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

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Message-ID: <20180216154846.7ge6seynwxjkopmp@localhost>
Date:   Fri, 16 Feb 2018 07:48:46 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Cc:     Brandon Streiff <brandon.streiff@...com>,
        Andrew Lunn <andrew@...n.ch>,
        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 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.

See:

*** net/dsa/slave.c:  dsa_slave_ioctl[266]
*** net/dsa/slave.c:  dsa_skb_tx_timestamp[416]
*** net/dsa/dsa.c:    dsa_skb_defer_rx_timestamp[152]
 
> Addresses-Coverity-ID: 1465287 ("Negative array index read")
> Addresses-Coverity-ID: 1465291 ("Negative array index read")

Please check the code before posting.  These false positives are
really annoying.

Thanks,
Richard