net/mlx5e: RX, Fix generating skb from non-linear xdp_buff for legacy RQ

XDP programs can release xdp_buff fragments when calling
bpf_xdp_adjust_tail(). The driver currently assumes the number of
fragments to be unchanged and may generate skb with wrong truesize or
containing invalid frags. Fix the bug by generating skb according to
xdp_buff after the XDP program runs.

Fixes: ea5d49bdae8b ("net/mlx5e: Add XDP multi buffer support to the non-linear legacy RQ")
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/1760644540-899148-2-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index 263d5628ee44ec856b69746163d29167ee1f1d00..17cab14b328b9c165d1c57ea2bd2df8dabd54c3e 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -1794,14 +1794,27 @@ mlx5e_skb_from_cqe_nonlinear(struct mlx5e_rq *rq, struct mlx5e_wqe_frag_info *wi
        }
 
        prog = rcu_dereference(rq->xdp_prog);
-       if (prog && mlx5e_xdp_handle(rq, prog, mxbuf)) {
-               if (__test_and_clear_bit(MLX5E_RQ_FLAG_XDP_XMIT, rq->flags)) {
-                       struct mlx5e_wqe_frag_info *pwi;
+       if (prog) {
+               u8 nr_frags_free, old_nr_frags = sinfo->nr_frags;
+
+               if (mlx5e_xdp_handle(rq, prog, mxbuf)) {
+                       if (__test_and_clear_bit(MLX5E_RQ_FLAG_XDP_XMIT,
+                                                rq->flags)) {
+                               struct mlx5e_wqe_frag_info *pwi;
+
+                               wi -= old_nr_frags - sinfo->nr_frags;
+
+                               for (pwi = head_wi; pwi < wi; pwi++)
+                                       pwi->frag_page->frags++;
+                       }
+                       return NULL; /* page/packet was consumed by XDP */
+               }
 
-                       for (pwi = head_wi; pwi < wi; pwi++)
-                               pwi->frag_page->frags++;
+               nr_frags_free = old_nr_frags - sinfo->nr_frags;
+               if (unlikely(nr_frags_free)) {
+                       wi -= nr_frags_free;
+                       truesize -= nr_frags_free * frag_info->frag_stride;
                }
-               return NULL; /* page/packet was consumed by XDP */
        }
 
        skb = mlx5e_build_linear_skb(