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From:   Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Date:   Fri, 26 Jul 2019 16:33:52 -0300
To:     Numfor Mbiziwo-Tiapo <nums@google.com>
Cc:     peterz@infradead.org, mingo@redhat.com,
        alexander.shishkin@linux.intel.com, jolsa@redhat.com,
        namhyung@kernel.org, songliubraving@fb.com, mbd@fb.com,
        linux-kernel@vger.kernel.org, irogers@google.com,
        eranian@google.com
Subject: Re: [PATCH 2/3] Fix ordered-events.c array-bounds error
Message-ID: <20190726193352.GI20482@kernel.org>
References: <20190724184512.162887-1-nums@google.com>
 <20190724184512.162887-3-nums@google.com>
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Em Wed, Jul 24, 2019 at 11:45:11AM -0700, Numfor Mbiziwo-Tiapo escreveu:
> Perf does not build with the ubsan (undefined behavior sanitizer)
> and there is an error that says:
> 
> tools/perf/util/debug.h:38:2:
>  error: array subscript is above array bounds [-Werror=array-bounds]
>   eprintf_time(n, var, t, fmt, ##__VA_ARGS__)
>   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> tools/perf/util/debug.h:40:34:
>  note: in expansion of macro ‘pr_time_N’
>  #define pr_oe_time(t, fmt, ...)  pr_time_N(1, debug_ordered_events,
>  t, pr_fmt(fmt), ##__VA_ARGS__)
> 
> util/ordered-events.c:329:2: note: in expansion of macro ‘pr_oe_time’
>   pr_oe_time(oe->next_flush, "next_flush - ordered_events__flush
>   POST %s, nr_events %u\n",
> 
> This can be reproduced by running (from the tip directory):
> make -C tools/perf USE_CLANG=1 EXTRA_CFLAGS="-fsanitize=undefined"
> 
> The error stems from the 'str' array in the __ordered_events__flush
> function in tools/perf/util/ordered-events.c. On line 319 of this
> file, they use values of the variable 'how' (which has the type enum
> oeflush - defined in ordered-events.h) as indices for the 'str' array.
> Since 'how' has 5 values and the 'str' array only has 3, when the 4th
> and 5th values of 'how' (OE_FLUSH__TOP and OE_FLUSH__TIME) are used as
> indices, this will go out of the bounds of the 'str' array.
> Adding the matching strings from the enum values into the 'str' array
> fixes this.

^[[acme@quaco perf]$ patch -p1 < /wb/1.patch
patching file tools/perf/util/ordered-events.c
patch: **** malformed patch at line 146: s *oe, enum oe_flush how,

[acme@quaco perf]$ git dif


Applying by hand
 
> Signed-off-by: Numfor Mbiziwo-Tiapo <nums@google.com>
> ---
>  tools/perf/util/ordered-events.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c
> index 897589507d97..c092b0c39d2b 100644
> --- a/tools/perf/util/ordered-events.c
> +++ b/tools/perf/util/ordered-events.c
> @@ -270,6 +270,8 @@ static int __ordered_events__flush(struct ordered_events *oe, enum oe_flush how,
>  		"FINAL",
>  		"ROUND",
>  		"HALF ",
> +		"TOP",
> +		"TIME",
>  	};
>  	int err;
>  	bool show_progress = false;
> -- 
> 2.22.0.657.g960e92d24f-goog

-- 

- Arnaldo