autofs-5.1.7 - fix inconsistent locking in parse_mount()

Some map entry cache locking inconsistencies have crept in.

In parse_mount() of the sun format parser the cache read lock is too
heavily used and has too broad a scope. This has lead to some operations
that should hold the write lock being called with only the read lock.

Signed-off-by: Ian Kent <raven@themaw.net>

3 files changed, 42 insertions, 21 deletions

diff --git a/CHANGELOG b/CHANGELOG
index c60a9ed3..d25b19c8 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -18,6 +18,7 @@
 - fix inconsistent locking in umount_subtree_mounts().
 - fix return from umount_subtree_mounts() on offset list delete.
 - pass mapent_cache to update_offset_entry().
+- fix inconsistent locking in parse_mount().
 
 25/01/2021 autofs-5.1.7
 - make bind mounts propagation slave by default.
diff --git a/lib/mounts.c b/lib/mounts.c
index 5ebfe5fd..0fcd4087 100644
--- a/lib/mounts.c
+++ b/lib/mounts.c
@@ -2491,6 +2491,12 @@ static int do_mount_autofs_offset(struct autofs_point *ap,
 		else {
 			debug(ap->logopt, "ignoring \"nohide\" trigger %s",
 			      oe->key);
+			/*
+			 * Ok, so we shouldn't modify the mapent but
+			 * mount requests are blocked at a point above
+			 * this and expire only uses the mapent key or
+			 * holds the cache write lock.
+			 */
 			free(oe->mapent);
 			oe->mapent = NULL;
 		}
@@ -2634,7 +2640,8 @@ static int do_umount_offset(struct autofs_point *ap, struct mapent *oe, const ch
 			/*
 			 * Ok, so we shouldn't modify the mapent but
 			 * mount requests are blocked at a point above
-			 * this and expire only uses the mapent key.
+			 * this and expire only uses the mapent key or
+			 * holds the cache write lock.
 			 */
 			if (oe->mapent) {
 				free(oe->mapent);
diff --git a/modules/parse_sun.c b/modules/parse_sun.c
index 95251bee..a6630a76 100644
--- a/modules/parse_sun.c
+++ b/modules/parse_sun.c
@@ -851,10 +851,12 @@ update_offset_entry(struct autofs_point *ap,
 			strcpy(m_mapent, loc);
 	}
 
+	cache_writelock(mc);
 	ret = cache_update_offset(mc, name, m_key, m_mapent, age);
 
 	if (!cache_set_offset_parent(mc, m_key))
 		error(ap->logopt, "failed to set offset parent");
+	cache_unlock(mc);
 
 	if (ret == CHE_DUPLICATE) {
 		warn(ap->logopt, MODPREFIX
@@ -1128,14 +1130,22 @@ static void cleanup_multi_triggers(struct autofs_point *ap,
 	return;
 }
 
-static int mount_subtree(struct autofs_point *ap, struct mapent *me,
+static int mount_subtree(struct autofs_point *ap, struct mapent_cache *mc,
 			 const char *name, char *loc, char *options, void *ctxt)
 {
+	struct mapent *me;
 	struct mapent *ro;
 	char *mm_root, *mm_base, *mm_key;
 	unsigned int mm_root_len;
 	int start, ret = 0, rv;
 
+	cache_readlock(mc);
+	me = cache_lookup_distinct(mc, name);
+	if (!me) {
+		cache_unlock(mc);
+		return 0;
+	}
+
 	rv = 0;
 
 	mm_key = me->multi->key;
@@ -1180,9 +1190,12 @@ static int mount_subtree(struct autofs_point *ap, struct mapent *me,
 			rv = parse_mapent(ro->mapent,
 				options, &myoptions, &ro_loc, ap->logopt);
 			if (!rv) {
+				cache_unlock(mc);
 				warn(ap->logopt,
 				      MODPREFIX "failed to parse root offset");
-				cache_delete_offset_list(me->mc, name);
+				cache_writelock(mc);
+				cache_delete_offset_list(mc, name);
+				cache_unlock(mc);
 				return 1;
 			}
 			ro_len = 0;
@@ -1199,9 +1212,10 @@ static int mount_subtree(struct autofs_point *ap, struct mapent *me,
 		if ((ro && rv == 0) || rv <= 0) {
 			ret = mount_multi_triggers(ap, me, mm_root, start, mm_base);
 			if (ret == -1) {
+				cleanup_multi_triggers(ap, me, mm_root, start, mm_base);
+				cache_unlock(mc);
 				error(ap->logopt, MODPREFIX
 					 "failed to mount offset triggers");
-				cleanup_multi_triggers(ap, me, mm_root, start, mm_base);
 				return 1;
 			}
 		}
@@ -1217,9 +1231,10 @@ static int mount_subtree(struct autofs_point *ap, struct mapent *me,
 		if (rv == 0) {
 			ret = mount_multi_triggers(ap, me->multi, name, start, mm_base);
 			if (ret == -1) {
+				cleanup_multi_triggers(ap, me, name, start, mm_base);
+				cache_unlock(mc);
 				error(ap->logopt, MODPREFIX
 					 "failed to mount offset triggers");
-				cleanup_multi_triggers(ap, me, name, start, mm_base);
 				return 1;
 			}
 		} else if (rv < 0) {
@@ -1227,8 +1242,11 @@ static int mount_subtree(struct autofs_point *ap, struct mapent *me,
 			unsigned int mm_root_base_len = mm_root_len + strlen(mm_base) + 1;
 	
