linux-kernel - Re: [PATCH] vfio/pci: Sanity check IGD OpRegion Size

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: <20210510011014.q6xfcmqopbqgepbq@yy-desk-7060>
Date:   Mon, 10 May 2021 09:10:14 +0800
From:   Yuan Yao <yuan.yao@...ux.intel.com>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     tkffaul@...look.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfio/pci: Sanity check IGD OpRegion Size

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@...look.com>
> Tested-by: Travis Faulhaber <tkffaul@...look.com>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.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+
> 
>