linux-kernel - Re: [PATCH v2] flow_dissector: prevent NULL pointer dereference in __skb_flow

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Message-ID: <ZfwxlB9vkI9Y88K8@nanopsycho>
Date: Thu, 21 Mar 2024 14:09:40 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Anastasia Belova <abelova@...ralinux.ru>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH v2] flow_dissector: prevent NULL pointer dereference in
 __skb_flow_dissect

Thu, Mar 21, 2024 at 01:34:46PM CET, abelova@...ralinux.ru wrote:
>skb is an optional parameter, so it may be NULL.
>Add check defore dereference in eth_hdr.
>
>Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
>Fixes: 690e36e726d0 ("net: Allow raw buffers to be passed into the flow dissector.")
>Signed-off-by: Anastasia Belova <abelova@...ralinux.ru>
>---
> net/core/flow_dissector.c | 2 ++
> 1 file changed, 2 insertions(+)
>
>diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
>index 272f09251343..68a8228ffae3 100644
>--- a/net/core/flow_dissector.c
>+++ b/net/core/flow_dissector.c
>@@ -1139,6 +1139,8 @@ bool __skb_flow_dissect(const struct net *net,
> 
> 	if (dissector_uses_key(flow_dissector,
> 			       FLOW_DISSECTOR_KEY_ETH_ADDRS)) {
>+		if (!skb)
>+			goto out_bad;

Please read my recent reply to v1.

pw-bot: cr


> 		struct ethhdr *eth = eth_hdr(skb);
> 		struct flow_dissector_key_eth_addrs *key_eth_addrs;
> 
>-- 
>2.30.2
>