netdev - [PATCH v2 net-next 7/8] net: add debug checks in napi_consume_skb and __napi_alloc

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Message-Id: <20220608160438.1342569-8-eric.dumazet@gmail.com>
Date:   Wed,  8 Jun 2022 09:04:37 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH v2 net-next 7/8] net: add debug checks in napi_consume_skb and __napi_alloc_skb()

From: Eric Dumazet <edumazet@...gle.com>

Commit 6454eca81eae ("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@...gle.com>
---
 net/core/skbuff.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index cf83d9b8f41dc28ae11391f2651e5abee3dcde8f..fec75f8bf1f416f05c14f76009a15412b2559b6e 100644
--- a/net/core/skbuff.c
+++ b/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;
-- 
2.36.1.255.ge46751e96f-goog