From: Christian Kastner <ckk@kvr.at>
Date: Fri, 25 Dec 2015 12:36:31 +0100
Subject: crontab must be a regular file

Ensure that the crontab opened in SPOOL_DIR a regular file.

Fix provided by Steve Greenland <stevegr@debian.org>.

Forwarded: no
Last-Update: 2015-12-25
Index: cron/crontab.c
===================================================================
--- cron.orig/crontab.c
+++ cron/crontab.c
@@ -143,6 +143,7 @@ parse_args(argc, argv)
 	char	*argv[];
 {
 	int		argch;
+	struct stat	statbuf;
 
 	if (!(pw = getpwuid(getuid()))) {
 		fprintf(stderr, "%s: your UID isn't in the passwd file.\n",
@@ -243,6 +244,15 @@ parse_args(argc, argv)
 				perror(Filename);
 				exit(ERROR_EXIT);
 			}
+			/* Make sure we opened a normal file. */
+			if (fstat(fileno(NewCrontab), &statbuf) < 0) {
+				perror("fstat");
+				exit(ERROR_EXIT);
+			}
+			if (!S_ISREG(statbuf.st_mode)) {
+				fprintf(stderr, "%s: Not a regular file.\n", Filename);
+				exit(ERROR_EXIT);
+			}
 			if (swap_uids_back() < OK) {
 				perror("swapping uids back");
 				exit(ERROR_EXIT);