linux-kernel - Re: [PATCH] Avoid that check_shl_overflow() triggers a compiler warning when building with W=1

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Message-ID: <20190307170230.GR1789@mtr-leonro.mtl.com>
Date:   Thu, 7 Mar 2019 17:02:36 +0000
From:   Leon Romanovsky <leonro@...lanox.com>
To:     Kees Cook <keescook@...omium.org>
CC:     Bart Van Assche <bvanassche@....org>,
        Jason Gunthorpe <jgg@...lanox.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [PATCH] Avoid that check_shl_overflow() triggers a compiler
 warning when building with W=1

On Thu, Mar 07, 2019 at 08:52:51AM -0800, Kees Cook wrote:
> On Thu, Mar 7, 2019 at 7:40 AM Leon Romanovsky <leonro@...lanox.com> wrote:
> >
> > On Thu, Mar 07, 2019 at 06:53:54AM -0800, Bart Van Assche wrote:
> > > On 3/6/19 11:24 PM, Leon Romanovsky wrote:
> > > > My simple patch passes too :).
> > >
> > > Can you repost your patch?
> >
> > https://patchwork.kernel.org/patch/10841079/
> >
> > As Rasmus wrote, the thing is to avoid a < 0 check. In my patch,
> > I converted a <= 0 to !(a > 0 || a == 0) expression.
>
> I'd be happy either way. Is there a larger benefit to having a safe
> "is_non_negative()" helper, or should we go with the minimal change to
> the shl macro?

I personally prefer simplest possible solution.

>
> -Kees
>
> --
> Kees Cook

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