netdev - Re: [PATCH v2] net: dsa: mv88e6xxx: hwtstamp: fix potential negative array index read

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Message-ID: <20180216155535.GE3080@lunn.ch>
Date:   Fri, 16 Feb 2018 16:55:35 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Richard Cochran <richardcochran@...il.com>
Cc:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        Brandon Streiff <brandon.streiff@...com>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: dsa: mv88e6xxx: hwtstamp: fix potential negative
 array index read

On Fri, Feb 16, 2018 at 07:48:46AM -0800, Richard Cochran wrote:
> On Thu, Feb 15, 2018 at 12:31:39PM -0600, Gustavo A. R. Silva wrote:
> > _port_ is being used as index to array port_hwtstamp before verifying
> > it is a non-negative number and a valid index at line 209 and 258:
> > 
> > if (port < 0 || port >= mv88e6xxx_num_ports(chip))
> > 
> > Fix this by checking _port_ before using it as index to array
> > port_hwtstamp.
> 
> NAK.   Port is already known to be valid in the callers.

Then we should take out the check. It is probably this check which is
causing the false positives.

	Andrew