Fix for #5730 (Query cache crashes server)

Recusive part leads to stack overflow


sql/sql_cache.cc:
  Recursion removed from Query_cache::allocate_data_chain

sql/sql_cache.cc

@@ -1843,7 +1843,6 @@ inline ulong Query_cache::get_min_append_result_data_size()
 /*
   Allocate one or more blocks to hold data
 */
-
 my_bool Query_cache::allocate_data_chain(Query_cache_block **result_block,
 					 ulong data_len,
 					 Query_cache_block *query_block,
@@ -1851,55 +1850,55 @@ my_bool Query_cache::allocate_data_chain(Query_cache_block **result_block,
 {
   ulong all_headers_len = (ALIGN_SIZE(sizeof(Query_cache_block)) +
 			   ALIGN_SIZE(sizeof(Query_cache_result)));
-  ulong len= data_len + all_headers_len;
-  ulong align_len= ALIGN_SIZE(len);
-  DBUG_ENTER("Query_cache::allocate_data_chain");
-  DBUG_PRINT("qcache", ("data_len %lu, all_headers_len %lu",
-		      data_len, all_headers_len));
-
   ulong min_size = (first_block_arg ?
 		    get_min_first_result_data_size():
 		    get_min_append_result_data_size());
-  *result_block = allocate_block(max(min_size, align_len),
-				 min_result_data_size == 0,
-				 all_headers_len + min_result_data_size,
-				 1);
-  my_bool success = (*result_block != 0);
-  if (success)
+  Query_cache_block *prev_block= NULL;
+  Query_cache_block *new_block;
+  DBUG_ENTER("Query_cache::allocate_data_chain");
+  DBUG_PRINT("qcache", ("data_len %lu, all_headers_len %lu",
+			data_len, all_headers_len));
+
+  do
   {
-    Query_cache_block *new_block= *result_block;
+    ulong len= data_len + all_headers_len;
+    ulong align_len= ALIGN_SIZE(len);
+
+    if (!(new_block= allocate_block(max(min_size, align_len),
+				    min_result_data_size == 0,
+				    all_headers_len + min_result_data_size,
+				    1)))
+    {
+      DBUG_PRINT("warning", ("Can't allocate block for results"));
+      DBUG_RETURN(FALSE);
+    }
+
     new_block->n_tables = 0;
-    new_block->used = 0;
+    new_block->used = min(len, new_block->length);
     new_block->type = Query_cache_block::RES_INCOMPLETE;
     new_block->next = new_block->prev = new_block;
     Query_cache_result *header = new_block->result();
     header->parent(query_block);
 
-    if (new_block->length < len)
-    {
-      /*
-	We got less memory then we need (no big memory blocks) =>
-	Continue to allocated more blocks until we got everything we need.
-      */
-      Query_cache_block *next_block;
-      if ((success = allocate_data_chain(&next_block,
-					 len - new_block->length,
-					 query_block, first_block_arg)))
-	double_linked_list_join(new_block, next_block);
-    }
-    if (success)
-    {
-      new_block->used = min(len, new_block->length);
-
-      DBUG_PRINT("qcache", ("Block len %lu used %lu",
+    DBUG_PRINT("qcache", ("Block len %lu used %lu",
 			  new_block->length, new_block->used));
-    }
+
+    if (prev_block)
+      double_linked_list_join(prev_block, new_block);
     else
-      DBUG_PRINT("warning", ("Can't allocate block for continue"));
-  }
-  else
-    DBUG_PRINT("warning", ("Can't allocate block for results"));
-  DBUG_RETURN(success);
+      *result_block= new_block;
+    if (new_block->length >= len)
+      break;
+
+    /*
+      We got less memory then we need (no big memory blocks) =>
+      Continue to allocated more blocks until we got everything we need.
+    */
+    data_len= len - new_block->length;
+    prev_block= new_block;
+  } while(1);
+
+  DBUG_RETURN(TRUE);
 }
 
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