[PATCH] Fix libxenstore memory leak when USE_PTHREAD is not defined

[PATCH] Fix libxenstore memory leak when USE_PTHREAD is not defined

[Andres Lagar-Cavilla]

 tools/xenstore/xs.c |  22 ++++++----------------
 1 files changed, 6 insertions(+), 16 deletions(-)


Remove usage of pthread_cleanup_push and _pop, and explicitly call free for
heap objects in error paths. Also remove cleanup_p* for a mutex unlock path. By
the way, set a suitable errno value for an error path that had none.

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>

diff -r 093d148b092f -r bccad6d1fc5f tools/xenstore/xs.c
--- a/tools/xenstore/xs.c
+++ b/tools/xenstore/xs.c
@@ -99,14 +99,6 @@ struct xs_handle {
 #define mutex_unlock(m)		pthread_mutex_unlock(m)
 #define condvar_signal(c)	pthread_cond_signal(c)
 #define condvar_wait(c,m)	pthread_cond_wait(c,m)
-#define cleanup_push(f, a)	\
-    pthread_cleanup_push((void (*)(void *))(f), (void *)(a))
-/*
- * Some definitions of pthread_cleanup_pop() are a macro starting with an
- * end-brace. GCC then complains if we immediately precede that with a label.
- * Hence we insert a dummy statement to appease the compiler in this situation.
- */
-#define cleanup_pop(run)        ((void)0); pthread_cleanup_pop(run)
 
 #define read_thread_exists(h)	(h->read_thr_exists)
 
@@ -126,8 +118,6 @@ struct xs_handle {
 #define mutex_unlock(m)		((void)0)
 #define condvar_signal(c)	((void)0)
 #define condvar_wait(c,m)	((void)0)
-#define cleanup_push(f, a)	((void)0)
-#define cleanup_pop(run)	((void)0)
 #define read_thread_exists(h)	(0)
 
 #endif
@@ -1059,7 +1049,6 @@ static int read_message(struct xs_handle
 	msg = malloc(sizeof(*msg));
 	if (msg == NULL)
 		goto error;
-	cleanup_push(free, msg);
 	if (!read_all(h->fd, &msg->hdr, sizeof(msg->hdr), nonblocking)) { /* Cancellation point */
 		saved_errno = errno;
 		goto error_freemsg;
@@ -1069,7 +1058,6 @@ static int read_message(struct xs_handle
 	body = msg->body = malloc(msg->hdr.len + 1);
 	if (body == NULL)
 		goto error_freemsg;
-	cleanup_push(free, body);
 	if (!read_all(h->fd, body, msg->hdr.len, 0)) { /* Cancellation point */
 		saved_errno = errno;
 		goto error_freebody;
@@ -1079,7 +1067,6 @@ static int read_message(struct xs_handle
 
 	if (msg->hdr.type == XS_WATCH_EVENT) {
 		mutex_lock(&h->watch_mutex);
-		cleanup_push(pthread_mutex_unlock, &h->watch_mutex);
 
 		/* Kick users out of their select() loop. */
 		if (list_empty(&h->watch_list) &&
@@ -1091,13 +1078,14 @@ static int read_message(struct xs_handle
 
 		condvar_signal(&h->watch_condvar);
 
-		cleanup_pop(1);
+		pthread_mutex_unlock(&h->watch_mutex);
 	} else {
 		mutex_lock(&h->reply_mutex);
 
 		/* There should only ever be one response pending! */
 		if (!list_empty(&h->reply_list)) {
 			mutex_unlock(&h->reply_mutex);
+			saved_errno = EEXIST; 
 			goto error_freebody;
 		}
 
@@ -1110,9 +1098,11 @@ static int read_message(struct xs_handle
 	ret = 0;
 
 error_freebody:
-	cleanup_pop(ret == -1);
+	if (ret)
+		free(body);
 error_freemsg:
-	cleanup_pop(ret == -1);
+	if (ret)
+		free(msg);
 error:
 	errno = saved_errno;

[PATCH] Fix libxenstore memory leak when USE_PTHREAD is not defined

[Andres Lagar-Cavilla]

 tools/xenstore/xs.c |  22 ++++++----------------
 1 files changed, 6 insertions(+), 16 deletions(-)


Remove usage of pthread_cleanup_push and _pop, and explicitly call free for
heap objects in error paths. Also remove cleanup_p* for a mutex unlock path. By
the way, set a suitable errno value for an error path that had none.

Resend due to small fix spotted, please ignore previous one.

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>

diff -r 588d0dc298a4 -r 9bfaf86e061f tools/xenstore/xs.c
--- a/tools/xenstore/xs.c
+++ b/tools/xenstore/xs.c
@@ -99,14 +99,6 @@ struct xs_handle {
 #define mutex_unlock(m)		pthread_mutex_unlock(m)
 #define condvar_signal(c)	pthread_cond_signal(c)
 #define condvar_wait(c,m)	pthread_cond_wait(c,m)
-#define cleanup_push(f, a)	\
-    pthread_cleanup_push((void (*)(void *))(f), (void *)(a))
-/*
- * Some definitions of pthread_cleanup_pop() are a macro starting with an
- * end-brace. GCC then complains if we immediately precede that with a label.
- * Hence we insert a dummy statement to appease the compiler in this situation.
- */
-#define cleanup_pop(run)        ((void)0); pthread_cleanup_pop(run)
 
 #define read_thread_exists(h)	(h->read_thr_exists)
 
@@ -126,8 +118,6 @@ struct xs_handle {
 #define mutex_unlock(m)		((void)0)
 #define condvar_signal(c)	((void)0)
 #define condvar_wait(c,m)	((void)0)
-#define cleanup_push(f, a)	((void)0)
-#define cleanup_pop(run)	((void)0)
 #define read_thread_exists(h)	(0)
 
 #endif
@@ -1059,7 +1049,6 @@ static int read_message(struct xs_handle
 	msg = malloc(sizeof(*msg));
 	if (msg == NULL)
 		goto error;
-	cleanup_push(free, msg);
 	if (!read_all(h->fd, &msg->hdr, sizeof(msg->hdr), nonblocking)) { /* Cancellation point */
 		saved_errno = errno;
 		goto error_freemsg;
@@ -1069,7 +1058,6 @@ static int read_message(struct xs_handle
 	body = msg->body = malloc(msg->hdr.len + 1);
 	if (body == NULL)
 		goto error_freemsg;
-	cleanup_push(free, body);
 	if (!read_all(h->fd, body, msg->hdr.len, 0)) { /* Cancellation point */
 		saved_errno = errno;
 		goto error_freebody;
@@ -1079,7 +1067,6 @@ static int read_message(struct xs_handle
 
 	if (msg->hdr.type == XS_WATCH_EVENT) {
 		mutex_lock(&h->watch_mutex);
-		cleanup_push(pthread_mutex_unlock, &h->watch_mutex);
 
 		/* Kick users out of their select() loop. */
 		if (list_empty(&h->watch_list) &&
@@ -1091,13 +1078,14 @@ static int read_message(struct xs_handle
 
 		condvar_signal(&h->watch_condvar);
 
-		cleanup_pop(1);
+		mutex_unlock(&h->watch_mutex);
 	} else {
 		mutex_lock(&h->reply_mutex);
 
 		/* There should only ever be one response pending! */
 		if (!list_empty(&h->reply_list)) {
 			mutex_unlock(&h->reply_mutex);
+			saved_errno = EEXIST; 
 			goto error_freebody;
 		}
 
@@ -1110,9 +1098,11 @@ static int read_message(struct xs_handle
 	ret = 0;
 
 error_freebody:
-	cleanup_pop(ret == -1);
+	if (ret)
+		free(body);
 error_freemsg:
-	cleanup_pop(ret == -1);
+	if (ret)
+		free(msg);
 error:
 	errno = saved_errno;

Re: [PATCH] Fix libxenstore memory leak when USE_PTHREAD is not defined

[Ian Campbell]

On Thu, 2012-09-13 at 17:09 +0100, Andres Lagar-Cavilla wrote:
> tools/xenstore/xs.c |  22 ++++++----------------
>  1 files changed, 6 insertions(+), 16 deletions(-)
> 
> 
> Remove usage of pthread_cleanup_push and _pop, and explicitly call free for
> heap objects in error paths. Also remove cleanup_p* for a mutex unlock path. By
> the way, set a suitable errno value for an error path that had none.
> 
> Resend due to small fix spotted, please ignore previous one.
> 
> Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>

Does this reintroduce the same issue as 21353:2dd3141b3e3e was supposed
to solve (i.e. leaks memory or mutexes if you pthread_cancel the thread
in the midst of things operation)?

Can we keep cleanup_push/pop for use with the mutexes and for the
malloc/free do:

#ifdef USE_PTHREAD
#define cleanup_push... as currently
#define cleanup_pop... as currently
#define cleanup_malloc(x) cleanup_push(free, x)
#define cleanup_free(doit, x)  cleanup_pop(doit)
#else
#define cleanup_push... nop as now
#define cleanup_pop... nop as now
#define cleanup_malloc... NOP
#define cleanup_free(doit, x) if (doit) free(x)
#endif

Does that work?
> 
> diff -r 588d0dc298a4 -r 9bfaf86e061f tools/xenstore/xs.c
> --- a/tools/xenstore/xs.c
> +++ b/tools/xenstore/xs.c
> @@ -99,14 +99,6 @@ struct xs_handle {
>  #define mutex_unlock(m)		pthread_mutex_unlock(m)
>  #define condvar_signal(c)	pthread_cond_signal(c)
>  #define condvar_wait(c,m)	pthread_cond_wait(c,m)
> -#define cleanup_push(f, a)	\
> -    pthread_cleanup_push((void (*)(void *))(f), (void *)(a))
> -/*
> - * Some definitions of pthread_cleanup_pop() are a macro starting with an
> - * end-brace. GCC then complains if we immediately precede that with a label.
> - * Hence we insert a dummy statement to appease the compiler in this situation.
> - */
> -#define cleanup_pop(run)        ((void)0); pthread_cleanup_pop(run)
>  
>  #define read_thread_exists(h)	(h->read_thr_exists)
>  
> @@ -126,8 +118,6 @@ struct xs_handle {
>  #define mutex_unlock(m)		((void)0)
>  #define condvar_signal(c)	((void)0)
>  #define condvar_wait(c,m)	((void)0)
> -#define cleanup_push(f, a)	((void)0)
> -#define cleanup_pop(run)	((void)0)
>  #define read_thread_exists(h)	(0)
>  
>  #endif
> @@ -1059,7 +1049,6 @@ static int read_message(struct xs_handle
>  	msg = malloc(sizeof(*msg));
>  	if (msg == NULL)
>  		goto error;
> -	cleanup_push(free, msg);
>  	if (!read_all(h->fd, &msg->hdr, sizeof(msg->hdr), nonblocking)) { /* Cancellation point */
>  		saved_errno = errno;
>  		goto error_freemsg;
> @@ -1069,7 +1058,6 @@ static int read_message(struct xs_handle
>  	body = msg->body = malloc(msg->hdr.len + 1);
>  	if (body == NULL)
>  		goto error_freemsg;
> -	cleanup_push(free, body);
>  	if (!read_all(h->fd, body, msg->hdr.len, 0)) { /* Cancellation point */
>  		saved_errno = errno;
>  		goto error_freebody;
> @@ -1079,7 +1067,6 @@ static int read_message(struct xs_handle
>  
>  	if (msg->hdr.type == XS_WATCH_EVENT) {
>  		mutex_lock(&h->watch_mutex);
> -		cleanup_push(pthread_mutex_unlock, &h->watch_mutex);
>  
>  		/* Kick users out of their select() loop. */
>  		if (list_empty(&h->watch_list) &&
> @@ -1091,13 +1078,14 @@ static int read_message(struct xs_handle
>  
>  		condvar_signal(&h->watch_condvar);
>  
> -		cleanup_pop(1);
> +		mutex_unlock(&h->watch_mutex);
>  	} else {
>  		mutex_lock(&h->reply_mutex);
>  
>  		/* There should only ever be one response pending! */
>  		if (!list_empty(&h->reply_list)) {
>  			mutex_unlock(&h->reply_mutex);
> +			saved_errno = EEXIST; 
>  			goto error_freebody;
>  		}
>  
> @@ -1110,9 +1098,11 @@ static int read_message(struct xs_handle
>  	ret = 0;
>  
>  error_freebody:
> -	cleanup_pop(ret == -1);
> +	if (ret)
> +		free(body);
>  error_freemsg:
> -	cleanup_pop(ret == -1);
> +	if (ret)
> +		free(msg);
>  error:
>  	errno = saved_errno;
>  

Re: [PATCH] Fix libxenstore memory leak when USE_PTHREAD is not defined

[Andres Lagar-Cavilla]

On Sep 14, 2012, at 5:02 AM, Ian Campbell wrote:

> On Thu, 2012-09-13 at 17:09 +0100, Andres Lagar-Cavilla wrote:
>> tools/xenstore/xs.c |  22 ++++++----------------
>> 1 files changed, 6 insertions(+), 16 deletions(-)
>> 
>> 
>> Remove usage of pthread_cleanup_push and _pop, and explicitly call free for
>> heap objects in error paths. Also remove cleanup_p* for a mutex unlock path. By
>> the way, set a suitable errno value for an error path that had none.
>> 
>> Resend due to small fix spotted, please ignore previous one.
>> 
>> Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
> 
> Does this reintroduce the same issue as 21353:2dd3141b3e3e was supposed
> to solve (i.e. leaks memory or mutexes if you pthread_cancel the thread
> in the midst of things operation)?
Oh I never saw that coming. The approach below is what I would have done. Let me give that a try.
Andres

