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

vsock/virtio: fix empty payload in tap skb for non-linear buffers

For non-linear skbs, virtio_transport_build_skb() goes through
virtio_transport_copy_nonlinear_skb() to copy the original payload
in the new skb to be delivered to the vsockmon tap device.
This manually initializes an iov_iter but does not set iov_iter.count.
Since the iov_iter is zero-initialized, the copy length is zero and no
payload is actually copied to the monitor interface, leaving data
un-initialized.

Fix this by removing the linear vs non-linear split and using
skb_copy_datagram_iter() with iov_iter_kvec() for all cases, as
vhost-vsock already does. This handles both linear and non-linear skbs,
properly initializes the iov_iter, and removes the now unused
virtio_transport_copy_nonlinear_skb().

While touching this code, let's also check the return value of
skb_copy_datagram_iter(), even though it's unlikely to fail.

References

• https://nvd.nist.gov/vuln/detail/CVE-2026-46207
• https://git.kernel.org/stable/c/06747f52ab157591cec7e5623a759473b66ef6f6
• https://git.kernel.org/stable/c/378b131a25bd1a5ee27ca199fe486c299d5350c5
• https://git.kernel.org/stable/c/3a3e3d90cbc79600544536723911657730759af3
• https://git.kernel.org/stable/c/52da6a74ca3de0fcda60301096b71534b3b18641