hfs: fix namelength memory corruption

Fix a stack corruption caused by a corrupted hfs filesystem.  If the
catalog name length is corrupted the memcpy overwrites the catalog btree
structure.  Since the field is limited to HFS_NAMELEN bytes in the
structure and the file format, we throw an error if it is too long.

Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>