From 314ddfca8a218d0e43b5d0a64f8081591734d292 Mon Sep 17 00:00:00 2001
From: Roland McGrath <mcgrathr@google.com>
Date: Thu, 9 Jan 2014 10:13:10 -0800
Subject: [PATCH] Fix buffer underrun in i386-dis.c.

opcodes/
	* i386-dis.c (print_insn): Do not touch all_prefixes[-1] when
	last_rex_prefix is -1.

(cherry picked from commit e2e6193d65a20e6b7fccba288e5d1bc45b78d194)
---
 opcodes/ChangeLog  | 6 ++++++
 opcodes/i386-dis.c | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index 0b72d5b..c168d65 100644
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,3 +1,9 @@
+2014-01-09  Bradley Nelson  <bradnelson@google.com>
+	    Roland McGrath  <mcgrathr@google.com>
+
+	* i386-dis.c (print_insn): Do not touch all_prefixes[-1] when
+	last_rex_prefix is -1.
+
 2013-11-20  Yufeng Zhang  <yufeng.zhang@arm.com>
 
 	* aarch64-opc.c (aarch64_pstatefields): Update.
diff --git a/opcodes/i386-dis.c b/opcodes/i386-dis.c
index 8e55724..d278272 100644
--- a/opcodes/i386-dis.c
+++ b/opcodes/i386-dis.c
@@ -12635,7 +12635,7 @@ print_insn (bfd_vma pc, disassemble_info *info)
     }
 
   /* Check if the REX prefix is used.  */
-  if (rex_ignored == 0 && (rex ^ rex_used) == 0)
+  if (rex_ignored == 0 && (rex ^ rex_used) == 0 && last_rex_prefix >= 0)
     all_prefixes[last_rex_prefix] = 0;
 
   /* Check if the SEG prefix is used.  */
-- 
1.9.2