| Message ID | 20211011143702.1786568-8-eesposit@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: nSVM: avoid TOC/TOU race when checking vmcb12 | expand |
On 11/10/21 16:37, Emanuele Giuseppe Esposito wrote: > ZE)) > return -EFAULT; > - if (copy_to_user(&user_vmcb->control, &svm->nested.ctl, > + nested_copy_vmcb_cache_to_control(&ctl_temp, &svm->nested.ctl); > + if (copy_to_user(&user_vmcb->control, &ctl_temp, > sizeof(user_vmcb->control))) > return -EFAULT; This needs a memset of ctl_temp so that kernel memory contents are not leaked to userspace. However, it's also better to avoid large structs on the stack, and do a quick kzalloc/kfree instead: - nested_copy_vmcb_cache_to_control(&ctl_temp, &svm->nested.ctl); - if (copy_to_user(&user_vmcb->control, &ctl_temp, - sizeof(user_vmcb->control))) + + ctl = kzalloc(sizeof(*ctl), GFP_KERNEL); + if (!ctl) + return -ENOMEM; + nested_copy_vmcb_cache_to_control(ctl, &svm->nested.ctl); + r = copy_to_user(&user_vmcb->control, ctl, + sizeof(user_vmcb->control)); + kfree(ctl); + if (r) return -EFAULT; I can do this change when committing too. Paolo
On Mon, 2021-10-11 at 10:37 -0400, Emanuele Giuseppe Esposito wrote: > This requires changing all vmcb_is_intercept(&svm->nested.ctl, ...) > calls with vmcb12_is_intercept(). > > In addition, in svm_get_nested_state() user space expects a > vmcb_control_area struct, so we need to copy back all fields > in a temporary structure to provide to the user space. > > Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> > --- > arch/x86/kvm/svm/nested.c | 41 +++++++++++++++++++++++---------------- > arch/x86/kvm/svm/svm.c | 4 ++-- > arch/x86/kvm/svm/svm.h | 8 ++++---- > 3 files changed, 30 insertions(+), 23 deletions(-) > > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c > index c84cded1dcf6..13be1002ad1c 100644 > --- a/arch/x86/kvm/svm/nested.c > +++ b/arch/x86/kvm/svm/nested.c > @@ -58,8 +58,9 @@ static void svm_inject_page_fault_nested(struct kvm_vcpu *vcpu, struct x86_excep > struct vcpu_svm *svm = to_svm(vcpu); > WARN_ON(!is_guest_mode(vcpu)); > > - if (vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_EXCEPTION_OFFSET + PF_VECTOR) && > - !svm->nested.nested_run_pending) { > + if (vmcb12_is_intercept(&svm->nested.ctl, > + INTERCEPT_EXCEPTION_OFFSET + PF_VECTOR) && > + !svm->nested.nested_run_pending) { > svm->vmcb->control.exit_code = SVM_EXIT_EXCP_BASE + PF_VECTOR; > svm->vmcb->control.exit_code_hi = 0; > svm->vmcb->control.exit_info_1 = fault->error_code; > @@ -121,7 +122,8 @@ static void nested_svm_uninit_mmu_context(struct kvm_vcpu *vcpu) > > void recalc_intercepts(struct vcpu_svm *svm) > { > - struct vmcb_control_area *c, *h, *g; > + struct vmcb_control_area *c, *h; > + struct vmcb_ctrl_area_cached *g; > unsigned int i; > > vmcb_mark_dirty(svm->vmcb, VMCB_INTERCEPTS); > @@ -172,7 +174,7 @@ static bool nested_svm_vmrun_msrpm(struct vcpu_svm *svm) > */ > int i; > > - if (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT))) > + if (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT))) > return true; > > for (i = 0; i < MSRPM_OFFSETS; i++) { > @@ -208,9 +210,9 @@ static bool nested_svm_check_bitmap_pa(struct kvm_vcpu *vcpu, u64 pa, u32 size) > } > > static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu, > - struct vmcb_control_area *control) > + struct vmcb_ctrl_area_cached *control) > { > - if (CC(!vmcb_is_intercept(control, INTERCEPT_VMRUN))) > + if (CC(!vmcb12_is_intercept(control, INTERCEPT_VMRUN))) > return