Bug #51893: crash with certain characters given to load_file

  function on windows

When making sure that the directory path ends up with a 
slash/backslash we need to check for the correct length of 
the buffer and trim at the appropriate location so we don't
write past the end of the buffer.

mysql-test/r/loaddata.result

@@ -495,4 +495,11 @@ SELECT * FROM t1;
 col0
 test
 DROP TABLE t1;
+#
+# Bug #51893: crash with certain characters given to load_file 
+#   function on windows
+#
+select load_file(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
+load_file(0x0A9FB76C661B409C4BEC88098C5DD71B1072F9691F2E827D7EC8F092B299868A3CE196C04F0FB18CAB4E1557EB72331D812379DE7A75CA21C32E7C722C59E5CC33EF262EF04187B0F0EE756FA984DF2EAD37B1E4ADB064C3C5038F2E3B2D661B1C1150AAEB5425512E14D7506166D92D4533872E662F4B2D142
+NULL
 End of 5.1 tests

mysql-test/t/loaddata.test

@@ -547,4 +547,12 @@ let $MYSQLD_DATADIR= `select @@datadir`;
 remove_file $MYSQLD_DATADIR/test/t1.txt;
 
 
+--echo #
+--echo # Bug #51893: crash with certain characters given to load_file 
+--echo #   function on windows
+--echo #
+
+select load_file(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
+
+
 --echo End of 5.1 tests

mysys/mf_pack.c

@@ -311,6 +311,9 @@ size_t normalize_dirname(char *to, const char *from)
 #endif
       buff[length - 1] != FN_LIBCHAR && buff[length - 1] != '/')
   {
+    /* we need reserve 2 bytes for the trailing slash and the zero */
+    if (length >= sizeof (buff) - 1)
+      length= sizeof (buff) - 2;
     buff[length]= FN_LIBCHAR;
     buff[length + 1]= '\0';
   }