audit: fix refcounting in audit-tree
authorMiklos Szeredi <mszeredi@suse.cz>
Wed, 15 Aug 2012 10:55:22 +0000 (12:55 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 14 Sep 2012 17:00:18 +0000 (10:00 -0700)
commit47b8bbd6c2aab324fa57f004f89abb40bb8478be
tree537905711303fcaad859a91e7351886ff792fd15
parentae2a5dd19bccd4fa52ee6bb78ad88b960d92c606
audit: fix refcounting in audit-tree

commit a2140fc0cb0325bb6384e788edd27b9a568714e2 upstream.

Refcounting of fsnotify_mark in audit tree is broken.  E.g:

                              refcount
create_chunk
  alloc_chunk                 1
  fsnotify_add_mark           2

untag_chunk
  fsnotify_get_mark           3
  fsnotify_destroy_mark
    audit_tree_freeing_mark   2
  fsnotify_put_mark           1
  fsnotify_put_mark           0
  via destroy_list
    fsnotify_mark_destroy    -1

This was reported by various people as triggering Oops when stopping auditd.

We could just remove the put_mark from audit_tree_freeing_mark() but that would
break freeing via inode destruction.  So this patch simply omits a put_mark
after calling destroy_mark or adds a get_mark before.

The additional get_mark is necessary where there's no other put_mark after
fsnotify_destroy_mark() since it assumes that the caller is holding a reference
(or the inode is keeping the mark pinned, not the case here AFAICS).

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Reported-by: Valentin Avram <aval13@gmail.com>
Reported-by: Peter Moody <pmoody@google.com>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernel/audit_tree.c