s3: smbd: Fix a couple of tricky slow-path cases - don't return a mangled name for...

s3: smbd: Fix a couple of tricky slow-path cases - don't return a mangled name for a name that cannot be converted.

For a name that contains an illegal Windows character, the
directory listing code returns the mangled 8.3 name as the
primary name for the file.

If the original (non-mangled) filename cannot be converted
to UCS2 on the wire via iconv due to conversion error, we
should skip that name when returning a directory listing,
as we can't map back from a returned 8.3 name to a usable
non-mangled filename if the client sends it back to us.

As this is only done in a very slow path (name must be mangled)
or in the old DOS protocol listing code I don't feel too bad
about using a talloc/free pair here.

Bug 10775 - smbd crashes when accessing garbage filenames

https://bugzilla.samba.org/show_bug.cgi?id=10775

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: David Disseldorp <ddiss@samba.org>