From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
To: Jonathan Davies <jonathan.davies@nutanix.com>
Cc: catalin.marinas@arm.com, christoffer.dall@arm.com,
fuad.tabba@linux.dev, joey.gouly@arm.com,
kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, maz@kernel.org, oupton@kernel.org,
seiden@linux.ibm.com, stable@vger.kernel.org,
suzuki.poulose@arm.com, weilin.chang@arm.com, will@kernel.org,
yaoyuan@linux.alibaba.com, yuzenghui@huawei.com
Subject: Re: [PATCH v3 2/2] KVM: arm64: nv: Fix null ptr deref on nested wp/unmap, teardown race
Date: Fri, 11 Sep 2026 09:44:04 +0100 [thread overview]
Message-ID: <aqO_SORFOAXDyXw_@gremlin> (raw)
In-Reply-To: <9829c704-9592-4235-b97c-dc1f5e4ea795@nutanix.com>
On Fri, Sep 11, 2026 at 09:12:20AM +0100, Jonathan Davies wrote:
> On Tue, 01 Sep 2026, "Lorenzo Stoakes (ARM)" <ljs@kernel.org> wrote:
> > This means that stage2_apply_range() can drop the kvm->mmu_lock and
> > thus concurrent progress can be made in lockstep with
> > kvm_arch_flush_shadow_all().
> >
> > If kvm_arch_flush_shadow_all() advances ahead of stage2_apply_range()
> > and completes its operation it guarantees a NULL pointer deref.
>
> I've reproducibly hit exactly this problem when running nested guests
> with concurrent memory compaction on the L0 host. This patch fixes it
> for me perfectly (applied to a 6.18 kernel).
>
> So, for what it's worth:
>
> Tested-by: Jonathan Davies <jonathan.davies@nutanix.com>
Amazing, thanks :)
--
Cheers, Lorenzo
next prev parent reply other threads:[~2026-09-11 8:44 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-01 17:28 [PATCH v3 0/2] KVM: arm64: Fix spurious warn, null ptr deref on S2 teardown race Lorenzo Stoakes (ARM)
2026-09-01 17:28 ` [PATCH v3 1/2] KVM: arm64: Fix spurious warning for benign stage 2 " Lorenzo Stoakes (ARM)
2026-09-01 17:46 ` sashiko-bot
2026-09-01 17:29 ` [PATCH v3 2/2] KVM: arm64: nv: Fix null ptr deref on nested wp/unmap, " Lorenzo Stoakes (ARM)
2026-09-01 17:46 ` sashiko-bot
2026-09-11 8:12 ` Jonathan Davies
2026-09-11 8:44 ` Lorenzo Stoakes (ARM) [this message]
2026-09-15 22:25 ` [PATCH v3 0/2] KVM: arm64: Fix spurious warn, null ptr deref on S2 " Oliver Upton
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