From c927c831e65cdf6aa6152d49820e58e6288a5dcc Mon Sep 17 00:00:00 2001
From: Nikita Popov <nikita.ppv@gmail.com>
Date: Fri, 11 Dec 2020 10:47:16 +0100
Subject: [PATCH] PDO MySQL: Fix leak with libmysqlclient and multiple rowsets

stmt->column_count gets reset before the next_rowset handler is
invoked, so we need to fetch the value from the result set instead.

Arguably PDO should be separating the destruction of the previous
result set and the switch to the next result set more cleanly...
---
 ext/pdo_mysql/mysql_statement.c | 75 +++++++++++++--------------------
 1 file changed, 29 insertions(+), 46 deletions(-)

diff --git a/ext/pdo_mysql/mysql_statement.c b/ext/pdo_mysql/mysql_statement.c
index 005f5890ab..46f39c985d 100644
--- a/ext/pdo_mysql/mysql_statement.c
+++ b/ext/pdo_mysql/mysql_statement.c
@@ -30,13 +30,34 @@
 
 #ifdef PDO_USE_MYSQLND
 #	define pdo_mysql_stmt_execute_prepared(stmt) pdo_mysql_stmt_execute_prepared_mysqlnd(stmt)
-#	define pdo_free_bound_result(res) zval_ptr_dtor(res.zv)
 #else
 #	define pdo_mysql_stmt_execute_prepared(stmt) pdo_mysql_stmt_execute_prepared_libmysql(stmt)
-#	define pdo_free_bound_result(res) efree(res.buffer)
 #endif
 
 
+static void pdo_mysql_free_result(pdo_mysql_stmt *S)
+{
+	if (S->result) {
+#ifndef PDO_USE_MYSQLND
+		if (S->bound_result) {
+			/* We can't use stmt->column_count here, because it gets reset before the
+			 * next_rowset handler is called. */
+			unsigned column_count = mysql_num_fields(S->result);
+			for (unsigned i = 0; i < column_count; i++) {
+				efree(S->bound_result[i].buffer);
+			}
+
+			efree(S->bound_result);
+			efree(S->out_null);
+			efree(S->out_length);
+			S->bound_result = NULL;
+		}
+#endif
+
+		mysql_free_result(S->result);
+		S->result = NULL;
+	}
+}
 
 static int pdo_mysql_stmt_dtor(pdo_stmt_t *stmt) /* {{{ */
 {
@@ -44,11 +65,8 @@ static int pdo_mysql_stmt_dtor(pdo_stmt_t *stmt) /* {{{ */
 
 	PDO_DBG_ENTER("pdo_mysql_stmt_dtor");
 	PDO_DBG_INF_FMT("stmt=%p", S->stmt);
-	if (S->result) {
-		/* free the resource */
-		mysql_free_result(S->result);
-		S->result = NULL;
-	}
+
+	pdo_mysql_free_result(S);
 	if (S->einfo.errmsg) {
 		pefree(S->einfo.errmsg, stmt->dbh->is_persistent);
 		S->einfo.errmsg = NULL;
@@ -68,18 +86,6 @@ static int pdo_mysql_stmt_dtor(pdo_stmt_t *stmt) /* {{{ */
 	if (S->in_length) {
 		efree(S->in_length);
 	}
-
-	if (S->bound_result)
-	{
-		int i;
-		for (i = 0; i < stmt->column_count; i++) {
-			pdo_free_bound_result(S->bound_result[i]);
-		}
-
-		efree(S->bound_result);
-		efree(S->out_null);
-		efree(S->out_length);
-	}
 #endif
 
 	if (!S->done && !Z_ISUNDEF(stmt->database_object_handle)
@@ -209,15 +215,6 @@ static int pdo_mysql_stmt_execute_prepared_libmysql(pdo_stmt_t *stmt) /* {{{ */
 		if (S->result) {
 			int calc_max_length = H->buffered && S->max_length == 1;
 			S->fields = mysql_fetch_fields(S->result);
-			if (S->bound_result) {
-				int i;
-				for (i = 0; i < stmt->column_count; i++) {
-					efree(S->bound_result[i].buffer);
-				}
-				efree(S->bound_result);
-				efree(S->out_null);
-				efree(S->out_length);
-			}
 
 			php_pdo_stmt_set_column_count(stmt, (int)mysql_num_fields(S->result));
 			S->bound_result = ecalloc(stmt->column_count, sizeof(MYSQL_BIND));
@@ -306,12 +303,7 @@ static int pdo_mysql_stmt_execute_prepared_mysqlnd(pdo_stmt_t *stmt) /* {{{ */
 		PDO_DBG_RETURN(0);
 	}
 
-	if (S->result) {
-		/* TODO: add a test to check if we really have zvals here... */
-		mysql_free_result(S->result);
-		S->result = NULL;
-	}
-
+	pdo_mysql_free_result(S);
 	PDO_DBG_RETURN(pdo_mysql_stmt_after_execute_prepared(stmt));
 }
 /* }}} */
@@ -330,10 +322,7 @@ static int pdo_mysql_stmt_execute(pdo_stmt_t *stmt) /* {{{ */
 	}
 
 	/* ensure that we free any previous unfetched results */
-	if (S->result) {
-		mysql_free_result(S->result);
-		S->result = NULL;
-	}
+	pdo_mysql_free_result(S);
 
 	if (mysql_real_query(H->server, stmt->active_query_string, stmt->active_query_stringlen) != 0) {
 		pdo_mysql_error_stmt(stmt);
@@ -355,10 +344,7 @@ static int pdo_mysql_stmt_next_rowset(pdo_stmt_t *stmt) /* {{{ */
 	if (S->stmt) {
 		mysql_stmt_free_result(S->stmt);
 	}
-	if (S->result) {
-		mysql_free_result(S->result);
-		S->result = NULL;
-	}
+	pdo_mysql_free_result(S);
 
 #ifdef PDO_USE_MYSQLND
 	if (S->stmt) {
@@ -845,10 +831,7 @@ static int pdo_mysql_stmt_cursor_closer(pdo_stmt_t *stmt) /* {{{ */
 	PDO_DBG_INF_FMT("stmt=%p", S->stmt);
 
 	S->done = 1;
-	if (S->result) {
-		mysql_free_result(S->result);
-		S->result = NULL;
-	}
+	pdo_mysql_free_result(S);
 	if (S->stmt) {
 		mysql_stmt_free_result(S->stmt);
 	}
-- 
2.40.0