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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Date:   Thu, 21 Sep 2023 08:15:36 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Suraj Jitindar Singh <surajjs@...zon.com>
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>,
        <kvmarm@...ts.cs.columbia.edu>, <linux-kernel@...r.kernel.org>,
        <sjitindarsingh@...il.com>, 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 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.

> Signed-off-by: Suraj Jitindar Singh <surajjs@...zon.com>

Again, I find this backport pretty pointless. What is the rationale
for it?

	M.

-- 
Without deviation from the norm, progress is not possible.