Re: [dpdk-dev] [PATCH] net/netvsc: replace compiler builtin overflow check

[Raslan Darawsheh <rasland@nvidia.com>]

Hi,

> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> Sent: Tuesday, September 8, 2020 1:07 PM
> To: dev@dpdk.org; Stephen Hemminger <sthemmin@microsoft.com>; NBU-
> Contact-kys <kys@microsoft.com>; NBU-Contact-haiyangz
> <haiyangz@microsoft.com>; NBU-Contact-longli <longli@microsoft.com>
> Cc: Ferruh Yigit <ferruh.yigit@intel.com>; Raslan Darawsheh
> <rasland@mellanox.com>
> Subject: [PATCH] net/netvsc: replace compiler builtin overflow check
> 
> '__builtin_add_overflow' added to gcc in version 5, earlier versions
> causing build error, like gcc 4.8.5 in RHEL7.
> 
> Replaced compiler builtin check with arithmetic check.
> 
> Fixes: cabb3c0f29f1 ("net/netvsc: check for overflow on packet info from
> host")
> 
> Reported-by: Raslan Darawsheh <rasland@mellanox.com>
> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>

Tested-by: Raslan Darawsheh <rasland@nvidia.com>

> ---
>  drivers/net/netvsc/hn_rxtx.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/netvsc/hn_rxtx.c b/drivers/net/netvsc/hn_rxtx.c
> index d8d3f07f56..3e8d3b407d 100644
> --- a/drivers/net/netvsc/hn_rxtx.c
> +++ b/drivers/net/netvsc/hn_rxtx.c
> @@ -666,7 +666,7 @@ 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, total_len;
> +	unsigned int data_off, data_len;
>  	unsigned int pktinfo_off, pktinfo_len;
>  	const struct rndis_packet_msg *pkt = data;
>  	struct hn_rxinfo info = {
> @@ -712,8 +712,8 @@ static void hn_rndis_rx_data(struct hn_rx_queue
> *rxq,
>  			goto error;
>  	}
> 
> -	if (__builtin_add_overflow(data_off, data_len, &total_len) ||
> -	    total_len > pkt->len)
> +	/* overflow check */
> +	if (data_len > data_len + data_off || data_len + data_off > pkt->len)
>  		goto error;
> 
>  	if (unlikely(data_len < RTE_ETHER_HDR_LEN))
> --
> 2.25.4

Kindest regards
Raslan Darawsheh