commit 22426465 upstream.

should clear on access_ok() failures.  Also remove the useless
range truncation logics.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[bwh: Backported to 3.2: no calls to check_object_size()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>