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

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Date:   Thu, 7 Mar 2019 08:52:51 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Leon Romanovsky <leonro@...lanox.com>
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 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?

-Kees

-- 
Kees Cook