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Date:   Mon, 14 Dec 2020 11:36:51 -0500
From:   Steven Rostedt <rostedt@goodmis.org>
To:     "Wangshaobo (bobo)" <bobo.shaobowang@huawei.com>
Cc:     Masami Hiramatsu <mhiramat@kernel.org>,
        <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: <20201214113651.04e550f6@gandalf.local.home>
In-Reply-To: <9dff21f8-4ab9-f9b2-64fd-cc8c5f731932@huawei.com>
References: <20201124115719.11799-1-bobo.shaobowang@huawei.com>
        <20201130161850.34bcfc8a@gandalf.local.home>
        <20201202083253.9dbc76704149261e131345bf@kernel.org>
        <9dff21f8-4ab9-f9b2-64fd-cc8c5f731932@huawei.com>
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On Wed, 2 Dec 2020 09:23:35 +0800
"Wangshaobo (bobo)" <bobo.shaobowang@huawei.com> wrote:

> Hi steve, Masami,
> 
> Thanks for your works, i will check code again and modify properly 
> according to steve's suggestion.
> 
> -- ShaoBo
> 

Anything happen with this? 

-- Steve


> 在 2020/12/2 7:32, Masami Hiramatsu 写道:
> > On Mon, 30 Nov 2020 16:18:50 -0500
> > Steven Rostedt <rostedt@goodmis.org> wrote:
> >  
> >> Masami,
> >>
> >> Can you review this patch, and also, should this go to -rc and stable?
> >>
> >> -- Steve  
> > Thanks for ping me!
> >  
> >> 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.  
> > Ah, OK. Anyway if re-register happens on kretprobe, it must lose instances
> > on the list before checking re-register in register_kprobe().
> > So the idea looks good to me.
> >
> >  
> >>> 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;  
> > If you call this here, you must make sure kprobe_addr() is called on rp->kp.
> > But if kretprobe_blacklist_size == 0, kprobe_addr() is not called before
> > this check. So it should be in between kprobe_on_func_entry() and
> > kretprobe_blacklist_size check, like this
> >
> > 	if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset))
> > 		return -EINVAL;
> >
> > 	addr = kprobe_addr(&rp->kp);
> > 	if (IS_ERR(addr))
> > 		return PTR_ERR(addr);
> > 	rp->kp.addr = addr;
> >
> > 	ret = check_kprobe_rereg(&rp->kp);
> > 	if (WARN_ON(ret))
> > 		return ret;
> >
> >          if (kretprobe_blacklist_size) {
> > 		for (i = 0; > > +	ret = check_kprobe_rereg(&rp->kp);
> >
> >
> > Thank you,
> >
> >