CVE-2026-52994
Description
In the Linux kernel, the following vulnerability has been resolved:
vsock/virtio: fix MSG_ZEROCOPY pinned-pages accounting
virtio_transport_init_zcopy_skb() uses iter->count as the size argument
for msg_zerocopy_realloc(), which in turn passes it to
mm_account_pinned_pages() for RLIMIT_MEMLOCK accounting. However, this
function is called after virtio_transport_fill_skb() has already consumed
the iterator via __zerocopy_sg_from_iter(), so on the last skb, iter->count
will be 0, skipping the RLIMIT_MEMLOCK enforcement.
Pass pkt_len (the total bytes being sent) as an explicit parameter to
virtio_transport_init_zcopy_skb() instead of reading the already-consumed
iter->count.
This matches TCP and UDP, which both call msg_zerocopy_realloc() with
the original message size.
Summary dbcve.org
The vsock/virtio transport in the Linux kernel fails to properly enforce RLIMIT_MEMLOCK during MSG_ZEROCOPY operations. After virtio_transport_fill_skb() consumes the iterator via __zerocopy_sg_from_iter(), subsequent calls to virtio_transport_init_zcopy_skb() read iter->count which becomes 0 on the last skb, causing memory pinning accounting to be skipped entirely. This allows local users to bypass memory locking limits.
Mitigation
Apply the upstream kernel patch to pass pkt_len (total bytes being sent) as an explicit parameter to virtio_transport_init_zcopy_skb() instead of relying on the consumed iter->count, matching TCP/UDP behavior.