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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Sat, 10 Oct 2020 09:54:57 +0200
Message-ID: <CACT4Y+ZF_umjBpyJiCb8YPQOOSofG-M9h0CB=xn3bCgK=Kr=9w@mail.gmail.com>
Subject: Re: [PATCH 1/2] net: store KCOV remote handle in sk_buff
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     Aleksandr Nogikh <a.nogikh@gmail.com>,
        David Miller <davem@davemloft.net>,
        Johannes Berg <johannes@sipsolutions.net>,
        Eric Dumazet <edumazet@google.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Marco Elver <elver@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        Aleksandr Nogikh <nogikh@google.com>
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Precedence: bulk

On Sat, Oct 10, 2020 at 1:16 AM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Wed,  7 Oct 2020 10:17:25 +0000 Aleksandr Nogikh wrote:
> > From: Aleksandr Nogikh <nogikh@google.com>
> >
> > Remote KCOV coverage collection enables coverage-guided fuzzing of the
> > code that is not reachable during normal system call execution. It is
> > especially helpful for fuzzing networking subsystems, where it is
> > common to perform packet handling in separate work queues even for the
> > packets that originated directly from the user space.
> >
> > Enable coverage-guided frame injection by adding a kcov_handle
> > parameter to sk_buff structure. Initialization in __alloc_skb ensures
> > that no socket buffer that was generated during a system call will be
> > missed.
> >
> > Code that is of interest and that performs packet processing should be
> > annotated with kcov_remote_start()/kcov_remote_stop().
> >
> > An alternative approach is to determine kcov_handle solely on the
> > basis of the device/interface that received the specific socket
> > buffer. However, in this case it would be impossible to distinguish
> > between packets that originated from normal background network
> > processes and those that were intentionally injected from the user
> > space.
> >
> > Signed-off-by: Aleksandr Nogikh <nogikh@google.com>
>
> Could you use skb_extensions for this?

Why? If for space, this is already under a non-production ifdef.