netdev - [PATCH net-next v2 2/4] net: skb: check the boundrary of drop reason in kfree_skb

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Message-Id: <20220512123313.218063-3-imagedong@tencent.com>
Date:   Thu, 12 May 2022 20:33:11 +0800
From:   menglong8.dong@...il.com
To:     kuba@...nel.org
Cc:     nhorman@...driver.com, davem@...emloft.net, edumazet@...gle.com,
        pabeni@...hat.com, yoshfuji@...ux-ipv6.org, dsahern@...nel.org,
        imagedong@...cent.com, kafai@...com, talalahmad@...gle.com,
        keescook@...omium.org, asml.silence@...il.com, willemb@...gle.com,
        vasily.averin@...ux.dev, ilias.apalodimas@...aro.org,
        luiz.von.dentz@...el.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH net-next v2 2/4] net: skb: check the boundrary of drop reason in kfree_skb_reason()

From: Menglong Dong <imagedong@...cent.com>

Sometimes, we may forget to reset skb drop reason to NOT_SPECIFIED after
we make it the return value of the functions with return type of enum
skb_drop_reason, such as tcp_inbound_md5_hash. Therefore, its value can
be SKB_NOT_DROPPED_YET(0), which is invalid for kfree_skb_reason().

So we check the range of drop reason in kfree_skb_reason() and reset it
to NOT_SPECIFIED and print a warning with DEBUG_NET_WARN_ON_ONCE() if it
is invalid.

Signed-off-by: Menglong Dong <imagedong@...cent.com>
---
 net/core/skbuff.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 15f7b6f99a8f..e49e43d4c34d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -771,6 +771,11 @@ void kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)
 	if (!skb_unref(skb))
 		return;
 
+	if (unlikely(reason <= 0 || reason >= SKB_DROP_REASON_MAX)) {
+		DEBUG_NET_WARN_ON_ONCE(1);
+		reason = SKB_DROP_REASON_NOT_SPECIFIED;
+	}
+
 	trace_kfree_skb(skb, __builtin_return_address(0), reason);
 	__kfree_skb(skb);
 }
-- 
2.36.1