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Date:   Mon, 29 Oct 2018 08:30:04 +0100
From:   Boris Brezillon <boris.brezillon@bootlin.com>
To:     Kees Cook <keescook@chromium.org>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        Marek Vasut <marek.vasut@gmail.com>,
        Richard Weinberger <richard@nod.at>,
        linux-mtd <linux-mtd@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Olof Johansson <olof@lixom.net>
Subject: Re: [PATCH] mtd: sa1100: avoid VLA in sa1100_setup_mtd
Message-ID: <20181029083004.54d535d2@bbrezillon>
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Hi Kees,

On Sun, 28 Oct 2018 19:13:26 -0700
Kees Cook <keescook@chromium.org> wrote:

> On Fri, Oct 12, 2018 at 2:22 AM, Boris Brezillon
> <boris.brezillon@bootlin.com> wrote:
> > On Fri, 12 Oct 2018 11:19:52 +0200
> > Arnd Bergmann <arnd@arndb.de> wrote:
> >  
> >> On Fri, Oct 12, 2018 at 11:16 AM Boris Brezillon
> >> <boris.brezillon@bootlin.com> wrote:  
> >> >
> >> > Hi Arnd,
> >> >
> >> > On Wed, 10 Oct 2018 20:44:50 +0200
> >> > Arnd Bergmann <arnd@arndb.de> wrote:
> >> >  
> >> > > Enabling -Wvla found another variable-length array with randconfig
> >> > > testing:
> >> > >
> >> > > drivers/mtd/maps/sa1100-flash.c: In function 'sa1100_setup_mtd':
> >> > > drivers/mtd/maps/sa1100-flash.c:224:10: error: ISO C90 forbids variable length array 'cdev' [-Werror=vla]
> >> > >
> >> > > As far as I can tell, there is an upper bound on the number of resources
> >> > > that can be passed, based on the number of CS lines on the bus.
> >> > > In practice, all boards we support have either one or two resources,
> >> > > but using six to be on the safe side has no extra cost.  
> >> >
> >> > Why not dynamically allocate cdev instead? That removes any kind of
> >> > guessing on the max value, and it shouldn't hurt much since this code is
> >> > in the probe path.  
> >>
> >> Fine with me as well, If you prefer that one, please just add
> >> Reported-by: Arnd Bergmann <arnd@arndb.de>  
> >
> > Oh, I thought I'd let you send a v2, but I can do it if you prefer.  
> 
> Olof just pointed out to me that neither fix landed for this? What's
> needed for this?

Nothing in particular, I was planning on sending a new version after
-rc1 is out and then queue it for 4.21 (5.1?) (this patch came in a bit
late, and I had already stopped taking patches for 4.20).

If you consider this a fix or want to have it in 4.20 for other reasons,
just let me know and I'll queue it to the -fixes branch.

Regards,

Boris