Re: [PATCH net] bpf: one perf event close won't free bpf program attached by another perf event

From: Yonghong Song <redacted>
Date: Mon, 18 Sep 2017 16:38:36 -0700

This patch fixes a bug exhibited by the following scenario:
  1. fd1 = perf_event_open with attr.config = ID1
  2. attach bpf program prog1 to fd1
  3. fd2 = perf_event_open with attr.config = ID1
     <this will be successful>
  4. user program closes fd2 and prog1 is detached from the tracepoint.
  5. user program with fd1 does not work properly as tracepoint
     no output any more.

The issue happens at step 4. Multiple perf_event_open can be called
successfully, but only one bpf prog pointer in the tp_event. In the
current logic, any fd release for the same tp_event will free
the tp_event->prog.

The fix is to free tp_event->prog only when the closing fd
corresponds to the one which registered the program.

Signed-off-by: Yonghong Song <redacted>

I've applied this and queued it up for -stable as it looks good
to me and 2 days is enough time for waiting for any other reviews.

Thanks.