| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.1 001/127] x86/mpx: Fix instruction decoder condition | Date | Wed, 27 Jan 2016 10:12:45 -0800 |
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4.1-stable review patch. If anyone has any objections, please let me know.
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From: Dave Hansen <dave.hansen@linux.intel.com>
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 <dan.carpenter@oracle.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: x86@kernel.org Cc: Dave Hansen <dave@sr71.net> Link: http://lkml.kernel.org/r/20151201003113.D800C1E0@viggo.jf.intel.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- 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 @@ -120,19 +120,19 @@ 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;
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