potential null deref in drivers/ide/ide-io.c start_request().

[Dan Carpenter <error27@gmail.com>]

Hello,

I am testing a code checker (http://repo.or.cz/w/smatch.git) and it found 
an issue in ide-io.c

The case where rq->rq_disk is null and blk_special_request(rq) returns 
zero on line 356 would cause an oops on line 367.

drivers/ide/ide-io.c
   356                  } else if (!rq->rq_disk && blk_special_request(rq))
   357                          /*
   358                           * TODO: Once all ULDs have been modified to
   359                           * check for specific op codes rather than
   360                           * blindly accepting any special request, the
   361                           * check for ->rq_disk above may be replaced
   362                           * by a more suitable mechanism or even
   363                           * dropped entirely.
   364                           */
   365                          return ide_special_rq(drive, rq);
   366  
   367                  drv = *(struct ide_driver **)rq->rq_disk->private_data;

regards,
dan carpenter