 			if (mm_root_base_len > PATH_MAX) {
+				cache_unlock(mc);
 				warn(ap->logopt, MODPREFIX "path too long");
-				cache_delete_offset_list(me->mc, name);
+				cache_writelock(mc);
+				cache_delete_offset_list(mc, name);
+				cache_unlock(mc);
 				return 1;
 			}
 
@@ -1237,13 +1255,15 @@ static int mount_subtree(struct autofs_point *ap, struct mapent *me,
 
 			ret = mount_multi_triggers(ap, me->multi, mm_root_base, start, mm_base);
 			if (ret == -1) {
+				cleanup_multi_triggers(ap, me, mm_root, start, mm_base);
+				cache_unlock(mc);
 				error(ap->logopt, MODPREFIX
 					 "failed to mount offset triggers");
-				cleanup_multi_triggers(ap, me, mm_root, start, mm_base);
 				return 1;
 			}
 		}
 	}
+	cache_unlock(mc);
 
 	/* Mount for base of tree failed */
 	if (rv > 0)
@@ -1484,7 +1504,6 @@ dont_expand:
 			return 1;
 		}
 
-		cache_multi_writelock(me);
 		/* So we know we're the multi-mount root */
 		if (!me->multi)
 			me->multi = me;
@@ -1509,14 +1528,13 @@ dont_expand:
 			if (source->flags & MAP_FLAG_FORMAT_AMD) {
 				free(options);
 				free(pmapent);
-				cache_multi_unlock(me);
 				cache_unlock(mc);
 				pthread_setcancelstate(cur_state, NULL);
 				return 0;
 			}
 		}
-
 		age = me->age;
+		cache_unlock(mc);
 
 		/* It's a multi-mount; deal with it */
 		do {
@@ -1537,8 +1555,8 @@ dont_expand:
 
 			if (!path) {
 				warn(ap->logopt, MODPREFIX "null path or out of memory");
+				cache_writelock(mc);
 				cache_delete_offset_list(mc, name);
-				cache_multi_unlock(me);
 				cache_unlock(mc);
 				free(options);
 				free(pmapent);
@@ -1554,8 +1572,8 @@ dont_expand:
 
 			l = parse_mapent(p, options, &myoptions, &loc, ap->logopt);
 			if (!l) {
+				cache_writelock(mc);
 				cache_delete_offset_list(mc, name);
-				cache_multi_unlock(me);
 				cache_unlock(mc);
 				free(path);
 				free(options);
@@ -1573,8 +1591,8 @@ dont_expand:
 
 			if (status != CHE_OK) {
 				warn(ap->logopt, MODPREFIX "error adding multi-mount");
+				cache_writelock(mc);
 				cache_delete_offset_list(mc, name);
-				cache_multi_unlock(me);
 				cache_unlock(mc);
 				free(path);
 				free(options);
@@ -1592,10 +1610,7 @@ dont_expand:
 			free(myoptions);
 		} while (*p == '/' || (*p == '"' && *(p + 1) == '/'));
 
-		rv = mount_subtree(ap, me, name, NULL, options, ctxt);
-
-		cache_multi_unlock(me);
-		cache_unlock(mc);
+		rv = mount_subtree(ap, mc, name, NULL, options, ctxt);
 
 		free(options);
 		free(pmapent);
@@ -1616,6 +1631,7 @@ dont_expand:
 		cache_readlock(mc);
 		if (*name == '/' &&
 		   (me = cache_lookup_distinct(mc, name)) && me->multi) {
+			cache_unlock(mc);
 			loc = strdup(p);
 			if (!loc) {
 				free(options);
@@ -1624,10 +1640,7 @@ dont_expand:
 				warn(ap->logopt, MODPREFIX "out of memory");
 				return 1;
 			}
-			cache_multi_writelock(me);
-			rv = mount_subtree(ap, me, name, loc, options, ctxt);
-			cache_multi_unlock(me);
-			cache_unlock(mc);
+			rv = mount_subtree(ap, mc, name, loc, options, ctxt);
 			free(loc);
 			free(options);
 			free(pmapent);