linux-kernel - Re: [PATCH] fprobe: add unlock to match a succeeded ftrace_test_recursion

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Message-Id: <20230703171905.ef83b1a7f4db82012db471fc@kernel.org>
Date:   Mon, 3 Jul 2023 17:19:05 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Ze Gao <zegao2021@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, Ze Gao <zegao@...cent.com>,
        Yafang <laoar.shao@...il.com>
Subject: Re: [PATCH] fprobe: add unlock to match a succeeded
 ftrace_test_recursion_trylock

On Mon,  3 Jul 2023 15:16:40 +0800
Ze Gao <zegao2021@...il.com> wrote:

Good catch! but please add description here, something like;

----
Unlock ftrace recursion lock when fprobe_kprobe_handler() is failed
because another kprobe is running.
----

The code itself is OK to me.


> Fixes: 3cc4e2c5fbae ("fprobe: make fprobe_kprobe_handler recursion free")
> Reported-by: Yafang <laoar.shao@...il.com>
> Closes: https://lore.kernel.org/linux-trace-kernel/CALOAHbC6UpfFOOibdDiC7xFc5YFUgZnk3MZ=3Ny6we=AcrNbew@mail.gmail.com/
> Signed-off-by: Ze Gao <zegao@...cent.com>
> ---
>  kernel/trace/fprobe.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
> index 18d36842faf5..93b3e361bb97 100644
> --- a/kernel/trace/fprobe.c
> +++ b/kernel/trace/fprobe.c
> @@ -102,12 +102,14 @@ static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
>  
>  	if (unlikely(kprobe_running())) {
>  		fp->nmissed++;
> -		return;
> +		goto recursion_unlock;
>  	}
>  
>  	kprobe_busy_begin();
>  	__fprobe_handler(ip, parent_ip, ops, fregs);
>  	kprobe_busy_end();
> +
> +recursion_unlock:
>  	ftrace_test_recursion_unlock(bit);
>  }
>  
> -- 
> 2.40.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>