3.19.8-ckt12 -stable review patch. If anyone has any objections, please let me
know.
------------------
From: Dave Hansen <dave.han...@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.carpen...@oracle.com>
Signed-off-by: Dave Hansen <dave.han...@linux.intel.com>
Cc: x...@kernel.org
Cc: Dave Hansen <d...@sr71.net>
Link: http://lkml.kernel.org/r/20151201003113.d800c...@viggo.jf.intel.com
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Signed-off-by: Kamal Mostafa <ka...@canonical.com>
---
arch/x86/mm/mpx.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 3df5f1a..feda8ca 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -120,19 +120,19 @@ static int get_reg_offset(struct insn *insn, struct
pt_regs *regs,
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;
--
1.9.1
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
