diff mbox series

[v1,5/6] virtio_net: Guard against buffer length overflow in xdp_linearize_page()

Message ID 20230119135721.83345-6-alexander.shishkin@linux.intel.com
State New
Headers
Series Harden a few virtio bits |

Commit Message

Alexander Shishkin Jan. 19, 2023, 1:57 p.m. UTC 
  When reassembling incoming buffers to an xdp_page, there is a potential
integer overflow in the buffer size test and trigger and out of bounds
memcpy().

Fix this by reordering the test so that both sides are of the same
signedness.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jesper Dangaard Brouer <hawk@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
---
 drivers/net/virtio_net.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Michael S. Tsirkin Jan. 20, 2023, 1:09 p.m. UTC | #1 
On Thu, Jan 19, 2023 at 03:57:20PM +0200, Alexander Shishkin wrote:
> When reassembling incoming buffers to an xdp_page, there is a potential
> integer overflow in the buffer size test and trigger and out of bounds
> memcpy().
> 
> Fix this by reordering the test so that both sides are of the same
> signedness.
> 
> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Jesper Dangaard Brouer <hawk@kernel.org>
> Cc: John Fastabend <john.fastabend@gmail.com>
> Cc: David S. Miller <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> ---
>  drivers/net/virtio_net.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 7723b2a49d8e..dfa51dd95f63 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -751,8 +751,10 @@ static struct page *xdp_linearize_page(struct receive_queue *rq,
>  
>  		/* guard against a misconfigured or uncooperative backend that
>  		 * is sending packet larger than the MTU.
> +		 * At the same time, make sure that an especially uncooperative
> +		 * backend can't overflow the test by supplying a large buflen.
>  		 */
> -		if ((page_off + buflen + tailroom) > PAGE_SIZE) {
> +		if (buflen > PAGE_SIZE - page_off - tailroom) {
>  			put_page(p);
>  			goto err_buf;
>  		}

I feel the issue should be addressed in virtqueue_get_buf.
In fact, when using DMA API, we already keep track of the
length in vring_desc_extra.

So, isn't this just the question of passing the length and
validating it e.g. in vring_unmap_one_split?
We can also use the index_nospec trick since otherwise
there could be speculation concerns.

> -- 
> 2.39.0
diff mbox series

Patch

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 7723b2a49d8e..dfa51dd95f63 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -751,8 +751,10 @@  static struct page *xdp_linearize_page(struct receive_queue *rq,
 
 		/* guard against a misconfigured or uncooperative backend that
 		 * is sending packet larger than the MTU.
+		 * At the same time, make sure that an especially uncooperative
+		 * backend can't overflow the test by supplying a large buflen.
 		 */
-		if ((page_off + buflen + tailroom) > PAGE_SIZE) {
+		if (buflen > PAGE_SIZE - page_off - tailroom) {
 			put_page(p);
 			goto err_buf;
 		}