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commit 0bfc96cb upstream.

[ Changes with respect to 3.3: return -ENOTTY from scsi_verify_blk_ioctl
  and -ENOIOCTLCMD from sd_compat_ioctl. ]

Linux allows executing the SG_IO ioctl on a partition or LVM volume, and
will pass the command to the underlying block device.  This is
well-known, but it is also a large security problem when (via Unix
permissions, ACLs, SELinux or a combination thereof) a program or user
needs to be granted access only to part of the disk.

This patch lets partitions forward a small set of harmless ioctls;
others are logged with printk so that we can see which ioctls are
actually sent.  In my tests only CDROM_GET_CAPABILITY actually occurred.
Of course it was being sent to a (partition on a) hard disk, so it would
have failed with ENOTTY and the patch isn't changing anything in
practice.  Still, I'm treating it specially to avoid spamming the logs.

In principle, this restriction should incl...