Re: [PATCH 0/4] tree-wide: fix comparison to bitshift when dealing with a mask

Julia Lawall
2018-02-06T13:16:17Z

On Tue, 6 Feb 2018, Dan Carpenter wrote:

> On Mon, Feb 05, 2018 at 09:09:57PM +0100, Wolfram Sang wrote:
> > In one Renesas driver, I found a typo which turned an intended bit shift ('<<')
> > into a comparison ('<'). Because this is a subtle issue, I looked tree wide for
> > similar patterns. This small patch series is the outcome.
> >
> > Buildbot and checkpatch are happy. Only compile-tested. To be applied
> > individually per sub-system, I think. I'd think only the net: amd: patch needs
> > to be conisdered for stable, but I leave this to people who actually know this
> > driver.
> >
> > CCing Dan. Maybe he has an idea how to add a test to smatch? In my setup, only
> > cppcheck reported a 'coding style' issue with a low prio.
> >
>
> Most of these are inside macros so it makes it complicated for Smatch
> to warn about them. It might be easier in Coccinelle. Julia the bugs
> look like this:
>
> - reissue_mask |= 0xffff < 4;
> + reissue_mask |= 0xffff << 4;

Thanks. I'll take a look. Do you have an example of the macro issue
handy?

julia

>
> regards,
> dan carpenter
>
> > Wolfram Sang (4):
> > v4l: vsp1: fix mask creation for MULT_ALPHA_RATIO
> > drm/exynos: fix comparison to bitshift when dealing with a mask
> > v4l: dvb-frontends: stb0899: fix comparison to bitshift when dealing
> > with a mask
> > net: amd-xgbe: fix comparison to bitshift when dealing with a mask
> >
> > drivers/gpu/drm/exynos/regs-fimc.h | 2 +-
> > drivers/media/dvb-frontends/stb0899_reg.h | 8 ++++----
> > drivers/media/platform/vsp1/vsp1_regs.h | 2 +-
> > drivers/net/ethernet/amd/xgbe/xgbe-drv.c | 2 +-
> > 4 files changed, 7 insertions(+), 7 deletions(-)
> >
> > --
> > 2.11.0
>