diff --git a/llvm/lib/Support/YAMLParser.cpp b/llvm/lib/Support/YAMLParser.cpp
--- a/llvm/lib/Support/YAMLParser.cpp
+++ b/llvm/lib/Support/YAMLParser.cpp
@@ -773,7 +773,7 @@
   IsSimpleKeyAllowed = true;
   Failed = false;
   std::unique_ptr<MemoryBuffer> InputBufferOwner =
-      MemoryBuffer::getMemBuffer(Buffer);
+      MemoryBuffer::getMemBuffer(Buffer, /*RequiresNullTerminator=*/false);
   SM.AddNewSourceBuffer(std::move(InputBufferOwner), SMLoc());
 }
 
@@ -1036,7 +1036,7 @@
 }
 
 void Scanner::skipComment() {
-  if (*Current != '#')
+  if (Current == End || *Current != '#')
     return;
   while (true) {
     // This may skip more than one byte, thus Column is only incremented
@@ -1051,7 +1051,7 @@
 
 void Scanner::scanToNextToken() {
   while (true) {
-    while (*Current == ' ' || *Current == '\t') {
+    while (Current != End && (*Current == ' ' || *Current == '\t')) {
       skip(1);
     }
 
@@ -1286,7 +1286,7 @@
              && wasEscaped(Start + 1, Current));
   } else {
     skip(1);
-    while (true) {
+    while (Current != End) {
       // Skip a ' followed by another '.
       if (Current + 1 < End && *Current == '\'' && *(Current + 1) == '\'') {
         skip(2);
@@ -1334,11 +1334,11 @@
   unsigned LeadingBlanks = 0;
   assert(Indent >= -1 && "Indent must be >= -1 !");
   unsigned indent = static_cast<unsigned>(Indent + 1);
-  while (true) {
+  while (Current != End) {
     if (*Current == '#')
       break;
 
-    while (!isBlankOrBreak(Current)) {
+    while (Current != End && !isBlankOrBreak(Current)) {
       if (  FlowLevel && *Current == ':'
           && !(isBlankOrBreak(Current + 1) || *(Current + 1) == ',')) {
         setError("Found unexpected ':' while scanning a plain scalar", Current);
@@ -1407,10 +1407,10 @@
 }
 
 bool Scanner::scanAliasOrAnchor(bool IsAlias) {
-  StringRef::iterator Start = Current;
-  unsigned ColStart = Column;
   skip(1);
-  while(true) {
+  unsigned ColStart = Column;
+  StringRef::iterator Start = Current;
+  while(Current != End) {
     if (   *Current == '[' || *Current == ']'
         || *Current == '{' || *Current == '}'
         || *Current == ','
diff --git a/llvm/unittests/Support/YAMLIOTest.cpp b/llvm/unittests/Support/YAMLIOTest.cpp
--- a/llvm/unittests/Support/YAMLIOTest.cpp
+++ b/llvm/unittests/Support/YAMLIOTest.cpp
@@ -3101,3 +3101,80 @@
   EXPECT_FALSE(yin2.setCurrentDocument());
   EXPECT_TRUE(yin2.error());
 }
+
+TEST(YAMLIO, TestScannerNoNullEmpty) {
+  std::vector<char> str{};
+  Input yin(llvm::StringRef(str.data(), str.size()));
+  yin.setCurrentDocument();
+  EXPECT_FALSE(yin.error());
+}
+
+TEST(YAMLIO, TestScannerNoNullSequenceOfNull) {
+  std::vector<char> str{'-'};
+  Input yin(llvm::StringRef(str.data(), str.size()));
+  yin.setCurrentDocument();
+  EXPECT_FALSE(yin.error());
+}
+
+TEST(YAMLIO, TestScannerNoNullSimpleSequence) {
+  std::vector<char> str{'-', ' ', 'a'};
+  Input yin(llvm::StringRef(str.data(), str.size()));
+  yin.setCurrentDocument();
+  EXPECT_FALSE(yin.error());
+}
+
+TEST(YAMLIO, TestScannerNoNullUnbalancedMap) {
+  std::vector<char> str{'{'};
+  Input yin(llvm::StringRef(str.data(), str.size()));
+  yin.setCurrentDocument();
+  EXPECT_TRUE(yin.error());
+}
+
+TEST(YAMLIO, TestScannerNoNullEmptyMap) {
+  std::vector<char> str{'{', '}'};
+  Input yin(llvm::StringRef(str.data(), str.size()));
+  yin.setCurrentDocument();
+  EXPECT_FALSE(yin.error());
+}
+
+TEST(YAMLIO, TestScannerNoNullUnbalancedSequence) {
+  std::vector<char> str{'['};
+  Input yin(llvm::StringRef(str.data(), str.size()));
+  yin.setCurrentDocument();
+  EXPECT_TRUE(yin.error());
+}
+
+TEST(YAMLIO, TestScannerNoNullEmptySequence) {
+  std::vector<char> str{'[', ']'};
+  Input yin(llvm::StringRef(str.data(), str.size()));
+  yin.setCurrentDocument();
+  EXPECT_FALSE(yin.error());
+}
+
+TEST(YAMLIO, TestScannerNoNullScalarUnbalancedDoubleQuote) {
+  std::vector<char> str{'-', ' ', '"'};
+  Input yin(llvm::StringRef(str.data(), str.size()));
+  yin.setCurrentDocument();
+  EXPECT_TRUE(yin.error());
+}
+
+TEST(YAMLIO, TestScannerNoNullScalarUnbalancedSingleQuote) {
+  std::vector<char> str{'-', ' ', '\''};
+  Input yin(llvm::StringRef(str.data(), str.size()));
+  yin.setCurrentDocument();
+  EXPECT_TRUE(yin.error());
+}
+
+TEST(YAMLIO, TestScannerNoNullEmptyAlias) {
+  std::vector<char> str{'-', ' ', '&'};
+  Input yin(llvm::StringRef(str.data(), str.size()));
+  yin.setCurrentDocument();
+  EXPECT_TRUE(yin.error());
+}
+
+TEST(YAMLIO, TestScannerNoNullEmptyAnchor) {
+  std::vector<char> str{'-', ' ', '*'};
+  Input yin(llvm::StringRef(str.data(), str.size()));
+  yin.setCurrentDocument();
+  EXPECT_TRUE(yin.error());
+}