[llvm] c299f35 - [SystemZ] Fix disassembler crashes

[Ulrich Weigand via llvm-commits]

Author: Ulrich Weigand
Date: 2020-10-20T10:21:42+02:00
New Revision: c299f3555d77aef598506b254dcf728928e616de

URL: https://github.com/llvm/llvm-project/commit/c299f3555d77aef598506b254dcf728928e616de
DIFF: https://github.com/llvm/llvm-project/commit/c299f3555d77aef598506b254dcf728928e616de.diff

LOG: [SystemZ] Fix disassembler crashes

The "Size" value returned by SystemZDisassembler::getInstruction is
used by common code even in the case where the routine returns
failure.  If that Size value exceeds the number of bytes remaining
in the section, that could cause disassembler crashes.

Fixed by never returning more than the number of bytes remaining.

Added: 
    

Modified: 
    llvm/lib/Target/SystemZ/Disassembler/SystemZDisassembler.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/SystemZ/Disassembler/SystemZDisassembler.cpp b/llvm/lib/Target/SystemZ/Disassembler/SystemZDisassembler.cpp
index e42aa14fe589..e81db1030c01 100644
--- a/llvm/lib/Target/SystemZ/Disassembler/SystemZDisassembler.cpp
+++ b/llvm/lib/Target/SystemZ/Disassembler/SystemZDisassembler.cpp
@@ -468,8 +468,10 @@ DecodeStatus SystemZDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
   }
 
   // Read any remaining bytes.
-  if (Bytes.size() < Size)
+  if (Bytes.size() < Size) {
+    Size = Bytes.size();
     return MCDisassembler::Fail;
+  }
 
   // Construct the instruction.
   uint64_t Inst = 0;