linux-kernel - Re: [PATCH stable 6.1.y 2/2] KVM: arm64: Prevent unconditional donation of unmapped regions from the host

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Message-ID: <2031eecaa417d4f6021717dcbbba133d784add72.camel@gmail.com>
Date:   Thu, 21 Sep 2023 15:25:19 -0700
From:   Suraj Jitindar Singh <sjitindarsingh@...il.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     stable@...r.kernel.org, james.morse@....com,
        alexandru.elisei@....com, suzuki.poulose@....com,
        oliver.upton@...ux.dev, catalin.marinas@....com,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Will Deacon <will@...nel.org>,
        Quentin Perret <qperret@...gle.com>
Subject: Re: [PATCH stable 6.1.y 2/2] KVM: arm64: Prevent unconditional
 donation of unmapped regions from the host

On Thu, 2023-09-21 at 08:15 +0100, Marc Zyngier wrote:
> On Wed, 20 Sep 2023 20:27:29 +0100,
> Suraj Jitindar Singh <surajjs@...zon.com> wrote:
> > 
> > From: Will Deacon <will@...nel.org>
> > 
> > commit 09cce60bddd6461a93a5bf434265a47827d1bc6f upstream.
> > 
> > Since host stage-2 mappings are created lazily, we cannot rely
> > solely on
> > the pte in order to recover the target physical address when
> > checking a
> > host-initiated memory transition as this permits donation of
> > unmapped
> > regions corresponding to MMIO or "no-map" memory.
> > 
> > Instead of inspecting the pte, move the addr_is_allowed_memory()
> > check
> > into the host callback function where it is passed the physical
> > address
> > directly from the walker.
> > 
> > Cc: Quentin Perret <qperret@...gle.com>
> > Fixes: e82edcc75c4e ("KVM: arm64: Implement do_share() helper for
> > sharing memory")
> > Signed-off-by: Will Deacon <will@...nel.org>
> > Signed-off-by: Marc Zyngier <maz@...nel.org>
> > Link:
> > https://lore.kernel.org/r/20230518095844.1178-1-will@kernel.org
> > [ bp: s/ctx->addr/addr in __check_page_state_visitor due to missing
> > commit
> >       "KVM: arm64: Combine visitor arguments into a context
> > structure"
> >       in stable.
> > ]
> 
> Same question.

Noting what changes were made to the patch from the upstream mainline
version when it was applied to the stable tree.

> 
> > Signed-off-by: Suraj Jitindar Singh <surajjs@...zon.com>
> 
> Again, I find this backport pretty pointless. What is the rationale
> for it?

The 2 patches were backported to address CVE-2023-21264.
This one addresses the CVE.

Thanks

> 
>         M.
>