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From:   Paul Moore <paul@paul-moore.com>
Date:   Thu, 17 Jun 2021 23:18:25 -0400
Message-ID: <CAHC9VhTv6Zn8gYaB6cG4wPzy_Ty0XjOM-QL4cZ525RnhFY4bTQ@mail.gmail.com>
Subject: Re: [PATCH] fs: Return raw xattr for security.* if there is size
 disagreement with LSMs
To:     Mimi Zohar <zohar@linux.ibm.com>
Cc:     Roberto Sassu <roberto.sassu@huawei.com>,
        Stefan Berger <stefanb@linux.ibm.com>,
        "viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
        "stephen.smalley.work@gmail.com" <stephen.smalley.work@gmail.com>,
        "casey@schaufler-ca.com" <casey@schaufler-ca.com>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-integrity@vger.kernel.org" <linux-integrity@vger.kernel.org>,
        "linux-security-module@vger.kernel.org" 
        <linux-security-module@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "selinux@vger.kernel.org" <selinux@vger.kernel.org>
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On Thu, Jun 17, 2021 at 11:28 AM Mimi Zohar <zohar@linux.ibm.com> wrote:
> On Thu, 2021-06-17 at 07:09 +0000, Roberto Sassu wrote:

...

> > An alternative would be to do the EVM verification twice if the
> > first time didn't succeed (with vfs_getxattr_alloc() and with the
> > new function that behaves like vfs_getxattr()).
>
> Unfortunately, I don't see an alternative.

... and while unfortunate, the impact should be non-existant if you
are using the right tools to label files or ensuring that you are
formatting labels properly if doing it by hand.

Handling a corner case is good, but I wouldn't add a lot of code
complexity trying to optimize it.

-- 
paul moore
www.paul-moore.com