linux-kernel - Re: [PATCH 6/8] tools/nolibc: tests: add test for -fstack-protector

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Message-ID: <ZCG8I7dVafU/BCGx@1wt.eu>
Date:   Mon, 27 Mar 2023 17:54:11 +0200
From:   Willy Tarreau <w@....eu>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     Thomas Weißschuh <thomas@...ch.de>,
        Thomas Weißschuh <linux@...ssschuh.net>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/8] tools/nolibc: tests: add test for -fstack-protector

On Mon, Mar 27, 2023 at 06:32:51PM +0300, Alexey Dobriyan wrote:
> On Sun, Mar 26, 2023 at 09:42:29PM +0200, Willy Tarreau wrote:
> > On Sun, Mar 26, 2023 at 10:38:39PM +0300, Alexey Dobriyan wrote:
> > > > I'm not seeing any issue with your approach instead, let's
> > > > keep it as-is for now (also it does what the stack protector is supposed
> > > > to catch anyway).
> > > 
> > > There are no guarantess about stack layout and dead writes.
> > > The test doesn't corrupt stack reliably, just 99.99% reliably.
> > 
> > Sure but it's for a regtest which can easily be adjusted and its
> > posrtability and ease of maintenance outweights its reliability,
> > especially when in practice what the code does is what we want to
> > test for. And if an extra zero needs to be added to the loop, it
> > can be at a lower cost than maintaining arch-specific asm code.
> 
> For the record, I disagree. Use volatile writes at least.

Yeah I agree on the volatile one.

Willy