linux-kernel - Re: [PATCH] x86/mm: Do not warn about PCI BIOS W+X mappings

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Date:   Mon, 8 Oct 2018 22:01:15 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Paul Menzel <pmenzel@...gen.mpg.de>,
        Joerg Roedel <joro@...tes.org>,
        Kees Cook <keescook@...omium.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH] x86/mm: Do not warn about PCI BIOS W+X mappings

On Mon, Oct 08, 2018 at 09:53:48PM +0200, Thomas Gleixner wrote:
> PCI BIOS requires the BIOS area 0x0A0000-0x0FFFFFF to be mapped W+X for
> various legacy reasons. When CONFIG_DEBUG_WX is enabled, this triggers the
> WX warning, but this is misleading because the mapping is required and is
> not a result of an accidental oversight.
> 
> Prevent the full warning when PCI BIOS is enabled and the detected WX
> mapping is in the BIOS area. Just emit a pr_warn() which denotes the
> fact. This is partially duplicating the info which the PCI BIOS code emits
> when it maps the area as executable, but that info is not in the context of
> the WX checking output.
> 
> Reported-by: Paul Menzel <pmenzel@...gen.mpg.de>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>

Tested-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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