[net-next PATCH 2/8] gso: Only allow GSO_PARTIAL if we can checksum the inner protocol

[Alexander Duyck]

This patch addresses a possible issue that can occur if we get into any odd
corner cases where we support TSO for a given protocol but not the checksum
or scatter-gather offload.  There are few drivers floating around that
setup their tunnels this way and by enforcing the checksum piece we can
avoid mangling any frames.

Signed-off-by: Alexander Duyck <adu...@mirantis.com>
---
 net/core/skbuff.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7ff7788b0151..d2871d081750 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3080,8 +3080,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
        unsigned int headroom;
        unsigned int len = head_skb->len;
        __be16 proto;
-       bool csum;
-       int sg = !!(features & NETIF_F_SG);
+       bool csum, sg;
        int nfrags = skb_shinfo(head_skb)->nr_frags;
        int err = -ENOMEM;
        int i = 0;
@@ -3093,13 +3092,14 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
        if (unlikely(!proto))
                return ERR_PTR(-EINVAL);
 
+       sg = !!(features & NETIF_F_SG);
        csum = !!can_checksum_protocol(features, proto);
 
        /* GSO partial only requires that we trim off any excess that
         * doesn't fit into an MSS sized block, so take care of that
         * now.
         */
-       if (features & NETIF_F_GSO_PARTIAL) {
+       if (sg && csum && (features & NETIF_F_GSO_PARTIAL)) {
                partial_segs = len / mss;
                mss *= partial_segs;
        }