mnt: Fail collect_mounts when applied to unmounted mounts

commit cd4a40174b71acd021877341684d8bb1dc8ea4ae upstream.

The only users of collect_mounts are in audit_tree.c

In audit_trim_trees and audit_add_tree_rule the path passed into
collect_mounts is generated from kern_path passed an audit_tree
pathname which is guaranteed to be an absolute path.   In those cases
collect_mounts is obviously intended to work on mounted paths and
if a race results in paths that are unmounted when collect_mounts
it is reasonable to fail early.

The paths passed into audit_tag_tree don't have the absolute path
check.  But are used to play with fsnotify and otherwise interact with
the audit_trees, so again operating only on mounted paths appears
reasonable.

Avoid having to worry about what happens when we try and audit
unmounted filesystems by restricting collect_mounts to mounts
that appear in the mount tree.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/namespace.c b/fs/namespace.c
index 38ed1e1..13b0f7b 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1709,8 +1709,11 @@ struct vfsmount *collect_mounts(struct path *path)
 {
        struct mount *tree;
        namespace_lock();
-       tree = copy_tree(real_mount(path->mnt), path->dentry,
-                        CL_COPY_ALL | CL_PRIVATE);
+       if (!check_mnt(real_mount(path->mnt)))
+               tree = ERR_PTR(-EINVAL);
+       else
+               tree = copy_tree(real_mount(path->mnt), path->dentry,
+                                CL_COPY_ALL | CL_PRIVATE);
        namespace_unlock();
        if (IS_ERR(tree))
                return ERR_CAST(tree);