> 
> Can we keep cleanup_push/pop for use with the mutexes and for the
> malloc/free do:
> 
> #ifdef USE_PTHREAD
> #define cleanup_push... as currently
> #define cleanup_pop... as currently
> #define cleanup_malloc(x) cleanup_push(free, x)
> #define cleanup_free(doit, x)  cleanup_pop(doit)
> #else
> #define cleanup_push... nop as now
> #define cleanup_pop... nop as now
> #define cleanup_malloc... NOP
> #define cleanup_free(doit, x) if (doit) free(x)
> #endif
> 
> Does that work?
>> 
>> diff -r 588d0dc298a4 -r 9bfaf86e061f tools/xenstore/xs.c
>> --- a/tools/xenstore/xs.c
>> +++ b/tools/xenstore/xs.c
>> @@ -99,14 +99,6 @@ struct xs_handle {
>> #define mutex_unlock(m)		pthread_mutex_unlock(m)
>> #define condvar_signal(c)	pthread_cond_signal(c)
>> #define condvar_wait(c,m)	pthread_cond_wait(c,m)
>> -#define cleanup_push(f, a)	\
>> -    pthread_cleanup_push((void (*)(void *))(f), (void *)(a))
>> -/*
>> - * Some definitions of pthread_cleanup_pop() are a macro starting with an
>> - * end-brace. GCC then complains if we immediately precede that with a label.
>> - * Hence we insert a dummy statement to appease the compiler in this situation.
>> - */
>> -#define cleanup_pop(run)        ((void)0); pthread_cleanup_pop(run)
>> 
>> #define read_thread_exists(h)	(h->read_thr_exists)
>> 
>> @@ -126,8 +118,6 @@ struct xs_handle {
>> #define mutex_unlock(m)		((void)0)
>> #define condvar_signal(c)	((void)0)
>> #define condvar_wait(c,m)	((void)0)
>> -#define cleanup_push(f, a)	((void)0)
>> -#define cleanup_pop(run)	((void)0)
>> #define read_thread_exists(h)	(0)
>> 
>> #endif
>> @@ -1059,7 +1049,6 @@ static int read_message(struct xs_handle
>> 	msg = malloc(sizeof(*msg));
>> 	if (msg == NULL)
>> 		goto error;
>> -	cleanup_push(free, msg);
>> 	if (!read_all(h->fd, &msg->hdr, sizeof(msg->hdr), nonblocking)) { /* Cancellation point */
>> 		saved_errno = errno;
>> 		goto error_freemsg;
>> @@ -1069,7 +1058,6 @@ static int read_message(struct xs_handle
>> 	body = msg->body = malloc(msg->hdr.len + 1);
>> 	if (body == NULL)
>> 		goto error_freemsg;
>> -	cleanup_push(free, body);
>> 	if (!read_all(h->fd, body, msg->hdr.len, 0)) { /* Cancellation point */
>> 		saved_errno = errno;
>> 		goto error_freebody;
>> @@ -1079,7 +1067,6 @@ static int read_message(struct xs_handle
>> 
>> 	if (msg->hdr.type == XS_WATCH_EVENT) {
>> 		mutex_lock(&h->watch_mutex);
>> -		cleanup_push(pthread_mutex_unlock, &h->watch_mutex);
>> 
>> 		/* Kick users out of their select() loop. */
>> 		if (list_empty(&h->watch_list) &&
>> @@ -1091,13 +1078,14 @@ static int read_message(struct xs_handle
>> 
>> 		condvar_signal(&h->watch_condvar);
>> 
>> -		cleanup_pop(1);
>> +		mutex_unlock(&h->watch_mutex);
>> 	} else {
>> 		mutex_lock(&h->reply_mutex);
>> 
>> 		/* There should only ever be one response pending! */
>> 		if (!list_empty(&h->reply_list)) {
>> 			mutex_unlock(&h->reply_mutex);
>> +			saved_errno = EEXIST; 
>> 			goto error_freebody;
>> 		}
>> 
>> @@ -1110,9 +1098,11 @@ static int read_message(struct xs_handle
>> 	ret = 0;
>> 
>> error_freebody:
>> -	cleanup_pop(ret == -1);
>> +	if (ret)
>> +		free(body);
>> error_freemsg:
>> -	cleanup_pop(ret == -1);
>> +	if (ret)
>> +		free(msg);
>> error:
>> 	errno = saved_errno;
>> 
> 
>