net: skb_is_gso_v6() requires skb_is_gso()

bnx2x makes a dangerous use of skb_is_gso_v6().

It should first make sure skb is a gso packet
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Eilon Greenstein <eilong@broadcom.com>
Acked-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c

@@ -3256,15 +3256,17 @@ static u32 bnx2x_xmit_type(struct bnx2x *bp, struct sk_buff *skb)
 	if (prot == IPPROTO_TCP)
 		rc |= XMIT_CSUM_TCP;
 
+	if (skb_is_gso(skb)) {
 		if (skb_is_gso_v6(skb)) {
 			rc |= (XMIT_GSO_V6 | XMIT_CSUM_TCP);
 			if (rc & XMIT_CSUM_ENC)
 				rc |= XMIT_GSO_ENC_V6;
-	} else if (skb_is_gso(skb)) {
+		} else {
 			rc |= (XMIT_GSO_V4 | XMIT_CSUM_TCP);
 			if (rc & XMIT_CSUM_ENC)
 				rc |= XMIT_GSO_ENC_V4;
 		}
+	}
 
 	return rc;
 }

include/linux/skbuff.h

@@ -2755,6 +2755,7 @@ static inline bool skb_is_gso(const struct sk_buff *skb)
 	return skb_shinfo(skb)->gso_size;
 }
 
+/* Note: Should be called only if skb_is_gso(skb) is true */
 static inline bool skb_is_gso_v6(const struct sk_buff *skb)
 {
 	return skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6;