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From: Paul Mackerras <paulus@ozlabs.org>
To: Greg Kurz <groug@kaod.org>
Cc: kvm-ppc@vger.kernel.org,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 0/3] KVM: PPC: Fix host kernel crash with PR KVM
Date: Thu, 19 Mar 2020 23:34:34 +0000	[thread overview]
Message-ID: <20200319233434.GF3260@blackberry> (raw)
In-Reply-To: <158455340419.178873.11399595021669446372.stgit@bahia.lan>

On Wed, Mar 18, 2020 at 06:43:24PM +0100, Greg Kurz wrote:
> Recent cleanup from Sean Christopherson introduced a use-after-free
> condition that crashes the kernel when shutting down the VM with
> PR KVM. It went unnoticed so far because PR isn't tested/used much
> these days (mostly used for nested on POWER8, not supported on POWER9
> where HV should be used for nested), and other KVM implementations for
> ppc are unaffected.
> 
> This all boils down to the fact that the path that frees the per-vCPU
> MMU data goes through a complex set of indirections. This obfuscates
> the code to the point that we didn't realize that the MMU data was
> now being freed too early. And worse, most of the indirection isn't
> needed because only PR KVM has some MMU data to free when the vCPU is
> destroyed.
> 
> Fix the issue (patch 1) and simplify the code (patch 2 and 3).

I have put this series in my kvm-ppc-next branch, and I believe
Michael Ellerman is putting patch 1 in his fixes branch so it gets
into 5.6.

Thanks,
Paul.

      parent reply	other threads:[~2020-03-19 23:34 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-18 17:43 [PATCH 0/3] KVM: PPC: Fix host kernel crash with PR KVM Greg Kurz
2020-03-18 17:43 ` [PATCH 1/3] KVM: PPC: Fix " Greg Kurz
2020-03-18 18:16   ` Sean Christopherson
2020-03-21 11:37   ` Michael Ellerman
2020-03-18 17:43 ` [PATCH 2/3] KVM: PPC: Move kvmppc_mmu_init() " Greg Kurz
2020-03-18 17:43 ` [PATCH 3/3] KVM: PPC: Kill kvmppc_ops::mmu_destroy() and kvmppc_mmu_destroy() Greg Kurz
2020-03-19 23:34 ` Paul Mackerras [this message]

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