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From:   Salvatore Mesoraca <s.mesoraca16@gmail.com>
Date:   Sun, 6 Oct 2019 17:49:24 +0100
Message-ID: <CAJHCu1JobL7aj51=4gvaoXPfWH8aNdYXgcBDq90wV4_jN2iUfw@mail.gmail.com>
Subject: Re: [PATCH v5 04/12] S.A.R.A.: generic DFA for string matching
To:     Jann Horn <jannh@google.com>
Cc:     kernel list <linux-kernel@vger.kernel.org>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        Linux-MM <linux-mm@kvack.org>,
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        "Serge E. Hallyn" <serge@hallyn.com>,
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Salvatore Mesoraca <s.mesoraca16@gmail.com> wrote:
>
> Jann Horn <jannh@google.com> wrote:
> >
> > On Sat, Jul 6, 2019 at 12:55 PM Salvatore Mesoraca
> > <s.mesoraca16@gmail.com> wrote:
> > > Creation of a generic Discrete Finite Automata implementation
> > > for string matching. The transition tables have to be produced
> > > in user-space.
> > > This allows us to possibly support advanced string matching
> > > patterns like regular expressions, but they need to be supported
> > > by user-space tools.
> >
> > AppArmor already has a DFA implementation that takes a DFA machine
> > from userspace and runs it against file paths; see e.g.
> > aa_dfa_match(). Did you look into whether you could move their DFA to
> > some place like lib/ and reuse it instead of adding yet another
> > generic rule interface to the kernel?
>
> Yes, using AppArmor DFA cloud be a possibility.
> Though, I didn't know how AppArmor's maintainers feel about this.
> I thought that was easier to just implement my own.
> Anyway I understand that re-using that code would be the optimal solution.
> I'm adding in CC AppArmor's maintainers, let's see what they think about this.

I don't want this to prevent SARA from being up-streamed.
Do you think that having another DFA here could be acceptable anyway?
Would it be better if I just drop the DFA an go back to simple string
matching to speed up things?

Thank you,

Salvatore