Index: clang/include/clang/Basic/SanitizerSpecialCaseList.h
===================================================================
--- clang/include/clang/Basic/SanitizerSpecialCaseList.h
+++ clang/include/clang/Basic/SanitizerSpecialCaseList.h
@@ -15,6 +15,7 @@
 
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/Sanitizers.h"
+#include "clang/Basic/SourceManager.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/SpecialCaseList.h"
 #include <memory>
@@ -24,10 +25,12 @@
 class SanitizerSpecialCaseList : public llvm::SpecialCaseList {
 public:
   static std::unique_ptr<SanitizerSpecialCaseList>
-  create(const std::vector<std::string> &Paths, std::string &Error);
+  create(const std::vector<std::string> &Paths, llvm::vfs::FileSystem &VFS,
+         std::string &Error);
 
   static std::unique_ptr<SanitizerSpecialCaseList>
-  createOrDie(const std::vector<std::string> &Paths);
+  createOrDie(const std::vector<std::string> &Paths,
+              llvm::vfs::FileSystem &VFS);
 
   // Query blacklisted entries if any bit in Mask matches the entry's section.
   bool inSection(SanitizerMask Mask, StringRef Prefix, StringRef Query,
Index: clang/lib/AST/ASTContext.cpp
===================================================================
--- clang/lib/AST/ASTContext.cpp
+++ clang/lib/AST/ASTContext.cpp
@@ -72,6 +72,7 @@
 #include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
@@ -81,6 +82,7 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
Index: clang/lib/Basic/SanitizerBlacklist.cpp
===================================================================
--- clang/lib/Basic/SanitizerBlacklist.cpp
+++ clang/lib/Basic/SanitizerBlacklist.cpp
@@ -16,7 +16,9 @@
 
 SanitizerBlacklist::SanitizerBlacklist(
     const std::vector<std::string> &BlacklistPaths, SourceManager &SM)
-    : SSCL(SanitizerSpecialCaseList::createOrDie(BlacklistPaths)), SM(SM) {}
+    : SSCL(SanitizerSpecialCaseList::createOrDie(
+          BlacklistPaths, SM.getFileManager().getVirtualFileSystem())),
+      SM(SM) {}
 
 bool SanitizerBlacklist::isBlacklistedGlobal(SanitizerMask Mask,
                                              StringRef GlobalName,
Index: clang/lib/Basic/SanitizerSpecialCaseList.cpp
===================================================================
--- clang/lib/Basic/SanitizerSpecialCaseList.cpp
+++ clang/lib/Basic/SanitizerSpecialCaseList.cpp
@@ -16,20 +16,32 @@
 
 std::unique_ptr<SanitizerSpecialCaseList>
 SanitizerSpecialCaseList::create(const std::vector<std::string> &Paths,
+                                 llvm::vfs::FileSystem &VFS,
                                  std::string &Error) {
   std::unique_ptr<clang::SanitizerSpecialCaseList> SSCL(
       new SanitizerSpecialCaseList());
-  if (SSCL->createInternal(Paths, Error)) {
-    SSCL->createSanitizerSections();
-    return SSCL;
+
+  for (const auto &Path : Paths) {
+    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> MaybeBuffer =
+        VFS.getBufferForFile(Path);
+    if (std::error_code EC = MaybeBuffer.getError()) {
+      Error = (Twine("can't open file '") + Path + "': " + EC.message()).str();
+      return nullptr;
+    }
+
+    if (!SSCL->createInternal(MaybeBuffer.get().get(), Error))
+      return nullptr;
   }
-  return nullptr;
+
+  SSCL->createSanitizerSections();
+  return SSCL;
 }
 
