Re: [PATCH 2/3] block: fail SCSI passthrough ioctls on partition devices

[Linus Torvalds]

On Thu, Dec 22, 2011 at 10:02 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> Linux allows executing the SG_IO ioctl on a partition or even on an
> 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 to a particular partition or logical
> volume but not to the full device.

So who actually *does* this in practice?

> +       /* In particular, rule out all resets and host-specific ioctls.  */
> +       return -ENOTTY;

This kind of crazy needs to go away.

If it's a permission problem, state that. Don't turn it into ENOTTY that then:

> +               return ret == -ENOTTY ? -ENOIOCTLCMD : ret;

gets turned into another random error number.

That's just crazy. No way am I ever applying patches *this* confused
without some serious explanation. And quite frankly, probably not even
then.

If it's a permission issue, return EPERM. Nothing else.

If returning EPERM causes problems for eject or other user tools,
explain it. And then just say "ok, we allow eject on a partition, and
it ejects the disk".

                       Linus
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