linux-kernel - Re: [PATCH v3 net-next] bpf: fix bpf_perf_event

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Message-Id: <20151026.215057.1299451307191406499.davem@davemloft.net>
Date:	Mon, 26 Oct 2015 21:50:57 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ast@...mgrid.com
Cc:	mingo@...nel.org, a.p.zijlstra@...llo.nl, wangnan0@...wei.com,
	hekuang@...wei.com, xiakaixu@...wei.com, daniel@...earbox.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 net-next] bpf: fix bpf_perf_event_read() helper

From: Alexei Starovoitov <ast@...mgrid.com>
Date: Thu, 22 Oct 2015 17:10:14 -0700

> Fix safety checks for bpf_perf_event_read():
> - only non-inherited events can be added to perf_event_array map
>   (do this check statically at map insertion time)
> - dynamically check that event is local and !pmu->count
> Otherwise buggy bpf program can cause kernel splat.
> 
> Also fix error path after perf_event_attrs()
> and remove redundant 'extern'.
> 
> Fixes: 35578d798400 ("bpf: Implement function bpf_perf_event_read() that get the selected hardware PMU conuter")
> Signed-off-by: Alexei Starovoitov <ast@...nel.org>

Applied, although my tendancy is to agree with the sentiment that you must
respect the entire universe of valid 64-bit counter values.  I do not buy
the arguments about values overlapping error codes being unlikely or not
worth worrying about.

Just FYI...
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