queue(3) instead of homegrown queues and lists. This also fixes

some potential memory leaks in error paths.  OK guenther@

7 files changed, 130 insertions, 170 deletions

diff --git a/usr.sbin/cron/atrun.c b/usr.sbin/cron/atrun.c
index c873ed1a164..517be19d6e9 100644
--- a/usr.sbin/cron/atrun.c
+++ b/usr.sbin/cron/atrun.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: atrun.c,v 1.34 2015/11/04 20:28:17 millert Exp $	*/
+/*	$OpenBSD: atrun.c,v 1.35 2015/11/09 01:12:27 millert Exp $	*/
 
 /*
  * Copyright (c) 2002-2003 Todd C. Miller <Todd.Miller@courtesan.com>
@@ -48,21 +48,20 @@
 #include "funcs.h"
 #include "globals.h"
 
-static void unlink_job(at_db *, atjob *);
 static void run_job(atjob *, char *);
 
 /*
  * Scan the at jobs dir and build up a list of jobs found.
  */
 int
-scan_atjobs(at_db *old_db, struct timespec *ts)
+scan_atjobs(at_db **db, struct timespec *ts)
 {
 	DIR *atdir = NULL;
 	int cwd, queue, pending;
 	time_t run_time;
 	char *ep;
-	at_db new_db;
-	atjob *job, *tjob;
+	at_db *new_db, *old_db = *db;
+	atjob *job;
 	struct dirent *file;
 	struct stat statbuf;
 
@@ -71,11 +70,11 @@ scan_atjobs(at_db *old_db, struct timespec *ts)
 		return (0);
 	}
 
-	if (old_db->mtime == statbuf.st_mtime) {
+	if (old_db != NULL && old_db->mtime == statbuf.st_mtime) {
 		return (0);
 	}
 
-	/* XXX - would be nice to stash the crontab cwd */
+	/* XXX - use fstatat/openat instead of chdir */
 	if ((cwd = open(".", O_RDONLY, 0)) < 0) {
 		log_it("CRON", getpid(), "CAN'T OPEN", ".");
 		return (0);
@@ -91,8 +90,14 @@ scan_atjobs(at_db *old_db, struct timespec *ts)
 		return (0);
 	}
 
-	new_db.mtime = statbuf.st_mtime;	/* stash at dir mtime */
-	new_db.head = new_db.tail = NULL;
+	if ((new_db = malloc(sizeof(*new_db))) == NULL) {
+		closedir(atdir);
+		fchdir(cwd);
+		close(cwd);
+		return (0);
+	}
+	new_db->mtime = statbuf.st_mtime;	/* stash at dir mtime */
+	TAILQ_INIT(&new_db->jobs);
 
 	pending = 0;
 	while ((file = readdir(atdir)) != NULL) {
@@ -113,11 +118,11 @@ scan_atjobs(at_db *old_db, struct timespec *ts)
 
 		job = malloc(sizeof(*job));
 		if (job == NULL) {
-			for (job = new_db.head; job != NULL; ) {
-				tjob = job;
-				job = job->next;
-				free(tjob);
+			while ((job = TAILQ_FIRST(&new_db->jobs))) {
+				TAILQ_REMOVE(&new_db->jobs, job, entries);
+				free(job);
 			}
+			free(new_db);
 			closedir(atdir);
 			fchdir(cwd);
 			close(cwd);
@@ -127,32 +132,26 @@ scan_atjobs(at_db *old_db, struct timespec *ts)
 		job->gid = statbuf.st_gid;
 		job->queue = queue;
 		job->run_time = run_time;
-		job->prev = new_db.tail;
-		job->next = NULL;
-		if (new_db.head == NULL)
-			new_db.head = job;
-		if (new_db.tail != NULL)
-			new_db.tail->next = job;
-		new_db.tail = job;
+		TAILQ_INSERT_TAIL(&new_db->jobs, job, entries);
 		if (ts != NULL && run_time <= ts->tv_sec)
 			pending = 1;
 	}
 	closedir(atdir);
 
