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vhost/vsock: Avoid allocating arbitrarily-sized SKBs

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commit 10a886aaed upstream.

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: <stable@vger.kernel.org>
Fixes: 71dc9ec9ac ("virtio/vsock: replace virtio_vsock_pkt with sk_buff")
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Will Deacon <will@kernel.org>
Message-Id: <20250717090116.11987-2-will@kernel.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Will Deacon 2025-07-17 10:01:08 +01:00 committed by Greg Kroah-Hartman
parent faf332a103
commit 21d9382c44
1 changed files with 4 additions and 2 deletions
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6
drivers/vhost/vsock.c
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@ -344,6 +344,9 @@ vhost_vsock_alloc_skb(struct vhost_virtqueue *vq,
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_virtqueue *vq,
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;
}