two fixes for potential security bugs

sql/log.cc

@@ -1797,6 +1797,7 @@ bool flush_error_log()
     char err_renamed[FN_REFLEN], *end;
     end= strmake(err_renamed,log_error_file,FN_REFLEN-4);
     strmov(end, "-old");
+    VOID(pthread_mutex_lock(&LOCK_error_log));
 #ifdef __WIN__
     char err_temp[FN_REFLEN+4];
     /*
@@ -1804,7 +1805,7 @@ bool flush_error_log()
      the current error file.
     */
     strmov(strmov(err_temp, err_renamed),"-tmp");
-    (void) my_delete(err_temp, MYF(0)); 
+    (void) my_delete(err_temp, MYF(0));
     if (freopen(err_temp,"a+",stdout))
     {
       freopen(err_temp,"a+",stderr);
@@ -1817,20 +1818,21 @@ bool flush_error_log()
       if ((fd = my_open(err_temp, O_RDONLY, MYF(0))) >= 0)
       {
         while ((bytes = (int) my_read(fd, (byte*) buf, IO_SIZE, MYF(0))) > 0)
-             my_fwrite(stderr, (byte*) buf, (uint) strlen(buf),MYF(0));
+             my_fwrite(stderr, (byte*) buf, bytes, MYF(0));
         my_close(fd, MYF(0));
       }
-      (void) my_delete(err_temp, MYF(0)); 
+      (void) my_delete(err_temp, MYF(0));
     }
     else
      result= 1;
 #else
-   my_rename(log_error_file,err_renamed,MYF(0));
-   if (freopen(log_error_file,"a+",stdout))
-     freopen(log_error_file,"a+",stderr);
-   else
-     result= 1;
+    my_rename(log_error_file,err_renamed,MYF(0));
+    if (freopen(log_error_file,"a+",stdout))
+      freopen(log_error_file,"a+",stderr);
+    else
+      result= 1;
 #endif
+    VOID(pthread_mutex_unlock(&LOCK_error_log));
   }
    return result;
 }

sql/sql_class.cc

@@ -564,7 +564,7 @@ select_export::prepare(List<Item> &list)
     return 1;
   }
   /* Create the file world readable */
-  if ((file=my_create(path, 0666, O_WRONLY, MYF(MY_WME))) < 0)
+  if ((file=my_create(path, 0666, O_WRONLY|O_EXCL, MYF(MY_WME))) < 0)
     return 1;
 #ifdef HAVE_FCHMOD
   (void) fchmod(file,0666);			// Because of umask()
@@ -803,7 +803,7 @@ select_dump::prepare(List<Item> &list __attribute__((unused)))
     return 1;
   }
   /* Create the file world readable */
-  if ((file=my_create(path, 0666, O_WRONLY, MYF(MY_WME))) < 0)
+  if ((file=my_create(path, 0666, O_WRONLY|O_EXCL, MYF(MY_WME))) < 0)
     return 1;
 #ifdef HAVE_FCHMOD
   (void) fchmod(file,0666);			// Because of umask()