linux-kernel - [PATCH 2/3] Fix ordered-events.c array-bounds error

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Message-Id: <20190724184512.162887-3-nums@google.com>
Date:   Wed, 24 Jul 2019 11:45:11 -0700
From:   Numfor Mbiziwo-Tiapo <nums@...gle.com>
To:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, songliubraving@...com, mbd@...com
Cc:     linux-kernel@...r.kernel.org, irogers@...gle.com,
        eranian@...gle.com, Numfor Mbiziwo-Tiapo <nums@...gle.com>
Subject: [PATCH 2/3] Fix ordered-events.c array-bounds error

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.

Signed-off-by: Numfor Mbiziwo-Tiapo <nums@...gle.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