linux-kernel - [PATCH 24/34] union-mount: Prevent bind mounts of union mounts

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Date:	Thu, 16 Sep 2010 15:12:15 -0700
From:	Valerie Aurora <vaurora@...hat.com>
To:	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	Miklos Szeredi <miklos@...redi.hu>,
	Christoph Hellwig <hch@...radead.org>,
	Andreas Gruenbacher <agruen@...e.de>,
	Nick Piggin <npiggin@...nel.dk>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, Valerie Aurora <vaurora@...hat.com>
Subject: [PATCH 24/34] union-mount: Prevent bind mounts of union mounts

Prevent bind mounts of parts of union mounts.

XXX - Bind mounting parts of union mounts is probably easy to
implement, but requires some careful thought about corner cases,
extensive testing, and some refactoring of the code.

Signed-off-by: Valerie Aurora <vaurora@...hat.com>
---
 fs/namespace.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 26efaf3..e3629dd 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1761,6 +1761,12 @@ static int do_loopback(struct path *path, char *old_name,
 	err = -EINVAL;
 	if (IS_MNT_UNBINDABLE(old_path.mnt))
 		goto out;
+	/*
+	 * XXX - Mounting a subtree of a union mount elsewhere
+	 * requires careful thought and some refactoring.
+	 */
+	if (IS_MNT_UNION(old_path.mnt))
+		goto out;
 
 	if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
 		goto out;
-- 
1.6.3.3

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