diff -up lockdev-scm-2011-10-07/src/lockdev.c.access lockdev-scm-2011-10-07/src/lockdev.c
--- lockdev-scm-2011-10-07/src/lockdev.c.access	2011-07-22 09:37:10.000000000 +0200
+++ lockdev-scm-2011-10-07/src/lockdev.c	2013-12-05 11:56:57.836961642 +0100
@@ -95,6 +95,10 @@
  *
  */
 
+#ifndef _GNU_SOURCE
+   #define _GNU_SOURCE
+#endif
+
 #include <errno.h>
 #include <signal.h>
 #include <stdio.h>
@@ -616,7 +620,10 @@ dev_lock (const char *devname)
 	if ( stat( device, &statbuf) == -1 ) {
 		close_n_return(-errno);
 	}
-	if ( access( device, W_OK ) == -1 ) {
+	/* check that the caller has write permission to the device
+	 * to prevent denial-of-service attack by unauthorized users
+	 */
+	if ( euidaccess( device, W_OK ) == -1 ) {
 		close_n_return(-errno);
 	}
 
@@ -780,7 +787,10 @@ dev_relock (const char  *devname,
 	if ( stat( device, &statbuf) == -1 ) {
 		close_n_return(-errno);
 	}
-	if ( access( device, W_OK ) == -1 ) {
+	/* check that the caller has write permission to the device
+	 * to prevent denial-of-service attack by unauthorized users
+	 */
+	if ( euidaccess( device, W_OK ) == -1 ) {
 		close_n_return(-errno);
 	}
 
@@ -870,7 +880,10 @@ dev_unlock (const char *devname,
 	if ( stat( device, &statbuf) == -1 ) {
 		close_n_return(-errno);
 	}
-	if ( access( device, W_OK ) == -1 ) {
+	/* check that the caller has write permission to the device
+	 * to prevent denial-of-service attack by unauthorized users
+	 */
+	if ( euidaccess( device, W_OK ) == -1 ) {
 		close_n_return(-errno);
 	}