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From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Thu, 28 Sep 2023 12:07:17 +0200
Message-ID: <CAJfpegtJwcS9=7dCAVCEoBwD_U2MX44a6B62iDsc78AZt6nM7Q@mail.gmail.com>
Subject: Re: [RFC PATCH 3/3] add listmnt(2) syscall
To:     Paul Moore <paul@paul-moore.com>
Cc:     Christian Brauner <brauner@kernel.org>,
        Miklos Szeredi <mszeredi@redhat.com>,
        Matthew House <mattlloydhouse@gmail.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-api@vger.kernel.org, linux-man@vger.kernel.org,
        linux-security-module@vger.kernel.org, Karel Zak <kzak@redhat.com>,
        Ian Kent <raven@themaw.net>,
        David Howells <dhowells@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <christian@brauner.io>,
        Amir Goldstein <amir73il@gmail.com>
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On Tue, 19 Sept 2023 at 18:48, Paul Moore <paul@paul-moore.com> wrote:

> > Ideally we avoid multiple capable(CAP_SYS_ADMIN) calls by only doing it
> > once and saving the return value. capable() call's aren't that cheap.
>
> Agreed.  The capability check doesn't do any subject/object
> comparisons so calling it for each mount is overkill.  However, I
> would think we would want the LSM hook called from inside the loop as
> that could involve a subject (@current) and object (individual mount
> point) comparison.

The security_sb_statfs() one?

Should a single failure result in a complete failure?

Why is it not enough to check permission on the parent?

Thanks,
Miklos