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

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Date:	Tue, 2 Aug 2016 22:17:05 +0900
From:	Masami Hiramatsu <mhiramat@...nel.org>
To:	Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
Cc:	linux-kernel@...r.kernel.org, ltc-kernel@...ml.intra.hitachi.co.jp,
	masumi.moritani.ju@...achi.com, Jiri Olsa <jolsa@...nel.org>,
	David Ahern <dsahern@...il.com>,
	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 Mon,  1 Aug 2016 13:30:25 +0900
Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com> 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.

OK, looks good to me:)

Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

Thanks!

> 
> 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
> -- 
> 2.7.4
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>