linux-kernel - Re: [PATCH] mtd: spi-nor: intel-spi: Do not try to make the SPI flash chip writable

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200824094448.GE1375436@lahna.fi.intel.com>
Date:   Mon, 24 Aug 2020 12:44:48 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Daniel Gutson <daniel@...ypsium.com>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alex Bazhaniuk <alex@...ypsium.com>,
        Richard Hughes <hughsient@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] mtd: spi-nor: intel-spi: Do not try to make the SPI
 flash chip writable

On Mon, Aug 24, 2020 at 11:31:40AM +0200, Arnd Bergmann wrote:
> On Mon, Aug 24, 2020 at 11:15 AM Mika Westerberg
> <mika.westerberg@...ux.intel.com> wrote:
> > On Mon, Aug 24, 2020 at 11:08:33AM +0200, Arnd Bergmann wrote:
> > > On Mon, Aug 24, 2020 at 10:22 AM Mika Westerberg
> > > <mika.westerberg@...ux.intel.com> wrote:
> > > > On Sat, Aug 22, 2020 at 06:06:03PM +0200, Arnd Bergmann wrote:
> > > > > On Wed, Aug 19, 2020 at 11:11 AM Mika Westerberg
> > > > >
> > > > > The mtd core just checks both the permissions on the device node (which
> > > > > default to 0600 without any special udev rules) and the MTD_WRITEABLE
> > > > > on the underlying device that is controlled by the module parameter
> > > > > in case of intel-spi{,-platform,-pci}.c.
> > > >
> > > > OK, thanks.
> > > >
> > > > Since we cannot really get rid of the module parameter (AFAIK there are
> > > > users for it), I still think we should just make the "writeable" to
> > > > apply to the PCI part as well. That should at least make it consistent,
> > > > and it also solves Daniel's case.
> > >
> > > Can you explain Daniel's case then? I still don't understand what he
> > > actually wants.
> > >
> > > As I keep repeating, the module parameter *does* apply to the pci
> > > driver front-end since it determines whether the driver will disallow
> > > writes to the mtd device without it. The only difference is that the pci
> > > driver will attempt to set the hardware bit without checking the
> > > module parameter first, while the platform driver does not. If the
> > > module parameter is not set however, the state of the hardware
> > > bit is never checked again.
> >
> > I think Daniel wants the PCI driver not to set the hardware bit by
> > default (same as the platform driver).
> 
> Sure, but *why*?

Because this is part of the platform firmware security check patch he is
also working on and, I guess making the flash chip writeable by default
is triggering some of the checks in that patch. Or something along those
lines ;-)