Re: [RFC PATCH v3 19/28] hw/virtio: Replace g_memdup() by g_memdup2()

[Eugenio Perez Martin]

On Fri, Sep 3, 2021 at 8:11 PM Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>
> Per 
> https://discourse.gnome.org/t/port-your-module-from-g-memdup-to-g-memdup2-now/5538
>
>   The old API took the size of the memory to duplicate as a guint,
>   whereas most memory functions take memory sizes as a gsize. This
>   made it easy to accidentally pass a gsize to g_memdup(). For large
>   values, that would lead to a silent truncation of the size from 64
>   to 32 bits, and result in a heap area being returned which is
>   significantly smaller than what the caller expects. This can likely
>   be exploited in various modules to cause a heap buffer overflow.
>
> Replace g_memdup() by the safer g_memdup2() wrapper.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
> Should we check in_num/out_num in range?

I'd say it is not needed to check: virtqueue_pop fills them by
iterating through the descriptor chain so the range is restricted to
[0, 1024].

Acked-by: Eugenio Pérez <eperezma@redhat.com>


> ---
>  hw/net/virtio-net.c       | 3 ++-
>  hw/virtio/virtio-crypto.c | 6 +++---
>  2 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 16d20cdee52..338fbeb8c57 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1449,7 +1449,8 @@ static void virtio_net_handle_ctrl(VirtIODevice *vdev, 
> VirtQueue *vq)
>          }
>
>          iov_cnt = elem->out_num;
> -        iov2 = iov = g_memdup(elem->out_sg, sizeof(struct iovec) * 
> elem->out_num);
> +        iov2 = iov = g_memdup2(elem->out_sg,
> +                               sizeof(struct iovec) * elem->out_num);
>          s = iov_to_buf(iov, iov_cnt, 0, &ctrl, sizeof(ctrl));
>          iov_discard_front(&iov, &iov_cnt, sizeof(ctrl));
>          if (s != sizeof(ctrl)) {
> diff --git a/hw/virtio/virtio-crypto.c b/hw/virtio/virtio-crypto.c
> index 54f9bbb789c..59886c1790d 100644
> --- a/hw/virtio/virtio-crypto.c
> +++ b/hw/virtio/virtio-crypto.c
> @@ -242,7 +242,7 @@ static void virtio_crypto_handle_ctrl(VirtIODevice *vdev, 
> VirtQueue *vq)
>          }
>
>          out_num = elem->out_num;
> -        out_iov_copy = g_memdup(elem->out_sg, sizeof(out_iov[0]) * out_num);
> +        out_iov_copy = g_memdup2(elem->out_sg, sizeof(out_iov[0]) * out_num);
>          out_iov = out_iov_copy;
>
>          in_num = elem->in_num;
> @@ -605,11 +605,11 @@ virtio_crypto_handle_request(VirtIOCryptoReq *request)
>      }
>
>      out_num = elem->out_num;
> -    out_iov_copy = g_memdup(elem->out_sg, sizeof(out_iov[0]) * out_num);
> +    out_iov_copy = g_memdup2(elem->out_sg, sizeof(out_iov[0]) * out_num);
>      out_iov = out_iov_copy;
>
>      in_num = elem->in_num;
> -    in_iov_copy = g_memdup(elem->in_sg, sizeof(in_iov[0]) * in_num);
> +    in_iov_copy = g_memdup2(elem->in_sg, sizeof(in_iov[0]) * in_num);
>      in_iov = in_iov_copy;
>
>      if (unlikely(iov_to_buf(out_iov, out_num, 0, &req, sizeof(req))
> --
> 2.31.1
>
>