linux-kernel - Re: [PATCH v5 0/3] net, mac80211, kernel: enable KCOV remote coverage collection for 802.11 frame handling

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Date:   Mon, 2 Nov 2020 19:00:35 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Aleksandr Nogikh <aleksandrnogikh@...il.com>
Cc:     davem@...emloft.net, johannes@...solutions.net,
        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,
        willemdebruijn.kernel@...il.com,
        Aleksandr Nogikh <nogikh@...gle.com>
Subject: Re: [PATCH v5 0/3] net, mac80211, kernel: enable KCOV remote
 coverage collection for 802.11 frame handling

On Thu, 29 Oct 2020 17:36:17 +0000 Aleksandr Nogikh wrote:
> From: Aleksandr Nogikh <nogikh@...gle.com>
> 
> This patch series enables remote KCOV coverage collection during
> 802.11 frames processing. These changes make it possible to perform
> coverage-guided fuzzing in search of remotely triggerable bugs.
> 
> Normally, KCOV collects coverage information for the code that is
> executed inside the system call context. It is easy to identify where
> that coverage should go and whether it should be collected at all by
> looking at the current process. If KCOV was enabled on that process,
> coverage will be stored in a buffer specific to that process.
> Howerever, it is not always enough as handling can happen elsewhere
> (e.g. in separate kernel threads).
> 
> When it is impossible to infer KCOV-related info just by looking at
> the currently running process, one needs to manually pass some
> information to the code that should be instrumented. The information
> takes the form of 64 bit integers (KCOV remote handles). Zero is the
> special value that corresponds to an empty handle. More details on
> KCOV and remote coverage collection can be found in
> Documentation/dev-tools/kcov.rst.
> 
> The series consists of three commits.
> 1. Apply a minor fix to kcov_common_handle() so that it returns a
> valid handle (zero) when called in an interrupt context.
> 2. Take the remote handle from KCOV and attach it to newly allocated
> SKBs as an skb extension. If the allocation happens inside a system
> call context, the SKB will be tied to the process that issued the
> syscall (if that process is interested in remote coverage collection).
> 3. Annotate the code that processes incoming 802.11 frames with
> kcov_remote_start()/kcov_remote_stop().

Applied, thanks.