vhost/vsock: always initialize seqpacket_allow

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: vhost/vsock: always initialize seqpacket_allow There are two issues around seqpacket_allow: 1. seqpacket_allow is not initialized when socket is created. Thus if features are never set, it will be read uninitialized. 2. if VIRTIO_VSOCK_F_SEQPACKET is set and then cleared, then seqpacket_allow will not be cleared appropriately (existing apps I know about don't usually do this but it's legal and there's no way to be sure no one relies on this). To fix: - initialize seqpacket_allow after allocation - set it unconditionally in set_features

References

• https://git.kernel.org/stable/c/ea558f10fb05a6503c6e655a1b7d81fdf8e5924c
• https://git.kernel.org/stable/c/3062cb100787a9ddf45de30004b962035cd497fb
• https://git.kernel.org/stable/c/30bd4593669443ac58515e23557dc8cef70d8582
• https://git.kernel.org/stable/c/eab96e8716cbfc2834b54f71cc9501ad4eec963b
• https://git.kernel.org/stable/c/1e1fdcbdde3b7663e5d8faeb2245b9b151417d22