Index: lib/sanitizer_common/sanitizer_common_interceptors.inc
===================================================================
--- lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -4671,7 +4671,7 @@
             __sanitizer_FILE *fp) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, freopen, path, mode, fp);
-  COMMON_INTERCEPTOR_READ_RANGE(ctx, path, REAL(strlen)(path) + 1);
+  if (path) COMMON_INTERCEPTOR_READ_RANGE(ctx, path, REAL(strlen)(path) + 1);
   COMMON_INTERCEPTOR_READ_RANGE(ctx, mode, REAL(strlen)(mode) + 1);
   COMMON_INTERCEPTOR_FILE_CLOSE(ctx, fp);
   __sanitizer_FILE *res = REAL(freopen)(path, mode, fp);
@@ -4702,7 +4702,7 @@
             __sanitizer_FILE *fp) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, freopen64, path, mode, fp);
-  COMMON_INTERCEPTOR_READ_RANGE(ctx, path, REAL(strlen)(path) + 1);
+  if (path) COMMON_INTERCEPTOR_READ_RANGE(ctx, path, REAL(strlen)(path) + 1);
   COMMON_INTERCEPTOR_READ_RANGE(ctx, mode, REAL(strlen)(mode) + 1);
   COMMON_INTERCEPTOR_FILE_CLOSE(ctx, fp);
   __sanitizer_FILE *res = REAL(freopen64)(path, mode, fp);
Index: test/asan/TestCases/Posix/freopen.cc
===================================================================
--- test/asan/TestCases/Posix/freopen.cc
+++ test/asan/TestCases/Posix/freopen.cc
@@ -0,0 +1,11 @@
+// RUN: %clangxx_asan -O0 %s -o %t && %run %t
+
+#include <assert.h>
+#include <stdio.h>
+
+int main() {
+  FILE *fp = fopen("/dev/null", "w");
+  assert(fp);
+  freopen(NULL, "a", fp);
+  fclose(fp);
+}