On Thu, 16 Jan 2025 20:56:39 +0100
Ariel Otilibili <ariel.otilibili@6wind.com> wrote:

> Both branches of the loop share the same logic. Now each one is a
> goto dispatcher; either to out (end of function), or to
> stats (continuation of the loop).
>
> Bugzilla ID: 1440
> Depends-on: patch-1 ("net/af_xdp: fix use after free in af_xdp_tx_zc()")
> Signed-off-by: Ariel Otilibili <ariel.otilibili@6wind.com>
> ---
>  drivers/net/af_xdp/rte_eth_af_xdp.c | 57 ++++++++++++++---------------
>  1 file changed, 27 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
> index 4326a29f7042..8b42704b6d9f 100644
> --- a/drivers/net/af_xdp/rte_eth_af_xdp.c
> +++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
> @@ -551,6 +551,7 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>       uint64_t addr, offset;
>       struct xsk_ring_cons *cq = &txq->pair->cq;
>       uint32_t free_thresh = cq->size >> 1;
> +     struct rte_mbuf *local_mbuf = NULL;
> 
>       if (xsk_cons_nb_avail(cq, free_thresh) >= free_thresh)
>               pull_umem_cq(umem, XSK_RING_CONS__DEFAULT_NUM_DESCS, cq);
> @@ -565,21 +566,10 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>                                                           &idx_tx))
>                                       goto out;
>                       }
> -                     desc = xsk_ring_prod__tx_desc(&txq->tx, idx_tx);
> -                     desc->len = mbuf->pkt_len;
> -                     addr = (uint64_t)mbuf - (uint64_t)umem->buffer -
> -                                     umem->mb_pool->header_size;
> -                     offset = rte_pktmbuf_mtod(mbuf, uint64_t) -
> -                                     (uint64_t)mbuf +
> -                                     umem->mb_pool->header_size;
> -                     offset = offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
> -                     desc->addr = addr | offset;
> -                     tx_bytes += mbuf->pkt_len;
> -                     count++;
> +
> +                     goto stats;
>               } else {
> -                     struct rte_mbuf *local_mbuf =
> -                                     rte_pktmbuf_alloc(umem->mb_pool);
> -                     void *pkt;
> +                     local_mbuf = rte_pktmbuf_alloc(umem->mb_pool);
> 
>                       if (local_mbuf == NULL)
>                               goto out;
> @@ -589,23 +579,30 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>                               goto out;
>                       }
> 
> -                     desc = xsk_ring_prod__tx_desc(&txq->tx, idx_tx);
> -                     desc->len = mbuf->pkt_len;
> -
> -                     addr = (uint64_t)local_mbuf - (uint64_t)umem->buffer -
> -                                     umem->mb_pool->header_size;
> -                     offset = rte_pktmbuf_mtod(local_mbuf, uint64_t) -
> -                                     (uint64_t)local_mbuf +
> -                                     umem->mb_pool->header_size;
> -                     pkt = xsk_umem__get_data(umem->buffer, addr + offset);
> -                     offset = offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
> -                     desc->addr = addr | offset;
> -                     rte_memcpy(pkt, rte_pktmbuf_mtod(mbuf, void *),
> -                                     desc->len);
> -                     tx_bytes += mbuf->pkt_len;
> -                     rte_pktmbuf_free(mbuf);
> -                     count++;
> +                     goto stats;
>               }
> +stats:
> +     struct rte_mbuf *tmp;
> +     void *pkt;
> +     tmp = mbuf->pool == umem->mb_pool ? mbuf : local_mbuf;
> +
> +     desc = xsk_ring_prod__tx_desc(&txq->tx, idx_tx);
> +     desc->len = mbuf->pkt_len;
> +
> +     addr = (uint64_t)tmp - (uint64_t)umem->buffer - umem->mb_pool->header_size;
> +     offset = rte_pktmbuf_mtod(tmp, uint64_t) - (uint64_t)tmp + umem->mb_pool->header_size;
> +     offset = offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
> +     desc->addr = addr | offset;
> +
> +     if (mbuf->pool == umem->mb_pool) {
> +             tx_bytes += mbuf->pkt_len;
> +     } else {
> +             pkt = xsk_umem__get_data(umem->buffer, addr + offset);
> +             rte_memcpy(pkt, rte_pktmbuf_mtod(mbuf, void *), desc->len);
> +             tx_bytes += mbuf->pkt_len;
> +             rte_pktmbuf_free(mbuf);
> +     }
> +     count++;
>       }
> 
>  out:

Indentation here is wrong, and looks suspect.
Either stats tag should be outside of loop
Or stats is inside loop, and both of those goto's are unnecessary