-	/* Free up old at db */
-	for (job = old_db->head; job != NULL; ) {
-		tjob = job;
-		job = job->next;
-		free(tjob);
+	/* Free up old at db and install new one */
+	if (old_db != NULL) {
+		while ((job = TAILQ_FIRST(&old_db->jobs))) {
+			TAILQ_REMOVE(&old_db->jobs, job, entries);
+			free(job);
+		}
+		free(old_db);
 	}
+	*db = new_db;
 
 	/* Change back to the normal cron dir. */
 	fchdir(cwd);
 	close(cwd);
 
-	/* Install the new database */
-	*old_db = new_db;
-
 	return (pending);
 }
 
@@ -165,9 +164,12 @@ atrun(at_db *db, double batch_maxload, time_t now)
 	char atfile[MAX_FNAME];
 	struct stat statbuf;
 	double la;
-	atjob *job, *batch;
+	atjob *job, *tjob, *batch = NULL;
+
+	if (db == NULL)
+		return;
 
-	for (batch = NULL, job = db->head; job; job = job->next) {
+	TAILQ_FOREACH_SAFE(job, &db->jobs, entries, tjob) {
 		/* Skip jobs in the future */
 		if (job->run_time > now)
 			continue;
@@ -175,11 +177,11 @@ atrun(at_db *db, double batch_maxload, time_t now)
 		snprintf(atfile, sizeof(atfile), "%s/%lld.%c", AT_DIR,
 		    (long long)job->run_time, job->queue);
 
-		if (stat(atfile, &statbuf) != 0)
-			unlink_job(db, job);	/* disapeared */
-
-		if (!S_ISREG(statbuf.st_mode))
-			continue;		/* should not happen */
+		if (lstat(atfile, &statbuf) != 0 || !S_ISREG(statbuf.st_mode)) {
+			TAILQ_REMOVE(&db->jobs, job, entries);
+			free(job);
+			continue;		/* disapeared or not a file */
+		}
 
 		/*
 		 * Pending jobs have the user execute bit set.
@@ -194,7 +196,8 @@ atrun(at_db *db, double batch_maxload, time_t now)
 			} else {
 				/* normal at job */
 				run_job(job, atfile);
-				unlink_job(db, job);
+				TAILQ_REMOVE(&db->jobs, job, entries);
+				free(job);
 			}
 		}
 	}
@@ -207,28 +210,12 @@ atrun(at_db *db, double batch_maxload, time_t now)
 		snprintf(atfile, sizeof(atfile), "%s/%lld.%c", AT_DIR,
 		    (long long)batch->run_time, batch->queue);
 		run_job(batch, atfile);
-		unlink_job(db, batch);
+		TAILQ_REMOVE(&db->jobs, batch, entries);
+		free(job);
 	}
 }
 
 /*
- * Remove the specified at job from the database.
- */
-static void
-unlink_job(at_db *db, atjob *job)
-{
-	if (job->prev == NULL)
-		db->head = job->next;
-	else
-		job->prev->next = job->next;
-
-	if (job->next == NULL)
-		db->tail = job->prev;
-	else
-		job->next->prev = job->prev;
-}
-
-/*
  * Run the specified job contained in atfile.
  */
 static void
diff --git a/usr.sbin/cron/cron.c b/usr.sbin/cron/cron.c
index 4111850981f..2d5b1e8f271 100644
--- a/usr.sbin/cron/cron.c
+++ b/usr.sbin/cron/cron.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cron.c,v 1.63 2015/11/06 23:47:42 millert Exp $	*/
+/*	$OpenBSD: cron.c,v 1.64 2015/11/09 01:12:27 millert Exp $	*/
 
