github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-06-04 12:35:52 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

KVM: SVM: Refuse to attempt VRMUN if an SEV-ES+ guest has an invalid VMSA

Browse Source 
Explicitly reject KVM_RUN with KVM_EXIT_FAIL_ENTRY if userspace "coerces"
KVM into running an SEV-ES+ guest with an invalid VMSA, e.g. by modifying
a vCPU's mp_state to be RUNNABLE after an SNP vCPU has undergone a Destroy
event.  On Destroy or failed Create, KVM marks the vCPU HALTED so that
*KVM* doesn't run the vCPU, but nothing prevents a misbehaving VMM from
manually making the vCPU RUNNABLE via KVM_SET_MP_STATE.

Attempting VMRUN with an invalid VMSA should be harmless, but knowingly
executing VMRUN with bad control state is at best dodgy.

Fixes: e366f92ea9 ("KVM: SEV: Support SEV-SNP AP Creation NAE event")
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Link: https://lore.kernel.org/r/20250227012541.3234589-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2025-02-26 17:25:34 -08:00
parent d4b69c3d14
commit 72d12715ed
3 changed files with 23 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
arch/x86/kvm/svm/sev.c
View File

@ -3451,10 +3451,19 @@ void sev_es_unmap_ghcb(struct vcpu_svm *svm)
svm->sev_es.ghcb = NULL;
}
void pre_sev_run(struct vcpu_svm *svm, int cpu)
int pre_sev_run(struct vcpu_svm *svm, int cpu)
{
struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, cpu);
unsigned int asid = sev_get_asid(svm->vcpu.kvm);
struct kvm *kvm = svm->vcpu.kvm;
unsigned int asid = sev_get_asid(kvm);
/*
* Reject KVM_RUN if userspace attempts to run the vCPU with an invalid
* VMSA, e.g. if userspace forces the vCPU to be RUNNABLE after an SNP
* AP Destroy event.
*/
if (sev_es_guest(kvm) && !VALID_PAGE(svm->vmcb->control.vmsa_pa))
return -EINVAL;
/* Assign the asid allocated with this SEV guest */
svm->asid = asid;
@ -3467,11 +3476,12 @@ void pre_sev_run(struct vcpu_svm *svm, int cpu)
*/
if (sd->sev_vmcbs[asid] == svm->vmcb &&
svm->vcpu.arch.last_vmentry_cpu == cpu)
return;
return 0;
sd->sev_vmcbs[asid] = svm->vmcb;
svm->vmcb->control.tlb_ctl = TLB_CONTROL_FLUSH_ASID;
vmcb_mark_dirty(svm->vmcb, VMCB_ASID);
return 0;
}
#define GHCB_SCRATCH_AREA_LIMIT (16ULL * PAGE_SIZE)

11
arch/x86/kvm/svm/svm.c
View File

@ -3599,7 +3599,7 @@ static int svm_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
return svm_invoke_exit_handler(vcpu, exit_code);
}
static void pre_svm_run(struct kvm_vcpu *vcpu)
static int pre_svm_run(struct kvm_vcpu *vcpu)
{
struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, vcpu->cpu);
struct vcpu_svm *svm = to_svm(vcpu);
@ -3621,6 +3621,8 @@ static void pre_svm_run(struct kvm_vcpu *vcpu)
/* FIXME: handle wraparound of asid_generation */
if (svm->current_vmcb->asid_generation != sd->asid_generation)
new_asid(svm, sd);
return 0;
}
static void svm_inject_nmi(struct kvm_vcpu *vcpu)
@ -4243,7 +4245,12 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu,
if (force_immediate_exit)
smp_send_reschedule(vcpu->cpu);
pre_svm_run(vcpu);
if (pre_svm_run(vcpu)) {
vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
vcpu->run->fail_entry.hardware_entry_failure_reason = SVM_EXIT_ERR;
vcpu->run->fail_entry.cpu = vcpu->cpu;
return EXIT_FASTPATH_EXIT_USERSPACE;
}
sync_lapic_to_cr8(vcpu);

2
arch/x86/kvm/svm/svm.h
View File

@ -742,7 +742,7 @@ void avic_refresh_virtual_apic_mode(struct kvm_vcpu *vcpu);
/* sev.c */
void pre_sev_run(struct vcpu_svm *svm, int cpu);
int pre_sev_run(struct vcpu_svm *svm, int cpu);
void sev_init_vmcb(struct vcpu_svm *svm);
void sev_vcpu_after_set_cpuid(struct vcpu_svm *svm);
int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in);