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SubjectRe: [PATCH v8 07/28] x86/mpx: Do not use SIB.base if its value is 101b and ModRM.mod = 0
On Fri, Aug 18, 2017 at 05:27:48PM -0700, Ricardo Neri wrote:
> Section 2.2.1.2 of the Intel 64 and IA-32 Architectures Software
> Developer's Manual volume 2A states that if a SIB byte is used and
> SIB.base is 101b and ModRM.mod is zero, then the base part of the base
> part of the effective address computation is null. To signal this
> situation, a -EDOM error is returned to indicate callers to ignore the
> base value present in the register operand.
>
> In this scenario, a 32-bit displacement follows the SIB byte. Displacement
> is obtained when the instruction decoder parses the operands.
>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
> Cc: Colin Ian King <colin.king@canonical.com>
> Cc: Lorenzo Stoakes <lstoakes@gmail.com>
> Cc: Qiaowei Ren <qiaowei.ren@intel.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Nathan Howard <liverlint@gmail.com>
> Cc: Adan Hawthorn <adanhawthorn@gmail.com>
> Cc: Joe Perches <joe@perches.com>
> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
> Cc: x86@kernel.org
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
> ---
> arch/x86/mm/mpx.c | 28 +++++++++++++++++++---------
> 1 file changed, 19 insertions(+), 9 deletions(-)

Reviewed-by: Borislav Petkov <bp@suse.de>

--
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--

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