 /* Copyright 1988,1990,1993,1994 by Paul Vixie
  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
@@ -59,8 +59,8 @@ static	volatile sig_atomic_t	got_sighup, got_sigchld;
 static	time_t			timeRunning, virtualTime, clockTime;
 static	int			cronSock;
 static	long			GMToff;
-static	cron_db			database;
-static	at_db			at_database;
+static	cron_db			*database;
+static	at_db			*at_database;
 static	double			batch_maxload = BATCH_MAXLOAD;
 static	int			NoFork;
 static	time_t			StartTime;
@@ -118,16 +118,10 @@ main(int argc, char *argv[])
 		log_it("CRON",getpid(),"STARTUP",CRON_VERSION);
 	}
 
-	database.head = NULL;
-	database.tail = NULL;
-	database.mtime = 0;
 	load_database(&database);
-	at_database.head = NULL;
-	at_database.tail = NULL;
-	at_database.mtime = 0;
 	scan_atjobs(&at_database, NULL);
 	set_time(TRUE);
-	run_reboot_jobs(&database);
+	run_reboot_jobs(database);
 	timeRunning = virtualTime = clockTime;
 
 	/*
@@ -169,7 +163,7 @@ main(int argc, char *argv[])
 		/* shortcut for the most common case */
 		if (timeDiff == 1) {
 			virtualTime = timeRunning;
-			find_jobs(virtualTime, &database, TRUE, TRUE);
+			find_jobs(virtualTime, database, TRUE, TRUE);
 		} else {
 			if (timeDiff > (3*MINUTE_COUNT) ||
 			    timeDiff < -(3*MINUTE_COUNT))
@@ -192,7 +186,7 @@ main(int argc, char *argv[])
 					if (job_runqueue())
 						sleep(10);
 					virtualTime++;
-					find_jobs(virtualTime, &database,
+					find_jobs(virtualTime, database,
 					    TRUE, TRUE);
 				} while (virtualTime < timeRunning);
 				break;
@@ -210,14 +204,14 @@ main(int argc, char *argv[])
 				 * housekeeping.
 				 */
 				/* run wildcard jobs for current minute */
-				find_jobs(timeRunning, &database, TRUE, FALSE);
+				find_jobs(timeRunning, database, TRUE, FALSE);
 
 				/* run fixed-time jobs for each minute missed */
 				do {
 					if (job_runqueue())
 						sleep(10);
 					virtualTime++;
-					find_jobs(virtualTime, &database,
+					find_jobs(virtualTime, database,
 					    FALSE, TRUE);
 					set_time(FALSE);
 				} while (virtualTime< timeRunning &&
@@ -233,7 +227,7 @@ main(int argc, char *argv[])
 				 * not be repeated.  Virtual time does not
 				 * change until we are caught up.
 				 */
-				find_jobs(timeRunning, &database, TRUE, FALSE);
+				find_jobs(timeRunning, database, TRUE, FALSE);
 				break;
 			default:
 				/*
@@ -241,7 +235,7 @@ main(int argc, char *argv[])
 				 * jump virtual time, and run everything
 				 */
 				virtualTime = timeRunning;
-				find_jobs(timeRunning, &database, TRUE, TRUE);
+				find_jobs(timeRunning, database, TRUE, TRUE);
 			}
 		}
 
@@ -249,7 +243,7 @@ main(int argc, char *argv[])
 		job_runqueue();
 
 		/* Run any jobs in the at queue. */
-		atrun(&at_database, batch_maxload,
+		atrun(at_database, batch_maxload,
 		    timeRunning * SECONDS_PER_MINUTE - GMToff);
 
 		/* Reload jobs as needed. */
@@ -264,8 +258,8 @@ run_reboot_jobs(cron_db *db)
 	user *u;
 	entry *e;
 
