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

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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>
This commit is contained in:
David Herrmann 2014-08-24 19:23:26 +02:00 committed by Dave Airlie
parent 4d6923733f
commit 00e7208997
1 changed files with 2 additions and 1 deletions
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3
drivers/gpu/drm/drm_crtc.c
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@ -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)