All of lore.kernel.org
 help / color / mirror / Atom feed
From: Paolo Bonzini <pbonzini@redhat.com>
To: Brijesh Singh <brijesh.singh@amd.com>, Al Viro <viro@ZenIV.linux.org.uk>
Cc: kvm@vger.kernel.org, "Radim Krčmář" <rkrcmar@redhat.com>,
	"Borislav Petkov" <bp@suse.de>,
	"Tom Lendacky" <thomas.lendacky@amd.com>,
	linux-kernel@vger.kernel.org, "Joerg Roedel" <joro@8bytes.org>
Subject: Re: [PATCH] KVM: SVM: Fix sparse: incorrect type in argument 1 (different base types)
Date: Fri, 23 Feb 2018 19:05:45 +0100	[thread overview]
Message-ID: <561de7e2-84a6-7372-b561-b035ff390ac5@redhat.com> (raw)
In-Reply-To: <f8b22e16-73b4-340a-7387-c8c7270e9432@amd.com>

On 22/02/2018 16:56, Brijesh Singh wrote:
> 
> 
> On 02/21/2018 02:18 PM, Al Viro wrote:
>> On Wed, Feb 21, 2018 at 01:59:55PM -0600, Brijesh Singh wrote:
>>
>>> Sure, checking access_ok() does not guarantee that later
>>> copy_from_user() will not fail. But it does eliminate one possible
>>> reason for the failure. We are trying to validate most of the user
>>> inputs before we invoke  SEV command.
>>
>> That makes no sense whatsoever.  If user is deliberately fuzzing
>> your code or trying to DoS it, that "validation" doesn't buy you
>> anything - they can just as well feed you NULL, after all.
>>
> 
> 
> Currently, we let user query the blob length with params.len == 0 ||
> param.uaddr == NULL. We could limit it to just params.len == 0.
> 
> 
>> What is the rationale for that?  "Userland is accidentally feeding
>> us garbage pointers" is the case where slowness is the least of your
>> concerns...
>>
> 
> My intent was to do some obvious failure checks on user inputs before
> invoking the HW. I do see your point that if userspace is feeding us
> garbage then slowness is least of our concern. If you think that we
> should not be using access_ok() in this particular case then I am okay
> with it.

Can you please send a patch?  Thanks!

Paolo

  reply	other threads:[~2018-02-23 18:05 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-19 16:12 [PATCH] KVM: SVM: Fix sparse: incorrect type in argument 1 (different base types) Brijesh Singh
2018-02-21 17:49 ` Al Viro
2018-02-21 19:59   ` Brijesh Singh
2018-02-21 20:18     ` Al Viro
2018-02-22 15:56       ` Brijesh Singh
2018-02-23 18:05         ` Paolo Bonzini [this message]
2018-02-23 18:26           ` Brijesh Singh

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=561de7e2-84a6-7372-b561-b035ff390ac5@redhat.com \
    --to=pbonzini@redhat.com \
    --cc=bp@suse.de \
    --cc=brijesh.singh@amd.com \
    --cc=joro@8bytes.org \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=rkrcmar@redhat.com \
    --cc=thomas.lendacky@amd.com \
    --cc=viro@ZenIV.linux.org.uk \
    /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.