netdev - Re: [PATCH v5 bpf-next 2/5] bpf: Introduce sleepable BPF programs

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Message-ID: <d0c6b6a6-7b82-e620-8ced-8a1acfaf6f6d@iogearbox.net>
Date:   Wed, 1 Jul 2020 01:26:44 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        davem@...emloft.net
Cc:     paulmck@...nel.org, netdev@...r.kernel.org, bpf@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH v5 bpf-next 2/5] bpf: Introduce sleepable BPF programs

On 6/30/20 6:33 AM, Alexei Starovoitov wrote:
[...]
>   
> +/* list of non-sleepable kernel functions that are otherwise
> + * available to attach by bpf_lsm or fmod_ret progs.
> + */
> +static int check_sleepable_blacklist(unsigned long addr)
> +{
> +#ifdef CONFIG_BPF_LSM
> +	if (addr == (long)bpf_lsm_task_free)
> +		return -EINVAL;
> +#endif
> +#ifdef CONFIG_SECURITY
> +	if (addr == (long)security_task_free)
> +		return -EINVAL;
> +#endif
> +	return 0;
> +}

Would be nice to have some sort of generic function annotation to describe
that code cannot sleep inside of it, and then filter based on that. Anyway,
is above from manual code inspection?

What about others like security_sock_rcv_skb() for example which could be
bh_lock_sock()'ed (or, generally hooks running in softirq context)?