Re: [PATCH] kretprobe: avoid re-registration of the same kretprobe earlier

[Wangshaobo (bobo)]

Hi Masami,

I will update and resend it soon

Thank you

-- ShaoBo

在 2020/12/15 11:31, Masami Hiramatsu 写道:
> Hi ShaoBo,
>
> On Wed, 2 Dec 2020 09:23:35 +0800
> "Wangshaobo (bobo)" <bobo.shaobowang@xxxxxxxxxx> wrote:
>
> > Hi steve, Masami,
> >
> > Thanks for your works, i will check code again and modify properly
> > according to steve's suggestion.
> Can you update your patch and resend it?
>
> Thank you,
>
> > -- ShaoBo
> >
> > 在 2020/12/2 7:32, Masami Hiramatsu 写道:
> > > On Mon, 30 Nov 2020 16:18:50 -0500
> > > Steven Rostedt <rostedt@xxxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > > > Signed-off-by: Cheng Jian <cj.chengjian@xxxxxxxxxx>
> > > > > ---
> > > > >    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,