All of lore.kernel.org
 help / color / mirror / Atom feed
From: Andrew Cooper <andrew.cooper3@citrix.com>
To: David Vrabel <david.vrabel@citrix.com>, Jan Beulich <JBeulich@suse.com>
Cc: StefanoStabellini <stefano.stabellini@citrix.com>,
	Ian Campbell <ian.campbell@citrix.com>,
	Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH] x86/hvm: Allow the guest to permit the use of userspace hypercalls
Date: Mon, 11 Jan 2016 18:32:17 +0000	[thread overview]
Message-ID: <5693F531.9000004@citrix.com> (raw)
In-Reply-To: <5693F3B9.5060407@citrix.com>

On 11/01/16 18:26, David Vrabel wrote:
> On 11/01/16 17:17, Andrew Cooper wrote:
>> So from one point of view, sufficient justification for this change is
>> "because the Linux way isn't the only valid way to do this".
> "Because we can" isn't a good justification for adding something new.

"Because I need this to sensibly regression test bits of the hypervisor" is.

> Particularly something that is trivially easy to (accidentally) misuse
> and open a big security hole between userspace and kernel.

This is no conceptual difference to incorrectly updating a pagetable, or
having wrong dpl checks in the IDT.

An OS which doesn't use the hypercall can't shoot itself.  An OS which
does use it has plenty of other ways to accidentally compromise itself.

> The vague idea for a userspace netfront that's floating around
> internally is also not a good reason for pushing this feature at this time.

It is a valid (albeit unwise) alternate usecase, showing that the
concept isn't unique to my situation.

~Andrew

  reply	other threads:[~2016-01-11 18:32 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-11 13:59 [PATCH] x86/hvm: Allow the guest to permit the use of userspace hypercalls Andrew Cooper
2016-01-11 14:32 ` Paul Durrant
2016-01-11 14:44 ` Jan Beulich
2016-01-11 17:17   ` Andrew Cooper
2016-01-11 18:26     ` David Vrabel
2016-01-11 18:32       ` Andrew Cooper [this message]
2016-01-11 18:40         ` David Vrabel
2016-01-11 18:50           ` Andrew Cooper
2016-01-12 12:07       ` Stefano Stabellini
2016-01-12 15:06         ` Jan Beulich
2016-01-12 17:05           ` Stefano Stabellini
2016-01-12 17:10             ` Juergen Gross
2016-01-12 17:23               ` Stefano Stabellini
2016-01-13  5:12                 ` Juergen Gross
2016-01-13 10:41                   ` Stefano Stabellini
2016-01-13 11:14                     ` Juergen Gross
2016-01-13 11:26                       ` Stefano Stabellini
2016-01-13 11:32                         ` Juergen Gross
2016-01-13 11:42         ` David Vrabel
2016-01-13 12:51           ` Stefano Stabellini
2016-01-12  7:33     ` Jan Beulich
2016-01-12 10:57       ` Andrew Cooper
2016-01-12 11:03         ` George Dunlap
2016-01-14 10:50 ` Ian Campbell

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=5693F531.9000004@citrix.com \
    --to=andrew.cooper3@citrix.com \
    --cc=JBeulich@suse.com \
    --cc=david.vrabel@citrix.com \
    --cc=ian.campbell@citrix.com \
    --cc=stefano.stabellini@citrix.com \
    --cc=xen-devel@lists.xen.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.