linux-kernel - Re: [PATCH v2 1/2] samples, selftests/seccomp: Zero out seccomp

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Message-ID: <CAMp4zn9s1wJyb9xHj4xYL5HTtM=gA07ZfBGTSW5j4ayUzaoZNQ@mail.gmail.com>
Date:   Mon, 30 Dec 2019 11:14:44 -0800
From:   Sargun Dhillon <sargun@...gun.me>
To:     Tycho Andersen <tycho@...ho.ws>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Jann Horn <jannh@...gle.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Kees Cook <keescook@...omium.org>,
        Aleksa Sarai <cyphar@...har.com>
Subject: Re: [PATCH v2 1/2] samples, selftests/seccomp: Zero out seccomp_notif

On Sat, Dec 28, 2019 at 4:18 PM Tycho Andersen <tycho@...ho.ws> wrote:
>
> On Sat, Dec 28, 2019 at 07:10:29PM -0500, Sargun Dhillon wrote:
> > On Sat, Dec 28, 2019 at 1:18 PM Tycho Andersen <tycho@...ho.ws> wrote:
> > >
> > >
> > > I know it's unrelated, but it's probably worth sending a patch to fix
> > > this to be sizes.seccomp_notif_resp instead of sizeof(*resp), since if
> > > the kernel is older this will over-zero things. I can do that, or you
> > > can add the patch to this series, just let me know which.
> >
> > I was thinking about this, and initially, I chose to make the smaller
> > change. I think it might make more sense to combine the patch,
> > given that the memset behaviour is "incorrect" if we do it based on
> > sizeof(*req), or sizeof(*resp).
> >
> > I'll go ahead and respin this patch with the change to call memset
> > based on sizes.
>
> I think it would be good to keep it as a separate patch, since it's an
> unrelated bug fix. That way if we have to revert these because of some
> breakage, we won't lose the fix.
>
> Cheers,
>
> Tycho

As I was doing this, I noticed that the self-tests all use hard-coded struct
sizes. When I was playing with extending the API, all of a sudden all the
self-tests started failing (until I recompiled them against newer headers).

Should we also change the self-tests to operate against the seccomp
sizes API, or was it intentional for the self-tests hard-coded the struct
definitions, and locked to the kernel version?