Fix for bug #41868: crash or memory overrun with concat + upper, date_format

                    functions
      
String::realloc() did not check whether the existing string data fits in the newly
allocated buffer for cases when reallocating a String object with external buffer
(i.e.alloced == FALSE).  This could lead to memory overruns in some cases.


mysql-test/r/func_str.result:
  Added a test case for bug #41868.
mysql-test/t/func_str.test:
  Added a test case for bug #41868.
sql/sql_class.cc:
  After each call to Item::send() in select_send::send_data() reset buffer to its
  original state to reduce unnecessary malloc() calls. See comments for bug #41868
  for detailed analysis.
sql/sql_string.cc:
  Fixed String::realloc() to check whether the existing string data fits in the newly allocated buffer for cases when reallocating a String object with external buffer.

1 files changed, 10 insertions, 10 deletions

diff --git a/client/sql_string.cc b/client/sql_string.cc
index 9d887ff031c..eb80e29ed49 100644
--- a/client/sql_string.cc
+++ b/client/sql_string.cc
@@ -72,26 +72,26 @@ bool String::realloc(uint32 alloc_length)
     if (alloced)
     {
       if ((new_ptr= (char*) my_realloc(Ptr,len,MYF(MY_WME))))
-      {
-	Ptr=new_ptr;
-	Alloced_length=len;
-      }
+        new_ptr[alloc_length]= 0;
       else
-	return TRUE;				// Signal error
+        return TRUE;				// Signal error
     }
     else if ((new_ptr= (char*) my_malloc(len,MYF(MY_WME))))
     {
+      if (str_length > len - 1)
+        str_length= 0;
       if (str_length)				// Avoid bugs in memcpy on AIX
-	memcpy(new_ptr,Ptr,str_length);
-      new_ptr[str_length]=0;
-      Ptr=new_ptr;
-      Alloced_length=len;
+        memcpy(new_ptr, Ptr, str_length);
+      new_ptr[str_length]= 0;
       alloced=1;
     }
     else
       return TRUE;			// Signal error
+    Ptr= new_ptr;
+    Alloced_length= len;
   }
-  Ptr[alloc_length]=0;			// This make other funcs shorter
+  else
+    Ptr[alloc_length]= 0;
   return FALSE;
 }