fixed e70e9ca6 from https://gitee.com/guzhihao4/third_party_musl/pulls/903

Fix memory leak in signal stack release

Release signal stack guard separately
Issue: #I73EUD
Test: Libctest pass & mmap check noleak
Signed-off-by: Nguzhihao4 <guzhihao4@huawei.com>
Change-Id: Idca65a1c87898ab3cbb0e84e1c39f0772dad89cc

porting/linux/user/src/internal/pthread_impl.h

@@ -74,6 +74,9 @@ struct pthread {
     volatile int killlock[1];
     char *dlerror_buf;
     void *stdio_locks;
+#ifdef RESERVE_SIGNAL_STACK
+    void *signal_stack;
+#endif
 
 	/* Part 3 -- the positions of these fields relative to
 	 * the end of the structure is external and internal ABI. */

porting/linux/user/src/thread/pthread_create.c

@@ -61,6 +61,7 @@ void __pthread_reserve_signal_stack()
 	sigaltstack(&signal_stack, NULL);
 
 	pthread_t self = __pthread_self();
+	self->signal_stack = stack;
 	char name[ANON_STACK_NAME_SIZE];
 	snprintf(name, ANON_STACK_NAME_SIZE, "signal_stack:%d", __pthread_self()->tid);
 	prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, signal_stack.ss_sp, signal_stack.ss_size, name);
@@ -69,13 +70,20 @@ void __pthread_reserve_signal_stack()
 
 void __pthread_release_signal_stack()
 {
+	pthread_t self = __pthread_self();
+	if (self->signal_stack == NULL) {
+		return;
+	}
+
 	stack_t signal_stack, old_stack;
 	memset(&signal_stack, 0, sizeof(signal_stack));
 	signal_stack.ss_flags = SS_DISABLE;
 	sigaltstack(&signal_stack, &old_stack);
+	munmap(self->signal_stack, __default_guardsize);
 	if (old_stack.ss_flags != SS_DISABLE) {
 		munmap(old_stack.ss_sp, old_stack.ss_size);
 	}
+	self->signal_stack = NULL;
 }
 
 weak_alias(__pthread_reserve_signal_stack, pthread_reserve_signal_stack);