[PATCH] usx2y cleanups and fixes

[PATCH] usx2y cleanups and fixes

Sigh...
	a) mixing of userland and kernel pointers is bad
	b) so's not checking result of kmalloc()
	c) so's not checking result of copy_from_user()
	d) use of do { .... break; ... break; ... } while(0); is *highly*
unidiomatic.  Do not confuse kernel with IOCCC, please. And if you have
religious aversion to multiple return statements in a function, at least
learn the reasons why it is frowned upon in many situations.  Hint: they
all apply to use of break in that manner.
	e) 0 instead of NULL

Signed-off-by: Al Viro <viro@parcelfarce.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>