linux-kernel - Re: [PATCH 2/9] tools: convert cpu_map.refcnt from atomic_t to refcount

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Message-ID: <20170222202940.GD20447@kernel.org>
Date:   Wed, 22 Feb 2017 17:29:40 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Elena Reshetova <elena.reshetova@...el.com>
Cc:     linux-kernel@...r.kernel.org, alsa-devel@...a-project.org,
        peterz@...radead.org, gregkh@...uxfoundation.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        mark.rutland@....com, akpm@...ux-foundation.org,
        matija.glavinic-pecotic.ext@...ia.com,
        Hans Liljestrand <ishkamiel@...il.com>,
        Kees Cook <keescook@...omium.org>,
        David Windsor <dwindsor@...il.com>
Subject: Re: [PATCH 2/9] tools: convert cpu_map.refcnt from atomic_t to
 refcount_t

Em Tue, Feb 21, 2017 at 05:34:56PM +0200, Elena Reshetova escreveu:
> refcount_t type and corresponding API should be
> used instead of atomic_t when the variable is used as
> a reference counter. This allows to avoid accidental
> refcounter overflows that might lead to use-after-free
> situations.

The following patch was needed for this one to build:

diff --git a/tools/perf/tests/cpumap.c b/tools/perf/tests/cpumap.c
index f168a85992d0..4478773cdb97 100644
--- a/tools/perf/tests/cpumap.c
+++ b/tools/perf/tests/cpumap.c
@@ -66,7 +66,7 @@ static int process_event_cpus(struct perf_tool *tool __maybe_unused,
 	TEST_ASSERT_VAL("wrong nr",  map->nr == 2);
 	TEST_ASSERT_VAL("wrong cpu", map->map[0] == 1);
 	TEST_ASSERT_VAL("wrong cpu", map->map[1] == 256);
-	TEST_ASSERT_VAL("wrong refcnt", atomic_read(&map->refcnt) == 1);
+	TEST_ASSERT_VAL("wrong refcnt", refcount_read(&map->refcnt) == 1);
 	cpu_map__put(map);
 	return 0;
 }
diff --git a/tools/perf/util/cpumap.h b/tools/perf/util/cpumap.h
index e84491636c1b..ab1aeed8cd5d 100644
--- a/tools/perf/util/cpumap.h
+++ b/tools/perf/util/cpumap.h
@@ -3,10 +3,10 @@
 
 #include <stdio.h>
 #include <stdbool.h>
-#include <linux/refcount.h>
 
 #include "perf.h"
 #include "util/debug.h"
+#include <linux/refcount.h>
 
 struct cpu_map {
 	refcount_t refcnt;
 
> Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
> Signed-off-by: Hans Liljestrand <ishkamiel@...il.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: David Windsor <dwindsor@...il.com>
> ---
>  tools/perf/util/cpumap.c | 16 ++++++++--------
>  tools/perf/util/cpumap.h |  4 ++--
>  2 files changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
> index 2c0b522..0e21e28 100644
> --- a/tools/perf/util/cpumap.c
> +++ b/tools/perf/util/cpumap.c
> @@ -28,7 +28,7 @@ static struct cpu_map *cpu_map__default_new(void)
>  			cpus->map[i] = i;
>  
>  		cpus->nr = nr_cpus;
> -		atomic_set(&cpus->refcnt, 1);
> +		refcount_set(&cpus->refcnt, 1);
>  	}
>  
>  	return cpus;
> @@ -42,7 +42,7 @@ static struct cpu_map *cpu_map__trim_new(int nr_cpus, int *tmp_cpus)
>  	if (cpus != NULL) {
>  		cpus->nr = nr_cpus;
>  		memcpy(cpus->map, tmp_cpus, payload_size);
> -		atomic_set(&cpus->refcnt, 1);
> +		refcount_set(&cpus->refcnt, 1);
>  	}
>  
>  	return cpus;
> @@ -251,7 +251,7 @@ struct cpu_map *cpu_map__dummy_new(void)
>  	if (cpus != NULL) {
>  		cpus->nr = 1;
>  		cpus->map[0] = -1;
> -		atomic_set(&cpus->refcnt, 1);
> +		refcount_set(&cpus->refcnt, 1);
>  	}
>  
>  	return cpus;
> @@ -268,7 +268,7 @@ struct cpu_map *cpu_map__empty_new(int nr)
>  		for (i = 0; i < nr; i++)
>  			cpus->map[i] = -1;
>  
> -		atomic_set(&cpus->refcnt, 1);
> +		refcount_set(&cpus->refcnt, 1);
>  	}
>  
>  	return cpus;
> @@ -277,7 +277,7 @@ struct cpu_map *cpu_map__empty_new(int nr)
>  static void cpu_map__delete(struct cpu_map *map)
>  {
>  	if (map) {
> -		WARN_ONCE(atomic_read(&map->refcnt) != 0,
> +		WARN_ONCE(refcount_read(&map->refcnt) != 0,
>  			  "cpu_map refcnt unbalanced\n");
>  		free(map);
>  	}
> @@ -286,13 +286,13 @@ static void cpu_map__delete(struct cpu_map *map)
>  struct cpu_map *cpu_map__get(struct cpu_map *map)
>  {
>  	if (map)
> -		atomic_inc(&map->refcnt);
> +		refcount_inc(&map->refcnt);
>  	return map;
>  }
>  
>  void cpu_map__put(struct cpu_map *map)
>  {
> -	if (map && atomic_dec_and_test(&map->refcnt))
> +	if (map && refcount_dec_and_test(&map->refcnt))
>  		cpu_map__delete(map);
>  }
>  
> @@ -356,7 +356,7 @@ int cpu_map__build_map(struct cpu_map *cpus, struct cpu_map **res,
>  	/* ensure we process id in increasing order */
>  	qsort(c->map, c->nr, sizeof(int), cmp_ids);
>  
> -	atomic_set(&c->refcnt, 1);
> +	refcount_set(&c->refcnt, 1);
>  	*res = c;
>  	return 0;
>  }
> diff --git a/tools/perf/util/cpumap.h b/tools/perf/util/cpumap.h
> index 06bd689..4f12a01 100644
> --- a/tools/perf/util/cpumap.h
> +++ b/tools/perf/util/cpumap.h
> @@ -3,13 +3,13 @@
>  
>  #include <stdio.h>
>  #include <stdbool.h>
> -#include <linux/atomic.h>
> +#include <linux/refcount.h>
>  
>  #include "perf.h"
>  #include "util/debug.h"
>  
>  struct cpu_map {
> -	atomic_t refcnt;
> +	refcount_t refcnt;
>  	int nr;
>  	int map[];
>  };
> -- 
> 2.7.4