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From: David Laight <David.Laight@ACULAB.COM>
To: "'Ard Biesheuvel'" <ard.biesheuvel@linaro.org>,
	Hans de Goede <hdegoede@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
	the arch/x86 maintainers <x86@kernel.org>,
	"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2] efi: Ignore unrealistically large option roms
Date: Tue, 1 May 2018 13:52:55 +0000	[thread overview]
Message-ID: <96034903ca984624a5972f7bb5aea975@AcuMS.aculab.com> (raw)
In-Reply-To: <CAKv+Gu9xxSy2XXN446etRC5xaXdeOBBBYBxZZy=0bZbdZA_K8Q@mail.gmail.com>

From: Ard Biesheuvel
> Sent: 28 April 2018 07:41
> On 27 April 2018 at 23:35, Hans de Goede <hdegoede@redhat.com> wrote:
> > setup_efi_pci() tries to save a copy of each PCI option ROM as this may
> > be necessary for the device driver for the PCI device to have access too.
> >
> > On some systems the efi_pci_io_protocol_64's romimage and romsize fields
> > contain invalid data, which looks a bit like pointers pointing back into
> > other EFI code or data. Interpreting these pointers as romsize leads to
> > a very large value and if we then try to alloc this amount of memory to
> > save a copy the alloc call fails.
> >
> > This leads to a "Failed to alloc mem for rom" error being printed on the
> > EFI console for each PCI device.
> >
> > This commit avoids the printing of these errors, by checking romsize
> > before doing the alloc and if it is larger then 256M silently ignore the
> > ROM fields instead of trying to alloc mem and fail.
> >
> 
> The UEFI spec limits the size of option ROMs to 16 MiB, so I'd prefer
> we use that as the upper bound instead.

Copying even 16MB of rom data into physical memory on the 'off chance' that
the kernel might need it seems a waste of memory.

I can't help feeling that some kind of caching would be more appropriate.

	David

  parent reply	other threads:[~2018-05-01 13:51 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-27 21:35 Hans de Goede
2018-04-28  6:40 ` Ard Biesheuvel
2018-04-28 20:11   ` Hans de Goede
2018-05-01 13:52   ` David Laight [this message]
2018-05-01 13:57     ` Ard Biesheuvel

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