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[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>
hifive-unleashed-5.1
Miklos Szeredi 2005-07-07 17:57:26 -07:00 committed by Linus Torvalds
parent 24ca2af1e7
commit ed42c879b7
1 changed files with 9 additions and 0 deletions
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9
fs/namespace.c
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@ -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