142 lines
4.3 KiB
Diff
142 lines
4.3 KiB
Diff
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autofs-5.1.8 - fix deadlock in lookups
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From: Ian Kent <raven@themaw.net>
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After adding locking to fix a crash during lookups we're seeing a
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deadlock becuase of recursive calls.
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But once the lookup is open we shouldn't need to open it again during
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the recursive call, fix it based on that.
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Signed-off-by: Ian Kent <raven@themaw.net>
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---
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CHANGELOG | 1
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daemon/lookup.c | 62 +++++++++++++++++++++++++++++++++-------------------
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daemon/master.c | 8 ++++++
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include/master.h | 1
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modules/parse_amd.c | 2 -
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5 files changed, 51 insertions(+), 23 deletions(-)
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--- autofs-5.1.7.orig/CHANGELOG
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+++ autofs-5.1.7/CHANGELOG
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@@ -117,6 +117,7 @@
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- don't immediately call function when waiting.
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- fix return status of mount_autofs().
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- don't close lookup at umount.
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+- fix deadlock in lookups.
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25/01/2021 autofs-5.1.7
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- make bind mounts propagation slave by default.
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--- autofs-5.1.7.orig/daemon/lookup.c
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+++ autofs-5.1.7/daemon/lookup.c
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@@ -318,31 +318,49 @@ static int do_read_map(struct autofs_poi
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struct lookup_mod *lookup;
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int status;
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- pthread_cleanup_push(map_module_lock_cleanup, map);
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- map_module_writelock(map);
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- if (!map->lookup) {
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- status = open_lookup(map->type, "", map->format,
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- map->argc, map->argv, &lookup);
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- if (status == NSS_STATUS_SUCCESS)
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- map->lookup = lookup;
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- else
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- debug(ap->logopt,
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- "lookup module %s open failed", map->type);
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- } else {
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- status = map->lookup->lookup_reinit(map->format,
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- map->argc, map->argv,
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- &map->lookup->context);
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- if (status)
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- warn(ap->logopt,
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- "lookup module %s reinit failed", map->type);
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- }
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- pthread_cleanup_pop(1);
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- if (status != NSS_STATUS_SUCCESS)
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- return status;
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-
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if (!map->stale)
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return NSS_STATUS_SUCCESS;
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+ /* If this readmap is the result of trying to mount a submount
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+ * the readlock may already be held if the map is the same as
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+ * that of the caller. In that case the map has already been
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+ * read so just skip the map open/reinit.
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+ */
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+ status = map_module_try_writelock(map);
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+ if (status) {
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+ if (!map->lookup) {
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+ error(ap->logopt, "map module lock not held as expected");
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+ return NSS_STATUS_UNAVAIL;
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+ }
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+ } else {
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+ if (!map->lookup) {
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+ pthread_cleanup_push(map_module_lock_cleanup, map);
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+ status = open_lookup(map->type, "", map->format,
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+ map->argc, map->argv, &lookup);
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+ pthread_cleanup_pop(0);
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+ if (status != NSS_STATUS_SUCCESS) {
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+ map_module_unlock(map);
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+ debug(ap->logopt,
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+ "lookup module %s open failed", map->type);
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+ return status;
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+ }
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+ map->lookup = lookup;
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+ } else {
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+ pthread_cleanup_push(map_module_lock_cleanup, map);
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+ status = map->lookup->lookup_reinit(map->format,
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+ map->argc, map->argv,
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+ &map->lookup->context);
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+ pthread_cleanup_pop(0);
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+ if (status) {
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+ map_module_unlock(map);
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+ warn(ap->logopt,
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+ "lookup module %s reinit failed", map->type);
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+ return status;
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+ }
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+ }
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+ map_module_unlock(map);
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+ }
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+
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master_source_current_wait(ap->entry);
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ap->entry->current = map;
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--- autofs-5.1.7.orig/daemon/master.c
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+++ autofs-5.1.7/daemon/master.c
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@@ -72,6 +72,14 @@ void map_module_writelock(struct map_sou
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fatal(status);
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}
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+int map_module_try_writelock(struct map_source *map)
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+{
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+ int status = pthread_rwlock_trywrlock(&map->module_lock);
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+ if (status && status != EBUSY && status != EDEADLK)
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+ fatal(status);
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+ return status;
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+}
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+
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void map_module_readlock(struct map_source *map)
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{
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int status = pthread_rwlock_rdlock(&map->module_lock);
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--- autofs-5.1.7.orig/include/master.h
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+++ autofs-5.1.7/include/master.h
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@@ -128,6 +128,7 @@ int master_list_empty(struct master *);
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int master_done(struct master *);
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int master_kill(struct master *);
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void map_module_writelock(struct map_source *map);
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+int map_module_try_writelock(struct map_source *map);
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void map_module_readlock(struct map_source *map);
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void map_module_unlock(struct map_source *map);
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void map_module_lock_cleanup(void *arg);
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--- autofs-5.1.7.orig/modules/parse_amd.c
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+++ autofs-5.1.7/modules/parse_amd.c
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@@ -1391,7 +1391,7 @@ static int do_host_mount(struct autofs_p
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cache_unlock(source->mc);
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master_source_current_wait(ap->entry);
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- ap->entry->current = source;
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+ ap->entry->current = instance;
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map_module_readlock(instance);
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lookup = instance->lookup;
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