Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756184Ab3DVIz7 (ORCPT ); Mon, 22 Apr 2013 04:55:59 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:39470 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753244Ab3DVIz6 (ORCPT ); Mon, 22 Apr 2013 04:55:58 -0400 Date: Mon, 22 Apr 2013 09:55:51 +0100 From: Luis Henriques To: Ben Hutchings Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com, Andrew Honig , Marcelo Tosatti Subject: Re: [PATCH 35/72] KVM: x86: Convert MSR_KVM_SYSTEM_TIME to use gfn_to_hva_cache functions (CVE-2013-1797) Message-ID: <20130422085551.GD3222@hercules> References: <1366276617-3553-1-git-send-email-luis.henriques@canonical.com> <1366276617-3553-36-git-send-email-luis.henriques@canonical.com> <1366602889.3408.144.camel@deadeye.wl.decadent.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1366602889.3408.144.camel@deadeye.wl.decadent.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6163 Lines: 178 On Mon, Apr 22, 2013 at 04:54:49AM +0100, Ben Hutchings wrote: > On Thu, 2013-04-18 at 10:16 +0100, Luis Henriques wrote: > > 3.5.7.11 -stable review patch. If anyone has any objections, please let me know. > > > > ------------------ > > > > From: Andy Honig > > > > commit 0b79459b482e85cb7426aa7da683a9f2c97aeae1 upstream. > > > > There is a potential use after free issue with the handling of > > MSR_KVM_SYSTEM_TIME. If the guest specifies a GPA in a movable or removable > > memory such as frame buffers then KVM might continue to write to that > > address even after it's removed via KVM_SET_USER_MEMORY_REGION. KVM pins > > the page in memory so it's unlikely to cause an issue, but if the user > > space component re-purposes the memory previously used for the guest, then > > the guest will be able to corrupt that memory. > > > > Tested: Tested against kvmclock unit test > > > > Signed-off-by: Andrew Honig > > Signed-off-by: Marcelo Tosatti > > [ luis: backported to 3.5: > > - Adjust context > > - Removed references to PVCLOCK_GUEST_STOPPED ] > > Signed-off-by: Luis Henriques > > This apparently needs to be followed by commit 8f964525a121 'KVM: Allow > cross page reads and writes from cached translations.', as some guests > don't follow the rules. Thanks Ben, I'll add it to the queue. Cheers, -- Luis > > Ben. > > > --- > > arch/x86/include/asm/kvm_host.h | 4 ++-- > > arch/x86/kvm/x86.c | 40 +++++++++++++++------------------------- > > 2 files changed, 17 insertions(+), 27 deletions(-) > > > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > > index db7c1f2..9a50912 100644 > > --- a/arch/x86/include/asm/kvm_host.h > > +++ b/arch/x86/include/asm/kvm_host.h > > @@ -410,8 +410,8 @@ struct kvm_vcpu_arch { > > gpa_t time; > > struct pvclock_vcpu_time_info hv_clock; > > unsigned int hw_tsc_khz; > > - unsigned int time_offset; > > - struct page *time_page; > > + struct gfn_to_hva_cache pv_time; > > + bool pv_time_enabled; > > > > struct { > > u64 msr_val; > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index ad5cf4b..5b4ac78 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -1118,7 +1118,6 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) > > { > > unsigned long flags; > > struct kvm_vcpu_arch *vcpu = &v->arch; > > - void *shared_kaddr; > > unsigned long this_tsc_khz; > > s64 kernel_ns, max_kernel_ns; > > u64 tsc_timestamp; > > @@ -1154,7 +1153,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) > > > > local_irq_restore(flags); > > > > - if (!vcpu->time_page) > > + if (!vcpu->pv_time_enabled) > > return 0; > > > > /* > > @@ -1212,14 +1211,9 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) > > */ > > vcpu->hv_clock.version += 2; > > > > - shared_kaddr = kmap_atomic(vcpu->time_page); > > - > > - memcpy(shared_kaddr + vcpu->time_offset, &vcpu->hv_clock, > > - sizeof(vcpu->hv_clock)); > > - > > - kunmap_atomic(shared_kaddr); > > - > > - mark_page_dirty(v->kvm, vcpu->time >> PAGE_SHIFT); > > + kvm_write_guest_cached(v->kvm, &vcpu->pv_time, > > + &vcpu->hv_clock, > > + sizeof(vcpu->hv_clock)); > > return 0; > > } > > > > @@ -1508,10 +1502,7 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data) > > > > static void kvmclock_reset(struct kvm_vcpu *vcpu) > > { > > - if (vcpu->arch.time_page) { > > - kvm_release_page_dirty(vcpu->arch.time_page); > > - vcpu->arch.time_page = NULL; > > - } > > + vcpu->arch.pv_time_enabled = false; > > } > > > > static void accumulate_steal_time(struct kvm_vcpu *vcpu) > > @@ -1606,6 +1597,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) > > break; > > case MSR_KVM_SYSTEM_TIME_NEW: > > case MSR_KVM_SYSTEM_TIME: { > > + u64 gpa_offset; > > kvmclock_reset(vcpu); > > > > vcpu->arch.time = data; > > @@ -1615,21 +1607,18 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) > > if (!(data & 1)) > > break; > > > > - /* ...but clean it before doing the actual write */ > > - vcpu->arch.time_offset = data & ~(PAGE_MASK | 1); > > + gpa_offset = data & ~(PAGE_MASK | 1); > > > > /* Check that the address is 32-byte aligned. */ > > - if (vcpu->arch.time_offset & > > - (sizeof(struct pvclock_vcpu_time_info) - 1)) > > + if (gpa_offset & (sizeof(struct pvclock_vcpu_time_info) - 1)) > > break; > > > > - vcpu->arch.time_page = > > - gfn_to_page(vcpu->kvm, data >> PAGE_SHIFT); > > + if (kvm_gfn_to_hva_cache_init(vcpu->kvm, > > + &vcpu->arch.pv_time, data & ~1ULL)) > > + vcpu->arch.pv_time_enabled = false; > > + else > > + vcpu->arch.pv_time_enabled = true; > > > > - if (is_error_page(vcpu->arch.time_page)) { > > - kvm_release_page_clean(vcpu->arch.time_page); > > - vcpu->arch.time_page = NULL; > > - } > > break; > > } > > case MSR_KVM_ASYNC_PF_EN: > > @@ -2616,7 +2605,7 @@ static int kvm_vcpu_ioctl_x86_set_xcrs(struct kvm_vcpu *vcpu, > > static int kvm_set_guest_paused(struct kvm_vcpu *vcpu) > > { > > struct pvclock_vcpu_time_info *src = &vcpu->arch.hv_clock; > > - if (!vcpu->arch.time_page) > > + if (!vcpu->arch.pv_time_enabled) > > return -EINVAL; > > src->flags |= PVCLOCK_GUEST_STOPPED; > > mark_page_dirty(vcpu->kvm, vcpu->arch.time >> PAGE_SHIFT); > > @@ -6216,6 +6205,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu) > > if (!zalloc_cpumask_var(&vcpu->arch.wbinvd_dirty_mask, GFP_KERNEL)) > > goto fail_free_mce_banks; > > > > + vcpu->arch.pv_time_enabled = false; > > kvm_async_pf_hash_reset(vcpu); > > kvm_pmu_init(vcpu); > > > > -- > Ben Hutchings > Klipstein's 4th Law of Prototyping and Production: > A fail-safe circuit will destroy others. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/