linux-kernel - Re: [PATCH 0/2] net, mac80211: enable KCOV remote coverage collection for 802.11 frame handling

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Date:   Wed, 07 Oct 2020 13:48:43 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Aleksandr Nogikh <a.nogikh@...il.com>, davem@...emloft.net,
        kuba@...nel.org
Cc:     edumazet@...gle.com, andreyknvl@...gle.com, dvyukov@...gle.com,
        elver@...gle.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
        nogikh@...gle.com
Subject: Re: [PATCH 0/2] net, mac80211: enable KCOV remote coverage
 collection for 802.11 frame handling

On Wed, 2020-10-07 at 10:17 +0000, Aleksandr Nogikh wrote:
> From: Aleksandr Nogikh <nogikh@...gle.com>
> 
> This patch series enables remote KCOV coverage collection for the
> mac80211 code that processes incoming 802.11 frames. These changes
> make it possible to perform coverage-guided fuzzing in search of
> remotely triggerable bugs.
> 
> 
> The series consists of two commits.
> 1. Remember kcov_handle for each sk_buff. This can later be used to
> enable remote coverage for other network subsystems.
> 2. Annotate the code that processes incoming 802.11 frames.
> 
> Aleksandr Nogikh (2):
>   net: store KCOV remote handle in sk_buff

Can you explain that a bit better? What is a "remote handle"? What does
it do in the SKB?

I guess I'd have to know more about "kcov_common_handle()" to understand
this bit.

>   mac80211: add KCOV remote annotations to incoming frame processing

This seems fine, but a bit too limited? You tagged
only ieee80211_tasklet_handler() which calls ieee80211_rx()
or ieee80211_tx_status(), but

1) I'm not even sure ieee80211_tx_status() counts (it's processing
locally generated frames after they round-tripped into the driver
(although in mesh it could be remote originated but retransmitted
frames, so I guess it makes some sense?); and

2) there are many other ways that ieee80211_rx() could get called.

It seems to me it'd make more sense to (also) annotate ieee80211_rx()
itself?

johannes