[PATCH review 09/19] mnt: Fail collect_mounts when applied to unmounted mounts

Eric W. Biederman ebiederm at xmission.com
Fri Apr 3 01:56:13 UTC 2015


The only users of collect_mounts are in audit_tree.c

In audit_tree_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 at xmission.com>
---
 fs/namespace.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 2b12b7a9455d..acc5583764dc 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1669,8 +1669,11 @@ 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);
-- 
2.2.1



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