linux-kernel - [PATCH AUTOSEL 4.14 41/44] perf ftrace: Fix failure to set cpumask when only one cpu is present

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Date:   Tue, 13 Aug 2019 22:18:30 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     He Zhe <zhe.he@...driver.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Stephane Eranian <eranian@...gle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.14 41/44] perf ftrace: Fix failure to set cpumask when only one cpu is present

From: He Zhe <zhe.he@...driver.com>

[ Upstream commit cf30ae726c011e0372fd4c2d588466c8b50a8907 ]

The buffer containing the string used to set cpumask is overwritten at
the end of the string later in cpu_map__snprint_mask due to not enough
memory space, when there is only one cpu.

And thus causes the following failure:

  $ perf ftrace ls
  failed to reset ftrace
  $

This patch fixes the calculation of the cpumask string size.

Signed-off-by: He Zhe <zhe.he@...driver.com>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Kan Liang <kan.liang@...ux.intel.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Fixes: dc23103278c5 ("perf ftrace: Add support for -a and -C option")
Link: http://lkml.kernel.org/r/1564734592-15624-1-git-send-email-zhe.he@windriver.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/perf/builtin-ftrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 25a42acabee18..13a33fb71a6da 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -162,7 +162,7 @@ static int set_tracing_cpumask(struct cpu_map *cpumap)
 	int last_cpu;
 
 	last_cpu = cpu_map__cpu(cpumap, cpumap->nr - 1);
-	mask_size = (last_cpu + 3) / 4 + 1;
+	mask_size = last_cpu / 4 + 2; /* one more byte for EOS */
 	mask_size += last_cpu / 32; /* ',' is needed for every 32th cpus */
 
 	cpumask = malloc(mask_size);
-- 
2.20.1