From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 1/3] kvm: arm/arm64: Take mmap_sem in stage2_unmap_vm Date: Wed, 15 Mar 2017 14:29:07 +0100 Message-ID: <07ccec83-8dbb-9d3a-e7f0-fef445d581a8@redhat.com> References: <1489503154-20705-1-git-send-email-suzuki.poulose@arm.com> <1489503154-20705-2-git-send-email-suzuki.poulose@arm.com> <20170315091755.GL1277@cbox> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, ard.biesheuvel@linaro.org, marc.zyngier@arm.com, andreyknvl@google.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, kcc@google.com, syzkaller@googlegroups.com, dvyukov@google.com, catalin.marinas@arm.com, kvmarm@lists.cs.columbia.edu To: Christoffer Dall , Suzuki K Poulose Return-path: In-Reply-To: <20170315091755.GL1277@cbox> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org 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