kasprintf relies on being able to replay the formatting and getting the
same result (in particular, the same length).  This will almost always
work, but it is possible that the object pointed to by a %s or %p
argument changed under us (so we might get truncated output).  Add a
somewhat paranoid sanity check and let's see if it ever triggers.
Signed-off-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Joe Perches <joe@perches.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Maurizio Lombardi <mlombard@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>