From 1696616a3e6e9d5eef2c39723ddaafb78a9a6eeb Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 17 Jul 2025 10:01:08 +0100 Subject: vhost/vsock: Avoid allocating arbitrarily-sized SKBs vhost_vsock_alloc_skb() returns NULL for packets advertising a length larger than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE in the packet header. However, this is only checked once the SKB has been allocated and, if the length in the packet header is zero, the SKB may not be freed immediately. Hoist the size check before the SKB allocation so that an iovec larger than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE + the header size is rejected outright. The subsequent check on the length field in the header can then simply check that the allocated SKB is indeed large enough to hold the packet. Cc: Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff") Reviewed-by: Stefano Garzarella Signed-off-by: Will Deacon Message-Id: <20250717090116.11987-2-will@kernel.org> Signed-off-by: Michael S. Tsirkin --- drivers/vhost/vsock.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/drivers/vhost/vsock.c +++ b/drivers/vhost/vsock.c @@ -344,6 +344,9 @@ vhost_vsock_alloc_skb(struct vhost_virtq len = iov_length(vq->iov, out); + if (len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE + VIRTIO_VSOCK_SKB_HEADROOM) + return NULL; + /* len contains both payload and hdr */ skb = virtio_vsock_alloc_skb(len, GFP_KERNEL); if (!skb) @@ -367,8 +370,7 @@ vhost_vsock_alloc_skb(struct vhost_virtq return skb; /* The pkt is too big or the length in the header is invalid */ - if (payload_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE || - payload_len + sizeof(*hdr) > len) { + if (payload_len + sizeof(*hdr) > len) { kfree_skb(skb); return NULL; }