Re: [Qemu-devel] [PATCH for 3.1 1/4] net: drop too large packet early

[Li Qiang]

Jason Wang <address@hidden> 于2018年11月29日周四 上午11:12写道：

> We try to detect and drop too large packet (>INT_MAX) in 1592a9947036
> ("net: ignore packet size greater than INT_MAX") during packet
> delivering. Unfortunately, this is not sufficient as we may hit
> another integer overflow when trying to queue such large packet in
> qemu_net_queue_append_iov():
>
> - size of the allocation may overflow on 32bit
> - packet->size is integer which may overflow even on 64bit
>
> Fixing this by move the check to qemu_sendv_packet_async() which is
> the entrance of all networking codes and reduce the limit to
> NET_BUFSIZE to be more conservative.
>
> Cc: address@hidden
> Cc: Li Qiang <address@hidden>
> Reported-by: Li Qiang <address@hidden>
> Signed-off-by: Jason Wang <address@hidden>
>

Looks ok to me.

Reviewed-by: Li Qiang <address@hidden>


> ---
>  net/net.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/net/net.c b/net/net.c
> index 07c194a8f6..affe1877cf 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -712,15 +712,11 @@ ssize_t qemu_deliver_packet_iov(NetClientState
> *sender,
>                                  void *opaque)
>  {
>      NetClientState *nc = opaque;
> -    size_t size = iov_size(iov, iovcnt);
>      int ret;
>
> -    if (size > INT_MAX) {
> -        return size;
> -    }
>
>      if (nc->link_down) {
> -        return size;
> +        return iov_size(iov, iovcnt);
>      }
>
>      if (nc->receive_disabled) {
> @@ -745,10 +741,15 @@ ssize_t qemu_sendv_packet_async(NetClientState
> *sender,
>                                  NetPacketSent *sent_cb)
>  {
>      NetQueue *queue;
> +    size_t size = iov_size(iov, iovcnt);
>      int ret;
>
> +    if (size > NET_BUFSIZE) {
> +        return size;
> +    }
> +
>      if (sender->link_down || !sender->peer) {
> -        return iov_size(iov, iovcnt);
> +        return size;
>      }
>
>      /* Let filters handle the packet first */
> --
> 2.17.1
>
>