BUG#25451091:CREATE TABLE DATA DIRECTORY / INDEX DIRECTORY

             SYMLINK CHECK RACE CONDITIONS

ANALYSIS:
=========
A potential defect exists in the handling of CREATE
TABLE .. DATA DIRECTORY/ INDEX DIRECTORY which gives way to
the user to gain access to another user table or a system
table.

FIX:
====
The lstat and fstat output of the target files are now
stored which help in determining the identity of the target
files thus preventing the unauthorized access to other
files.

1 files changed, 14 insertions, 2 deletions

diff --git a/include/my_sys.h b/include/my_sys.h
index 472c2ba5ca0..9983ee3319f 100644
--- a/include/my_sys.h
+++ b/include/my_sys.h
@@ -1,4 +1,4 @@
-/* Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -49,6 +49,7 @@ typedef struct my_aio_result {
 #ifdef _WIN32
 #include <malloc.h> /*for alloca*/
 #endif
+#include <sys/stat.h>
 
 #define MY_INIT(name)   { my_progname= name; my_init(); }
 
@@ -491,6 +492,16 @@ typedef struct st_io_cache		/* Used when cacheing files */
 
 typedef int (*qsort2_cmp)(const void *, const void *, const void *);
 
+/*
+  Subset of struct stat fields filled by stat/lstat/fstat that uniquely
+  identify a file
+*/
+typedef struct st_file_id
+{
+  dev_t st_dev;
+  ino_t st_ino;
+} ST_FILE_ID;
+
 	/* defines for mf_iocache */
 
 	/* Test if buffer is inited */
@@ -569,8 +580,9 @@ extern File my_create(const char *FileName,int CreateFlags,
 extern int my_close(File Filedes,myf MyFlags);
 extern int my_mkdir(const char *dir, int Flags, myf MyFlags);
 extern int my_readlink(char *to, const char *filename, myf MyFlags);
-extern int my_is_symlink(const char *filename);
+extern int my_is_symlink(const char *filename, ST_FILE_ID *file_id);
 extern int my_realpath(char *to, const char *filename, myf MyFlags);
+extern int my_is_same_file(File file, const ST_FILE_ID *file_id);
 extern File my_create_with_symlink(const char *linkname, const char *filename,
 				   int createflags, int access_flags,
 				   myf MyFlags);