Merge sin.intern.azundris.com:/misc/mysql/31588/41-31588

into  sin.intern.azundris.com:/misc/mysql/31588/50-31588


sql/set_var.cc:
  Auto merged
mysql-test/r/variables.result:
  SCCS merged
mysql-test/t/variables.test:
  SCCS merged

3 files changed, 12 insertions, 2 deletions

diff --git a/mysql-test/r/variables.result b/mysql-test/r/variables.result
index 3d76f8e4a90..d5fc8f57f8a 100644
--- a/mysql-test/r/variables.result
+++ b/mysql-test/r/variables.result
@@ -673,6 +673,9 @@ set @@query_prealloc_size = @test;
 select @@query_prealloc_size = @test;
 @@query_prealloc_size = @test
 1
+set global sql_mode=repeat('a',80);
+ERROR 42000: Variable 'sql_mode' can't be set to the value of 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
+End of 4.1 tests
 create table t1 (a int);
 select a into @x from t1;
 Warnings:
diff --git a/mysql-test/t/variables.test b/mysql-test/t/variables.test
index 0ad85a32568..ed9fc91587d 100644
--- a/mysql-test/t/variables.test
+++ b/mysql-test/t/variables.test
@@ -535,7 +535,14 @@ set @test = @@query_prealloc_size;
 set @@query_prealloc_size = @test;
 select @@query_prealloc_size = @test;
 
-# End of 4.1 tests
+#
+# Bug#31588 buffer overrun when setting variables
+#
+# Buffer-size Off By One. Should throw valgrind-warning without fix #31588.
+--error 1231
+set global sql_mode=repeat('a',80);
+
+--echo End of 4.1 tests
 
 #
 # Bug#6282 Packet error with SELECT INTO
diff --git a/sql/set_var.cc b/sql/set_var.cc
index fbfe174434d..f848703e525 100644
--- a/sql/set_var.cc
+++ b/sql/set_var.cc
@@ -1752,7 +1752,7 @@ bool sys_var::check_set(THD *thd, set_var *var, TYPELIB *enum_names)
 					    &not_used));
     if (error_len)
     {
-      strmake(buff, error, min(sizeof(buff), error_len));
+      strmake(buff, error, min(sizeof(buff) - 1, error_len));
       goto err;
     }
   }