linux-kernel - Re: [PATCH 3/1] xfstests: generic/062: Do not run on newer kernels

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Message-ID: <CAPL3RVH9MDoDAdiZ-nm3a4BgmRyZJUc_PV_MpsEWiuh6QPi+pA@mail.gmail.com>
Date:   Fri, 3 Sep 2021 10:42:34 -0400
From:   Bruce Fields <bfields@...hat.com>
To:     Andreas Gruenbacher <agruenba@...hat.com>
Cc:     Vivek Goyal <vgoyal@...hat.com>, fstests <fstests@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, virtio-fs@...hat.com,
        Daniel Walsh <dwalsh@...hat.com>,
        David Gilbert <dgilbert@...hat.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        LSM <linux-security-module@...r.kernel.org>,
        selinux@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>,
        Miklos Szeredi <miklos@...redi.hu>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        stephen.smalley.work@...il.com, Dave Chinner <david@...morbit.com>,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 3/1] xfstests: generic/062: Do not run on newer kernels

Well, we could also look at supporting trusted.* xattrs over NFS.  I
don't know much about them, but it looks like it wouldn't be a lot of
work to specify, especially now that we've already got user xattrs?
We'd just write a new internet draft that refers to the existing
user.* xattr draft for most of the details.

--b.

On Fri, Sep 3, 2021 at 2:56 AM Andreas Gruenbacher <agruenba@...hat.com> wrote:
>
> On Fri, Sep 3, 2021 at 8:31 AM Andreas Gruenbacher <agruenba@...hat.com> wrote:
> > On Thu, Sep 2, 2021 at 5:47 PM Vivek Goyal <vgoyal@...hat.com> wrote:
> > > xfstests: generic/062: Do not run on newer kernels
> > >
> > > This test has been written with assumption that setting user.* xattrs will
> > > fail on symlink and special files. When newer kernels support setting
> > > user.* xattrs on symlink and special files, this test starts failing.
> >
> > It's actually a good thing that this test case triggers for the kernel
> > change you're proposing; that change should never be merged. The
> > user.* namespace is meant for data with the same access permissions as
> > the file data, and it has been for many years. We may have
> > applications that assume the existing behavior. In addition, this
> > change would create backwards compatibility problems for things like
> > backups.
> >
> > I'm not convinced that what you're actually proposing (mapping
> > security.selinux to a different attribute name) actually makes sense,
> > but that's a question for the selinux folks to decide. Mapping it to a
> > user.* attribute is definitely wrong though. The modified behavior
> > would affect anybody, not only users of selinux and/or virtiofs. If
> > mapping attribute names is actually the right approach, then you need
> > to look at trusted.* xattrs, which exist specifically for this kind of
> > purpose. You've noted that trusted.* xattrs aren't supported over nfs.
> > That's unfortunate, but not an acceptable excuse for messing up user.*
> > xattrs.
>
> Another possibility would be to make selinux use a different
> security.* attribute for this nested selinux case. That way, the
> "host" selinux would retain some control over the labels the "guest"
> uses.
>
> Thanks,
> Andreas
>