linux-kernel - Re: [PATCHv6 bpf-next 04/16] bpf: Force uprobe bpf program to always return 0

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Message-ID: <CAEf4BzaWyreKRmLSL0Z+698dqE6Xj8rze3zP=Ygb7WuhJZ-ibg@mail.gmail.com>
Date: Thu, 10 Oct 2024 19:20:25 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Jiri Olsa <jolsa@...nel.org>
Cc: Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org, Martin KaFai Lau <kafai@...com>, 
	Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, 
	John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...omium.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCHv6 bpf-next 04/16] bpf: Force uprobe bpf program to always
 return 0

On Thu, Oct 10, 2024 at 1:10 PM Jiri Olsa <jolsa@...nel.org> wrote:
>
> As suggested by Andrii make uprobe multi bpf programs to always return 0,
> so they can't force uprobe removal.
>
> Keeping the int return type for uprobe_prog_run, because it will be used
> in following session changes.
>
> Fixes: 89ae89f53d20 ("bpf: Add multi uprobe link")
> Suggested-by: Andrii Nakryiko <andrii@...nel.org>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  kernel/trace/bpf_trace.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>

Acked-by: Andrii Nakryiko <andrii@...nel.org>

> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index fdab7ecd8dfa..3c1e5a561df4 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -3209,7 +3209,6 @@ static int uprobe_prog_run(struct bpf_uprobe *uprobe,
>         struct bpf_prog *prog = link->link.prog;
>         bool sleepable = prog->sleepable;
>         struct bpf_run_ctx *old_run_ctx;
> -       int err = 0;
>
>         if (link->task && !same_thread_group(current, link->task))
>                 return 0;
> @@ -3222,7 +3221,7 @@ static int uprobe_prog_run(struct bpf_uprobe *uprobe,
>         migrate_disable();
>
>         old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
> -       err = bpf_prog_run(link->link.prog, regs);
> +       bpf_prog_run(link->link.prog, regs);
>         bpf_reset_run_ctx(old_run_ctx);
>
>         migrate_enable();
> @@ -3231,7 +3230,7 @@ static int uprobe_prog_run(struct bpf_uprobe *uprobe,
>                 rcu_read_unlock_trace();
>         else
>                 rcu_read_unlock();
> -       return err;
> +       return 0;
>  }
>
>  static bool
> --
> 2.46.2
>