Re: [PATCH] kretprobe: Prevent triggering kretprobe from within kprobe_flush_task

[Masami Hiramatsu <mhiramat@kernel.org>]

Hi Jiri,

On Thu, 16 Apr 2020 11:13:20 +0200
Jiri Olsa <jolsa@redhat.com> wrote:

> On Thu, Apr 16, 2020 at 10:55:06AM +0900, Masami Hiramatsu wrote:
> 
> SNIP
> 
> > >           trampoline_handler
> > >             kretprobe_hash_lock(current, &head, &flags);  <--- deadlock
> > > 
> > > Adding kprobe_busy_begin/end helpers that mark code with fake
> > > probe installed to prevent triggering of another kprobe within
> > > this code.
> > > 
> > > Using these helpers in kprobe_flush_task, so the probe recursion
> > > protection check is hit and the probe is never set to prevent
> > > above lockup.
> > > 
> > > Reported-by: "Ziqian SUN (Zamir)" <zsun@redhat.com>
> > > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > 
> > Thanks Jiri and Ziqian!
> > 
> > Looks good to me.
> > 
> > Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
> > 
> > BTW, this is a kind of bugfix. So should it add a Fixes tag?
> > 
> > Fixes: ef53d9c5e4da ('kprobes: improve kretprobe scalability with hashed locking')
> > Cc: stable@vger.kernel.org
> 
> ah right, do you want me to repost with those?

Yeah, if you don't mind.

Thank you,

> 
> thanks,
> jirka
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>