Re: [PATCH v3 1/4] rethook: use preempt_{disable, enable}_notrace in rethook_trampoline_handler

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
To: Ze Gao <zegao2021@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Borislav Petkov <bp@alien8.de>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vasily Gorbik <gor@linux.ibm.com>,
	x86@kernel.org, bpf@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
	Conor Dooley <conor@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
	Yonghong Song <yhs@fb.com>, Ze Gao <zegao@tencent.com>,
	stable@vger.kernel.org
Subject: Re: [PATCH v3 1/4] rethook: use preempt_{disable, enable}_notrace in rethook_trampoline_handler
Date: Wed, 17 May 2023 20:59:47 +0900	[thread overview]
Message-ID: <20230517205947.c1710ed175519b59f56e09b1@kernel.org> (raw)
In-Reply-To: <20230517034510.15639-2-zegao@tencent.com>

Hi Ze Gao,

On Wed, 17 May 2023 11:45:06 +0800
Ze Gao <zegao2021@gmail.com> wrote:

> This patch replaces preempt_{disable, enable} with its corresponding
> notrace version in rethook_trampoline_handler so no worries about stack
> recursion or overflow introduced by preempt_count_{add, sub} under
> fprobe + rethook context.
> 
> Fixes: 54ecbe6f1ed5 ("rethook: Add a generic return hook")
> Signed-off-by: Ze Gao <zegao@tencent.com>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> Cc: <stable@vger.kernel.org>
> Link: https://lore.kernel.org/linux-trace-kernel/20230516071830.8190-2-zegao@tencent.com

Note that you don't need to add Link tag of the previous version for each patch.
I'll add it when I pick it :)

Thank you,

> ---
>  kernel/trace/rethook.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c
> index 32c3dfdb4d6a..60f6cb2b486b 100644
> --- a/kernel/trace/rethook.c
> +++ b/kernel/trace/rethook.c
> @@ -288,7 +288,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs,
>  	 * These loops must be protected from rethook_free_rcu() because those
>  	 * are accessing 'rhn->rethook'.
>  	 */
> -	preempt_disable();
> +	preempt_disable_notrace();
>  
>  	/*
>  	 * Run the handler on the shadow stack. Do not unlink the list here because
> @@ -321,7 +321,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs,
>  		first = first->next;
>  		rethook_recycle(rhn);
>  	}
> -	preempt_enable();
> +	preempt_enable_notrace();
>  
>  	return correct_ret_addr;
>  }
> -- 
> 2.40.1
> 

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