linux-kernel - Re: [PATCH] memory: gpmc: fix out of bounds read and dereference on gpmc

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Date:   Wed, 24 Feb 2021 10:55:52 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Roger Quadros <rogerq@...nel.org>,
        Tony Lindgren <tony@...mide.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-omap@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memory: gpmc: fix out of bounds read and dereference on
 gpmc_cs[]

On Tue, Feb 23, 2021 at 07:38:21PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently the array gpmc_cs is indexed by cs before it cs is range checked
> and the pointer read from this out-of-index read is dereferenced. Fix this
> by performing the range check on cs before the read and the following
> pointer dereference.
> 
> Addresses-Coverity: ("Negative array index read")
> Fixes: 186401937927 ("memory: gpmc: Move omap gpmc code to live under drivers")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/memory/omap-gpmc.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
> index cfa730cfd145..f80c2ea39ca4 100644
> --- a/drivers/memory/omap-gpmc.c
> +++ b/drivers/memory/omap-gpmc.c
> @@ -1009,8 +1009,8 @@ EXPORT_SYMBOL(gpmc_cs_request);
>  
>  void gpmc_cs_free(int cs)
>  {
> -	struct gpmc_cs_data *gpmc = &gpmc_cs[cs];
> -	struct resource *res = &gpmc->mem;

There is no actual dereferencing going on here, it just taking the
addresses.  But the patch is also harmless and improves readability.

regards,
dan carpenter