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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 17 Dec 2018 11:06:46 -0800
Message-ID: <CAHk-=wjsMJeEkJbE3QhM3SY-DT9VsnMWNQKMNsG9TetnjREWDQ@mail.gmail.com>
Subject: Re: [PATCH RESEND] KEYS: fix parsing invalid pkey info string
To:     ebiggers@kernel.org, James Morris James Morris <jmorris@namei.org>,
        Mimi Zohar <zohar@linux.vnet.ibm.com>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Peter Huewe <peterhuewe@gmx.de>
Cc:     David Howells <dhowells@redhat.com>, keyrings@vger.kernel.org,
        Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
        syzkaller-bugs@googlegroups.com
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On Mon, Dec 17, 2018 at 10:49 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> So the *simplest* fix would seem to be to literally remove all those
> "= -1" for the Opt_err initialization.  Making the code smaller,
> simpler, and fixing the bug in the process.

Something like this

    git  grep -l 'Opt_err = -1' | xargs sed -i 's/Opt_err = -1/Opt_err/'

would do it, but I also notice that
security/integrity/ima/ima_policy.c then has some truly funky code
that plays around with the enum numbers , ie

  #define pt(token)     policy_tokens[token + Opt_err].pattern

which actually depends on the ordering of policy_tokens[], and depends
on the exact values, ie it literally (and quite insanely) sets Opt_err
to -1, and then Opt_measure to 1, and leaves 0 unused. That code
seriously makes no sense at all, and is fundamentally broken.

It would be better to use

    #define pt(token)     policy_tokens[token - Opt_measure].pattern

instead, but even then you should have a huge comment about how the
policy_tokens[] array absolutely has to be properly ordered.

Honestly, for being about "security", all of this code seems to be
doing some really questionable things with all those Opt_xyz enums.

                     Linus