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

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Message-ID: <eba7420b-80e3-6f4d-7f19-06b068bc5977@canonical.com>
Date:   Wed, 24 Feb 2021 08:46:35 +0000
From:   Colin Ian King <colin.king@...onical.com>
To:     Dan Carpenter <dan.carpenter@...cle.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 24/02/2021 07:55, Dan Carpenter wrote:
> 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.

Plus compilers are getting smarter with static analysis so some day in
the future they will warn about this.


> 
> regards,
> dan carpenter
>