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.
