Brad Spengler pointed out that some KVM security fixes are missing from the 3.2 branches. Three recent commits were marked as such: c300aa64ddf5 KVM: x86: fix for buffer overflow in handling of MSR_KVM_SYSTEM_TIME (CVE-2013-1796) 0b79459b482e KVM: x86: Convert MSR_KVM_SYSTEM_TIME to use gfn_to_hva_cache functions (CVE-2013-1797) a2c118bfab8b KVM: Fix bounds checking in ioapic indirect register reads (CVE-2013-1798) The first and third of these can be cherry-picked cleanly onto 3.2.y, while the second required backporting; I've attached my backported version of that. The result passed the kvmclock unit tests, but the apic unit tests failed on my test system (running Debian unstable): qemu: hardware error: isa irq 16 invalid However this is not a regression and is presumably a bug in QEMU, not the kernel code. All these changes are already present in Debian's 3.2-based kernel package and I don't think we've had any reports of regressions. These fixes are also needed for all other 3.x.y branches, but I haven't tested on other branches. Ben. -- Ben Hutchings The first rule of tautology club is the first rule of tautology club.
From: Andy Honig <ahonig@xxxxxxxxxx>
Date: Wed, 20 Feb 2013 14:48:10 -0800
Subject: KVM: x86: Convert MSR_KVM_SYSTEM_TIME to use gfn_to_hva_cache
functions (CVE-2013-1797)
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 <ahonig@xxxxxxxxxx>
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
[bwh: Backported to 3.2:
- Adjust context
- We do not implement the PVCLOCK_GUEST_STOPPED flag]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 4 ++--
arch/x86/kvm/x86.c | 47 +++++++++++++++++----------------------
2 files changed, 22 insertions(+), 29 deletions(-)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -393,8 +393,8 @@ 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;
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1105,7 +1105,6 @@ static int kvm_guest_time_update(struct
{
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;
@@ -1141,7 +1140,7 @@ static int kvm_guest_time_update(struct
local_irq_restore(flags);
- if (!vcpu->time_page)
+ if (!vcpu->pv_time_enabled)
return 0;
/*
@@ -1199,14 +1198,9 @@ static int kvm_guest_time_update(struct
*/
vcpu->hv_clock.version += 2;
- shared_kaddr = kmap_atomic(vcpu->time_page, KM_USER0);
-
- memcpy(shared_kaddr + vcpu->time_offset, &vcpu->hv_clock,
- sizeof(vcpu->hv_clock));
-
- kunmap_atomic(shared_kaddr, KM_USER0);
-
- 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;
}
@@ -1496,10 +1490,7 @@ static int kvm_pv_enable_async_pf(struct
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)
@@ -1591,6 +1582,7 @@ int kvm_set_msr_common(struct kvm_vcpu *
break;
case MSR_KVM_SYSTEM_TIME_NEW:
case MSR_KVM_SYSTEM_TIME: {
+ u64 gpa_offset;
kvmclock_reset(vcpu);
vcpu->arch.time = data;
@@ -1600,21 +1592,17 @@ int kvm_set_msr_common(struct kvm_vcpu *
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 (is_error_page(vcpu->arch.time_page)) {
- kvm_release_page_clean(vcpu->arch.time_page);
- vcpu->arch.time_page = NULL;
- }
+ 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;
break;
}
case MSR_KVM_ASYNC_PF_EN:
@@ -6559,6 +6547,7 @@ int kvm_arch_vcpu_init(struct kvm_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);
return 0;
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