Re: [PATCH 1/2] net: store KCOV remote handle in sk_buff

[Dmitry Vyukov]

On Sat, Oct 10, 2020 at 1:16 AM Jakub Kicinski <kuba@xxxxxxxxxx> wrote:
>
> On Wed,  7 Oct 2020 10:17:25 +0000 Aleksandr Nogikh wrote:
> > From: Aleksandr Nogikh <nogikh@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
>
> Could you use skb_extensions for this?

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