Commit ed42c879 authored Jul 07, 2005 by Miklos Szeredi Committed by Linus Torvalds Jul 07, 2005

[PATCH] namespace.c: fix expiring of detached mount



This patch fixes a bug noticed by Al Viro:

   However, we still have a problem here - just what would
   happen if vfsmount is detached while we were grabbing namespace
   semaphore?  Refcount alone is not useful here - we might be held by
   whoever had detached the vfsmount.  IOW, we should check that it's
   still attached (i.e. that mnt->mnt_parent != mnt).  If it's not -
   just leave it alone, do mntput() and let whoever holds it deal with
   the sucker.  No need to put it back on lists.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 24ca2af1

fs/namespace.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -829,6 +829,15 @@ static void expire_mount(struct vfsmount mnt, struct list_head mounts)
		{
		spin_lock(&vfsmount_lock);

		/*
		* Check if mount is still attached, if not, let whoever holds it deal
		* with the sucker
		*/
		if (mnt->mnt_parent == mnt) {
		spin_unlock(&vfsmount_lock);
		return;
		}

		/*
		* Check that it is still dead: the count should now be 2 - as
		* contributed by the vfsmount parent and the mntget above