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

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Message-Id: <20150625.063331.1437042913073267200.davem@davemloft.net>
Date:	Thu, 25 Jun 2015 06:33:31 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	geert@...ux-m68k.org
Cc:	tom@...bertland.com, jiri@...nulli.us, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] flow_dissector: Pre-initialize ip_proto in
 __skb_flow_dissect()

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.