From: Reid Kleckner <rnk@google.com>
Date: Thu, 19 Nov 2015 21:51:55 +0000 (+0000)
Subject: Fix UMRs in Mips disassembler on invalid instruction streams
X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=commitdiff_plain;h=eaaa0ed96c699e2369dacc46a723a0c76a88152a

Fix UMRs in Mips disassembler on invalid instruction streams

The Insn and Size local variables were used without initialization.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253607 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/Mips/Disassembler/MipsDisassembler.cpp b/lib/Target/Mips/Disassembler/MipsDisassembler.cpp
index f25df1ef715..f9601839b44 100644
--- a/lib/Target/Mips/Disassembler/MipsDisassembler.cpp
+++ b/lib/Target/Mips/Disassembler/MipsDisassembler.cpp
@@ -867,6 +867,8 @@ DecodeStatus MipsDisassembler::getInstruction(MCInst &Instr, uint64_t &Size,
 
   if (IsMicroMips) {
     Result = readInstruction16(Bytes, Address, Size, Insn, IsBigEndian);
+    if (Result == MCDisassembler::Fail)
+      return MCDisassembler::Fail;
 
     if (hasMips32r6()) {
       DEBUG(dbgs() << "Trying MicroMipsR616 table (16-bit instructions):\n");
@@ -913,12 +915,17 @@ DecodeStatus MipsDisassembler::getInstruction(MCInst &Instr, uint64_t &Size,
       Size = 4;
       return Result;
     }
+    // This is an invalid instruction. Let the disassembler move forward by the
+    // minimum instruction size.
+    Size = 2;
     return MCDisassembler::Fail;
   }
 
   Result = readInstruction32(Bytes, Address, Size, Insn, IsBigEndian, false);
-  if (Result == MCDisassembler::Fail)
+  if (Result == MCDisassembler::Fail) {
+    Size = 4;
     return MCDisassembler::Fail;
+  }
 
   if (hasCOP3()) {
     DEBUG(dbgs() << "Trying COP3_ table (32-bit opcodes):\n");
@@ -979,6 +986,7 @@ DecodeStatus MipsDisassembler::getInstruction(MCInst &Instr, uint64_t &Size,
     return Result;
   }
 
+  Size = 4;
   return MCDisassembler::Fail;
 }