From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dan Carpenter , Dave Hansen , x86@kernel.org, Dave Hansen , Thomas Gleixner Subject: [PATCH 4.3 002/157] x86/mpx: Fix instruction decoder condition Date: Wed, 27 Jan 2016 10:11:09 -0800 Message-Id: <20160127180932.670572900@linuxfoundation.org> In-Reply-To: <20160127180932.533735338@linuxfoundation.org> References: <20160127180932.533735338@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dave Hansen commit 8e8efe0379bd93e8219ca0fc6fa80b5dd85b09cb upstream. MPX decodes instructions in order to tell which bounds register was violated. Part of this decoding involves looking at the "REX prefix" which is a special instrucion prefix used to retrofit support for new registers in to old instructions. The X86_REX_*() macros are defined to return actual bit values: #define X86_REX_R(rex) ((rex) & 4) *not* boolean values. However, the MPX code was checking for them like they were booleans. This might have led to us mis-decoding the "REX prefix" and giving false information out to userspace about bounds violations. X86_REX_B() actually is bit 1, so this is really only broken for the X86_REX_X() case. Fix the conditionals up to tolerate the non-boolean values. Fixes: fcc7ffd67991 "x86, mpx: Decode MPX instruction to get bound violation information" Reported-by: Dan Carpenter Signed-off-by: Dave Hansen Cc: x86@kernel.org Cc: Dave Hansen Link: http://lkml.kernel.org/r/20151201003113.D800C1E0@viggo.jf.intel.com Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/mpx.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/arch/x86/mm/mpx.c +++ b/arch/x86/mm/mpx.c @@ -101,19 +101,19 @@ static int get_reg_offset(struct insn *i switch (type) { case REG_TYPE_RM: regno = X86_MODRM_RM(insn->modrm.value); - if (X86_REX_B(insn->rex_prefix.value) == 1) + if (X86_REX_B(insn->rex_prefix.value)) regno += 8; break; case REG_TYPE_INDEX: regno = X86_SIB_INDEX(insn->sib.value); - if (X86_REX_X(insn->rex_prefix.value) == 1) + if (X86_REX_X(insn->rex_prefix.value)) regno += 8; break; case REG_TYPE_BASE: regno = X86_SIB_BASE(insn->sib.value); - if (X86_REX_B(insn->rex_prefix.value) == 1) + if (X86_REX_B(insn->rex_prefix.value)) regno += 8; break;