netdev - Re: Self-XORing BPF registers is undefined behavior

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Message-ID: <91a115bb-24d3-3765-a082-555b5999bb42@solarflare.com>
Date:   Wed, 3 Jun 2020 16:37:04 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Alexander Potapenko <glider@...gle.com>
CC:     Daniel Borkmann <daniel@...earbox.net>,
        Michal Kubecek <mkubecek@...e.cz>,
        Alexei Starovoitov <ast@...nel.org>,
        Dmitriy Vyukov <dvyukov@...gle.com>,
        Networking <netdev@...r.kernel.org>
Subject: Re: Self-XORing BPF registers is undefined behavior

On 02/06/2020 18:32, Alexei Starovoitov wrote:
> The target for bpf codegen is JITs.
> bpf interpreter is simulating hw.
> For now if you want UB fuzzer running in your environment please add
> _out_of_tree_ patch that inits all interpreter registers to zero.
+1 to all the above.

Also, note that you can still fuzz BPF JITs by building the kernel
 without the interpreter: CONFIG_BPF_JIT_ALWAYS_ON.