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Date:   Fri, 6 Mar 2020 19:43:22 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Miklos Szeredi <miklos@szeredi.hu>
Cc:     Ian Kent <raven@themaw.net>, David Howells <dhowells@redhat.com>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        Steven Whitehouse <swhiteho@redhat.com>,
        Miklos Szeredi <mszeredi@redhat.com>,
        Christian Brauner <christian@brauner.io>,
        Jann Horn <jannh@google.com>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        Linux API <linux-api@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH 00/17] VFS: Filesystem information and notifications [ver
 #17]
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On Fri, Mar 06, 2020 at 05:25:49PM +0100, Miklos Szeredi wrote:
> On Tue, Mar 03, 2020 at 08:46:09AM +0100, Miklos Szeredi wrote:
> > 
> > I'm doing a patch.   Let's see how it fares in the face of all these
> > preconceptions.
> 
> Here's a first cut.  Doesn't yet have superblock info, just mount info.
> Probably has rough edges, but appears to work.

For starters, you have just made namespace_sem held over copy_to_user().
This is not going to fly.