Patch "mnt: Fail collect_mounts when applied to unmounted mounts" has been added to the 4.0-stable tree

This is a note to let you know that I've just added the patch titled

mnt: Fail collect_mounts when applied to unmounted mounts

to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mnt-fail-collect_mounts-when-applied-to-unmounted-mounts.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Eric W. Biederman" <[email protected]>
Date: Wed, 7 Jan 2015 14:28:26 -0600
Subject: mnt: Fail collect_mounts when applied to unmounted mounts

From: "Eric W. Biederman" <[email protected]>

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.

---
 fs/namespace.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

@@ -1709,8 +1709,11 @@ struct vfsmount *collect_mounts(struct p
 {
 	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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.0/mnt-fail-collect_mounts-when-applied-to-unmounted-mounts.patch queue-4.0/fs_pin-allow-for-the-possibility-that-m_list-or-s_list-go-unused.patch