From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH net] bpf, trace: use READ_ONCE for retrieving file ptr
Date: Tue, 07 Jun 2016 14:48:46 -0700 (PDT)
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Cc: alexei.starovoitov@gmail.com, xiakaixu@huawei.com,
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From: Daniel Borkmann <daniel@iogearbox.net>
Date: Sat,  4 Jun 2016 20:50:59 +0200

> In bpf_perf_event_read() and bpf_perf_event_output(), we must use
> READ_ONCE() for fetching the struct file pointer, which could get
> updated concurrently, so we must prevent the compiler from potential
> refetching.
> 
> We already do this with tail calls for fetching the related bpf_prog,
> but not so on stored perf events. Semantics for both are the same
> with regards to updates.
> 
> Fixes: a43eec304259 ("bpf: introduce bpf_perf_event_output() helper")
> Fixes: 35578d798400 ("bpf: Implement function bpf_perf_event_read() that get the selected hardware PMU conuter")
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> Acked-by: Alexei Starovoitov <ast@kernel.org>

Applied and queued up for -stable, thanks.