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SubjectRe: [PATCH] perf: Check permission only for parent tracepoint event
At Wed, 16 Jul 2014 14:33:29 +0200,
Jiri Olsa wrote:
>
> There's no need to check cloned event's permission once the
> parent was already checked.
>
> Also the code is checking 'current' process permissions, which
> is not owner process for cloned events, thus could end up with
> wrong permission check result.
>
> Reported-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
> Cc: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Link: http://lkml.kernel.org/r/1405079782-8139-1-git-send-email-jolsa@kernel.org
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> kernel/trace/trace_event_perf.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
> index 5d12bb407b44..4b9c114ee9de 100644
> --- a/kernel/trace/trace_event_perf.c
> +++ b/kernel/trace/trace_event_perf.c
> @@ -30,6 +30,18 @@ static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
> return ret;
> }
>
> + /*
> + * We checked and allowed to create parent,
> + * allow children without checking.
> + */
> + if (p_event->parent)
> + return 0;
> +
> + /*
> + * It's ok to check current process (owner) permissions in here,
> + * because code below is called only via perf_event_open syscall.
> + */
> +
> /* The ftrace function trace is allowed only for root. */
> if (ftrace_event_is_function(tp_event)) {
> if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
> --
> 1.8.3.1
>

Tested-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>

Thanks.



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