linux-kernel - Re: [PATCH V4] virt: sev: Prevent IV reuse in SNP guest driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Y3TVcJnQ/Ym6dGz2@zn.tnic>
Date:   Wed, 16 Nov 2022 13:20:00 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Peter Gonda <pgonda@...gle.com>
Cc:     thomas.lendacky@....com, Dionna Glaze <dionnaglaze@...gle.com>,
        Michael Roth <michael.roth@....com>,
        Haowen Bai <baihaowen@...zu.com>,
        Yang Yingliang <yangyingliang@...wei.com>,
        Marc Orr <marcorr@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Ashish Kalra <Ashish.Kalra@....com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH V4] virt: sev: Prevent IV reuse in SNP guest driver

On Tue, Nov 15, 2022 at 02:47:31PM -0700, Peter Gonda wrote:
> > > +      * certificate data buffer retry the same guest request without the
> > > +      * extended data request.
> > > +      */
> > > +     if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST &&
> > > +         err == SNP_GUEST_REQ_INVALID_LEN) {
> > > +             const unsigned int certs_npages = snp_dev->input.data_npages;
> > > +
> > > +             exit_code = SVM_VMGEXIT_GUEST_REQUEST;
> > > +             rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
> > > +
> > > +             err = SNP_GUEST_REQ_INVALID_LEN;
> >
> > Huh, why are we overwriting err here?
> 
> I have added a comment for the next revision.
> 
> We are overwriting err here so that userspace is alerted that they
> supplied a buffer too small.

Sure but you're not checking rc either. What if that reissue fails for
whatever other reason? -EIO for example...

-- 
Regards/Gruss,
    Boris.

SUSE Software Solutions Germany GmbH
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Martje Boudien Moerman
(HRB 36809, AG Nürnberg)