Re: [syzbot] [kvm?] [net?] [virt?] WARNING in virtio_transport_send_pkt_info

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Aug 11, 2025 at 11:59:30AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    37816488247d Merge tag 'net-6.17-rc1' of git://git.kernel...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=10b3b2f0580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e143c1cd9dadd720
> dashboard link: https://syzkaller.appspot.com/bug?extid=b4d960daf7a3c7c2b7b1
> compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10f0f042580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14855434580000
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-37816488.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/74b3ac8946d4/vmlinux-37816488.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/a2b391aacaec/bzImage-37816488.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b4d960daf7a3c7c2b7b1@syzkaller.appspotmail.com
> 
> ------------[ cut here ]------------
> 'send_pkt()' returns 0, but 65536 expected
> WARNING: CPU: 0 PID: 5503 at net/vmw_vsock/virtio_transport_common.c:428 virtio_transport_send_pkt_info+0xd11/0xf00 net/vmw_vsock/virtio_transport_common.c:426
> Modules linked in:
> CPU: 0 UID: 0 PID: 5503 Comm: syz.0.17 Not tainted 6.16.0-syzkaller-12063-g37816488247d #0 PREEMPT(full) 
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> RIP: 0010:virtio_transport_send_pkt_info+0xd11/0xf00 net/vmw_vsock/virtio_transport_common.c:426
> Code: 0f 0b 90 bd f2 ff ff ff eb bc e8 8a 20 65 f6 c6 05 94 cf 32 04 01 90 48 c7 c7 00 c3 b8 8c 44 89 f6 4c 89 ea e8 40 af 28 f6 90 <0f> 0b 90 90 e9 e1 fe ff ff e8 61 20 65 f6 90 0f 0b 90 e9 c5 f7 ff
> RSP: 0018:ffffc900027ff530 EFLAGS: 00010246
> RAX: d7fcdfc663889c00 RBX: 0000000000010000 RCX: ffff888000e1a440
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
> RBP: ffffffff8f8764d0 R08: ffff88801fc24253 R09: 1ffff11003f8484a
> R10: dffffc0000000000 R11: ffffed1003f8484b R12: dffffc0000000000
> R13: 0000000000010000 R14: 0000000000000000 R15: ffff888058b48024
> FS:  000055556bda1500(0000) GS:ffff88808d218000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000020000003f000 CR3: 000000003f6db000 CR4: 0000000000352ef0
> Call Trace:
>  <TASK>
>  virtio_transport_stream_enqueue net/vmw_vsock/virtio_transport_common.c:1111 [inline]
>  virtio_transport_seqpacket_enqueue+0x143/0x1c0 net/vmw_vsock/virtio_transport_common.c:839
>  vsock_connectible_sendmsg+0xac7/0x1050 net/vmw_vsock/af_vsock.c:2140
>  sock_sendmsg_nosec net/socket.c:714 [inline]
>  __sock_sendmsg+0x21c/0x270 net/socket.c:729
>  ____sys_sendmsg+0x52d/0x830 net/socket.c:2614
>  ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2668
>  __sys_sendmmsg+0x227/0x430 net/socket.c:2757
>  __do_sys_sendmmsg net/socket.c:2784 [inline]
>  __se_sys_sendmmsg net/socket.c:2781 [inline]
>  __x64_sys_sendmmsg+0xa0/0xc0 net/socket.c:2781
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fddc238ebe9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffd48081028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
> RAX: ffffffffffffffda RBX: 00007fddc25b5fa0 RCX: 00007fddc238ebe9
> RDX: 0000000000000001 RSI: 0000200000000100 RDI: 0000000000000004
> RBP: 00007fddc2411e19 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000024008094 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fddc25b5fa0 R14: 00007fddc25b5fa0 R15: 0000000000000004
>  </TASK>
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 8ca76151d2c8219edea82f1925a2a25907ff6a9d



> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup