linux-kernel - Re: [PATCH 4/9] tools: convert dso.refcnt from atomic_t to refcount

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Date:   Wed, 22 Feb 2017 17:37:46 -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 4/9] tools: convert dso.refcnt from atomic_t to refcount_t

Em Tue, Feb 21, 2017 at 05:34:58PM +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.

Fixed by moving the include refcnt.h to later in the includes:

In file included from /home/acme/git/linux/tools/perf/util/dso.h:4:0,
                 from /home/acme/git/linux/tools/perf/util/machine.h:7,
                 from tests/thread-mg-share.c:2:
/home/acme/git/linux/tools/include/linux/refcount.h: In function ‘refcount_inc_not_zero’:
/home/acme/git/linux/tools/include/linux/refcount.h:95:23: error: ‘UINT_MAX’ undeclared (first use in this function)
  REFCOUNT_WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
                       ^
/home/acme/git/linux/tools/include/linux/refcount.h:47:41: note: in definition of macro ‘REFCOUNT_WARN’
 #define REFCOUNT_WARN(cond, str) (void)(cond)
                                         ^~~~
/home/acme/git/linux/tools/include/linux/refcount.h:95:23: note: each undeclared identifier is reported only once for each function it appears in
  REFCOUNT_WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
                       ^
/home/acme/git/linux/tools/include/linux/refcount.h:47:41: note: in definition of macro ‘REFCOUNT_WARN’
 #define REFCOUNT_WARN(cond, str) (void)(cond)

 
> 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/dso.c | 6 +++---
>  tools/perf/util/dso.h | 4 ++--
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> index 3abe337..f88aa44 100644
> --- a/tools/perf/util/dso.c
> +++ b/tools/perf/util/dso.c
> @@ -1109,7 +1109,7 @@ struct dso *dso__new(const char *name)
>  		INIT_LIST_HEAD(&dso->node);
>  		INIT_LIST_HEAD(&dso->data.open_entry);
>  		pthread_mutex_init(&dso->lock, NULL);
> -		atomic_set(&dso->refcnt, 1);
> +		refcount_set(&dso->refcnt, 1);
>  	}
>  
>  	return dso;
> @@ -1147,13 +1147,13 @@ void dso__delete(struct dso *dso)
>  struct dso *dso__get(struct dso *dso)
>  {
>  	if (dso)
> -		atomic_inc(&dso->refcnt);
> +		refcount_inc(&dso->refcnt);
>  	return dso;
>  }
>  
>  void dso__put(struct dso *dso)
>  {
> -	if (dso && atomic_dec_and_test(&dso->refcnt))
> +	if (dso && refcount_dec_and_test(&dso->refcnt))
>  		dso__delete(dso);
>  }
>  
> diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
> index ecc4bbd..12350b1 100644
> --- a/tools/perf/util/dso.h
> +++ b/tools/perf/util/dso.h
> @@ -1,7 +1,7 @@
>  #ifndef __PERF_DSO
>  #define __PERF_DSO
>  
> -#include <linux/atomic.h>
> +#include <linux/refcount.h>
>  #include <linux/types.h>
>  #include <linux/rbtree.h>
>  #include <sys/types.h>
> @@ -187,7 +187,7 @@ struct dso {
>  		void	 *priv;
>  		u64	 db_id;
>  	};
> -	atomic_t	 refcnt;
> +	refcount_t	 refcnt;
>  	char		 name[0];
>  };
>  
> -- 
> 2.7.4