Re: [PATCH v2 1/2] net/af_xdp: fix use after free in af_xdp_tx_zc()

[Maryam Tahhan <mtahhan@redhat.com>]

On 16/01/2025 17:51, Ariel Otilibili wrote:
> tx_bytes is computed after both legs are tested. This might
> produce a use after memory free.
>
> The computation is now moved into each leg.
>
> Bugzilla ID: 1440
> Fixes: d8a210774e1d ("net/af_xdp: support unaligned umem chunks")
> Signed-off-by: Ariel Otilibili <ariel.otilibili@6wind.com>
> ---
>   drivers/net/af_xdp/rte_eth_af_xdp.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
> index 814398ba4b44..4326a29f7042 100644
> --- a/drivers/net/af_xdp/rte_eth_af_xdp.c
> +++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
> @@ -574,6 +574,7 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>   					umem->mb_pool->header_size;
>   			offset = offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
>   			desc->addr = addr | offset;
> +			tx_bytes += mbuf->pkt_len;
>   			count++;
>   		} else {
>   			struct rte_mbuf *local_mbuf =
> @@ -601,11 +602,10 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>   			desc->addr = addr | offset;
>   			rte_memcpy(pkt, rte_pktmbuf_mtod(mbuf, void *),
>   					desc->len);
> +			tx_bytes += mbuf->pkt_len;
>   			rte_pktmbuf_free(mbuf);
>   			count++;
>   		}
> -
> -		tx_bytes += mbuf->pkt_len;
>   	}
>   
>   out:

I think that you could've just set tx_bytes to the desc->len as this is 
being set in all scenarios...

tx_bytes += desc->len;