Date:   Fri, 12 Nov 2021 11:15:01 -0800
From:   Eric Biggers <ebiggers@kernel.org>
To:     Roberto Sassu <roberto.sassu@huawei.com>
Cc:     tytso@mit.edu, corbet@lwn.net, viro@zeniv.linux.org.uk,
        hughd@google.com, akpm@linux-foundation.org,
        linux-fscrypt@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 2/5] fsverity: Revalidate built-in signatures at
 file open
Message-ID: <YY69NaucW+0t474Q@gmail.com>
References: <20211112124411.1948809-1-roberto.sassu@huawei.com>
 <20211112124411.1948809-3-roberto.sassu@huawei.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20211112124411.1948809-3-roberto.sassu@huawei.com>
Precedence: bulk

On Fri, Nov 12, 2021 at 01:44:08PM +0100, Roberto Sassu wrote:
> Fsverity signatures are validated only upon request by the user by setting
> the requirement through procfs or sysctl.
> 
> However, signatures are validated only when the fsverity-related
> initialization is performed on the file. If the initialization happened
> while the signature requirement was disabled, the signature is not
> validated again.

I'm not sure this really matters.  If someone has started using a verity file
before the require_signatures sysctl was set, then there is already a race
condition; this patch doesn't fix that.  Don't you need to set the
require_signatures sysctl early enough anyway?

- Eric