linux-kernel - Re: [PATCH] mtd: sa1100: avoid VLA in sa1100_setup

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Message-ID: <20181012112259.56f3c44f@bbrezillon>
Date:   Fri, 12 Oct 2018 11:22:59 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mtd: sa1100: avoid VLA in sa1100_setup_mtd

On Fri, 12 Oct 2018 11:19:52 +0200
Arnd Bergmann <arnd@...db.de> wrote:

> On Fri, Oct 12, 2018 at 11:16 AM Boris Brezillon
> <boris.brezillon@...tlin.com> wrote:
> >
> > Hi Arnd,
> >
> > On Wed, 10 Oct 2018 20:44:50 +0200
> > Arnd Bergmann <arnd@...db.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@...db.de>

Oh, I thought I'd let you send a v2, but I can do it if you prefer.