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?).
Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
---
drivers/gpu/drm/drm_crtc.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 266a01d..ff647fa 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -3738,9 +3738,24 @@ int drm_mode_create_dumb_ioctl(struct drm_device *dev,
void *data, struct drm_file *file_priv)
{
struct drm_mode_create_dumb *args = data;
+ u32 Bpp, stride, size;
if (!dev->driver->dumb_create)
return -ENOSYS;
+ if (!args->width || !args->height || !args->bpp)
+ return -EINVAL;
+
+ /* overflow checks for 32bit size calculations */
+ Bpp = (args->bpp + 7) / 8;
+ if (Bpp > 0xffffffffU / args->width)
+ return -EINVAL;
+ stride = Bpp * args->width;
+ if (args->height > 0xffffffffU / stride)
+ return -EINVAL;
+ size = args->height * stride;
+ if (PAGE_ALIGN(size) < size)
+ return -EINVAL;
+
return dev->driver->dumb_create(file_priv, dev, args);
}
--
1.8.5.3
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