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.

client/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.
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, 5 insertions, 0 deletions

diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 91c0aa66761..9ff602bb62e 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -1047,6 +1047,11 @@ bool select_send::send_data(List<Item> &items)
       my_message(ER_OUT_OF_RESOURCES, ER(ER_OUT_OF_RESOURCES), MYF(0));
       break;
     }
+    /*
+      Reset buffer to its original state, as it may have been altered in
+      Item::send().
+    */
+    buffer.set(buff, sizeof(buff), &my_charset_bin);
   }
   thd->sent_row_count++;
   if (!thd->vio_ok())