linux-kernel - Re: [PATCH][V3][net-next] net: sctp: fix array overrun read on sctp_timer

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Message-ID: <20170124122233.GA16184@hmswarspite.think-freely.org>
Date:   Tue, 24 Jan 2017 07:22:33 -0500
From:   Neil Horman <nhorman@...driver.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Vlad Yasevich <vyasevich@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][V3][net-next] net: sctp: fix array overrun read on
 sctp_timer_tbl

On Tue, Jan 24, 2017 at 09:25:54AM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Table sctp_timer_tbl is missing a TIMEOUT_RECONF string so
> add this in. Also compare timeout with the size of the array
> sctp_timer_tbl rather than SCTP_EVENT_TIMEOUT_MAX.  Also add
> a build time check that SCTP_EVENT_TIMEOUT_MAX is correct
> so we don't ever get this kind of mismatch between the table
> and SCTP_EVENT_TIMEOUT_MAX in the future.
> 
> Kudos to Marcelo Ricardo Leitner for spotting the missing string
> and suggesting the build time sanity check.
> 
> Fixes CoverityScan CID#1397639 ("Out-of-bounds read")
> 
> Fixes: 7b9438de0cd4 ("sctp: add stream reconf timer")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  net/sctp/debug.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sctp/debug.c b/net/sctp/debug.c
> index 95d7b15..2e47eb2 100644
> --- a/net/sctp/debug.c
> +++ b/net/sctp/debug.c
> @@ -159,6 +159,7 @@ static const char *const sctp_timer_tbl[] = {
>  	"TIMEOUT_T4_RTO",
>  	"TIMEOUT_T5_SHUTDOWN_GUARD",
>  	"TIMEOUT_HEARTBEAT",
> +	"TIMEOUT_RECONF",
>  	"TIMEOUT_SACK",
>  	"TIMEOUT_AUTOCLOSE",
>  };
> @@ -166,7 +167,9 @@ 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)
> +	BUILD_BUG_ON(SCTP_EVENT_TIMEOUT_MAX + 1 != ARRAY_SIZE(sctp_timer_tbl));
> +
> +	if (id.timeout < ARRAY_SIZE(sctp_timer_tbl))
>  		return sctp_timer_tbl[id.timeout];
>  	return "unknown_timer";
>  }
> -- 
> 2.10.2
> 
> 
Acked-by: Neil Horman <nhorman@...driver.com>