autofs/autofs-5.1.7-fix-inconsistent-locking-in-umount_subtree_mounts.patch

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autofs-5.1.7 - fix inconsistent locking in umount_subtree_mounts()
From: Ian Kent <raven@themaw.net>
Some map entry cache locking inconsistencies have crept in.
In umount_subtree_mounts() the cache write lock should be held when
deleting multi-mount cache entries.
Signed-off-by: Ian Kent <raven@themaw.net>
---
CHANGELOG | 1 +
daemon/automount.c | 42 ++++++++++++++++++++++++++++++------------
lib/mounts.c | 8 --------
3 files changed, 31 insertions(+), 20 deletions(-)
diff --git a/CHANGELOG b/CHANGELOG
index 1dded118..64e619ec 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -15,6 +15,7 @@
- eliminate clean_stale_multi_triggers().
- simplify mount_subtree() mount check.
- fix mnts_get_expire_list() expire list construction.
+- fix inconsistent locking in umount_subtree_mounts().
25/01/2021 autofs-5.1.7
- make bind mounts propagation slave by default.
diff --git a/daemon/automount.c b/daemon/automount.c
index 7fa92877..93bd8556 100644
--- a/daemon/automount.c
+++ b/daemon/automount.c
@@ -527,8 +527,11 @@ static int umount_subtree_mounts(struct autofs_point *ap, const char *path, unsi
struct mapent_cache *mc;
struct mapent *me;
unsigned int is_mm_root = 0;
+ int cur_state;
int left;
+ pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cur_state);
+
me = lookup_source_mapent(ap, path, LKP_DISTINCT);
if (!me) {
char *ind_key;
@@ -548,11 +551,11 @@ static int umount_subtree_mounts(struct autofs_point *ap, const char *path, unsi
left = 0;
if (me && me->multi) {
- char root[PATH_MAX];
+ char root[PATH_MAX + 1];
+ char key[PATH_MAX + 1];
+ struct mapent *tmp;
+ int status;
char *base;
- int cur_state;
-
- pthread_cleanup_push(cache_lock_cleanup, mc);
if (!strchr(me->multi->key, '/'))
/* Indirect multi-mount root */
@@ -567,25 +570,40 @@ static int umount_subtree_mounts(struct autofs_point *ap, const char *path, unsi
else
base = me->key + strlen(root);
- pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cur_state);
- /* Lock the closest parent nesting point for umount */
- cache_multi_writelock(me->parent);
- if (umount_multi_triggers(ap, me, root, base)) {
+ left = umount_multi_triggers(ap, me, root, base);
+ if (left) {
warn(ap->logopt,
"some offset mounts still present under %s", path);
+ }
+
+ strcpy(key, me->key);
+
+ cache_unlock(mc);
+ cache_writelock(mc);
+ tmp = cache_lookup_distinct(mc, key);
+ /* mapent went away while we waited? */
+ if (tmp != me) {
+ cache_unlock(mc);
+ pthread_setcancelstate(cur_state, NULL);
+ return 0;
+ }
+
+ if (!left && is_mm_root) {
+ status = cache_delete_offset_list(mc, me->key);
+ if (status != CHE_OK)
+ warn(ap->logopt, "couldn't delete offset list");
left++;
}
- cache_multi_unlock(me->parent);
+
if (ap->entry->maps &&
(ap->entry->maps->flags & MAP_FLAG_FORMAT_AMD))
cache_pop_mapent(me);
- pthread_setcancelstate(cur_state, NULL);
- pthread_cleanup_pop(0);
}
-
if (me)
cache_unlock(mc);
+ pthread_setcancelstate(cur_state, NULL);
+
if (left || is_autofs_fs)
return left;
diff --git a/lib/mounts.c b/lib/mounts.c
index 87813b16..5ebfe5fd 100644
--- a/lib/mounts.c
+++ b/lib/mounts.c
@@ -2736,9 +2736,6 @@ int umount_multi_triggers(struct autofs_point *ap, struct mapent *me, char *root
left = do_umount_multi_triggers(ap, me, root, base);
if (!left && me->multi == me) {
- struct mapent_cache *mc = me->mc;
- int status;
-
/*
* Special case.
* If we can't umount the root container then we can't
@@ -2756,11 +2753,6 @@ int umount_multi_triggers(struct autofs_point *ap, struct mapent *me, char *root
}
}
- /* We're done - clean out the offsets */
- status = cache_delete_offset_list(mc, me->key);
- if (status != CHE_OK)
- warn(ap->logopt, "couldn't delete offset list");
-
/* check for mounted mount entry and remove it if found */
mnts_remove_mount(root, MNTS_MOUNTED);
}