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

[Jiri Olsa]

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@xxxxxxxxxx>
> > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> 
> Thanks Jiri and Ziqian!
> 
> Looks good to me.
> 
> Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxxxx

ah right, do you want me to repost with those?

thanks,
jirka