autofs/autofs-5.1.8-allow-null-map-in-indirect-maps.patch

autofs-5.1.8 - allow -null map in indirect maps

From: Ian Kent <raven@themaw.net>

We have had reports of GUI programs (such as Nautilus) probing for files
such as .hidden in the parent directory of the directory being accessed.

If using an indirect mount map with a wildcard map entry autofs is duty
bound to try and mount these which usually results in a mount failure but
can also cause lengthy delays in some cases.

There are some challenges to modifying application code and even if it
can be done it's always open to being broken later by developers that
aren't aware of the reasoning behind the original changes.

Now, there is a machanism in autofs that can be used to ignore certain
map entries, the "builtin map -null", see auto.master(5). Currently it
can be used only in the master map but this change extends it to be used
in indirect mount maps as well. In this way it can be used to handle
problematic entries by simply adding a map entry that uses the builtin
-null map.

For example:
.hidden	-null
*	someserver:/remote/home/&

This mechanism is not standard so if one is using systems other than
those with Linux autofs and central map storage, such as LDAP, then
it would be necessary to configure nsswitch to ensure the files map
source is consulted first followed by the remote map source. Then the
-null map entries included in a local file map that uses plus map
inclusion to move on the the central map source if there is no match.

For example, in /etc/auto.home we can have:
.hidden	-null
+auto.home

Signed-off-by: Ian Kent <raven@themaw.net>
---
 CHANGELOG            |    1 +
 daemon/indirect.c    |   12 +++++++++++-
 daemon/lookup.c      |    4 ++++
 include/parse_subs.h |    1 +
 lib/parse_subs.c     |   13 +++++++++++++
 man/auto.master.5.in |    9 +++++++--
 6 files changed, 37 insertions(+), 3 deletions(-)

--- autofs-5.1.7.orig/CHANGELOG
+++ autofs-5.1.7/CHANGELOG
@@ -157,6 +157,7 @@
 - fix some sss error return cases.
 - fix incorrect matching of cached wildcard key.
 - fix expire retry looping.
+- allow -null map in indirect maps.
 
 25/01/2021 autofs-5.1.7
 - make bind mounts propagation slave by default.
--- autofs-5.1.7.orig/daemon/indirect.c
+++ autofs-5.1.7/daemon/indirect.c
@@ -796,13 +796,23 @@ int handle_packet_missing_indirect(struc
 		return 0;
 	}
 
-	/* Check if we recorded a mount fail for this key anywhere */
 	me = lookup_source_mapent(ap, pkt->name, LKP_DISTINCT);
 	if (me) {
+		/* Check if we recorded a mount fail for this key */
 		if (me->status >= monotonic_time(NULL)) {
 			ops->send_fail(ap->logopt, ap->ioctlfd,
 				       pkt->wait_queue_token, -ENOENT);
 			cache_unlock(me->mc);
+			master_mutex_unlock();
+			pthread_setcancelstate(state, NULL);
+			return 0;
+		}
+
+		/* Ignore nulled indirect map entries */
+		if (starts_with_null_opt(me->mapent)) {
+			ops->send_fail(ap->logopt, ap->ioctlfd,
+				       pkt->wait_queue_token, -ENOENT);
+			cache_unlock(me->mc);
 			master_mutex_unlock();
 			pthread_setcancelstate(state, NULL);
 			return 0;
--- autofs-5.1.7.orig/daemon/lookup.c
+++ autofs-5.1.7/daemon/lookup.c
@@ -772,6 +772,10 @@ int lookup_ghost(struct autofs_point *ap
 				goto next;
 			}
 
+			/* Ignore nulled indirect map entries */
+			if (starts_with_null_opt(me->mapent))
+				goto next;
+
 			fullpath = make_browse_path(ap->logopt,
 						    ap->path, me->key, ap->pref);
 			if (!fullpath)
--- autofs-5.1.7.orig/include/parse_subs.h
+++ autofs-5.1.7/include/parse_subs.h
@@ -122,6 +122,7 @@ int strmcmp(const char *, const char *,
 char *dequote(const char *, int, unsigned int);
 int span_space(const char *, unsigned int);
 char *sanitize_path(const char *, int, unsigned int, unsigned int);
+int starts_with_null_opt(const char *);
 char *merge_options(const char *, const char *);
 int expandamdent(const char *, char *, const struct substvar *);
 int expand_selectors(struct autofs_point *, const char *, char **, struct substvar *);
--- autofs-5.1.7.orig/lib/parse_subs.c
+++ autofs-5.1.7/lib/parse_subs.c
@@ -878,6 +878,19 @@ char *sanitize_path(const char *path, in
 	return s_path;
 }
 
+int starts_with_null_opt(const char *str)
+{
+	if (str && strlen(str) >= 5 && *str == '-') {
+		char sep = *(str + 5);
+
+		if (sep == 0 || sep == ' ' || sep == ',') {
+			if (!strncmp(str, "-null", 5))
+				return 1;
+		}
+	}
+	return 0;
+}
+
 static char *hasopt(const char *str, const char *opt)
 {
 	const size_t optlen = strlen(opt);
--- autofs-5.1.7.orig/man/auto.master.5.in
+++ autofs-5.1.7/man/auto.master.5.in
@@ -269,13 +269,18 @@ master map entry.
 If "\-null" is given as the map it is used to tell automount(8) to ignore a subsequent
 master map entry with the given path.
 .P
-It can only be used for paths that appear in the master map (or in direct mount maps).
+It can be used for paths that appear in the master map or in direct mount maps (but
+not in direct mount maps themselves) or as a key in an indirect mount map.
+.P
+An indirect mount map key can be nulled. If so the map key is ignored and does not
+result in a mount attempt (essentially the key lookup is abandoned early on).
 .P
 An indirect mount map top level mount point path can be nulled. If so no mounts from
 the nulled mount are performed (essentially it isn't mounted).
 .P
 Direct mount map path entries can be nulled. Since they must be present at startup
-they are (notionally) part of the master map.
+they are (notionally) part of the master map so direct mount paths that use the -null
+map may be used in the master map to ignore subsequent direct mount map entries.
 .P
 A nulled master map entry path will ignore a single subsequent matching entry. Any
 matching entry following that will be treated as it normally would be. An example