From: Yuan Yao <yuan.yao@linux.intel.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: tkffaul@outlook.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] vfio/pci: Sanity check IGD OpRegion Size
Date: Mon, 10 May 2021 09:10:14 +0800 [thread overview]
Message-ID: <20210510011014.q6xfcmqopbqgepbq@yy-desk-7060> (raw)
In-Reply-To: <162041357421.21800.16214130780777455390.stgit@omen>
On Fri, May 07, 2021 at 12:53:17PM -0600, Alex Williamson wrote:
> The size field of the IGD OpRegion table is supposed to indicate table
> size in KB, but we've seen at least one report of a BIOS that appears
> to incorrectly report size in bytes. The default size is 8 (*1024 =
> 8KB), but an incorrect implementation may report 8192 (*1024 = 8MB)
> and can cause a variety of mapping errors.
>
> It's believed that 8MB would be an implausible, if not absurd, actual
> size, so we can probably be pretty safe in assuming this is a BIOS bug
> where the intended size is likely 8KB.
>
> Reported-by: Travis Faulhaber <tkffaul@outlook.com>
> Tested-by: Travis Faulhaber <tkffaul@outlook.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
> drivers/vfio/pci/vfio_pci_igd.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci_igd.c b/drivers/vfio/pci/vfio_pci_igd.c
> index 228df565e9bc..c89a4797cd18 100644
> --- a/drivers/vfio/pci/vfio_pci_igd.c
> +++ b/drivers/vfio/pci/vfio_pci_igd.c
> @@ -86,7 +86,16 @@ static int vfio_pci_igd_opregion_init(struct vfio_pci_device *vdev)
> return -EINVAL;
> }
>
> - size *= 1024; /* In KB */
> + /*
> + * The OpRegion size field is specified as size in KB, but there have been
> + * user reports where this field appears to report size in bytes. If we
> + * read 8192, assume this is the case.
> + */
> + if (size == OPREGION_SIZE)
Is "size >= OPREGION_SIZE" or "size >= smaller but still implausible value
(like 4096)" better for covering more bad BIOS implementation cases ?
> + pci_warn(vdev->pdev,
> + "BIOS Bug, IGD OpRegion reports invalid size, assuming default 8KB\n");
> + else
> + size *= 1024; /* In KB */
>
> /*
> * Support opregion v2.1+
>
>
next prev parent reply other threads:[~2021-05-10 1:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-07 18:53 [PATCH] vfio/pci: Sanity check IGD OpRegion Size Alex Williamson
2021-05-08 4:50 ` Zhenyu Wang
2021-05-10 1:10 ` Yuan Yao [this message]
2021-05-10 1:34 ` Alex Williamson
2021-05-10 3:14 ` Yuan Yao
2021-05-10 6:12 ` Christoph Hellwig
2021-05-13 14:43 ` Alex Williamson
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