Re: [dpdk-dev] [PATCH 4/4] net/netvsc: check for overflow on packet info from host

[Luca Boccassi <bluca@debian.org>]

On Mon, 2020-08-10 at 19:33 -0700, longli@linuxonhyperv.com wrote:
> From: Stephen Hemminger <stephen@networkplumber.org>
> 
> The data from the host is trusted but checked by the driver.
> One check that is missing is that the packet offset and length
> might cause wraparound.
> 
> Cc: stable@dpdk.org
> 
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
>  drivers/net/netvsc/hn_rxtx.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/netvsc/hn_rxtx.c b/drivers/net/netvsc/hn_rxtx.c
> index a388ff258..d8d3f07f5 100644
> --- a/drivers/net/netvsc/hn_rxtx.c
> +++ b/drivers/net/netvsc/hn_rxtx.c
> @@ -666,7 +666,8 @@ static void hn_rndis_rx_data(struct hn_rx_queue *rxq,
>  			     struct hn_rx_bufinfo *rxb,
>  			     void *data, uint32_t dlen)
>  {
> -	unsigned int data_off, data_len, pktinfo_off, pktinfo_len;
> +	unsigned int data_off, data_len, total_len;
> +	unsigned int pktinfo_off, pktinfo_len;
>  	const struct rndis_packet_msg *pkt = data;
>  	struct hn_rxinfo info = {
>  		.vlan_info = HN_NDIS_VLAN_INFO_INVALID,
> @@ -711,7 +712,8 @@ static void hn_rndis_rx_data(struct hn_rx_queue *rxq,
>  			goto error;
>  	}
>  
> -	if (unlikely(data_off + data_len > pkt->len))
> +	if (__builtin_add_overflow(data_off, data_len, &total_len) ||
> +	    total_len > pkt->len)
>  		goto error;
>  
>  	if (unlikely(data_len < RTE_ETHER_HDR_LEN))

This patch breaks the build with GCC < 5 (CentOS 7, RHEL 7, SLE 12) as
__builtin_add_overflow is not available. Could you please send a follow
up to fix it?

-- 
Kind regards,
Luca Boccassi