some filesystem(cd9660,ntfs,udf) accepts redundant UTF-8

[Takehiko NOZAKI]

RFC3629 added following Security consideration:

Security may also be impacted by a characteristic of several character encodings, including UTF-8: the "same thing" (as far as a user can tell) can be represented by several distinct character sequences.

but our UTF-8 -> UCS implementation for filesystem is too old to check redundant byte sequence.

[Takehiko NOZAKI]

src/sys/fs/unicode.[ch] is correctly checking redundant utf8 byte sequence, it is not vulnerable, no fix is needed.

[Takehiko NOZAKI]

done, HFS+ is not affected this problem.

[Takehiko NOZAKI]

BUGFIX: Issue #22 -- some filesystem(cd9660,ntfs,udf) accepts redundant UTF-8.

→ <<cset d52f113eadb6>>