Re: [PATCH v2] [media] v4l2-common: fix overflow in v4l_bound_align_image()

[Greg KH]

On Wed, Sep 10, 2014 at 06:51:09PM +0200, Maciej Matraszek wrote:
> Fix clamp_align() used in v4l_bound_align_image() to prevent overflow when
> passed large value like UINT32_MAX. In the current implementation:
>     clamp_align(UINT32_MAX, 8, 8192, 3)
> returns 8, because in line:
>     x = (x + (1 << (align - 1))) & mask;
> x overflows to (-1 + 4) & 0x7 = 3, while expected value is 8192.
> 
> v4l_bound_align_image() is heavily used in VIDIOC_S_FMT
> and VIDIOC_SUBDEV_S_FMT ioctls handlers, and documentation of the latter
> explicitly states that:
> 
> "The modified format should be as close as possible to the original request."
>   -- http://linuxtv.org/downloads/v4l-dvb-apis/vidioc-subdev-g-fmt.html
> 
> Thus one would expect, that passing UINT32_MAX as format width and height
> will result in setting maximum possible resolution for the device.
> Particularly, when the driver doesn't support VIDIOC_ENUM_FRAMESIZES ioctl,
> which is common in the codebase.
> 
> Fixes: b0d3159be9a3 ("V4L/DVB (11901): v4l2: Create helper function for bounding and aligning images")
> Signed-off-by: Maciej Matraszek <m.matraszek@xxxxxxxxxxx>
> Acked-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> 
> ---

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read Documentation/stable_kernel_rules.txt
for how to do this properly.

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