false; > > if (CC(control->asid == 0)) > @@ -960,7 +962,7 @@ static int nested_svm_exit_handled_msr(struct vcpu_svm *svm) > u32 offset, msr, value; > int write, mask; > > - if (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT))) > + if (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT))) > return NESTED_EXIT_HOST; > > msr = svm->vcpu.arch.regs[VCPU_REGS_RCX]; > @@ -987,7 +989,7 @@ static int nested_svm_intercept_ioio(struct vcpu_svm *svm) > u8 start_bit; > u64 gpa; > > - if (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_IOIO_PROT))) > + if (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_IOIO_PROT))) > return NESTED_EXIT_HOST; > > port = svm->vmcb->control.exit_info_1 >> 16; > @@ -1018,12 +1020,12 @@ static int nested_svm_intercept(struct vcpu_svm *svm) > vmexit = nested_svm_intercept_ioio(svm); > break; > case SVM_EXIT_READ_CR0 ... SVM_EXIT_WRITE_CR8: { > - if (vmcb_is_intercept(&svm->nested.ctl, exit_code)) > + if (vmcb12_is_intercept(&svm->nested.ctl, exit_code)) > vmexit = NESTED_EXIT_DONE; > break; > } > case SVM_EXIT_READ_DR0 ... SVM_EXIT_WRITE_DR7: { > - if (vmcb_is_intercept(&svm->nested.ctl, exit_code)) > + if (vmcb12_is_intercept(&svm->nested.ctl, exit_code)) > vmexit = NESTED_EXIT_DONE; > break; > } > @@ -1041,7 +1043,7 @@ static int nested_svm_intercept(struct vcpu_svm *svm) > break; > } > default: { > - if (vmcb_is_intercept(&svm->nested.ctl, exit_code)) > + if (vmcb12_is_intercept(&svm->nested.ctl, exit_code)) > vmexit = NESTED_EXIT_DONE; > } > } > @@ -1119,7 +1121,7 @@ static void nested_svm_inject_exception_vmexit(struct vcpu_svm *svm) > > static inline bool nested_exit_on_init(struct vcpu_svm *svm) > { > - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_INIT); > + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_INIT); > } > > static int svm_check_nested_events(struct kvm_vcpu *vcpu) > @@ -1250,6 +1252,7 @@ static int svm_get_nested_state(struct kvm_vcpu *vcpu, > u32 user_data_size) > { > struct vcpu_svm *svm; > + struct vmcb_control_area ctl_temp; > struct kvm_nested_state kvm_state = { > .flags = 0, > .format = KVM_STATE_NESTED_FORMAT_SVM, > @@ -1291,7 +1294,8 @@ static int svm_get_nested_state(struct kvm_vcpu *vcpu, > */ > if (clear_user(user_vmcb, KVM_STATE_NESTED_SVM_VMCB_SIZE)) > return -EFAULT; > - if (copy_to_user(&user_vmcb->control, &svm->nested.ctl, > + nested_copy_vmcb_cache_to_control(&ctl_temp, &svm->nested.ctl); > + if (copy_to_user(&user_vmcb->control, &ctl_temp, > sizeof(user_vmcb->control))) > return -EFAULT; > if (copy_to_user(&user_vmcb->save, &svm->vmcb01.ptr->save, > @@ -1362,8 +1366,9 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, > goto out_free; > > ret = -EINVAL; > - if (!nested_vmcb_check_controls(vcpu, ctl)) > - goto out_free; > + nested_copy_vmcb_control_to_cache(svm, ctl); > + if (!nested_vmcb_check_controls(vcpu, &svm->nested.ctl)) > + goto out_free_ctl; I also don't like this, like about writing and clearing of svm->nested.save in patch 4. Unlike the former case, this case is functionally correct, but still a failure will leave partially initialized state (which you zero at the end to make it better, but it is best that failure would leave the state untouched). Since loading/saving the nested state is anything but performance critical code, I would prefer to also copy control area to a temp variable, and then pass it to __nested_vmcb_check_controls. Other than that, this patch looks good. Best regards, Maxim Levitsky > > /* > * Processor