netdev - Re: [PATCH net] bpf, trace: use READ

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Message-Id: <20160607.144846.1662240162265441902.davem@davemloft.net>
Date:	Tue, 07 Jun 2016 14:48:46 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	daniel@...earbox.net
Cc:	alexei.starovoitov@...il.com, xiakaixu@...wei.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH net] bpf, trace: use READ_ONCE for retrieving file ptr

From: Daniel Borkmann <daniel@...earbox.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@...earbox.net>
> Acked-by: Alexei Starovoitov <ast@...nel.org>

Applied and queued up for -stable, thanks.