On Thu, 21 Sep 2023 23:22:54 +0100, "Jitindar Singh, Suraj" surajjs@amazon.com wrote:
On Thu, 2023-09-21 at 08:13 +0100, Marc Zyngier wrote:
On Wed, 20 Sep 2023 20:27:28 +0100, Suraj Jitindar Singh surajjs@amazon.com wrote:
From: Quentin Perret qperret@google.com
commit 43c1ff8b75011bc3e3e923adf31ba815864a2494 upstream.
Memory regions marked as "no-map" in the host device-tree routinely include TrustZone carev-outs and DMA pools. Although donating such pages to the hypervisor may not breach confidentiality, it could be used to corrupt its state in uncontrollable ways. To prevent this, let's block host-initiated memory transitions targeting "no-map" pages altogether in nVHE protected mode as there should be no valid reason to do this in current operation.
Thankfully, the pKVM EL2 hypervisor has a full copy of the host's list of memblock regions, so we can easily check for the presence of the MEMBLOCK_NOMAP flag on a region containing pages being donated from the host.
Reviewed-by: Philippe Mathieu-Daudé philmd@linaro.org Tested-by: Vincent Donnefort vdonnefort@google.com Signed-off-by: Quentin Perret qperret@google.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/r/20221110190259.26861-8-will@kernel.org [ bp: clean ]
What is this?
Noting any details about the backport. In this case it was a clean backport.
I don't think this has anything to do here. If you want to add a note indicating what was changed in the patch, make it *extremely* visible in the commit message, and not hidden as some obscure form of metadata.
Signed-off-by: Suraj Jitindar Singh surajjs@amazon.com
What is the rationale for backporting this? It wasn't tagged as Cc: to stable for a reason: pKVM isn't functional upstream, and won't be for the next couple of cycles *at least*.
So at it stands, I'm against such a backport.
The 2 patches were backported to address CVE-2023-21264. This one provides context for the proceeding patch.
I care about CVEs as much as I care about holes in my socks (i.e. very little). If there is a concern, it should be brought up on the list as a discussion, and not as a consequence of some script kiddie automatically generating CVEs.
I wasn't aware that it's non functional. Does this mean that the code won't be compiled or just that it can't actually be run currently from the upstream codebase?
This code is inactive unless you pass the correct option on the command line, and as it is brings zero benefit over standard KVM. The only place this matters is in the Android kernel, as it has full support for pKVM, and has the fix already. We carry it upstream at a courtesy to the pKVM developers, but that's about it.
I guess I'm trying to understand if the conditions of the CVE are a real concern even if it isn't technically functional.
This CVE is a waste of precious bytes, and I have no interest in seeing this backported.
Thanks,
M.