slsm: tree: fix incorrect usage of va_start()/va_end()

security/slsm/tree.c

@@ -198,11 +198,16 @@ int slsm_str_append(struct slsm_str *buf, const char *fmt, ...) {
 	va_list args;
 	int written;
 
-	va_start(args, fmt);
-	while ((written = vsnprintf(buf->buf + buf->used, buf->size - buf->used, fmt, args) + 1)
-			> buf->size - buf->used) {
+	while (1) {
 		char *new_buf;
 		size_t new_size = buf->size * 2;
+
+		va_start(args, fmt); // must call va_start per loop iteration
+		written = vsnprintf(buf->buf + buf->used, buf->size - buf->used, fmt, args) + 1;
+		if (written <= buf->size - buf->used)
+			break;
+		va_end(args);
+
 		if (new_size > (ssize_t)new_size)
 			return -EFBIG;
 
@@ -213,7 +218,6 @@ int slsm_str_append(struct slsm_str *buf, const char *fmt, ...) {
 		buf->buf = new_buf;
 		buf->size = new_size;
 	}
-	va_end(args);
 
 	buf->used += (size_t)written;