Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753681AbdCON3O (ORCPT ); Wed, 15 Mar 2017 09:29:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56232 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751147AbdCON3M (ORCPT ); Wed, 15 Mar 2017 09:29:12 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 52E2880F6D Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=pbonzini@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 52E2880F6D Subject: Re: [PATCH 1/3] kvm: arm/arm64: Take mmap_sem in stage2_unmap_vm To: Christoffer Dall , Suzuki K Poulose References: <1489503154-20705-1-git-send-email-suzuki.poulose@arm.com> <1489503154-20705-2-git-send-email-suzuki.poulose@arm.com> <20170315091755.GL1277@cbox> Cc: linux-arm-kernel@lists.infradead.org, andreyknvl@google.com, dvyukov@google.com, marc.zyngier@arm.com, christoffer.dall@linaro.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, kcc@google.com, syzkaller@googlegroups.com, will.deacon@arm.com, catalin.marinas@arm.com, mark.rutland@arm.com, ard.biesheuvel@linaro.org, stable@vger.kernel.org From: Paolo Bonzini Message-ID: <07ccec83-8dbb-9d3a-e7f0-fef445d581a8@redhat.com> Date: Wed, 15 Mar 2017 14:29:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <20170315091755.GL1277@cbox> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Wed, 15 Mar 2017 13:29:12 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1462 Lines: 48 On 15/03/2017 10:17, Christoffer Dall wrote: > On Tue, Mar 14, 2017 at 02:52:32PM +0000, Suzuki K Poulose wrote: >> From: Marc Zyngier >> >> We don't hold the mmap_sem while searching for the VMAs when >> we try to unmap each memslot for a VM. Fix this properly to >> avoid unexpected results. >> >> Fixes: commit 957db105c997 ("arm/arm64: KVM: Introduce stage2_unmap_vm") >> Cc: stable@vger.kernel.org # v3.19+ >> Cc: Christoffer Dall >> Signed-off-by: Marc Zyngier >> Signed-off-by: Suzuki K Poulose >> --- >> arch/arm/kvm/mmu.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c >> index 962616f..f2e2e0c 100644 >> --- a/arch/arm/kvm/mmu.c >> +++ b/arch/arm/kvm/mmu.c >> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm) >> int idx; >> >> idx = srcu_read_lock(&kvm->srcu); >> + down_read(¤t->mm->mmap_sem); >> spin_lock(&kvm->mmu_lock); >> >> slots = kvm_memslots(kvm); >> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm) >> stage2_unmap_memslot(kvm, memslot); >> >> spin_unlock(&kvm->mmu_lock); >> + up_read(¤t->mm->mmap_sem); >> srcu_read_unlock(&kvm->srcu, idx); >> } >> >> -- >> 2.7.4 >> > > Are we sure that holding mmu_lock is valid while holding the mmap_sem? Sure, spinlock-inside-semaphore and spinlock-inside-mutex is always okay. Paolo