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

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Message-ID: <20180206131044.oso33fvv553trrd7@mwanda>
Date:   Tue, 6 Feb 2018 16:10:44 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Julia Lawall <Julia.Lawall@...6.fr>
Cc:     linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 0/4] tree-wide: fix comparison to bitshift when dealing
 with a mask

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;

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