net: napi_reuse_skb() should check pfmemalloc

Do not reuse skb if it was pfmemalloc tainted, otherwise
future frame might be dropped anyway.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Roman Gushchin <klamm@yandex-team.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -4157,6 +4157,10 @@ EXPORT_SYMBOL(napi_gro_receive);
 
 static void napi_reuse_skb(struct napi_struct *napi, struct sk_buff *skb)
 {
+	if (unlikely(skb->pfmemalloc)) {
+		consume_skb(skb);
+		return;
+	}
 	__skb_pull(skb, skb_headlen(skb));
 	/* restore the reserve we had after netdev_alloc_skb_ip_align() */
 	skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN - skb_headroom(skb));