From: David Herrmann <dh.herrmann@gmail.com>
Date: Mon, 20 Jan 2014 19:09:55 +0000 (+0100)
Subject: drm/crtc: add sanity checks to create_dumb()
X-Git-Tag: v3.15-rc1~51^2~57^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b28cd41f9e9bb8085f7362c80833fc129628d3d6;p=pandora-kernel.git

drm/crtc: add sanity checks to create_dumb()

Lets make sure some basic expressions are always true:
  bpp != NULL
  width != NULL
  height != NULL
  stride = bpp * width < 2^32
  size = stride * height < 2^32
  PAGE_ALIGN(size) < 2^32

At least the udl driver doesn't check for multiplication-overflows, so
lets just make sure it will never happen. These checks allow drivers to do
any 32bit math without having to test for mult-overflows themselves.

The two divisions might hurt performance a bit, but dumb_create() is only
used for scanout-buffers, so that should be fine. We could use 64bit math
to avoid the divisions, but that may be slow on 32bit machines.. Or maybe
there should just be a "safe_mult32()" helper, which currently doesn't
exist (I think?).

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
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