netdev - Re: [PATCH net] trace/bpf: remove helper bpf_perf_prog_read

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Date:   Tue, 20 Mar 2018 23:21:00 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Yonghong Song <yhs@...com>, ast@...com, netdev@...r.kernel.org
Cc:     kernel-team@...com
Subject: Re: [PATCH net] trace/bpf: remove helper bpf_perf_prog_read_value
 from tracepoint type programs

On 03/20/2018 07:19 PM, Yonghong Song wrote:
> Commit 4bebdc7a85aa ("bpf: add helper bpf_perf_prog_read_value")
> added helper bpf_perf_prog_read_value so that perf_event type program
> can read event counter and enabled/running time.
> This commit, however, introduced a bug which allows this helper
> for tracepoint type programs. This is incorrect as bpf_perf_prog_read_value
> needs to access perf_event through its bpf_perf_event_data_kern type context,
> which is not available for tracepoint type program.
> 
> This patch fixed the issue by separating bpf_func_proto between tracepoint
> and perf_event type programs and removed bpf_perf_prog_read_value
> from tracepoint func prototype.
> 
> Fixes: Commit 4bebdc7a85aa ("bpf: add helper bpf_perf_prog_read_value")
> Reported-by: Alexei Starovoitov <ast@...nel.org>
> Signed-off-by: Yonghong Song <yhs@...com>

Sigh, also makes sense to split given this is so subtle. Applied to bpf,
thanks Yonghong!