UPSTREAM: bug: switch data corruption check to __must_check

(cherry-picked from 85caa95b9f19bb3a26d7e025d1134760b69e0c40)

The CHECK_DATA_CORRUPTION() macro was designed to have callers do
something meaningful/protective on failure.  However, using "return
false" in the macro too strictly limits the design patterns of callers.
Instead, let callers handle the logic test directly, but make sure that
the result IS checked by forcing __must_check (which appears to not be
able to be used directly on macro expressions).

Change-Id: I23a87276163e3760c6eba44d6072e495fd8ec65d
Link: http://lkml.kernel.org/r/20170206204547.GA125312@beast


Signed-off-by: Kees Cook <keescook@chromium.org>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Satya Tangirala <satyat@google.com>