php: Uninitialized pointer in phar_make_dirstream()

The pharmakedirstream function in ext/phar/dirstream.c in PHP before 5.6.18 and 7.x before 7.0.3 mishandles zero-size ././@LongLink files, which allows remote attackers to cause a denial of service uninitialized pointer dereference or possibly have unspecified other impact via a crafted TAR archi...