linux-kernel - [PATCH net V3 1/2] net/mlx5e: RX, Fix generating skb from non-linear xdp

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Message-ID: <1760644540-899148-2-git-send-email-tariqt@nvidia.com>
Date: Thu, 16 Oct 2025 22:55:39 +0300
From: Tariq Toukan <tariqt@...dia.com>
To: Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>
CC: Saeed Mahameed <saeedm@...dia.com>, Tariq Toukan <tariqt@...dia.com>,
	"Mark Bloch" <mbloch@...dia.com>, Leon Romanovsky <leon@...nel.org>, "Alexei
 Starovoitov" <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
	"Jesper Dangaard Brouer" <hawk@...nel.org>, John Fastabend
	<john.fastabend@...il.com>, <netdev@...r.kernel.org>,
	<linux-rdma@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<bpf@...r.kernel.org>, Gal Pressman <gal@...dia.com>, Moshe Shemesh
	<moshe@...dia.com>, Dragos Tatulea <dtatulea@...dia.com>, Amery Hung
	<ameryhung@...il.com>, <martin.lau@...nel.org>, <noren@...dia.com>,
	<cpaasch@...nai.com>, <kernel-team@...a.com>
Subject: [PATCH net V3 1/2] net/mlx5e: RX, Fix generating skb from non-linear xdp_buff for legacy RQ

From: Amery Hung <ameryhung@...il.com>

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@...dia.com>
Signed-off-by: Amery Hung <ameryhung@...il.com>
Signed-off-by: Tariq Toukan <tariqt@...dia.com>
---
 .../net/ethernet/mellanox/mlx5/core/en_rx.c   | 25 ++++++++++++++-----
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index 263d5628ee44..17cab14b328b 100644
--- 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(
-- 
2.31.1