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

[Shannon Nelson]

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 <snel...@pensando.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