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

From: Paul Menzel
Date: Thu Oct 11 2018 - 19:23:48 EST

Dear Thomas,

Am 08.10.2018 um 21:53 schrieb Thomas Gleixner:
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@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
arch/x86/mm/dump_pagetables.c | 35 +++++++++++++++++++++++++++--------
1 file changed, 27 insertions(+), 8 deletions(-)

Thank you for the patch. I tested it on the ASRock E350M1 with coreboot and the SeaBIOS payload, and the insecure warning is gone.

Tested-by: Paul Menzel <pmenzel@xxxxxxxxxxxxx>

Should this be tagged for the stable series?

Kind regards,