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Date:   Thu, 31 May 2018 22:20:48 +0100
From:   Al Viro <viro@ZenIV.linux.org.uk>
To:     David Howells <dhowells@redhat.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 31/32] [RFC] fs: Add a move_mount() system call [ver #8]
Message-ID: <20180531212048.GJ30522@ZenIV.linux.org.uk>
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On Fri, May 25, 2018 at 01:08:44AM +0100, David Howells wrote:
> [!] NOTE: This patch doesn't quite work to move an O_CLONE_MOUNT-produced
>     vfsmount as move_mount() checks that the source vfsmount mnt_ns matches
>     the calling process's mnt_ns - but the vfsmount's mnt_ns isn't set
>     until one attempts to actually mount it into the namespace.

*shrug*

Turn those checks into
	error = -EINVAL;
	/* mountpoint should be ours */
	if (!check_mnt(p))
		goto out1;
	/* and the thing moved should be either ours or completely unattached */
	if (old->mnt_ns && !check_mnt(old))
		goto out1;