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

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?

thanks, jirka