[PATCH] namespace.c: fix bind mount from foreign namespace
I'm resending this patch, because I still believe it's the correct fix.
Tested before/after applying the patch with a test application
available from:
http://www.inf.bme.hu/~mszeredi/nstest.c
Bind mount from a foreign namespace results in an un-removable mount.
The reason is that mnt->mnt_namespace is copied from the old mount in
clone_mnt(). Because of this check_mnt() in sys_umount() will fail.
The solution is to set mnt->mnt_namespace to current->namespace in
clone_mnt(). clone_mnt() is either called from do_loopback() or
copy_tree(). copy_tree() is called from do_loopback() or
copy_namespace().
When called (directly or indirectly) from do_loopback(), always
current->namspace is being modified: check_mnt(nd->mnt). So setting
mnt->mnt_namespace to current->namspace is the right thing to do.
When called from copy_namespace(), the setting of mnt_namespace is
irrelevant, since mnt_namespace is reset later in that function for
all copied mounts.
Jamie said:
This patch is correct. The old code was buggy for more fundamental and
serious reason: it broke the invariant that a tree of vfsmnts all have the
same value of mnt_namespace (and the same for the mnt_list list).
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Acked-by: Jamie Lokier <jamie@shareable.org>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/namespace.c b/fs/namespace.c
index 587eb0d..79bd8a4 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -160,7 +160,7 @@
mnt->mnt_root = dget(root);
mnt->mnt_mountpoint = mnt->mnt_root;
mnt->mnt_parent = mnt;
- mnt->mnt_namespace = old->mnt_namespace;
+ mnt->mnt_namespace = current->namespace;
/* stick the duplicate mount on the same expiry list
* as the original if that was on one */