net: add debug checks in napi_consume_skb and __napi_alloc_skb()

Commit 6454eca ("net: Use lockdep_assert_in_softirq()
in napi_consume_skb()") added a check in napi_consume_skb()
which is a bit weak.

napi_consume_skb() and __napi_alloc_skb() should only
be used from BH context, not from hard irq or nmi context,
otherwise we could have races.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/skbuff.c

@@ -560,6 +560,7 @@ struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
 	struct sk_buff *skb;
 	void *data;
 
+	DEBUG_NET_WARN_ON_ONCE(!in_softirq());
 	len += NET_SKB_PAD + NET_IP_ALIGN;
 
 	/* If requested length is either too small or too big,
@@ -981,7 +982,7 @@ void napi_consume_skb(struct sk_buff *skb, int budget)
 		return;
 	}
 
-	lockdep_assert_in_softirq();
+	DEBUG_NET_WARN_ON_ONCE(!in_softirq());
 
 	if (!skb_unref(skb))
 		return;