3.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Andy Honig <[email protected]> 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 <[email protected]> Signed-off-by: Marcelo Tosatti <[email protected]> Cc: Ben Hutchings <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/x86/include/asm/kvm_host.h | 4 ++-- arch/x86/kvm/x86.c | 39 ++++++++++++++------------------------- 2 files changed, 16 insertions(+), 27 deletions(-) --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -407,8 +407,8 @@ 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 @@ -1114,7 +1114,6 @@ 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; @@ -1150,7 +1149,7 @@ static int kvm_guest_time_update(struct local_irq_restore(flags); - if (!vcpu->time_page) + if (!vcpu->pv_time_enabled) return 0; /* @@ -1208,14 +1207,9 @@ static int kvm_guest_time_update(struct */ 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; } @@ -1504,10 +1498,7 @@ 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) @@ -1602,6 +1593,7 @@ 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; @@ -1611,21 +1603,17 @@ 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: @@ -6172,6 +6160,7 @@ 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); kvm_pmu_init(vcpu); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
