linux-kernel - Re: [PATCH bpf-next] bpf: Improve bpf_probe_write

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Message-ID: <CANpmjNNm7szX_9D9z2iYr4xyN57th0WMOmiipTCYYkSo-Z6rLA@mail.gmail.com>
Date: Wed, 27 Nov 2024 11:39:24 +0100
From: Marco Elver <elver@...gle.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, bpf@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Nikola Grcevski <nikola.grcevski@...fana.com>
Subject: Re: [PATCH bpf-next] bpf: Improve bpf_probe_write_user() warning message

On Tue, 26 Nov 2024 at 22:32, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
[...]
> should we just drop this warning altogether? After all, we can call

I'm in favour.

> crash_kexec() without any warnings, if we have the right capabilities.
> bpf_probe_write_user() is much less destructive and at worst will
> cause memory corruption within a single process (assuming
> CAP_SYS_ADMIN, of course). If yes, I think we should drop
> bpf_get_probe_write_proto() function altogether and refactor
> bpf_tracing_func_proto() to have
> bpf_token_capable(CAP_SYS_ADMIN)-guarded section, just like
> bpf_base_func_proto() has.

Let me do that too. But as a separate patch 2/2 as it simplifies
backporting the removal of the warning to older kernels.