendmsg+0x210/0x214 net/phonet/socket.c:422
lr : pn_socket_autobind net/phonet/socket.c:213 [inline]
lr : pn_socket_sendmsg+0x210/0x214 net/phonet/socket.c:422

sp : ffff800021017a40
x29: ffff800021017aa0 x28: ffff700004202f64 x27: 1fffe0001d4cc6c3
x26: dfff800000000000 x25: ffff700004202f48 x24: ffff800021017a60
x23: ffff0000ea663618 x22: 0000000000000000 x21: ffff0000d4428c80
x20: ffff800021017be0 x19: 0000000000000020 x18: 0000000000000000
x17: 0000000000000000 x16: ffff8000082d92bc x15: 0000000000000000
x14: 0000000000000001 x13: 1fffe0001a8851a3 x12: 0000000000ff0100
x11: ff00800010f16a70 x10: 0000000000000000 x9 : ffff800010f16a70
x8 : ffff0000d3125340 x7 : ffff80000fd55fa0 x6 : 0000000000000000

x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000

x2 : ffff800021017860 x1 : 0000000000000000 x0 : 0000000000000000

Call trace:
pn_socket_autobind net/phonet/socket.c:213 [inline]
pn_socket_sendmsg+0x210/0x214 net/phonet/socket.c:422
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
__sys_sendto+0x324/0x440 net/socket.c:2152
__do_sys_sendto net/socket.c:2164 [inline]
__se_sys_sendto net/socket.c:2160 [inline]
__arm64_sys_sendto+0xd8/0xf8 net/socket.c:2160
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: aa1603e0 97c37ac7 17ffffc1 97c37a4e (d4210000)
---[ end trace 0000000000000000 ]---


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