linux-kernel - Re: [PATCH v12 54/84] KVM: arm64: Mark "struct page" pfns accessed/dirty before dropping mmu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZrFl3faiGHQ5oLjf@google.com>
Date: Mon, 5 Aug 2024 16:53:01 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Oliver Upton <oliver.upton@...ux.dev>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>, 
	Tianrui Zhao <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>, 
	Huacai Chen <chenhuacai@...nel.org>, Michael Ellerman <mpe@...erman.id.au>, 
	Anup Patel <anup@...infault.org>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Christian Borntraeger <borntraeger@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>, 
	Claudio Imbrenda <imbrenda@...ux.ibm.com>, kvm@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	loongarch@...ts.linux.dev, linux-mips@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	David Matlack <dmatlack@...gle.com>, David Stevens <stevensd@...omium.org>, 
	Fuad Tabba <tabba@...gle.com>
Subject: Re: [PATCH v12 54/84] KVM: arm64: Mark "struct page" pfns
 accessed/dirty before dropping mmu_lock

On Mon, Aug 05, 2024, Oliver Upton wrote:
> > > ---
> > >  arch/arm64/kvm/mmu.c | 10 ++++++----
> > >  1 file changed, 6 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > > index 22ee37360c4e..ce13c3d884d5 100644
> > > --- a/arch/arm64/kvm/mmu.c
> > > +++ b/arch/arm64/kvm/mmu.c
> > > @@ -1685,15 +1685,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> > >  	}
> > >  
> > >  out_unlock:
> > > +	if (writable && !ret)
> > > +		kvm_set_pfn_dirty(pfn);
> > 
> > I'm guessing you meant kvm_release_pfn_dirty() here, because this leaks
> > a reference.

Doh, I did indeed.  Alternatively, this could be:

	if (writable && !ret)
		kvm_set_pfn_dirty(pfn);

	kvm_release_pfn_clean(pfn);

It won't matter in the end, because this just becomes:

	kvm_release_faultin_page(kvm, page, !!ret, writable);

So I guess the question is if you prefer to make the switch to an if-else in this
path, or more implicitly in the conversion to kvm_release_faultin_page().

I made the same goof for RISC-V, perhaps to prove that I too can copy+paste arm64's
MMU code ;-)