-	for (u = db->head; u != NULL; u = u->next) {
-		for (e = u->crontab; e != NULL; e = e->next) {
+	TAILQ_FOREACH(u, &db->users, entries) {
+		SLIST_FOREACH(e, &u->crontab, entries) {
 			if (e->flags & WHEN_REBOOT)
 				job_add(e, u);
 		}
@@ -296,8 +290,8 @@ find_jobs(time_t vtime, cron_db *db, int doWild, int doNonWild)
 	 * is why we keep 'e->dow_star' and 'e->dom_star'.  yes, it's bizarre.
 	 * like many bizarre things, it's the standard.
 	 */
-	for (u = db->head; u != NULL; u = u->next) {
-		for (e = u->crontab; e != NULL; e = e->next) {
+	TAILQ_FOREACH(u, &db->users, entries) {
+		SLIST_FOREACH(e, &u->crontab, entries) {
 			if (bit_test(e->minute, minute) &&
 			    bit_test(e->hour, hour) &&
 			    bit_test(e->month, month) &&
@@ -375,7 +369,7 @@ cron_sleep(time_t target, sigset_t *mask)
 				(void) read(fd, &poke, 1);
 				close(fd);
 				if (poke & RELOAD_CRON) {
-					database.mtime = 0;
+					database->mtime = 0;
 					load_database(&database);
 				}
 				if (poke & RELOAD_AT) {
@@ -385,9 +379,9 @@ cron_sleep(time_t target, sigset_t *mask)
 					 * jobs immediately.
 					 */
 					clock_gettime(CLOCK_REALTIME, &t2);
-					at_database.mtime = 0;
+					at_database->mtime = 0;
 					if (scan_atjobs(&at_database, &t2))
-						atrun(&at_database,
+						atrun(at_database,
 						    batch_maxload, t2.tv_sec);
 				}
 			}
diff --git a/usr.sbin/cron/database.c b/usr.sbin/cron/database.c
index d9c41d94c08..f0e3990c0f8 100644
--- a/usr.sbin/cron/database.c
+++ b/usr.sbin/cron/database.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: database.c,v 1.28 2015/11/04 20:28:17 millert Exp $	*/
+/*	$OpenBSD: database.c,v 1.29 2015/11/09 01:12:27 millert Exp $	*/
 
 /* Copyright 1988,1990,1993,1994 by Paul Vixie
  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
@@ -43,13 +43,13 @@ static	void		process_crontab(const char *, const char *,
 					cron_db *, cron_db *);
 
 void
-load_database(cron_db *old_db)
+load_database(cron_db **db)
 {
 	struct stat statbuf, syscron_stat;
-	cron_db new_db;
+	cron_db *new_db, *old_db = *db;
 	struct dirent *dp;
 	DIR *dir;
-	user *u, *nu;
+	user *u;
 
 	/* before we start loading any data, do a stat on SPOOL_DIR
 	 * so that if anything changes as of this moment (i.e., before we've
@@ -67,12 +67,9 @@ load_database(cron_db *old_db)
 
 	/* if spooldir's mtime has not changed, we don't need to fiddle with
 	 * the database.
-	 *
-	 * Note that old_db->mtime is initialized to 0 in main(), and
-	 * so is guaranteed to be different than the stat() mtime the first
-	 * time this function is called.
 	 */
-	if (old_db->mtime == HASH(statbuf.st_mtime, syscron_stat.st_mtime)) {
+	if (old_db != NULL &&
+	    old_db->mtime == HASH(statbuf.st_mtime, syscron_stat.st_mtime)) {
 		return;
 	}
 
@@ -81,12 +78,14 @@ load_database(cron_db *old_db)
 	 * actually changed.  Whatever is left in the old database when
 	 * we're done is chaff -- crontabs that disappeared.
 	 */
-	new_db.mtime = HASH(statbuf.st_mtime, syscron_stat.st_mtime);
-	new_db.head = new_db.tail = NULL;
+	if ((new_db = malloc(sizeof(*new_db))) == NULL)
+		return;
+	new_db->mtime = HASH(statbuf.st_mtime, syscron_stat.st_mtime);
+	TAILQ_INIT(&new_db->users);
 
 	if (syscron_stat.st_mtime) {
 		process_crontab("root", NULL, SYSCRONTAB, &syscron_stat,
-				&new_db, old_db);
+				new_db, old_db);
 	}
 
