From c8a3d3bcd7dc2893790c38695a8ecd79c4fbad99 Mon Sep 17 00:00:00 2001 From: David Howells Date: Mon, 17 Feb 2014 15:01:47 +0000 Subject: FS-Cache: Handle removal of unadded object to the fscache_object_list rb tree commit 7026f1929e18921fd67bf478f475a8fdfdff16ae upstream. When FS-Cache allocates an object, the following sequence of events can occur: -->fscache_alloc_object() -->cachefiles_alloc_object() [via cache->ops->alloc_object] <--[returns new object] -->fscache_attach_object() <--[failed] -->cachefiles_put_object() [via cache->ops->put_object] -->fscache_object_destroy() -->fscache_objlist_remove() -->rb_erase() to remove the object from fscache_object_list. resulting in a crash in the rbtree code. The problem is that the object is only added to fscache_object_list on the success path of fscache_attach_object() where it calls fscache_objlist_add(). So if fscache_attach_object() fails, the object won't have been added to the objlist rbtree. We do, however, unconditionally try to remove the object from the tree. Thanks to NeilBrown for finding this and suggesting this solution. Reported-by: NeilBrown Signed-off-by: David Howells Tested-by: (a customer of) NeilBrown Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c index e1959ef..b5ebc2d 100644 --- a/fs/fscache/object-list.c +++ b/fs/fscache/object-list.c @@ -50,6 +50,8 @@ void fscache_objlist_add(struct fscache_object *obj) struct fscache_object *xobj; struct rb_node **p = &fscache_object_list.rb_node, *parent = NULL; + ASSERT(RB_EMPTY_NODE(&obj->objlist_link)); + write_lock(&fscache_object_list_lock); while (*p) { @@ -75,6 +77,9 @@ void fscache_objlist_add(struct fscache_object *obj) */ void fscache_objlist_remove(struct fscache_object *obj) { + if (RB_EMPTY_NODE(&obj->objlist_link)) + return; + write_lock(&fscache_object_list_lock); BUG_ON(RB_EMPTY_ROOT(&fscache_object_list)); diff --git a/fs/fscache/object.c b/fs/fscache/object.c index 86d75a6..fec4134 100644 --- a/fs/fscache/object.c +++ b/fs/fscache/object.c @@ -314,6 +314,9 @@ void fscache_object_init(struct fscache_object *object, object->cache = cache; object->cookie = cookie; object->parent = NULL; +#ifdef CONFIG_FSCACHE_OBJECT_LIST + RB_CLEAR_NODE(&object->objlist_link); +#endif object->oob_event_mask = 0; for (t = object->oob_table; t->events; t++) -- cgit v0.10.2