linux-kernel - Re: [PATCH 4.4 33/49] net: sctp: fix array overrun read on sctp_timer

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Message-ID: <1512707691.18523.239.camel@codethink.co.uk>
Date:   Fri, 08 Dec 2017 04:34:51 +0000
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org, Colin Ian King <colin.king@...onical.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: Re: [PATCH 4.4 33/49] net: sctp: fix array overrun read on
 sctp_timer_tbl

On Thu, 2017-12-07 at 14:07 +0100, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me
> know.
> 
> ------------------
> 
> From: Colin Ian King <colin.king@...onical.com>
> 
> 
> [ Upstream commit 0e73fc9a56f22f2eec4d2b2910c649f7af67b74d ]
> 
> The comparison on the timeout can lead to an array overrun
> read on sctp_timer_tbl because of an off-by-one error. Fix
> this by using < instead of <= and also compare to the array
> size rather than SCTP_EVENT_TIMEOUT_MAX.
> 
> Fixes CoverityScan CID#1397639 ("Out-of-bounds read")

SCTP_EVENT_TIMEOUT_MAX is one less than the array size, so the bounds
check using <= was correct.  This is cleanup, not a bug fix.

Ben.

> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> Signed-off-by: David S. Miller <davem@...emloft.net>
> Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>  net/sctp/debug.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/net/sctp/debug.c
> +++ b/net/sctp/debug.c
> @@ -166,7 +166,7 @@ static const char *const sctp_timer_tbl[
>  /* Lookup timer debug name. */
>  const char *sctp_tname(const sctp_subtype_t id)
>  {
> -	if (id.timeout <= SCTP_EVENT_TIMEOUT_MAX)
> +	if (id.timeout < ARRAY_SIZE(sctp_timer_tbl))
>  		return sctp_timer_tbl[id.timeout];
>  	return "unknown_timer";
>  }
> 
> 
> 
-- 
Ben Hutchings
Software Developer, Codethink Ltd.