This changes the allocation of cached_vmcs12 to use kzalloc instead of kmalloc. This removes the information leak found by Syzkaller (see Reported-by) in this case and prevents similar leaks from happening based on cached_vmcs12. It also changes vmx_get_nested_state to copy out the full 4k VMCS12_SIZE in copy_to_user rather than only the size of the struct. Tested: rebuilt against head, booted, and ran the syszkaller repro https://syzkaller.appspot.com/text?tag=ReproC&x=174efca3400000 without observing any problems. Reported-by: syzbot+ded1696f6b50b615b630@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Tom Roeder <tmroeder@xxxxxxxxxx> --- Changelog since v1: - Changed the copy_to_user calls in vmx_get_nested_state to copy the full 4k buffer. arch/x86/kvm/vmx/nested.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 2616bd2c7f2c7..ce81539238547 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -4140,11 +4140,11 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu) if (r < 0) goto out_vmcs02; - vmx->nested.cached_vmcs12 = kmalloc(VMCS12_SIZE, GFP_KERNEL); + vmx->nested.cached_vmcs12 = kzalloc(VMCS12_SIZE, GFP_KERNEL); if (!vmx->nested.cached_vmcs12) goto out_cached_vmcs12; - vmx->nested.cached_shadow_vmcs12 = kmalloc(VMCS12_SIZE, GFP_KERNEL); + vmx->nested.cached_shadow_vmcs12 = kzalloc(VMCS12_SIZE, GFP_KERNEL); if (!vmx->nested.cached_shadow_vmcs12) goto out_cached_shadow_vmcs12; @@ -5263,13 +5263,17 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu, copy_shadow_to_vmcs12(vmx); } - if (copy_to_user(user_kvm_nested_state->data, vmcs12, sizeof(*vmcs12))) + /* + * Copy over the full allocated size of vmcs12 rather than just the size + * of the struct. + */ + if (copy_to_user(user_kvm_nested_state->data, vmcs12, VMCS12_SIZE)) return -EFAULT; if (nested_cpu_has_shadow_vmcs(vmcs12) && vmcs12->vmcs_link_pointer != -1ull) { if (copy_to_user(user_kvm_nested_state->data + VMCS12_SIZE, - get_shadow_vmcs12(vcpu), sizeof(*vmcs12))) + get_shadow_vmcs12(vcpu), VMCS12_SIZE)) return -EFAULT; } -- 2.20.1.321.g9e740568ce-goog
