diff --git a/libc/Android.mk b/libc/Android.mk
index 6a77deb..a781967 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -257,6 +257,7 @@
 	tzcode/strftime.c \
 	tzcode/strptime.c \
 	bionic/__set_errno.c \
+	bionic/__umask_chk.c \
 	bionic/bionic_clone.c \
 	bionic/cpuacct.c \
 	bionic/arc4random.c \
diff --git a/libc/bionic/__umask_chk.c b/libc/bionic/__umask_chk.c
new file mode 100644
index 0000000..5bb6a3b
--- /dev/null
+++ b/libc/bionic/__umask_chk.c
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#undef _FORTIFY_SOURCE
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <private/logd.h>
+#include <stdlib.h>
+
+/*
+ * Runtime implementation of __umask_chk.
+ *
+ * Validate that umask is called with sane mode.
+ *
+ * This umask check is called if _FORTIFY_SOURCE is defined and
+ * greater than 0.
+ */
+mode_t __umask_chk(mode_t mode)
+{
+    if ((mode & 0777) != mode) {
+        __libc_android_log_print(ANDROID_LOG_FATAL, "libc",
+            "*** FORTIFY_SOURCE: umask called with invalid mask ***\n");
+        abort();
+    }
+
+    return umask(mode);
+}
diff --git a/libc/include/sys/stat.h b/libc/include/sys/stat.h
index bee648e..62e0d8b 100644
--- a/libc/include/sys/stat.h
+++ b/libc/include/sys/stat.h
@@ -122,6 +122,27 @@
 extern int    mknod(const char *, mode_t, dev_t);
 extern mode_t umask(mode_t);
 
+#if defined(__BIONIC_FORTIFY_INLINE)
+
+extern mode_t __umask_chk(mode_t);
+extern mode_t __umask_real(mode_t)
+    __asm__(__USER_LABEL_PREFIX__ "umask");
+extern void __umask_error()
+    __attribute__((__error__("umask called with invalid mode")));
+
+__BIONIC_FORTIFY_INLINE
+mode_t umask(mode_t mode) {
+  if (__builtin_constant_p(mode)) {
+    if ((mode & 0777) != mode) {
+      __umask_error();
+    }
+    return __umask_real(mode);
+  }
+  return __umask_chk(mode);
+}
+#endif /* defined(__BIONIC_FORTIFY_INLINE) */
+
+
 #define  stat64    stat
 #define  fstat64   fstat
 #define  lstat64   lstat