linux-kernel - Re: [PATCH 1/2 v4] perf sched: fix wrong conversion of task state

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Date:	Mon, 1 Aug 2016 07:52:24 -0600
From:	David Ahern <dsahern@...il.com>
To:	Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>,
	linux-kernel@...r.kernel.org
Cc:	ltc-kernel@...ml.intra.hitachi.co.jp,
	masumi.moritani.ju@...achi.com, Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH 1/2 v4] perf sched: fix wrong conversion of task state

On 7/31/16 10:30 PM, Tomoki Sekiyama wrote:
> Currently sched_out_state() converts the prev_state u64 bitmask to a char
> using the bitmask as an index, which may cause invalid memory access.
> This fixes the issue by using the __ffs() returned value as an index.
>
> Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
> Fixes: cdce9d738b91e ("perf sched: Add sched latency profiling")
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: David Ahern <dsahern@...il.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> ---
> Changes from v3:
>   Added Fixes:
>   Split the patch into 2 pieces.
>
>  tools/perf/builtin-sched.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index 0dfe8df..ce9bef6 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -897,9 +897,10 @@ static int thread_atoms_insert(struct perf_sched *sched, struct thread *thread)
>
>  static char sched_out_state(u64 prev_state)
>  {
> -	const char *str = TASK_STATE_TO_CHAR_STR;
> +	const char str[] = TASK_STATE_TO_CHAR_STR;
> +	unsigned int bit = prev_state ? __ffs(prev_state) + 1 : 0;
>
> -	return str[prev_state];
> +	return bit < ARRAY_SIZE(str) - 1 ? str[bit] : '?';
>  }
>
>  static int
>


Acked-by: David Ahern <dsahern@...il.com>