linux-kernel - Re: [RFC PATCH V2 08/18] x86/hyperv: decrypt vmbus pages for sev-snp enlightened guest

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: <ec2b1723-1698-ac64-279b-c47b38b8d16f@gmail.com>
Date:   Mon, 26 Dec 2022 12:19:51 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        "luto@...nel.org" <luto@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "seanjc@...gle.com" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "jgross@...e.com" <jgross@...e.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "kirill@...temov.name" <kirill@...temov.name>,
        "jiangshan.ljs@...group.com" <jiangshan.ljs@...group.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "ashish.kalra@....com" <ashish.kalra@....com>,
        "srutherford@...gle.com" <srutherford@...gle.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "anshuman.khandual@....com" <anshuman.khandual@....com>,
        "pawan.kumar.gupta@...ux.intel.com" 
        <pawan.kumar.gupta@...ux.intel.com>,
        "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
        "daniel.sneddon@...ux.intel.com" <daniel.sneddon@...ux.intel.com>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        "sandipan.das@....com" <sandipan.das@....com>,
        "ray.huang@....com" <ray.huang@....com>,
        "brijesh.singh@....com" <brijesh.singh@....com>,
        "michael.roth@....com" <michael.roth@....com>,
        "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "venu.busireddy@...cle.com" <venu.busireddy@...cle.com>,
        "sterritt@...gle.com" <sterritt@...gle.com>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "samitolvanen@...gle.com" <samitolvanen@...gle.com>,
        "fenghua.yu@...el.com" <fenghua.yu@...el.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: [RFC PATCH V2 08/18] x86/hyperv: decrypt vmbus pages for sev-snp
 enlightened guest

On 12/14/2022 2:08 AM, Michael Kelley (LINUX) wrote:
> From: Tianyu Lan <ltykernel@...il.com> Sent: Friday, November 18, 2022 7:46 PM
>>
> 
> The Subject prefix for this patch should be "Drivers: hv: vmbus:"

Sure. Will update in the next version.

> 
>> Vmbus int, synic and post message pages are shared with hypervisor
>> and so decrypt these pages in the sev-snp guest.
>>
>> Signed-off-by: Tianyu Lan <tiala@...rosoft.com>
>> ---
>>   drivers/hv/connection.c | 13 +++++++++++++
>>   drivers/hv/hv.c         | 32 +++++++++++++++++++++++++++++++-
>>   2 files changed, 44 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
>> index 9dc27e5d367a..43141225ea15 100644
>> --- a/drivers/hv/connection.c
>> +++ b/drivers/hv/connection.c
>> @@ -215,6 +215,15 @@ int vmbus_connect(void)
>>   		(void *)((unsigned long)vmbus_connection.int_page +
>>   			(HV_HYP_PAGE_SIZE >> 1));
>>
>> +	if (hv_isolation_type_snp() || hv_isolation_type_en_snp()) {
> 
> This decryption should be done only for a fully enlightened SEV-SNP
> guest, not for a vTOM guest.
> 
>> +		ret = set_memory_decrypted((unsigned long)
>> +				vmbus_connection.int_page, 1);
>> +		if (ret)
>> +			goto cleanup;
> 
> This cleanup path doesn't work correctly.  It calls
> vmbus_disconnect(), which will try to re-encrypt the memory.
> But if the original decryption failed, re-encrypting is the wrong
> thing to do.
> 
> It looks like this same bug exists in current code if the decryption
> of the monitor pages fails or if just one of the original memory
> allocations fails.  vmbus_disconnect() doesn't know whether it
> should re-encrypt the pages.

Agree. It's necessary to handle decryption failure case by case in stead 
of re-encryting all pages. Will fix this in the next version. Thanks to 
point out.