Index: lib/asan/asan_interceptors.h
===================================================================
--- lib/asan/asan_interceptors.h
+++ lib/asan/asan_interceptors.h
@@ -74,8 +74,12 @@
 
 #if SANITIZER_LINUX && !SANITIZER_ANDROID
 # define ASAN_INTERCEPT___STRDUP 1
+# define ASAN_INTERCEPT_STRNDUP 1
+# define ASAN_INTERCEPT___STRNDUP 1
 #else
 # define ASAN_INTERCEPT___STRDUP 0
+# define ASAN_INTERCEPT_STRNDUP 0
+# define ASAN_INTERCEPT___STRNDUP 0
 #endif
 
 DECLARE_REAL(int, memcmp, const void *a1, const void *a2, uptr size)
Index: lib/asan/asan_interceptors.cc
===================================================================
--- lib/asan/asan_interceptors.cc
+++ lib/asan/asan_interceptors.cc
@@ -570,6 +570,42 @@
 }
 #endif // ASAN_INTERCEPT___STRDUP
 
+#if ASAN_INTERCEPT_STRNDUP
+INTERCEPTOR(char*, strndup, const char *s, uptr size) {
+  void *ctx;
+  ASAN_INTERCEPTOR_ENTER(ctx, strndup);
+  if (UNLIKELY(!asan_inited)) return internal_strndup(s, size);
+  ENSURE_ASAN_INITED();
+  uptr from_length = REAL(strlen)(s);
+  uptr copy_length = Min(size, from_length + 1);
+  if (flags()->replace_str) {
+    ASAN_READ_RANGE(ctx, s, copy_length);
+  }
+  GET_STACK_TRACE_MALLOC;
+  void *new_mem = asan_malloc(copy_length, &stack);
+  REAL(memcpy)(new_mem, s, copy_length - 1);
+  return reinterpret_cast<char*>(new_mem);
+}
+#endif // ASAN_INTERCEPT_STRNDUP
+
+#if ASAN_INTERCEPT___STRNDUP
+INTERCEPTOR(char*, __strndup, const char *s, uptr size) {
+  void *ctx;
+  ASAN_INTERCEPTOR_ENTER(ctx, strndup);
+  if (UNLIKELY(!asan_inited)) return internal_strndup(s, size);
+  ENSURE_ASAN_INITED();
+  uptr from_length = REAL(strlen)(s);
+  uptr copy_length = Min(size, from_length + 1);
+  if (flags()->replace_str) {
+    ASAN_READ_RANGE(ctx, s, copy_length);
+  }
+  GET_STACK_TRACE_MALLOC;
+  void *new_mem = asan_malloc(copy_length, &stack);
+  REAL(memcpy)(new_mem, s, copy_length - 1);
+  return reinterpret_cast<char*>(new_mem);
+}
+#endif // ASAN_INTERCEPT___STRNDUP
+
 INTERCEPTOR(SIZE_T, wcslen, const wchar_t *s) {
   void *ctx;
   ASAN_INTERCEPTOR_ENTER(ctx, wcslen);
@@ -722,6 +758,12 @@
 #if ASAN_INTERCEPT___STRDUP
   ASAN_INTERCEPT_FUNC(__strdup);
 #endif
+#if ASAN_INTERCEPT_STRNDUP
+  ASAN_INTERCEPT_FUNC(strndup);
+#endif
+#if ASAN_INTERCEPT___STRNDUP
+  ASAN_INTERCEPT_FUNC(__strndup);
+#endif
 #if ASAN_INTERCEPT_INDEX && ASAN_USE_ALIAS_ATTRIBUTE_FOR_INDEX
   ASAN_INTERCEPT_FUNC(index);
 #endif
Index: lib/asan/tests/asan_str_test.cc
===================================================================
--- lib/asan/tests/asan_str_test.cc
+++ lib/asan/tests/asan_str_test.cc
@@ -154,6 +154,27 @@
   free(str);
 }
 
+#if SANITIZER_TEST_HAS_STRNDUP
+TEST(AddressSanitizer, MAYBE_StrNDupOOBTest) {
+  size_t size = Ident(42);
+  char *str = MallocAndMemsetString(size);
+  char *new_str;
+  // Normal strdup calls.
+  str[size - 1] = '\0';
+  new_str = strndup(str, size - 13);
+  free(new_str);
+  new_str = strndup(str + size - 1, 13);
+  free(new_str);
+  // Argument points to not allocated memory.
+  EXPECT_DEATH(Ident(strndup(str - 1, 13)), LeftOOBReadMessage(1));
+  EXPECT_DEATH(Ident(strndup(str + size, 13)), RightOOBReadMessage(0));
+  // Overwrite the terminating '\0' and hit unallocated memory.
+  str[size - 1] = 'z';
+  EXPECT_DEATH(Ident(strndup(str, size + 13)), RightOOBReadMessage(0));
+  free(str);
+}
+#endif // SANITIZER_TEST_HAS_STRNDUP
+
 TEST(AddressSanitizer, StrCpyOOBTest) {
   size_t to_size = Ident(30);
   size_t from_size = Ident(6);  // less than to_size
Index: lib/sanitizer_common/tests/sanitizer_test_utils.h
===================================================================
--- lib/sanitizer_common/tests/sanitizer_test_utils.h
+++ lib/sanitizer_common/tests/sanitizer_test_utils.h
@@ -124,4 +124,10 @@
 # define SANITIZER_TEST_HAS_PRINTF_L 0
 #endif
 
+#if defined(__linux__) && !defined(__ANDROID__)
+# define SANITIZER_TEST_HAS_STRNDUP 1
+#else
+# define SANITIZER_TEST_HAS_STRNDUP 0
+#endif
+
 #endif  // SANITIZER_TEST_UTILS_H
Index: test/asan/TestCases/strndup_oob_test.cc
===================================================================
--- /dev/null
+++ test/asan/TestCases/strndup_oob_test.cc
@@ -0,0 +1,27 @@
+// RUN: %clangxx_asan -O0 %s -o %t && not %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_asan -O1 %s -o %t && not %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_asan -O2 %s -o %t && not %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_asan -O3 %s -o %t && not %run %t 2>&1 | FileCheck %s
+
+// When built as C on Linux, strndup is transformed to __strndup.
+// RUN: %clangxx_asan -O3 -xc %s -o %t && not %run %t 2>&1 | FileCheck %s
+
+// REQUIRES: linux
+// XFAIL: android
+
+#include <string.h>
+
+char kString[] = "foo";
+
+int main(int argc, char **argv) {
+  char *copy = strndup(kString, 2);
+  int x = copy[2 + argc];  // BOOM
+  // CHECK: AddressSanitizer: heap-buffer-overflow
+  // CHECK: #0 {{.*}}main {{.*}}strndup_oob_test.cc:[[@LINE-2]]
+  // CHECK-LABEL: allocated by thread T{{.*}} here:
+  // CHECK: #{{[01]}} {{.*}}strndup
+  // CHECK: #{{.*}}main {{.*}}strndup_oob_test.cc:[[@LINE-6]]
+  // CHECK-LABEL: SUMMARY
+  // CHECK: strndup_oob_test.cc:[[@LINE-7]]
+  return x;
+}