Fix integer overflow in PCHReader when reading the length of an

identifier.  This caused a crash when reading PCH files that contained
long identifier names.

The issue is that 'StrLenPtr' was previously a 'const char *', meaning
the byte loaded from it would be interpretted as a signed integer.  If
the topmost bit was set, conversion to 'unsigned' would extend that
bit, causing an overflow.

The solution is to make 'StrLenPtr' an 'unsigned char *', always
treating the value as an unsigned integer.

This fixes: <rdar://problem/7328900>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@84925 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Frontend/PCHReader.cpp b/lib/Frontend/PCHReader.cpp
index e804bfc90eb8d47264f8e773b5c5a4685e6420e7..d4302f44c8b70d3f57757e4278f1637d4462d305 100644 (file)
--- a/lib/Frontend/PCHReader.cpp
+++ b/lib/Frontend/PCHReader.cpp
@@ -2515,7 +2515,7 @@ IdentifierInfo *PCHReader::DecodeIdentifierInfo(unsigned ID) {
     // All of the strings in the PCH file are preceded by a 16-bit
     // length. Extract that 16-bit length to avoid having to execute
     // strlen().
-    const char *StrLenPtr = Str - 2;
+    const unsigned char *StrLenPtr = (const unsigned char*) Str - 2;
     unsigned StrLen = (((unsigned) StrLenPtr[0])
                        | (((unsigned) StrLenPtr[1]) << 8)) - 1;
     IdentifiersLoaded[ID - 1]