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Date:   Mon, 30 Nov 2020 16:18:50 -0500
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Masami Hiramatsu <mhiramat@kernel.org>
Cc:     Wang ShaoBo <bobo.shaobowang@huawei.com>,
        <naveen.n.rao@linux.ibm.com>, <anil.s.keshavamurthy@intel.com>,
        <davem@davemloft.net>, <linux-kernel@vger.kernel.org>,
        <huawei.libin@huawei.com>, <cj.chengjian@huawei.com>
Subject: Re: [PATCH] kretprobe: avoid re-registration of the same kretprobe
 earlier
Message-ID: <20201130161850.34bcfc8a@gandalf.local.home>
In-Reply-To: <20201124115719.11799-1-bobo.shaobowang@huawei.com>
References: <20201124115719.11799-1-bobo.shaobowang@huawei.com>
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Masami,

Can you review this patch, and also, should this go to -rc and stable?

-- Steve


On Tue, 24 Nov 2020 19:57:19 +0800
Wang ShaoBo <bobo.shaobowang@huawei.com> wrote:

> Our system encountered a re-init error when re-registering same kretprobe,
> where the kretprobe_instance in rp->free_instances is illegally accessed
> after re-init.
> 
> Implementation to avoid re-registration has been introduced for kprobe
> before, but lags for register_kretprobe(). We must check if kprobe has
> been re-registered before re-initializing kretprobe, otherwise it will
> destroy the data struct of kretprobe registered, which can lead to memory
> leak, system crash, also some unexpected behaviors.
> 
> we use check_kprobe_rereg() to check if kprobe has been re-registered
> before calling register_kretprobe(), for giving a warning message and
> terminate registration process.
> 
> Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
> Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
> ---
>  kernel/kprobes.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 41fdbb7953c6..7f54a70136f3 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2117,6 +2117,14 @@ int register_kretprobe(struct kretprobe *rp)
>  		}
>  	}
>  
> +	/*
> +	 * Return error if it's being re-registered,
> +	 * also give a warning message to the developer.
> +	 */
> +	ret = check_kprobe_rereg(&rp->kp);
> +	if (WARN_ON(ret))
> +		return ret;
> +
>  	rp->kp.pre_handler = pre_handler_kretprobe;
>  	rp->kp.post_handler = NULL;
>  	rp->kp.fault_handler = NULL;