CVE-2025-38413

In the Linux kernel, the following vulnerability has been resolved:

virtio-net: xsk: rx: fix the frame's length check

When calling buftoxdp, the len argument is the frame data's length without virtio header's length (vi->hdr_len). We check that len with

xsk_pool_get_rx_frame_size() + vi->hdr_len

to ensure the provided len does not larger than the allocated chunk size. The additional vi->hdrlen is because in virtnetaddrecvbufxsk, we use part of XDPPACKETHEADROOM for virtio header and ask the vhost to start placing data from

hard_start + XDP_PACKET_HEADROOM - vi->hdr_len

not hardstart + XDPPACKET_HEADROOM

But the first buffer has virtio_header, so the maximum frame's length in the first buffer can only be

xsk_pool_get_rx_frame_size()

not xskpoolgetrxframesize() + vi->hdrlen

like in the current check.

This commit adds an additional argument to buftoxdp differentiate between the first buffer and other ones to correctly calculate the maximum frame's length.