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

[David Miller <davem@davemloft.net>]

From: Yonghong Song <yhs@fb.com>
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 <yhs@fb.com>

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.