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Message-ID: <7a947cfaa00f9bfce32ef9fac7a9f46f5dfab52f.camel@kernel.org>
Date: Fri, 04 Aug 2023 12:00:39 -0400
From: Jeff Layton <jlayton@...nel.org>
To: David Howells <dhowells@...hat.com>,
Paul Moore <paul@...l-moore.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>,
Trond Myklebust <trond.myklebust@...merspace.com>,
Anna Schumaker <anna@...nel.org>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Stephen Smalley <stephen.smalley.work@...il.com>,
Eric Paris <eparis@...isplace.org>,
Casey Schaufler <casey@...aufler-ca.com>,
Scott Mayhew <smayhew@...hat.com>,
Stephen Smalley <sds@...ho.nsa.gov>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-nfs@...r.kernel.org, linux-security-module@...r.kernel.org,
selinux@...r.kernel.org
Subject: Re: [PATCH v6] vfs, security: Fix automount superblock LSM init
problem, preventing NFS sb sharing
On Fri, 2023-08-04 at 16:22 +0100, David Howells wrote:
> David Howells <dhowells@...hat.com> wrote:
>
> > IIRC, the issue is when you make a mount with an explicit context= setting and
> > make another mount from some way down the export tree that doesn't have an
> > explicit setting, e.g.:
> >
> > mount carina:/ /mnt -o context=system_u:object_r:root_t:s0
> > mount carina:/nfs/scratch /mnt2
> >
> > and then cause an automount to walk from one to the other:
> >
> > stat /mnt/nfs/scratch/foo
>
> Actually, the order there isn't quite right. The problem is with this order:
>
> # mount carina:/ /mnt -o context=system_u:object_r:root_t:s0
> # stat /mnt/nfs/scratch/bus
> File: /mnt/nfs/scratch/bus
> Size: 124160 Blocks: 248 IO Block: 1048576 regular file
> Device: 0,55 Inode: 131 Links: 1
> ...
> # mount carina:/nfs/scratch /mnt2
> mount.nfs: /mnt2 is busy or already mounted or sharecache fail
>
> with the error:
>
> SELinux: mount invalid. Same superblock, different security settings for (dev 0:52, type nfs4)
>
That seems like the correct behavior to me. You tried to mount the same
mount with a different sec context. If you want that, then you need to
use -o nosharecache.
I'll send a v7 in a bit.
--
Jeff Layton <jlayton@...nel.org>
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