 	/* we used to keep this dir open all the time, for the sake of
@@ -95,6 +94,17 @@ load_database(cron_db *old_db)
 	 */
 	if (!(dir = opendir(SPOOL_DIR))) {
 		log_it("CRON", getpid(), "OPENDIR FAILED", SPOOL_DIR);
+		/* Restore system crontab entry as needed. */
+		if (!TAILQ_EMPTY(&new_db->users) &&
+		    (u = TAILQ_FIRST(&old_db->users))) {
+			if (strcmp(u->name, "*system*") == 0) {
+				TAILQ_REMOVE(&old_db->users, u, entries);
+				free_user(u);
+				TAILQ_INSERT_HEAD(&old_db->users,
+				    TAILQ_FIRST(&new_db->users), entries);
+			}
+		}
+		free(new_db);
 		return;
 	}
 
@@ -117,7 +127,7 @@ load_database(cron_db *old_db)
 			continue;	/* XXX log? */
 
 		process_crontab(fname, fname, tabname,
-				&statbuf, &new_db, old_db);
+				&statbuf, new_db, old_db);
 	}
 	closedir(dir);
 
@@ -129,51 +139,30 @@ load_database(cron_db *old_db)
 
 	/* whatever's left in the old database is now junk.
 	 */
-	for (u = old_db->head;  u != NULL;  u = nu) {
-		nu = u->next;
-		unlink_user(old_db, u);
-		free_user(u);
+	if (old_db != NULL) {
+		while ((u = TAILQ_FIRST(&old_db->users))) {
+			TAILQ_REMOVE(&old_db->users, u, entries);
+			free_user(u);
+		}
+		free(old_db);
 	}
 
 	/* overwrite the database control block with the new one.
 	 */
-	*old_db = new_db;
-}
-
-void
-link_user(cron_db *db, user *u)
-{
-	if (db->head == NULL)
-		db->head = u;
-	if (db->tail)
-		db->tail->next = u;
-	u->prev = db->tail;
-	u->next = NULL;
-	db->tail = u;
-}
-
-void
-unlink_user(cron_db *db, user *u)
-{
-	if (u->prev == NULL)
-		db->head = u->next;
-	else
-		u->prev->next = u->next;
-
-	if (u->next == NULL)
-		db->tail = u->prev;
-	else
-		u->next->prev = u->prev;
+	*db = new_db;
 }
 
 user *
 find_user(cron_db *db, const char *name)
 {
-	user *u;
+	user *u = NULL;
 
-	for (u = db->head;  u != NULL;  u = u->next)
-		if (strcmp(u->name, name) == 0)
-			break;
+	if (db != NULL) {
+		TAILQ_FOREACH(u, &db->users, entries) {
+			if (strcmp(u->name, name) == 0)
+				break;
+		}
+	}
 	return (u);
 }
 
@@ -234,8 +223,8 @@ process_crontab(const char *uname, const char *fname, const char *tabname,
 		 * in, then we can just use our existing entry.
 		 */
 		if (u->mtime == statbuf->st_mtime) {
-			unlink_user(old_db, u);
-			link_user(new_db, u);
+			TAILQ_REMOVE(&old_db->users, u, entries);
+			TAILQ_INSERT_TAIL(&new_db->users, u, entries);
 			goto next_crontab;
 		}
 
