Quoting Dan Carpenter (2018-05-09 09:12:54) > There is a comment here which says that DIV_ROUND_UP() can overflow and > that's where the problem comes from. Say you pick: > > args->bpp = UINT_MAX - 7; > args->width = 4; > args->height = 1; > > The integer overflow in DIV_ROUND_UP() means "cpp" is UINT_MAX / 8 and > because of how we picked args->width that means cpp < UINT_MAX / 4. > > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> > --- > v2: correct a typo in the commit message > > diff --git a/drivers/gpu/drm/drm_dumb_buffers.c b/drivers/gpu/drm/drm_dumb_buffers.c > index 39ac15ce4702..45b0b5bbb5f8 100644 > --- a/drivers/gpu/drm/drm_dumb_buffers.c > +++ b/drivers/gpu/drm/drm_dumb_buffers.c > @@ -65,7 +65,8 @@ int drm_mode_create_dumb_ioctl(struct drm_device *dev, > return -EINVAL; > > /* overflow checks for 32bit size calculations */ > - /* NOTE: DIV_ROUND_UP() can overflow */ > + if (args->bpp > UINT_MAX - 8) > + return -EINVAL; #define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d) both args->bpp and cpp are u32, so should we use U32_MAX to be typesafe? > cpp = DIV_ROUND_UP(args->bpp, 8); > if (!cpp || cpp > 0xffffffffU / args->width) And these constants should also be U32_MAX? -Chris -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
