[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
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@ -829,6 +829,15 @@ static void expire_mount(struct vfsmount *mnt, struct list_head *mounts)
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{
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{
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spin_lock(&vfsmount_lock);
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spin_lock(&vfsmount_lock);
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/*
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* Check if mount is still attached, if not, let whoever holds it deal
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* with the sucker
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*/
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if (mnt->mnt_parent == mnt) {
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spin_unlock(&vfsmount_lock);
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return;
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}
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/*
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/*
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* Check that it is still dead: the count should now be 2 - as
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* Check that it is still dead: the count should now be 2 - as
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* contributed by the vfsmount parent and the mntget above
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* contributed by the vfsmount parent and the mntget above
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