Index: lib/sanitizer_common/sanitizer_common.h
===================================================================
--- lib/sanitizer_common/sanitizer_common.h
+++ lib/sanitizer_common/sanitizer_common.h
@@ -378,7 +378,7 @@
 void ReportErrorSummary(const char *error_type, const StackTrace *trace,
                         const char *alt_tool_name = nullptr);
 
-void ReportMmapWriteExec();
+void ReportMmapWriteExec(int prot);
 
 // Math
 #if SANITIZER_WINDOWS && !defined(__clang__) && !defined(__GNUC__)
Index: lib/sanitizer_common/sanitizer_common_interceptors.inc
===================================================================
--- lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -6888,13 +6888,29 @@
             OFF_T off) {
   void *ctx;
   if (common_flags()->detect_write_exec)
-    ReportMmapWriteExec();
+    ReportMmapWriteExec(prot);
   if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
     return (void *)internal_mmap(addr, sz, prot, flags, fd, off);
   COMMON_INTERCEPTOR_ENTER(ctx, mmap, addr, sz, prot, flags, fd, off);
   COMMON_INTERCEPTOR_MMAP_IMPL(ctx, mmap, addr, sz, prot, flags, fd, off);
 }
-#define INIT_MMAP COMMON_INTERCEPT_FUNCTION(mmap);
+
+#if !SANITIZER_MAC
+INTERCEPTOR(int, mprotect, void *addr, SIZE_T sz, int prot) {
+  void *ctx;
+  if (common_flags()->detect_write_exec)
+    ReportMmapWriteExec(prot);
+  if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
+    return (int)internal_mprotect(addr, sz, prot);
+  COMMON_INTERCEPTOR_ENTER(ctx, mprotect, addr, sz, prot);
+  return REAL(mprotect)(addr, sz, prot);
+}
+#define INIT_MMAP \
+  COMMON_INTERCEPT_FUNCTION(mmap); \
+  COMMON_INTERCEPT_FUNCTION(mprotect);
+#else
+#define INIT_MMAP COMMON_INTERCEPT_FUNCTION(mmap)
+#endif
 #else
 #define INIT_MMAP
 #endif
@@ -6904,7 +6920,7 @@
             OFF64_T off) {
   void *ctx;
   if (common_flags()->detect_write_exec)
-    ReportMmapWriteExec();
+    ReportMmapWriteExec(prot);
   if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
     return (void *)internal_mmap(addr, sz, prot, flags, fd, off);
   COMMON_INTERCEPTOR_ENTER(ctx, mmap64, addr, sz, prot, flags, fd, off);
Index: lib/sanitizer_common/sanitizer_common_libcdep.cc
===================================================================
--- lib/sanitizer_common/sanitizer_common_libcdep.cc
+++ lib/sanitizer_common/sanitizer_common_libcdep.cc
@@ -24,6 +24,7 @@
 
 #if SANITIZER_POSIX
 #include "sanitizer_posix.h"
+#include <sys/mman.h>
 #endif
 
 namespace __sanitizer {
@@ -81,8 +82,11 @@
 #endif
 }
 
-void ReportMmapWriteExec() {
-#if !SANITIZER_GO && !SANITIZER_ANDROID
+void ReportMmapWriteExec(int prot) {
+#if SANITIZER_POSIX && (!SANITIZER_GO && !SANITIZER_ANDROID)
+  if ((prot & (PROT_WRITE | PROT_EXEC)) != (PROT_WRITE | PROT_EXEC))
+    return;
+
   ScopedErrorReportLock l;
   SanitizerCommonDecorator d;
 
Index: lib/sanitizer_common/sanitizer_malloc_mac.inc
===================================================================
--- lib/sanitizer_common/sanitizer_malloc_mac.inc
+++ lib/sanitizer_common/sanitizer_malloc_mac.inc
@@ -73,6 +73,8 @@
 // mprotect(malloc_zones, ..., PROT_READ).  This interceptor will catch that and
 // make sure we are still the first (default) zone.
 INTERCEPTOR(int, mprotect, void *addr, size_t len, int prot) {
+  if (common_flags()->detect_write_exec)
+    ReportMmapWriteExec(prot);
   if (addr == malloc_zones && prot == PROT_READ) {
     if (malloc_num_zones > 1 && malloc_zones[0] != &sanitizer_zone) {
       for (unsigned i = 1; i < malloc_num_zones; i++) {
Index: test/sanitizer_common/TestCases/Linux/mmap_write_exec.cpp
===================================================================
--- test/sanitizer_common/TestCases/Linux/mmap_write_exec.cpp
+++ test/sanitizer_common/TestCases/Linux/mmap_write_exec.cpp
@@ -1,15 +1,37 @@
 // RUN: %clangxx %s -o %t
 // RUN: %env_tool_opts=detect_write_exec=1 %run %t 2>&1 | FileCheck %s
-// ubsan and lsan do not install mmap interceptors
-// UNSUPPORTED: ubsan, lsan
+// RUN: %env_tool_opts=detect_write_exec=0 %run %t 2>&1 | FileCheck %s \
+// RUN:   --check-prefix=CHECK-DISABLED
+// ubsan and lsan do not install mmap interceptors UNSUPPORTED: ubsan, lsan
 
 // TODO: Fix option on Android, it hangs there for unknown reasons.
 // XFAIL: android
 
+#include <stdio.h>
 #include <sys/mman.h>
 
 int main(int argc, char **argv) {
   char *p = (char *)mmap(0, 1024, PROT_READ | PROT_WRITE | PROT_EXEC,
                          MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
   // CHECK: WARNING: {{.*}}Sanitizer: writable-executable page usage
+  // CHECK: #{{[0-9]+.*}}main{{.*}}mmap_write_exec.cpp:[[@LINE-3]]
+  // CHECK: SUMMARY: {{.*}}Sanitizer: w-and-x-usage
+
+  char *q = (char *)mmap(p, 64, PROT_READ | PROT_WRITE,
+                         MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0);
+  (void)mprotect(q, 64, PROT_WRITE | PROT_EXEC);
+  // CHECK: WARNING: {{.*}}Sanitizer: writable-executable page usage
+  // CHECK: #{{[0-9]+.*}}main{{.*}}mmap_write_exec.cpp:[[@LINE-2]]
+  // CHECK: SUMMARY: {{.*}}Sanitizer: w-and-x-usage
+
+  char *a = (char *)mmap(0, 1024, PROT_READ | PROT_WRITE,
+                         MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  char *b = (char *)mmap(a, 64, PROT_READ | PROT_WRITE,
+                         MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0);
+  (void)mprotect(q, 64, PROT_READ | PROT_EXEC);
+  // CHECK-NOT: Sanitizer
+
+  printf("done\n");
+  // CHECK-DISABLED-NOT: Sanitizer
+  // CHECK-DISABLED: done
 }