Index: apps/app_voicemail.c
===================================================================
--- apps/app_voicemail.c	(revision 10407)
+++ apps/app_voicemail.c	(working copy)
@@ -47,6 +47,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/mman.h>
+#include <sys/file.h>
 #include <time.h>
 #include <dirent.h>
 
@@ -634,7 +635,7 @@
 	
 	FILE *configin;
 	FILE *configout;
-	int linenum=0;
+	int linenum=0, fdout=-1, i;
 	char inbuf[256];
 	char orig[256];
 	char currcontext[256] ="";
@@ -647,11 +648,29 @@
 
 	snprintf(tmpin, sizeof(tmpin), "%s/voicemail.conf", ast_config_AST_CONFIG_DIR);
 	snprintf(tmpout, sizeof(tmpout), "%s/voicemail.conf.new", ast_config_AST_CONFIG_DIR);
-	configin = fopen(tmpin,"r");
-	if (configin)
-		configout = fopen(tmpout,"w+");
+	/* Open the "out" file first to avoid a race condition */
+
+	/* Try for 100us to get a lock */
+	for (i = 0; i <= 10; i++) {
+		configout = fopen(tmpout, "w+");
+		fdout = fileno(configout);
+
+		if ((fdout != -1) && (!lockf(fdout, F_TLOCK, 0)))
+			break;
+
+		fclose(configout);
+		configout = NULL;
+		if (i == 10) {
+			ast_log(LOG_WARNING, "Unable to obtain a lock on '%s' for writing: %s\n", tmpout, strerror(errno));
+		} else
+			usleep(10);
+	}
+
+	if (configout)
+		configin = fopen(tmpin, "r");
 	else
-		configout = NULL;
+		configin = NULL;
+	
 	if (!configin || !configout) {
 		if (configin)
 			fclose(configin);
@@ -661,7 +680,7 @@
 			fclose(configout);
 		else
 			ast_log(LOG_WARNING, "Warning: Unable to open '%s' for writing: %s\n", tmpout, strerror(errno));
-			return;
+		return;
 	}
 
 	while (!feof(configin)) {
@@ -751,13 +770,16 @@
 		}
 	}
 	fclose(configin);
-	fclose(configout);
 
 	stat(tmpin, &statbuf);
 	chmod(tmpout, statbuf.st_mode);
 	chown(tmpout, statbuf.st_uid, statbuf.st_gid);
-	unlink(tmpin);
 	rename(tmpout, tmpin);
+
+	/* Only release the lock when we're done moving the file.  This prevents
+	 * a race condition. */
+	lockf(fdout, F_ULOCK, 0);
+	fclose(configout);
 	reset_user_pw(vmu->context, vmu->mailbox, newpassword);
 	ast_copy_string(vmu->password, newpassword, sizeof(vmu->password));
 }