 std::unique_ptr<SanitizerSpecialCaseList>
-SanitizerSpecialCaseList::createOrDie(const std::vector<std::string> &Paths) {
+SanitizerSpecialCaseList::createOrDie(const std::vector<std::string> &Paths,
+                                      llvm::vfs::FileSystem &VFS) {
   std::string Error;
-  if (auto SSCL = create(Paths, Error))
+  if (auto SSCL = create(Paths, VFS, Error))
     return SSCL;
   llvm::report_fatal_error(Error);
 }
Index: clang/test/CodeGen/Inputs/sanitizer-blacklist-vfsoverlay.yaml
===================================================================
--- /dev/null
+++ clang/test/CodeGen/Inputs/sanitizer-blacklist-vfsoverlay.yaml
@@ -0,0 +1,15 @@
+{
+  'version': 0,
+  'roots': [
+    { 'name': '@DIR@', 'type': 'directory',
+      'contents': [
+        { 'name': 'only-virtual-file.blacklist', 'type': 'file',
+          'external-contents': '@REAL_FILE@'
+        },
+        { 'name': 'invalid-virtual-file.blacklist', 'type': 'file',
+          'external-contents': '@NONEXISTENT_FILE@'
+        }
+      ]
+    }
+  ]
+}
Index: clang/test/CodeGen/ubsan-blacklist-vfs.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/ubsan-blacklist-vfs.c
@@ -0,0 +1,36 @@
+// Verify ubsan doesn't emit checks for blacklisted functions and files
+// RUN: echo "fun:hash" > %t-func.blacklist
+// RUN: echo "src:%s" | sed -e 's/\\/\\\\/g' > %t-file.blacklist
+
+// RUN: rm -f %t-vfsoverlay.yaml
+// RUN: rm -f %t-nonexistent.blacklist
+// RUN: sed -e "s|@DIR@|%/T|g" %S/Inputs/sanitizer-blacklist-vfsoverlay.yaml | sed -e "s|@REAL_FILE@|%/t-func.blacklist|g" | sed -e "s|@NONEXISTENT_FILE@|%/t-nonexistent.blacklist|g" > %t-vfsoverlay.yaml
+// RUN: %clang_cc1 -fsanitize=unsigned-integer-overflow -ivfsoverlay %t-vfsoverlay.yaml -fsanitize-blacklist=%/T/only-virtual-file.blacklist -emit-llvm %s -o - | FileCheck %s --check-prefix=FUNC
+
+// RUN: not %clang_cc1 -fsanitize=unsigned-integer-overflow -ivfsoverlay %t-vfsoverlay.yaml -fsanitize-blacklist=%/T/invalid-virtual-file.blacklist -emit-llvm %s -o - 2>&1 | FileCheck %s --check-prefix=INVALID-MAPPED-FILE
+// INVALID-MAPPED-FILE: invalid-virtual-file.blacklist': {{[Nn]}}o such file or directory
+
+// RUN: not %clang_cc1 -fsanitize=unsigned-integer-overflow -ivfsoverlay %t-vfsoverlay.yaml -fsanitize-blacklist=%t-nonexistent.blacklist -emit-llvm %s -o - 2>&1 | FileCheck %s --check-prefix=INVALID
+// INVALID: nonexistent.blacklist': {{[Nn]}}o such file or directory
+
+unsigned i;
+
+// DEFAULT: @hash
+// FUNC: @hash
+// FILE: @hash
+unsigned hash() {
+// DEFAULT: call {{.*}}void @__ubsan
+// FUNC-NOT: call {{.*}}void @__ubsan
+// FILE-NOT: call {{.*}}void @__ubsan
+  return i * 37;
+}
+
+// DEFAULT: @add
+// FUNC: @add
+// FILE: @add
+unsigned add() {
+// DEFAULT: call {{.*}}void @__ubsan
+// FUNC: call {{.*}}void @__ubsan
+// FILE-NOT: call {{.*}}void @__ubsan
+  return i + 1;
+}
Index: llvm/lib/Support/SpecialCaseList.cpp
===================================================================
--- llvm/lib/Support/SpecialCaseList.cpp
+++ llvm/lib/Support/SpecialCaseList.cpp
@@ -116,8 +116,10 @@
 bool SpecialCaseList::createInternal(const MemoryBuffer *MB,
                                      std::string &Error) {
   StringMap<size_t> Sections;
-  if (!parse(MB, Sections, Error))
+  if (!parse(MB, Sections, Error)) {
+    Error = (Twine("error parsing buffer: " + Error)).str();
     return false;
+  }
   return true;
 }