CVE-2026-63970vsock/virtio: bind uarg before filling zerocopy skb

Official description

In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: bind uarg before filling zerocopy skb virtio_transport_send_pkt_info() allocates or reuses the zerocopy uarg before entering the send loop, but virtio_transport_alloc_skb() still fills the skb before it inherits that uarg. When fixed-buffer vectored zerocopy hits MAX_SKB_FRAGS, io_sg_from_iter() may partially attach managed frags and return -EMSGSIZE. The rollback path call kfree_skb() to free an skb that carries SKBFL_MANAGED_FRAG_REFS but no uarg, so skb_release_data() falls through to ordinary frag unref. Pass the uarg into virtio_transport_alloc_skb() and bind it immediately before virtio_transport_fill_skb(). This keeps control or no-payload skbs untouched while ensuring success and rollback share one lifetime rule.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/72194f65050958e4c8e069adb6c5d89ef81ca197
• https://git.kernel.org/stable/c/b62e2b2b4a50953ca952f3cd3f77dd62dc50fd5d
• https://git.kernel.org/stable/c/5d317573f1d48e76cce5fb6250452b6e4102e0fb
• https://git.kernel.org/stable/c/1e584c304cfb94a759417130b1fc6d30b30c4cce