From: Marc Zyngier maz@kernel.org
commit ef3e40a7ea8dbe2abd0a345032cd7d5023b9684f upstream.
When using the PtrAuth feature in a guest, we need to save the host's keys before allowing the guest to program them. For that, we dump them in a per-CPU data structure (the so called host context).
But both call sites that do this are in preemptible context, which may end up in disaster should the vcpu thread get preempted before reentering the guest.
Instead, save the keys eagerly on each vcpu_load(). This has an increased overhead, but is at least safe.
Cc: stable@vger.kernel.org Reviewed-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Marc Zyngier maz@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/include/asm/kvm_emulate.h | 6 ------ arch/arm64/kvm/handle_exit.c | 19 ++----------------- virt/kvm/arm/arm.c | 18 +++++++++++++++++- 3 files changed, 19 insertions(+), 24 deletions(-)
--- a/arch/arm64/include/asm/kvm_emulate.h +++ b/arch/arm64/include/asm/kvm_emulate.h @@ -112,12 +112,6 @@ static inline void vcpu_ptrauth_disable( vcpu->arch.hcr_el2 &= ~(HCR_API | HCR_APK); }
-static inline void vcpu_ptrauth_setup_lazy(struct kvm_vcpu *vcpu) -{ - if (vcpu_has_ptrauth(vcpu)) - vcpu_ptrauth_disable(vcpu); -} - static inline unsigned long vcpu_get_vsesr(struct kvm_vcpu *vcpu) { return vcpu->arch.vsesr_el2; --- a/arch/arm64/kvm/handle_exit.c +++ b/arch/arm64/kvm/handle_exit.c @@ -162,31 +162,16 @@ static int handle_sve(struct kvm_vcpu *v return 1; }
-#define __ptrauth_save_key(regs, key) \ -({ \ - regs[key ## KEYLO_EL1] = read_sysreg_s(SYS_ ## key ## KEYLO_EL1); \ - regs[key ## KEYHI_EL1] = read_sysreg_s(SYS_ ## key ## KEYHI_EL1); \ -}) - /* * Handle the guest trying to use a ptrauth instruction, or trying to access a * ptrauth register. */ void kvm_arm_vcpu_ptrauth_trap(struct kvm_vcpu *vcpu) { - struct kvm_cpu_context *ctxt; - - if (vcpu_has_ptrauth(vcpu)) { + if (vcpu_has_ptrauth(vcpu)) vcpu_ptrauth_enable(vcpu); - ctxt = vcpu->arch.host_cpu_context; - __ptrauth_save_key(ctxt->sys_regs, APIA); - __ptrauth_save_key(ctxt->sys_regs, APIB); - __ptrauth_save_key(ctxt->sys_regs, APDA); - __ptrauth_save_key(ctxt->sys_regs, APDB); - __ptrauth_save_key(ctxt->sys_regs, APGA); - } else { + else kvm_inject_undefined(vcpu); - } }
/* --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -332,6 +332,12 @@ void kvm_arch_vcpu_unblocking(struct kvm preempt_enable(); }
+#define __ptrauth_save_key(regs, key) \ +({ \ + regs[key ## KEYLO_EL1] = read_sysreg_s(SYS_ ## key ## KEYLO_EL1); \ + regs[key ## KEYHI_EL1] = read_sysreg_s(SYS_ ## key ## KEYHI_EL1); \ +}) + void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) { int *last_ran; @@ -365,7 +371,17 @@ void kvm_arch_vcpu_load(struct kvm_vcpu else vcpu_set_wfx_traps(vcpu);
- vcpu_ptrauth_setup_lazy(vcpu); + if (vcpu_has_ptrauth(vcpu)) { + struct kvm_cpu_context *ctxt = vcpu->arch.host_cpu_context; + + __ptrauth_save_key(ctxt->sys_regs, APIA); + __ptrauth_save_key(ctxt->sys_regs, APIB); + __ptrauth_save_key(ctxt->sys_regs, APDA); + __ptrauth_save_key(ctxt->sys_regs, APDB); + __ptrauth_save_key(ctxt->sys_regs, APGA); + + vcpu_ptrauth_disable(vcpu); + } }
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)