Commit 00e72089 authored Aug 24, 2014 by David Herrmann Committed by Dave Airlie Aug 28, 2014

drm: fix division-by-zero on dumb_create()



Kinda unexpected, but DIV_ROUND_UP() can overflow if passed an argument
bigger than UINT_MAX - DIVISOR. Fix this by testing for "!cpp" before
using it in the following division.

Note that DIV_ROUND_UP() is defined as:
        #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))

..this will obviously overflow if (n + d - 1) is bigger than UINT_MAX.

Reported-by: Tommi Rantala <tt.rantala@gmail.com>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

parent 4d692373

drivers/gpu/drm/drm_crtc.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -4696,8 +4696,9 @@ int drm_mode_create_dumb_ioctl(struct drm_device *dev,
		return -EINVAL;

		/* overflow checks for 32bit size calculations */
		/* NOTE: DIV_ROUND_UP() can overflow */
		cpp = DIV_ROUND_UP(args->bpp, 8);
		if (cpp > 0xffffffffU / args->width)
		if (!cpp \|\| cpp > 0xffffffffU / args->width)
		return -EINVAL;
		stride = cpp * args->width;
		if (args->height > 0xffffffffU / stride)