@@ -246,14 +235,14 @@ process_crontab(const char *uname, const char *fname, const char *tabname,
 		 * users will be deleted from the old database when
 		 * we finish with the crontab...
 		 */
-		unlink_user(old_db, u);
+		TAILQ_REMOVE(&old_db->users, u, entries);
 		free_user(u);
 		log_it(fname, getpid(), "RELOAD", tabname);
 	}
 	u = load_user(crontab_fd, pw, fname);
 	if (u != NULL) {
 		u->mtime = statbuf->st_mtime;
-		link_user(new_db, u);
+		TAILQ_INSERT_TAIL(&new_db->users, u, entries);
 	}
 
  next_crontab:
diff --git a/usr.sbin/cron/funcs.h b/usr.sbin/cron/funcs.h
index a0229140e45..e15568c3bc5 100644
--- a/usr.sbin/cron/funcs.h
+++ b/usr.sbin/cron/funcs.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: funcs.h,v 1.24 2015/11/04 12:53:05 millert Exp $	*/
+/*	$OpenBSD: funcs.h,v 1.25 2015/11/09 01:12:27 millert Exp $	*/
 
 /*
  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
@@ -23,11 +23,9 @@
  */
 
 void		set_cron_cwd(void),
-		load_database(cron_db *),
+		load_database(cron_db **),
 		job_add(entry *, user *),
 		do_command(entry *, user *),
-		link_user(cron_db *, user *),
-		unlink_user(cron_db *, user *),
 		free_user(user *),
 		env_free(char **),
 		unget_char(int, FILE *),
@@ -45,7 +43,7 @@ int		job_runqueue(void),
 		cron_pclose(FILE *, pid_t),
 		allowed(const char *, const char *, const char *),
 		safe_p(const char *, const char *),
-		scan_atjobs(at_db *, struct timespec *);
+		scan_atjobs(at_db **, struct timespec *);
 
 int		strtot(const char *nptr, char **endptr, time_t *tp);
 
diff --git a/usr.sbin/cron/job.c b/usr.sbin/cron/job.c
index f206ebbf71e..b67b74d5ce1 100644
--- a/usr.sbin/cron/job.c
+++ b/usr.sbin/cron/job.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: job.c,v 1.12 2015/11/04 20:28:17 millert Exp $	*/
+/*	$OpenBSD: job.c,v 1.13 2015/11/09 01:12:27 millert Exp $	*/
 
 /* Copyright 1988,1990,1993,1994 by Paul Vixie
  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
@@ -29,12 +29,13 @@
 #include "funcs.h"
 
 typedef	struct _job {
-	struct _job	*next;
+	SIMPLEQ_ENTRY(_job) entries;
 	entry		*e;
 	user		*u;
 } job;
 
-static job	*jhead = NULL, *jtail = NULL;
+
+static SIMPLEQ_HEAD(job_queue, _job) jobs = SIMPLEQ_HEAD_INITIALIZER(jobs);
 
 void
 job_add(entry *e, user *u)
@@ -42,37 +43,31 @@ job_add(entry *e, user *u)
 	job *j;
 
 	/* if already on queue, keep going */
-	for (j = jhead; j != NULL; j = j->next)
+	SIMPLEQ_FOREACH(j, &jobs, entries)
 		if (j->e == e && j->u == u)
 			return;
 
 	/* build a job queue element */
 	if ((j = malloc(sizeof(job))) == NULL)
 		return;
-	j->next = NULL;
 	j->e = e;
 	j->u = u;
 
 	/* add it to the tail */
-	if (jhead == NULL)
-		jhead = j;
-	else
-		jtail->next = j;
-	jtail = j;
+	SIMPLEQ_INSERT_TAIL(&jobs, j, entries);
 }
 
 int
 job_runqueue(void)
 {
-	job *j, *jn;
+	job *j;
 	int run = 0;
 
-	for (j = jhead; j; j = jn) {
+	while ((j = SIMPLEQ_FIRST(&jobs))) {
+		SIMPLEQ_REMOVE_HEAD(&jobs, entries);
 		do_command(j->e, j->u);
-		jn = j->next;
 		free(j);
 		run++;
 	}
-	jhead = jtail = NULL;
 	return (run);
 }
diff --git a/usr.sbin/cron/structs.h b/usr.sbin/cron/structs.h
index d3ac43c88ce..e9e73816b00 100644
--- a/usr.sbin/cron/structs.h
+++ b/usr.sbin/cron/structs.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: structs.h,v 1.6 2015/11/04 20:28:17 millert Exp $	*/
+/*	$OpenBSD: structs.h,v 1.7 2015/11/09 01:12:27 millert Exp $	*/
 
