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

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Message-ID: <2026286.1660828477@warthog.procyon.org.uk>
Date:   Thu, 18 Aug 2022 14:14:37 +0100
From:   David Howells <dhowells@...hat.com>
To:     Paul Moore <paul@...l-moore.com>
Cc:     dhowells@...hat.com, 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

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.

David