gve: fix for null pointer dereference.

Avoid passing NULL skb to __skb_put() function call if
napi_alloc_skb() returns NULL.

Fixes: 37149e93 ("gve: Implement packet continuation for RX.")
Signed-off-by: Ameer Hamza <amhamza.mgc@gmail.com>
Link: https://lore.kernel.org/r/20211205183810.8299-1-amhamza.mgc@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/google/gve/gve_utils.c

@@ -68,6 +68,9 @@ struct sk_buff *gve_rx_copy(struct net_device *dev, struct napi_struct *napi,
 		set_protocol = ctx->curr_frag_cnt == ctx->expected_frag_cnt - 1;
 	} else {
 		skb = napi_alloc_skb(napi, len);
+
+		if (unlikely(!skb))
+			return NULL;
 		set_protocol = true;
 	}
 	__skb_put(skb, len);