state contains L2 state. Check that it is > @@ -1371,7 +1376,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, > */ > cr0 = kvm_read_cr0(vcpu); > if (((cr0 & X86_CR0_CD) == 0) && (cr0 & X86_CR0_NW)) > - goto out_free; > + goto out_free_ctl; > > /* > * Validate host state saved from before VMRUN (see > @@ -1417,7 +1422,6 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, > svm->nested.vmcb12_gpa = kvm_state->hdr.svm.vmcb_pa; > > svm_copy_vmrun_state(&svm->vmcb01.ptr->save, save); > - nested_copy_vmcb_control_to_cache(svm, ctl); > > svm_switch_vmcb(svm, &svm->nested.vmcb02); > nested_vmcb02_prepare_control(svm); > @@ -1427,6 +1431,9 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, > out_free_save: > memset(&svm->nested.save, 0, sizeof(struct vmcb_save_area_cached)); > > +out_free_ctl: > + memset(&svm->nested.ctl, 0, sizeof(struct vmcb_ctrl_area_cached)); > + > out_free: > kfree(save); > kfree(ctl); > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 1b6d25c6e0ae..d866eea39777 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -2465,7 +2465,7 @@ static bool check_selective_cr0_intercepted(struct kvm_vcpu *vcpu, > bool ret = false; > > if (!is_guest_mode(vcpu) || > - (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_SELECTIVE_CR0)))) > + (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_SELECTIVE_CR0)))) > return false; > > cr0 &= ~SVM_CR0_SELECTIVE_MASK; > @@ -4184,7 +4184,7 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu, > info->intercept == x86_intercept_clts) > break; > > - if (!(vmcb_is_intercept(&svm->nested.ctl, > + if (!(vmcb12_is_intercept(&svm->nested.ctl, > INTERCEPT_SELECTIVE_CR0))) > break; > > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h > index 78006245e334..051b7d0a13a1 100644 > --- a/arch/x86/kvm/svm/svm.h > +++ b/arch/x86/kvm/svm/svm.h > @@ -156,7 +156,7 @@ struct svm_nested_state { > bool nested_run_pending; > > /* cache for control fields of the guest */ > - struct vmcb_control_area ctl; > + struct vmcb_ctrl_area_cached ctl; > struct vmcb_save_area_cached save; > > bool initialized; > @@ -491,17 +491,17 @@ static inline bool nested_svm_virtualize_tpr(struct kvm_vcpu *vcpu) > > static inline bool nested_exit_on_smi(struct vcpu_svm *svm) > { > - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_SMI); > + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_SMI); > } > > static inline bool nested_exit_on_intr(struct vcpu_svm *svm) > { > - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_INTR); > + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_INTR); > } > > static inline bool nested_exit_on_nmi(struct vcpu_svm *svm) > { > - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_NMI); > + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_NMI); > } > > int enter_svm_guest_mode(struct kvm_vcpu *vcpu, u64 vmcb_gpa, struct vmcb *vmcb12);
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index c84cded1dcf6..13be1002ad1c 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -58,8 +58,9 @@ static void svm_inject_page_fault_nested(struct kvm_vcpu *vcpu, struct x86_excep struct vcpu_svm *svm = to_svm(vcpu); WARN_ON(!is_guest_mode(vcpu)); - if (vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_EXCEPTION_OFFSET + PF_VECTOR) && - !svm->nested.nested_run_pending) { + if (vmcb12_is_intercept(&svm->nested.ctl, + INTERCEPT_EXCEPTION_OFFSET + PF_VECTOR) && + !svm->nested.nested_run_pending) { svm->vmcb->control.exit_code = SVM_EXIT_EXCP_BASE + PF_VECTOR; svm->vmcb->control.exit_code_hi = 0; svm->vmcb->control.exit_info_1 = fault->error_code; @@ -121,7 +122,8 @@ static void nested_svm_uninit_mmu_context(struct kvm_vcpu *vcpu) void recalc_intercepts(struct vcpu_svm *svm) { - struct vmcb_control_area *c, *h, *g; + struct vmcb_control_area *c, *h; + struct vmcb_ctrl_area_cached *g; unsigned int i; vmcb_mark_dirty(svm->vmcb, VMCB_INTERCEPTS); @@ -172,7 +174,7 @@ static bool nested_svm_vmrun_msrpm(struct vcpu_svm *svm) */ int i; - if (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT))) + if (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT))) return true; for (i = 0; i < MSRPM_OFFSETS; i++) { @@ -208,9 +210,9 @@ static bool nested_svm_check_bitmap_pa(struct kvm_vcpu *vcpu, u64 pa, u32 size) } static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu, - struct vmcb_control_area *control) + struct vmcb_ctrl_area_cached *control) { - if (CC(!vmcb_is_intercept(control, INTERCEPT_VMRUN))) + if (CC(!vmcb12_is_intercept(control, INTERCEPT_VMRUN))) return false; if (CC(control->asid == 0)) @@ -960,7 +962,7 @@ static int nested_svm_exit_handled_msr(struct vcpu_svm *svm) u32 offset, msr, value; int write, mask; - if (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT))) + if (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT))) return NESTED_EXIT_HOST; msr = svm->vcpu.arch.regs[VCPU_REGS_RCX]; @@ -987,7 +989,7 @@ static int nested_svm_intercept_ioio(struct vcpu_svm *svm) u8 start_bit; u64 gpa; - if (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_IOIO_PROT))) + if (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_IOIO_PROT))) return NESTED_EXIT_HOST; port = svm->vmcb->control.exit_info_1 >> 16; @@ -1018,12 +1020,12 @@ static int nested_svm_intercept(struct vcpu_svm *svm) vmexit = nested_svm_intercept_ioio(svm); break; case SVM_EXIT_READ_CR0 ... SVM_EXIT_WRITE_CR8: { - if (vmcb_is_intercept(&svm->nested.ctl, exit_code)) + if (vmcb12_is_intercept(&svm->nested.ctl, exit_code)) vmexit = NESTED_EXIT_DONE; break; } case SVM_EXIT_READ_DR0 ... SVM_EXIT_WRITE_DR7: { - if (vmcb_is_intercept(&svm->nested.ctl, exit_code)) + if (vmcb12_is_intercept(&svm->nested.ctl, exit_code)) vmexit = NESTED_EXIT_DONE; break; } @@ -1041,7 +1043,7 @@ static int nested_svm_intercept(struct vcpu_svm *svm) break; } default: { - if (vmcb_is_intercept(&svm->nested.ctl, exit_code)) + if (vmcb12_is_intercept(&svm->nested.ctl, exit_code)) vmexit = NESTED_EXIT_DONE; } } @@ -1119,7 +1121,7 @@ static void nested_svm_inject_exception_vmexit(struct vcpu_svm *svm) static inline bool nested_exit_on_init(struct vcpu_svm *svm) { - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_INIT); + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_INIT); } static int svm_check_nested_events(struct kvm_vcpu *vcpu) @@ -1250,6 +1252,7 @@ static int svm_get_nested_state(struct kvm_vcpu *vcpu, u32 user_data_size) { struct vcpu_svm *svm; + struct vmcb_control_area ctl_temp; struct kvm_nested_state kvm_state = { .flags = 0, .format = KVM_STATE_NESTED_FORMAT_SVM, @@ -1291,7 +1294,8 @@ static int svm_get_nested_state(struct kvm_vcpu *vcpu, */ if (clear_user(user_vmcb, KVM_STATE_NESTED_SVM_VMCB_SIZE)) return -EFAULT; - if (copy_to_user(&user_vmcb->control, &svm->nested.ctl, + nested_copy_vmcb_cache_to_control(&ctl_temp, &svm->nested.ctl); + if (copy_to_user(&user_vmcb->control, &ctl_temp, sizeof(user_vmcb->control))) return -EFAULT; if (copy_to_user(&user_vmcb->save, &svm->vmcb01.ptr->save, @@ -1362,8 +1366,9 