On Tue 30-04-19 14:18:21, Al Viro wrote:
> On Tue, Apr 30, 2019 at 03:07:39PM +0200, Jan Kara wrote:
> > On Tue 30-04-19 04:11:44, Al Viro wrote:
> > > On Tue, Apr 30, 2019 at 04:55:01AM +0200, Jan Kara wrote:
> > >
> > > > Yeah, you're right. And if we push the patch a bit further to not take
> > > > loop_ctl_mutex for invalid ioctl number, that would fix the problem. I
> > > > can send a fix.
> > >
> > > Huh? We don't take it until in lo_simple_ioctl(), and that patch doesn't
> > > get to its call on invalid ioctl numbers. What am I missing here?
> >
> > Doesn't it? blkdev_ioctl() calls into __blkdev_driver_ioctl() for
> > unrecognized ioctl numbers. That calls into lo_ioctl() in case of a loop
> > device. lo_ioctl() calls into lo_simple_ioctl() for ioctl numbers it
> > doesn't recognize and lo_simple_ioctl() will lock loop_ctl_mutex as you
> > say.
>
> Not with the patch upthread. lo_ioctl() part was
>
> @@ -1567,10 +1564,9 @@ static int lo_ioctl(struct block_device *bdev, fmode_t
> mode,
> case LOOP_SET_BLOCK_SIZE:
> if (!(mode & FMODE_WRITE) && !capable(CAP_SYS_ADMIN))
> return -EPERM;
> - /* Fall through */
> + return lo_simple_ioctl(lo, cmd, arg);
> default:
> - err = lo_simple_ioctl(lo, cmd, arg);
> - break;
> + return -EINVAL;
> }
>
> return err;
>
> so anything unrecognized doesn't make it to lo_simple_ioctl() at all.
Ah, right. I've missed that in your patch. So your patch should be really
fixing the problem. Will you post it officially? Thanks!
Honza
--
Jan Kara <j...@suse.com>
SUSE Labs, CR
