linux-kernel - Re: [PATCH] flow_dissector: Pre-initialize ip_proto in __skb_flow

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Message-ID: <20150625134838.GA2455@nanopsycho.ki.iif.hu>
Date:	Thu, 25 Jun 2015 15:48:38 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	David Miller <davem@...emloft.net>
Cc:	geert@...ux-m68k.org, tom@...bertland.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] flow_dissector: Pre-initialize ip_proto in
 __skb_flow_dissect()

Thu, Jun 25, 2015 at 03:33:31PM CEST, davem@...emloft.net wrote:
>From: Geert Uytterhoeven <geert@...ux-m68k.org>
>Date: Thu, 25 Jun 2015 15:10:32 +0200
>
>> net/core/flow_dissector.c: In function ‘__skb_flow_dissect’:
>> net/core/flow_dissector.c:132: warning: ‘ip_proto’ may be used uninitialized in this function
>> 
>> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>> ---
>> This may be a false positive, but the state machine in
>> __skb_flow_dissect() is a bit hard to follow.
>> As I believe it is controlled by a packet received from the network, the
>> only safe thing to do is to pre-initialize ip_proto.
>
>Actually I think this is a real bug, because for the ETH_P_MPLS_* cases I cannot
>see what will always set ip_proto before it gets used as an input.

I think that MPLS cases are ok. In this case, return is always hit.
I believe this is false positive.


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