linux-kernel - Re: [PATCH v3] nfs: Fix automount superblock LSM init problem, preventing sb sharing

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Message-ID: <CAHC9VhSVRgSK_ShwShcYnnDOg+mR0V9WEodVmJ=c5_UzK3KLiQ@mail.gmail.com>
Date:   Thu, 18 Aug 2022 22:07:01 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     David Howells <dhowells@...hat.com>
Cc:     Ondrej Mosnacek <omosnace@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>,
        Scott Mayhew <smayhew@...hat.com>,
        Jeff Layton <jlayton@...nel.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        linux-nfs <linux-nfs@...r.kernel.org>,
        SElinux list <selinux@...r.kernel.org>,
        Linux Security Module list 
        <linux-security-module@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        dwysocha@...hat.com,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] nfs: Fix automount superblock LSM init problem,
 preventing sb sharing

On Thu, Aug 18, 2022 at 9:14 AM David Howells <dhowells@...hat.com> wrote:
> Paul Moore <paul@...l-moore.com> wrote:
>
> > I guess my question is this: for inodes inside the superblock, does
> > their superblock pointer point to the submount's superblock, or the
> > parent filesystem's superblock?
>
> They have to point to the submount superblock.  Too many things would break, I
> think, if inode->i_sb pointed to the wrong place.  As far as the VFS is
> concerned, apart from the way it is mounted, it's a perfectly normal
> superblock.

If the submount inodes point back to the submount's superblock then it
seems reasonable that the rootcontext should remain unset to me.

-- 
paul-moore.com