[syzbot] [net?] WARNING in __dev_queue_xmit (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f9a2394a2348 Merge tag 'mm-hotfixes-stable-2026-08-06-18-4..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=165f2132580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3e8a402093abe6b2
dashboard link: https://syzkaller.appspot.com/bug?extid=30b93b6845b19cc38581
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12038fb9580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13357e49580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ef40f2831e11/disk-f9a2394a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/083195a6f16a/vmlinux-f9a2394a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/08e150858f10/bzImage-f9a2394a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+30b93b...@syzkaller.appspotmail.com

------------[ cut here ]------------
skb_assert_len
WARNING: ./include/linux/skbuff.h:2753 at skb_assert_len include/linux/skbuff.h:2753 [inline], CPU#0: syz-executor184/5631
WARNING: ./include/linux/skbuff.h:2753 at __dev_queue_xmit+0x1fb8/0x3820 net/core/dev.c:4781, CPU#0: syz-executor184/5631
Modules linked in:
CPU: 0 UID: 0 PID: 5631 Comm: syz-executor184 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:skb_assert_len include/linux/skbuff.h:2753 [inline]
RIP: 0010:__dev_queue_xmit+0x1fbf/0x3820 net/core/dev.c:4781
Code: 48 c7 44 24 10 00 00 00 00 e9 50 fe ff ff e8 28 45 26 f8 90 0f 0b 90 e9 d6 e1 ff ff 48 8d 3d 48 00 c6 06 48 c7 c6 7c bf 43 8e <67> 48 0f b9 3a 80 3d ee 0a a0 06 01 0f 85 86 03 00 00 e8 fa 44 26
RSP: 0018:ffffc900038c7660 EFLAGS: 00010246
RAX: ffffffff89a09fa1 RBX: ffff88801b04e5d0 RCX: 0000000000000000
RDX: ffff88807f661f00 RSI: ffffffff8e43bf7c RDI: ffffffff9066bdc0
RBP: ffffc900038c7910 R08: ffff88807ae068a7 R09: 1ffff1100f5c0d14
R10: dffffc0000000000 R11: ffffed100f5c0d15 R12: dffffc0000000000
R13: 1ffff92000718eec R14: 0000000000000000 R15: ffff88801b04e5d0
FS: 0000555586b70400(0000) GS:ffff888124f55000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005628d19fb000 CR3: 0000000073c3e000 CR4: 00000000003526f0
Call Trace:
<TASK>
tpacket_snd net/packet/af_packet.c:2907 [inline]
packet_sendmsg+0x1f38/0x4e80 net/packet/af_packet.c:3134
sock_sendmsg_nosec+0x13a/0x180 net/socket.c:775
__sock_sendmsg net/socket.c:790 [inline]
__sys_sendto+0x408/0x5a0 net/socket.c:2252
__do_sys_sendto net/socket.c:2259 [inline]
__se_sys_sendto net/socket.c:2255 [inline]
__x64_sys_sendto+0xde/0x100 net/socket.c:2255
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fda58f481c9
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff9aa6f188 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000200000000200 RCX: 00007fda58f481c9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007fda58fb3489 R08: 0000200000000000 R09: 0000000000000014
R10: 0000000004000010 R11: 0000000000000246 R12: 00007fda58fb33f1
R13: 0000000000000001 R14: 00007fff9aa6f1e0 R15: 0000000000000003
</TASK>
----------------
Code disassembly (best guess):
0: 48 c7 44 24 10 00 00 movq $0x0,0x10(%rsp)
7: 00 00
9: e9 50 fe ff ff jmp 0xfffffe5e
e: e8 28 45 26 f8 call 0xf826453b
13: 90 nop
14: 0f 0b ud2
16: 90 nop
17: e9 d6 e1 ff ff jmp 0xffffe1f2
1c: 48 8d 3d 48 00 c6 06 lea 0x6c60048(%rip),%rdi # 0x6c6006b
23: 48 c7 c6 7c bf 43 8e mov $0xffffffff8e43bf7c,%rsi
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: 80 3d ee 0a a0 06 01 cmpb $0x1,0x6a00aee(%rip) # 0x6a00b24
36: 0f 85 86 03 00 00 jne 0x3c2
3c: e8 .byte 0xe8
3d: fa cli
3e: 44 rex.R
3f: 26 es


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