Fix libxenstore memory leak when USE_PTHREAD is not defined

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 <[email protected]>

diff -r 588d0dc298a4 -r 9bfaf86e061f tools/xenstore/xs.c

tools/xenstore/xs.c +6 -16

@@ -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;
 

Quoted 8 lines · 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.

Quoted 3 lines

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

Signed-off-by Andres Lagar-Cavilla <[email protected]>

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?

Quoted 82 lines

diff -r 588d0dc298a4 -r 9bfaf86e061f tools/xenstore/xs.c

tools/xenstore/xs.c +2 -14

@@ -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:

tools/xenstore/xs.c +2 -1

-	cleanup_pop(ret == -1);
+	if (ret)
+		free(body);

error_freemsg:

tools/xenstore/xs.c +2 -1

-	cleanup_pop(ret == -1);
+	if (ret)
+		free(msg);

error:

	errno = saved_errno;