 /*
  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
@@ -17,10 +17,12 @@
  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <sys/queue.h>
+
 struct passwd;
 
 typedef	struct _entry {
-	struct _entry	*next;
+	SLIST_ENTRY(_entry) entries;
 	struct passwd	*pwd;
 	char		**envp;
 	char		*cmd;
@@ -46,19 +48,19 @@ typedef	struct _entry {
 			 */
 
 typedef	struct _user {
-	struct _user	*next, *prev;	/* links */
+	TAILQ_ENTRY(_user) entries;	/* links */
 	char		*name;
 	time_t		mtime;		/* last modtime of crontab */
-	entry		*crontab;	/* this person's crontab */
+	SLIST_HEAD(crontab_list, _entry) crontab;	/* this person's crontab */
 } user;
 
 typedef	struct _cron_db {
-	user		*head, *tail;	/* links */
+	TAILQ_HEAD(user_list, _user) users;
 	time_t		mtime;		/* last modtime on spooldir */
 } cron_db;
 
 typedef struct _atjob {
-	struct _atjob	*next, *prev;	/* links */
+	TAILQ_ENTRY(_atjob) entries;	/* links */
 	uid_t		uid;		/* uid of the job */
 	gid_t		gid;		/* gid of the job */
 	int		queue;		/* name of the at queue */
@@ -66,10 +68,6 @@ typedef struct _atjob {
 } atjob;
 
 typedef struct _at_db {
-	atjob		*head, *tail;	/* links */
+	TAILQ_HEAD(atjob_list, _atjob) jobs;
 	time_t		mtime;		/* last modtime on spooldir */
 } at_db;
-				/* in the C tradition, we only create
-				 * variables for the main program, just
-				 * extern them elsewhere.
-				 */
diff --git a/usr.sbin/cron/user.c b/usr.sbin/cron/user.c
index d31d58056bc..2b896a32e3e 100644
--- a/usr.sbin/cron/user.c
+++ b/usr.sbin/cron/user.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: user.c,v 1.16 2015/11/04 20:28:17 millert Exp $	*/
+/*	$OpenBSD: user.c,v 1.17 2015/11/09 01:12:27 millert Exp $	*/
 
 /* Copyright 1988,1990,1993,1994 by Paul Vixie
  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
@@ -34,13 +34,13 @@
 void
 free_user(user *u)
 {
-	entry *e, *ne;
+	entry *e;
 
-	free(u->name);
-	for (e = u->crontab;  e != NULL;  e = ne) {
-		ne = e->next;
+	while ((e = SLIST_FIRST(&u->crontab))) {
+		SLIST_REMOVE_HEAD(&u->crontab, entries);
 		free_entry(e);
 	}
+	free(u->name);
 	free(u);
 }
 
@@ -69,7 +69,7 @@ load_user(int crontab_fd, struct passwd	*pw, const char *name)
 		errno = save_errno;
 		return (NULL);
 	}
-	u->crontab = NULL;
+	SLIST_INIT(&u->crontab);
 
 	/* init environment.  this will be copied/augmented for each entry.
 	 */
@@ -86,11 +86,10 @@ load_user(int crontab_fd, struct passwd	*pw, const char *name)
 	while ((status = load_env(envstr, file)) >= 0) {
 		switch (status) {
 		case FALSE:
+			/* Not an env variable, parse as crontab entry. */
 			e = load_entry(file, NULL, pw, envp);
-			if (e) {
-				e->next = u->crontab;
-				u->crontab = e;
-			}
+			if (e)
+				SLIST_INSERT_HEAD(&u->crontab, e, entries);
 			break;
 		case TRUE:
 			if ((tenvp = env_set(envp, envstr)) == NULL) {