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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Khalid Manaa , Ben Ben-Ishay Cc: Dragos Tatulea , Simon Horman , netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net v2] net/mlx5e: SHAMPO, Fix IP length overflow on large HW GRO sessions Date: Mon, 17 Aug 2026 14:16:18 -0400 Message-Id: <20260817181618.2786456-1-cosmosocket@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit mlx5e_hw_gro_skb_has_enough_space() bounds a HW GRO session by the payload held in the skb fragments only. The L3/L4 headers that header-data split placed in the linear area are not accounted for, and the limit is inclusive of GRO_LEGACY_MAX_SIZE. On a 4K page system a session can therefore grow to 16 full page fragments (65536 bytes) plus the 40 bytes of IPv4/TCP headers in the linear part, giving skb->len = 65576. mlx5e_shampo_update_hdr() writes the IP length itself: __be16 newlen = htons(skb->len - nhoff); csum_replace2(&ipv4->check, ipv4->tot_len, newlen); ipv4->tot_len = newlen; The result wraps. ip_rcv_core() then trims the 64KB skb down to the wrapped tot_len, silently dropping the payload. The IPv6 path wraps identically in ipv6hdr->payload_len. Both branches of the check are inclusive of GRO_LEGACY_MAX_SIZE, so a session can reach skb->len == 65536 and wrap tot_len to zero. In the page_size >= GRO_LEGACY_MAX_SIZE branch skb->len already covers the linear area, so that off by one is the only problem there. The fragment based branch additionally omits the linear area entirely. Account for skb_headlen() in the fragment based branch and make both comparisons strictly less than GRO_LEGACY_MAX_SIZE, so that skb->len can never exceed 65535. The new bound is strictly tighter than the old one, so the implicit limit on the fragment count (at most 65536 / page_size, well below MAX_SKB_FRAGS) is preserved. Fixes: 92552d3abd32 ("net/mlx5e: HW_GRO cqe handler implementation") Signed-off-by: Tianyu Zuo --- v2: commit message only, per review from Dragos and Tariq. v1: https://lore.kernel.org/netdev/20260729204745.166584-1-cosmosocket@gmail.com/ drivers/net/ethernet/mellanox/mlx5/core/en_rx.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c index 6fbc0441c4b8..2e9676305439 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c @@ -2222,9 +2222,10 @@ static bool mlx5e_hw_gro_skb_has_enough_space(struct sk_buff *skb, int nr_frags = skb_shinfo(skb)->nr_frags; if (page_size >= GRO_LEGACY_MAX_SIZE) - return skb->len + data_bcnt <= GRO_LEGACY_MAX_SIZE; + return skb->len + data_bcnt < GRO_LEGACY_MAX_SIZE; else - return page_size * nr_frags + data_bcnt <= GRO_LEGACY_MAX_SIZE; + return skb_headlen(skb) + page_size * nr_frags + data_bcnt < + GRO_LEGACY_MAX_SIZE; } static void mlx5e_handle_rx_cqe_mpwrq_shampo(struct mlx5e_rq *rq, struct mlx5_cqe64 *cqe) base-commit: 51b093a7ba27476e1f639455f005e8d2e75390e4 -- 2.34.1