On Mon, Oct 05, 2026 at 08:51:01AM +0900, Daehyeon Ko wrote:
vhost_vsock_alloc_skb() sizes the skb from iov_length(), the total guest descriptor length. virtio_transport_inc_rx_pkt() instead adds hdr->len to rx_bytes and buf_used, and budgets each queued skb as SKB_TRUESIZE(0). The guest controls the descriptor length and hdr->len independently.A guest can therefore provide a 64 KiB descriptor while declaring a zero payload. The descriptor-sized skb remains queued, rx_bytes and buf_used remain unchanged, and only the fixed queue-entry budget limits retention. This is not a lifetime leak: the skb is freed when dequeued or at socket teardown. Repeating this across connections can nevertheless exhaust host memory. On Linux v7.2, 455 such descriptors retained 30,255,680 bytes for a 262,144-byte receive buffer; a full-payload control retained 265,984 bytes. Vhost previously read hdr->len and allocated pkt->buf from that value. The conversion from virtio_vsock_pkt to sk_buff instead allocated receive skbs from the descriptor length, introducing the allocation-accounting mismatch. Copy the header into a stack object and validate hdr->len before allocating the skb. Size the allocation as sizeof(hdr) + payload_len so descriptor capacity no longer determines queued memory. Check payload_len against len - sizeof(hdr) to avoid addition overflow on 32-bit hosts. Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff") Cc: [email protected] Assisted-by: LLM Signed-off-by: Daehyeon Ko <[email protected]> ---
Oooops, I missed this, LGTM, thanks for the fix! Reviewed-by: Stefano Garzarella <[email protected]>
