From: Joerg Roedel <joro@8bytes.org>
To: Dave Hansen <dave.hansen@intel.com>
Cc: x86@kernel.org, Joerg Roedel <jroedel@suse.de>,
hpa@zytor.com, Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Jiri Slaby <jslaby@suse.cz>,
Dan Williams <dan.j.williams@intel.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Juergen Gross <jgross@suse.com>,
Kees Cook <keescook@chromium.org>,
David Rientjes <rientjes@google.com>,
Cfir Cohen <cfir@google.com>, Erdem Aktas <erdemaktas@google.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mike Stunes <mstunes@vmware.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Martin Radev <martin.b.radev@gmail.com>,
Arvind Sankar <nivedita@alum.mit.edu>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 6/7] x86/boot/compressed/64: Check SEV encryption in 32-bit boot-path
Date: Wed, 10 Feb 2021 17:46:42 +0100 [thread overview]
Message-ID: <20210210164642.GE7302@8bytes.org> (raw)
In-Reply-To: <0526b64e-8ef0-2e3c-06a7-e07835be160c@intel.com>
On Wed, Feb 10, 2021 at 08:25:11AM -0800, Dave Hansen wrote:
> This is all very cute. But, if this fails, it means that the .data
> section is now garbage, right?. I guess failing here is less
> entertaining than trying to run the kernel with random garbage in .data,
> but it doesn't make it very far either way, right?
Yes, if this fails the .data section is garbage, and more importantly,
the .text section of the decompressed kernel image would be garbage too.
The kernel won't get very far, but could possibly be tricked into
releasing secrets to the hypervisor.
> Why bother with rdrand, though? Couldn't you just pick any old piece of
> .data and compare before and after?
It is important that the Hypervisor can't predict what data will be
written. It is written with paging off, so it will implicitly be
encrypted. If the Hypervisor knows the data, it could use the small time
window until it is read again to remap the gpa to a page with the
expected data.
Regards,
Joerg
next prev parent reply other threads:[~2021-02-10 16:48 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-10 10:21 [PATCH 0/7] x86/seves: Support 32-bit boot path and other updates Joerg Roedel
2021-02-10 10:21 ` [PATCH 1/7] x86/boot/compressed/64: Cleanup exception handling before booting kernel Joerg Roedel
2021-02-10 10:21 ` [PATCH 2/7] x86/boot/compressed/64: Reload CS in startup_32 Joerg Roedel
2021-02-10 10:21 ` [PATCH 3/7] x86/boot/compressed/64: Setup IDT in startup_32 boot path Joerg Roedel
2021-02-24 10:49 ` Borislav Petkov
2021-02-10 10:21 ` [PATCH 4/7] x86/boot/compressed/64: Add 32-bit boot #VC handler Joerg Roedel
2021-02-25 12:13 ` Borislav Petkov
2021-02-10 10:21 ` [PATCH 5/7] x86/boot/compressed/64: Add CPUID sanity check to 32-bit boot-path Joerg Roedel
2021-02-10 10:21 ` [PATCH 6/7] x86/boot/compressed/64: Check SEV encryption in " Joerg Roedel
2021-02-10 16:25 ` Dave Hansen
2021-02-10 16:46 ` Joerg Roedel [this message]
2021-02-10 16:47 ` Dave Hansen
2021-02-10 20:44 ` Tom Lendacky
2021-03-02 19:43 ` Borislav Petkov
2021-03-09 10:02 ` Joerg Roedel
2021-02-10 10:21 ` [PATCH 7/7] x86/sev-es: Replace open-coded hlt-loops with sev_es_terminate() Joerg Roedel
2021-02-10 14:58 ` [PATCH 0/7] x86/seves: Support 32-bit boot path and other updates Konrad Rzeszutek Wilk
2021-02-10 15:12 ` Joerg Roedel
2021-02-10 15:19 ` Konrad Rzeszutek Wilk
2021-02-10 15:27 ` Joerg Roedel
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