builtin/mv: fix out of bounds write

When commit a88c915 (mv: move submodules using a gitfile, 2013-07-30)
added the submodule_gitfile array, it was not added to the block that
enlarges the arrays when we are moving a directory so that we do not
have to worry about it being a directory when we perform the actual
move.  After this, the loop continues over the enlarged set of sources.

Since we assume that submodule_gitfile has size argc, if any of the
items in the source directory are submodules we are guaranteed to write
beyond the end of submodule_gitfile.

Fix this by realloc'ing submodule_gitfile at the same time as the other
arrays.

Reported-by: Guillaume Gelin <contact@ramnes.eu>
Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/mv.c

@@ -179,6 +179,9 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 						modes = xrealloc(modes,
 								(argc + last - first)
 								* sizeof(enum update_mode));
+						submodule_gitfile = xrealloc(submodule_gitfile,
+								(argc + last - first)
+								* sizeof(char *));
 					}
 
 					dst = add_slash(dst);
@@ -192,6 +195,7 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 							prefix_path(dst, dst_len,
 								path + length + 1);
 						modes[argc + j] = INDEX;
+						submodule_gitfile[argc + j] = NULL;
 					}
 					argc += last - first;
 				}