LU-4423 llite: Integer overflow in ll_ioctl_fiemap

In ll_ioctl_fiemap(), a user-supplied value is used to calculate a
length of a buffer which is later allocated with user data.

Commit from upstream kernel 7bc3dfa37ba6f6ea81c362eb1993bd20c0828eae

Change-Id: Ia1d255f9570fe1b136f1b0dd7caabe26b7b36665
Signed-off-by: Vitaly Osipov <vitaly.osipov@gmail.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: http://review.whamcloud.com/11413
Tested-by: Jenkins
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>