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, goto out_free; ret = -EINVAL; - if (!nested_vmcb_check_controls(vcpu, ctl)) - goto out_free; + nested_copy_vmcb_control_to_cache(svm, ctl); + if (!nested_vmcb_check_controls(vcpu, &svm->nested.ctl)) + goto out_free_ctl; /* * Processor state contains L2 state. Check that it is @@ -1371,7 +1376,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, */ cr0 = kvm_read_cr0(vcpu); if (((cr0 & X86_CR0_CD) == 0) && (cr0 & X86_CR0_NW)) - goto out_free; + goto out_free_ctl; /* * Validate host state saved from before VMRUN (see @@ -1417,7 +1422,6 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, svm->nested.vmcb12_gpa = kvm_state->hdr.svm.vmcb_pa; svm_copy_vmrun_state(&svm->vmcb01.ptr->save, save); - nested_copy_vmcb_control_to_cache(svm, ctl); svm_switch_vmcb(svm, &svm->nested.vmcb02); nested_vmcb02_prepare_control(svm); @@ -1427,6 +1431,9 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, out_free_save: memset(&svm->nested.save, 0, sizeof(struct vmcb_save_area_cached)); +out_free_ctl: + memset(&svm->nested.ctl, 0, sizeof(struct vmcb_ctrl_area_cached)); + out_free: kfree(save); kfree(ctl); diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 1b6d25c6e0ae..d866eea39777 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -2465,7 +2465,7 @@ static bool check_selective_cr0_intercepted(struct kvm_vcpu *vcpu, bool ret = false; if (!is_guest_mode(vcpu) || - (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_SELECTIVE_CR0)))) + (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_SELECTIVE_CR0)))) return false; cr0 &= ~SVM_CR0_SELECTIVE_MASK; @@ -4184,7 +4184,7 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu, info->intercept == x86_intercept_clts) break; - if (!(vmcb_is_intercept(&svm->nested.ctl, + if (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_SELECTIVE_CR0))) break; diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index 78006245e334..051b7d0a13a1 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -156,7 +156,7 @@ struct svm_nested_state { bool nested_run_pending; /* cache for control fields of the guest */ - struct vmcb_control_area ctl; + struct vmcb_ctrl_area_cached ctl; struct vmcb_save_area_cached save; bool initialized; @@ -491,17 +491,17 @@ static inline bool nested_svm_virtualize_tpr(struct kvm_vcpu *vcpu) static inline bool nested_exit_on_smi(struct vcpu_svm *svm) { - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_SMI); + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_SMI); } static inline bool nested_exit_on_intr(struct vcpu_svm *svm) { - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_INTR); + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_INTR); } static inline bool nested_exit_on_nmi(struct vcpu_svm *svm) { - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_NMI); + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_NMI); } int enter_svm_guest_mode(struct kvm_vcpu *vcpu, u64 vmcb_gpa, struct vmcb *vmcb12);
This requires changing all vmcb_is_intercept(&svm->nested.ctl, ...) calls with vmcb12_is_intercept(). In addition, in svm_get_nested_state() user space expects a vmcb_control_area struct, so we need to copy back all fields in a temporary structure to provide to the user space. Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> --- arch/x86/kvm/svm/nested.c | 41 +++++++++++++++++++++++---------------- arch/x86/kvm/svm/svm.c | 4 ++-- arch/x86/kvm/svm/svm.h | 8 ++++---- 3 files changed, 30 insertions(+), 23 deletions(-)