netdev - [PATCH net] ionic: linearize tso skb with too many frags

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Message-Id: <20210316185243.30053-1-snelson@pensando.io>
Date:   Tue, 16 Mar 2021 11:52:43 -0700
From:   Shannon Nelson <snelson@...sando.io>
To:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org
Cc:     drivers@...sando.io, Shannon Nelson <snelson@...sando.io>
Subject: [PATCH net] ionic: linearize tso skb with too many frags

We were linearizing non-TSO skbs that had too many frags, but
we weren't checking number of frags on TSO skbs.  This could
lead to a bad page reference when we received a TSO skb with
more frags than the Tx descriptor could support.

Fixes: 0f3154e6bcb3 ("ionic: Add Tx and Rx handling")
Signed-off-by: Shannon Nelson <snelson@...sando.io>
---
 .../net/ethernet/pensando/ionic/ionic_txrx.c  | 28 ++++++++++---------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
index 162a1ff1e9d2..462b0d106be4 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
@@ -1079,25 +1079,27 @@ static int ionic_tx_descs_needed(struct ionic_queue *q, struct sk_buff *skb)
 {
 	int sg_elems = q->lif->qtype_info[IONIC_QTYPE_TXQ].max_sg_elems;
 	struct ionic_tx_stats *stats = q_to_tx_stats(q);
+	int ndescs;
 	int err;
 
-	/* If TSO, need roundup(skb->len/mss) descs */
+	/* If TSO, need roundup(skb->len/mss) descs
+	 * If non-TSO, just need 1 desc and nr_frags sg elems
+	 */
 	if (skb_is_gso(skb))
-		return (skb->len / skb_shinfo(skb)->gso_size) + 1;
+		ndescs = (skb->len / skb_shinfo(skb)->gso_size) + 1;
+	else
+		ndescs = 1;
 
-	/* If non-TSO, just need 1 desc and nr_frags sg elems */
-	if (skb_shinfo(skb)->nr_frags <= sg_elems)
-		return 1;
+	/* If too many frags, linearize */
+	if (skb_shinfo(skb)->nr_frags > sg_elems) {
+		err = skb_linearize(skb);
+		if (err)
+			return err;
 
-	/* Too many frags, so linearize */
-	err = skb_linearize(skb);
-	if (err)
-		return err;
-
-	stats->linearize++;
+		stats->linearize++;
+	}
 
-	/* Need 1 desc and zero sg elems */
-	return 1;
+	return ndescs;
 }
 
 static int ionic_maybe_stop_tx(struct ionic_queue *q, int ndescs)
-- 
2.17.1