[SCSI] megaraid: missing bounds check in mimd_to_kioc()

pthru32->dataxferlen comes from the user so we need to check that it's
not too large so we don't overflow the buffer.

Reported-by: Nico Golde <nico@ngolde.de>
Reported-by: Fabian Yamaguchi <fabs@goesec.de>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Sumit Saxena <sumit.saxena@lsi.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/megaraid/megaraid_mm.c

@@ -486,6 +486,8 @@ mimd_to_kioc(mimd_t __user *umimd, mraid_mmadp_t *adp, uioc_t *kioc)
 
 	pthru32->dataxferaddr	= kioc->buf_paddr;
 	if (kioc->data_dir & UIOC_WR) {
+		if (pthru32->dataxferlen > kioc->xferlen)
+			return -EINVAL;
 		if (copy_from_user(kioc->buf_vaddr, kioc->user_data,
 						pthru32->dataxferlen)) {
 			return (-EFAULT);