linux-kernel - Re: Regression for MS

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Message-ID: <9383.1560418050@warthog.procyon.org.uk>
Date:   Thu, 13 Jun 2019 10:27:30 +0100
From:   David Howells <dhowells@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     dhowells@...hat.com, "Eric W. Biederman" <ebiederm@...ssion.com>,
        Christian Brauner <christian@...uner.io>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: Regression for MS_MOVE on kernel v5.1

[Adding Eric to the cc list since he implemented MNT_LOCKED]

Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> > The commit changes the internal logic to lock mounts when propagating
> > mounts (user+)mount namespaces and - I believe - causes do_mount_move()
> > to fail at:
> 
> You mean 'do_move_mount()'.
> 
> > if (old->mnt.mnt_flags & MNT_LOCKED)
> >         goto out;
> >
> > If that's indeed the case we should either revert this commit (reverts
> > cleanly, just tested it) or find a fix.
> 
> Hmm.. I'm not entirely sure of the logic here, and just looking at
> that commit 3bd045cc9c4b ("separate copying and locking mount tree on
> cross-userns copies") doesn't make me go "Ahh" either.
> 
> Al? My gut feel is that we need to just revert, since this was in 5.1
> and it's getting reasonably late in 5.2 too. But maybe you go "guys,
> don't be silly, this is easily fixed with this one-liner".