netdev - [PATCH net] gve: Secure enough bytes in the first TX desc for all TCP pkts

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Message-ID: <20230330220939.2341562-1-shailend@google.com>
Date:   Thu, 30 Mar 2023 15:09:39 -0700
From:   Shailend Chand <shailend@...gle.com>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org,
        Shailend Chand <shailend@...gle.com>
Subject: [PATCH net] gve: Secure enough bytes in the first TX desc for all TCP pkts

Non-GSO TCP packets whose SKBs' linear portion did not include the
entire TCP header were not populating the first Tx descriptor with
as many bytes as the vNIC expected. This change ensures that all
TCP packets populate the first descriptor with the correct number of
bytes.

Fixes: 893ce44df565 ("gve: Add basic driver framework for Compute Engine Virtual NIC")
Signed-off-by: Shailend Chand <shailend@...gle.com>
---
 drivers/net/ethernet/google/gve/gve_tx.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/google/gve/gve_tx.c b/drivers/net/ethernet/google/gve/gve_tx.c
index 4888bf05fbed..e28b3fe26153 100644
--- a/drivers/net/ethernet/google/gve/gve_tx.c
+++ b/drivers/net/ethernet/google/gve/gve_tx.c
@@ -284,8 +284,8 @@ static inline int gve_skb_fifo_bytes_required(struct gve_tx_ring *tx,
 	int bytes;
 	int hlen;
 
-	hlen = skb_is_gso(skb) ? skb_checksum_start_offset(skb) +
-				 tcp_hdrlen(skb) : skb_headlen(skb);
+	hlen = skb_is_gso(skb) ? skb_checksum_start_offset(skb) + tcp_hdrlen(skb) :
+				 min_t(int, 182, skb->len);
 
 	pad_bytes = gve_tx_fifo_pad_alloc_one_frag(&tx->tx_fifo,
 						   hlen);
@@ -454,13 +454,11 @@ static int gve_tx_add_skb_copy(struct gve_priv *priv, struct gve_tx_ring *tx, st
 	pkt_desc = &tx->desc[idx];
 
 	l4_hdr_offset = skb_checksum_start_offset(skb);
-	/* If the skb is gso, then we want the tcp header in the first segment
-	 * otherwise we want the linear portion of the skb (which will contain
-	 * the checksum because skb->csum_start and skb->csum_offset are given
-	 * relative to skb->head) in the first segment.
+	/* If the skb is gso, then we want the tcp header alone in the first segment
+	 * otherwise we want the spec-stipulated minimum of 182B.
 	 */
 	hlen = is_gso ? l4_hdr_offset + tcp_hdrlen(skb) :
-			skb_headlen(skb);
+			min_t(int, 182, skb->len);
 
 	info->skb =  skb;
 	/* We don't want to split the header, so if necessary, pad to the end
-- 
2.40.0.348.gf938b09366-goog