MDEV-10465 general_log_file can be abused

This issue was discovered by
Dawid Golunski (http://legalhackers.com)

5 files changed, 39 insertions, 0 deletions

diff --git a/mysql-test/suite/sys_vars/r/general_log_file_basic.result b/mysql-test/suite/sys_vars/r/general_log_file_basic.result
index 369ef7844db..54b450a2fce 100644
--- a/mysql-test/suite/sys_vars/r/general_log_file_basic.result
+++ b/mysql-test/suite/sys_vars/r/general_log_file_basic.result
@@ -12,6 +12,12 @@ SET @@global.general_log_file = mytest.log;
 ERROR 42000: Incorrect argument type to variable 'general_log_file'
 SET @@global.general_log_file = 12;
 ERROR 42000: Incorrect argument type to variable 'general_log_file'
+SET @@global.general_log_file = 'my.cnf';
+ERROR 42000: Variable 'general_log_file' can't be set to the value of 'my.cnf'
+SET @@global.general_log_file = '/tmp/my.cnf';
+ERROR 42000: Variable 'general_log_file' can't be set to the value of '/tmp/my.cnf'
+SET @@global.general_log_file = '.my.cnf';
+ERROR 42000: Variable 'general_log_file' can't be set to the value of '.my.cnf'
 '#----------------------FN_DYNVARS_004_03------------------------#'
 SELECT @@global.general_log_file = VARIABLE_VALUE 
 FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES 
diff --git a/mysql-test/suite/sys_vars/r/slow_query_log_file_basic.result b/mysql-test/suite/sys_vars/r/slow_query_log_file_basic.result
index f45c568ff4a..e2ed7d63fdb 100644
--- a/mysql-test/suite/sys_vars/r/slow_query_log_file_basic.result
+++ b/mysql-test/suite/sys_vars/r/slow_query_log_file_basic.result
@@ -9,6 +9,12 @@ SET @@global.slow_query_log_file = mytest.log;
 ERROR 42000: Incorrect argument type to variable 'slow_query_log_file'
 SET @@global.slow_query_log_file = 12;
 ERROR 42000: Incorrect argument type to variable 'slow_query_log_file'
+SET @@global.slow_query_log_file = 'my.cnf';
+ERROR 42000: Variable 'slow_query_log_file' can't be set to the value of 'my.cnf'
+SET @@global.slow_query_log_file = '/tmp/my.cnf';
+ERROR 42000: Variable 'slow_query_log_file' can't be set to the value of '/tmp/my.cnf'
+SET @@global.general_log_file = '.my.cnf';
+ERROR 42000: Variable 'general_log_file' can't be set to the value of '.my.cnf'
 '#----------------------FN_DYNVARS_004_03------------------------#'
 SELECT @@global.slow_query_log_file = VARIABLE_VALUE 
 FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES 
diff --git a/mysql-test/suite/sys_vars/t/general_log_file_basic.test b/mysql-test/suite/sys_vars/t/general_log_file_basic.test
index 12362fa123c..cdb2cc4b36e 100644
--- a/mysql-test/suite/sys_vars/t/general_log_file_basic.test
+++ b/mysql-test/suite/sys_vars/t/general_log_file_basic.test
@@ -58,6 +58,16 @@ SET @@global.general_log_file = mytest.log;
 --error ER_WRONG_TYPE_FOR_VAR
 SET @@global.general_log_file = 12;
 
+#
+# MDEV-10465
+#
+--error ER_WRONG_VALUE_FOR_VAR
+SET @@global.general_log_file = 'my.cnf';
+--error ER_WRONG_VALUE_FOR_VAR
+SET @@global.general_log_file = '/tmp/my.cnf';
+--error ER_WRONG_VALUE_FOR_VAR
+SET @@global.general_log_file = '.my.cnf';
+
 
 --echo '#----------------------FN_DYNVARS_004_03------------------------#'
 ############################################################################## 
diff --git a/mysql-test/suite/sys_vars/t/slow_query_log_file_basic.test b/mysql-test/suite/sys_vars/t/slow_query_log_file_basic.test
index 28fc17f6077..835cb251e39 100644
--- a/mysql-test/suite/sys_vars/t/slow_query_log_file_basic.test
+++ b/mysql-test/suite/sys_vars/t/slow_query_log_file_basic.test
@@ -56,6 +56,16 @@ SET @@global.slow_query_log_file = mytest.log;
 --error ER_WRONG_TYPE_FOR_VAR
 SET @@global.slow_query_log_file = 12;
 
+#
+# MDEV-10465
+#
+--error ER_WRONG_VALUE_FOR_VAR
+SET @@global.slow_query_log_file = 'my.cnf';
+--error ER_WRONG_VALUE_FOR_VAR
+SET @@global.slow_query_log_file = '/tmp/my.cnf';
+--error ER_WRONG_VALUE_FOR_VAR
+SET @@global.general_log_file = '.my.cnf';
+
 --echo '#----------------------FN_DYNVARS_004_03------------------------#'
 ############################################################################## 
 # Check if the value in GLOBAL Tables matches values in variable             #
diff --git a/sql/sys_vars.cc b/sql/sys_vars.cc
index bf7ed231d77..2ed5be3bf3b 100644
--- a/sql/sys_vars.cc
+++ b/sql/sys_vars.cc
@@ -3033,6 +3033,13 @@ static bool check_log_path(sys_var *self, THD *thd, set_var *var)
     return true;
   }
 
+  static const LEX_CSTRING my_cnf= { STRING_WITH_LEN("my.cnf") };
+  if (val->length >= my_cnf.length)
+  {
+    if (strcasecmp(val->str + val->length - my_cnf.length, my_cnf.str) == 0)
+      return true; // log file name ends with "my.cnf"
+  }
+
   char path[FN_REFLEN];
   size_t path_length= unpack_filename(path, val->str);