linux-kernel - Re: [PATCH] [v3] media: s3c-camif: fix out-of-bounds array access

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Message-ID: <20180116165243.ll4llily5rtctddt@paasikivi.fi.intel.com>
Date:   Tue, 16 Jan 2018 18:52:43 +0200
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Sylwester Nawrocki <sylvester.nawrocki@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        linux-media@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v3] media: s3c-camif: fix out-of-bounds array access

On Tue, Jan 16, 2018 at 05:47:24PM +0100, Arnd Bergmann wrote:
> While experimenting with older compiler versions, I ran
> into a warning that no longer shows up on gcc-4.8 or newer:
> 
> drivers/media/platform/s3c-camif/camif-capture.c: In function '__camif_subdev_try_format':
> drivers/media/platform/s3c-camif/camif-capture.c:1265:25: error: array subscript is below array bounds
> 
> This is an off-by-one bug, leading to an access before the start of the
> array, while newer compilers silently assume this undefined behavior
> cannot happen and leave the loop at index 0 if no other entry matches.
> 
> As Sylvester explains, we actually need to ensure that the
> value is within the range, so this reworks the loop to be
> easier to parse correctly, and an additional check to fall
> back on the first format value for any unexpected input.
> 
> I found an existing gcc bug for it and added a reduced version
> of the function there.
> 
> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69249#c3
> Fixes: babde1c243b2 ("[media] V4L: Add driver for S3C24XX/S3C64XX SoC series camera interface")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Thanks!

Acked-by: Sakari Ailus <sakari.ailus@...ux.intel.com>

-- 
Sakari Ailus
sakari.ailus@...ux.intel.com