From: Nikita Popov <nikita.ppv@gmail.com>
Date: Tue, 23 Feb 2021 10:46:34 +0000 (+0100)
Subject: Remove free_chunk API
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=771b0bd1df4d6e5c38001c6309a5064846e7d326;p=php

Remove free_chunk API

This API only works in very limited circumstances -- relying on
it will invariably lead to leaks. The correct way to "free" something
from the pool is to use the checkpoint API.
---

diff --git a/ext/mysqlnd/mysqlnd_block_alloc.c b/ext/mysqlnd/mysqlnd_block_alloc.c
index 9ff96d0374..5c80ad028b 100644
--- a/ext/mysqlnd/mysqlnd_block_alloc.c
+++ b/ext/mysqlnd/mysqlnd_block_alloc.c
@@ -22,38 +22,12 @@
 #include "mysqlnd_debug.h"
 #include "mysqlnd_priv.h"
 
-/* {{{ mysqlnd_mempool_free_chunk */
-static void
-mysqlnd_mempool_free_chunk(MYSQLND_MEMORY_POOL * pool, void * ptr)
-{
-	DBG_ENTER("mysqlnd_mempool_free_chunk");
-	/* Try to back-off and guess if this is the last block allocated */
-#ifndef ZEND_TRACK_ARENA_ALLOC
-	if (ptr == pool->last) {
-		/*
-			This was the last allocation. Lucky us, we can free
-			a bit of memory from the pool. Next time we will return from the same ptr.
-		*/
-		pool->arena->ptr = (char*)ptr;
-		pool->last = NULL;
-	}
-#endif
-	DBG_VOID_RETURN;
-}
-/* }}} */
-
-
 /* {{{ mysqlnd_mempool_get_chunk */
 static void *
 mysqlnd_mempool_get_chunk(MYSQLND_MEMORY_POOL * pool, size_t size)
 {
-	void *ptr = NULL;
 	DBG_ENTER("mysqlnd_mempool_get_chunk");
-
-	ptr = zend_arena_alloc(&pool->arena, size);
-	pool->last = ptr;
-
-	DBG_RETURN(ptr);
+	DBG_RETURN(zend_arena_alloc(&pool->arena, size));
 }
 /* }}} */
 
@@ -69,10 +43,8 @@ mysqlnd_mempool_create(size_t arena_size)
 	arena = zend_arena_create(MAX(arena_size, ZEND_MM_ALIGNED_SIZE(sizeof(zend_arena))));
 	ret = zend_arena_alloc(&arena, sizeof(MYSQLND_MEMORY_POOL));
 	ret->arena = arena;
-	ret->last = NULL;
 	ret->checkpoint = NULL;
 	ret->get_chunk = mysqlnd_mempool_get_chunk;
-	ret->free_chunk = mysqlnd_mempool_free_chunk;
 	DBG_RETURN(ret);
 }
 /* }}} */
@@ -109,7 +81,6 @@ mysqlnd_mempool_restore_state(MYSQLND_MEMORY_POOL * pool)
 #endif
 	if (pool->checkpoint) {
 		zend_arena_release(&pool->arena, pool->checkpoint);
-		pool->last = NULL;
 		pool->checkpoint = NULL;
 	}
 	DBG_VOID_RETURN;
diff --git a/ext/mysqlnd/mysqlnd_structs.h b/ext/mysqlnd/mysqlnd_structs.h
index 3a9b1fb340..7929cc1153 100644
--- a/ext/mysqlnd/mysqlnd_structs.h
+++ b/ext/mysqlnd/mysqlnd_structs.h
@@ -51,11 +51,9 @@ typedef struct st_mysqlnd_memory_pool MYSQLND_MEMORY_POOL;
 struct st_mysqlnd_memory_pool
 {
 	zend_arena		*arena;
-	void			*last;
 	void            *checkpoint;
 
 	void*	(*get_chunk)(MYSQLND_MEMORY_POOL * pool, size_t size);
-	void	(*free_chunk)(MYSQLND_MEMORY_POOL * pool, void * ptr);
 };
 
 
diff --git a/ext/mysqlnd/mysqlnd_wireprotocol.c b/ext/mysqlnd/mysqlnd_wireprotocol.c
index c345e5d7ec..635ef3f6e8 100644
--- a/ext/mysqlnd/mysqlnd_wireprotocol.c
+++ b/ext/mysqlnd/mysqlnd_wireprotocol.c
@@ -1416,10 +1416,6 @@ php_mysqlnd_read_row_ex(MYSQLND_PFC * pfc,
 			set_packet_error(error_info, CR_SERVER_GONE_ERROR, UNKNOWN_SQLSTATE, mysqlnd_server_gone);
 		}
 	}
-	if (ret == FAIL && buffer->ptr) {
-		pool->free_chunk(pool, buffer->ptr);
-		buffer->ptr = NULL;
-	}
 	DBG_RETURN(ret);
 }
 /* }}} */
@@ -1733,23 +1729,6 @@ end:
 /* }}} */
 
 
-/* {{{ php_mysqlnd_rowp_free_mem */
-static void
-php_mysqlnd_rowp_free_mem(void * _packet)
-{
-	MYSQLND_PACKET_ROW *p;
-
-	DBG_ENTER("php_mysqlnd_rowp_free_mem");
-	p = (MYSQLND_PACKET_ROW *) _packet;
-	if (p->row_buffer.ptr) {
-		p->result_set_memory_pool->free_chunk(p->result_set_memory_pool, p->row_buffer.ptr);
-		p->row_buffer.ptr = NULL;
-	}
-	DBG_VOID_RETURN;
-}
-/* }}} */
-
-
 /* {{{ php_mysqlnd_stats_read */
 static enum_func_status
 php_mysqlnd_stats_read(MYSQLND_CONN_DATA * conn, void * _packet)
@@ -2196,7 +2175,7 @@ mysqlnd_packet_methods packet_methods[PROT_LAST] =
 	{
 		php_mysqlnd_rowp_read, /* read */
 		NULL, /* write */
-		php_mysqlnd_rowp_free_mem,
+		NULL,
 	}, /* PROT_ROW_PACKET */
 	{
 		php_mysqlnd_stats_read, /* read */