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KVM: arm64: Inject exception on out-of-IPA-range translation fault

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When taking a translation fault for an IPA that is outside of
the range defined by the hypervisor (between the HW PARange and
the IPA range), we stupidly treat it as an IO and forward the access
to userspace. Of course, userspace can't do much with it, and things
end badly.

Arguably, the guest is braindead, but we should at least catch the
case and inject an exception.

Check the faulting IPA against:
- the sanitised PARange: inject an address size fault
- the IPA size: inject an abort

Reported-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2022-04-21 15:38:10 +01:00
parent 8f6379e207
commit 85ea6b1ec9
3 changed files with 48 additions and 0 deletions
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1
arch/arm64/include/asm/kvm_emulate.h
View file

@ -40,6 +40,7 @@ void kvm_inject_undefined(struct kvm_vcpu *vcpu);
void kvm_inject_vabt(struct kvm_vcpu *vcpu);
void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr);
void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);
void kvm_inject_size_fault(struct kvm_vcpu *vcpu);
void kvm_vcpu_wfi(struct kvm_vcpu *vcpu);

28
arch/arm64/kvm/inject_fault.c
View file

@ -145,6 +145,34 @@ void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr)
inject_abt64(vcpu, true, addr);
}
void kvm_inject_size_fault(struct kvm_vcpu *vcpu)
{
unsigned long addr, esr;
addr = kvm_vcpu_get_fault_ipa(vcpu);
addr |= kvm_vcpu_get_hfar(vcpu) & GENMASK(11, 0);
if (kvm_vcpu_trap_is_iabt(vcpu))
kvm_inject_pabt(vcpu, addr);
else
kvm_inject_dabt(vcpu, addr);
/*
* If AArch64 or LPAE, set FSC to 0 to indicate an Address
* Size Fault at level 0, as if exceeding PARange.
*
* Non-LPAE guests will only get the external abort, as there
* is no way to to describe the ASF.
*/
if (vcpu_el1_is_32bit(vcpu) &&
!(vcpu_read_sys_reg(vcpu, TCR_EL1) & TTBCR_EAE))
return;
esr = vcpu_read_sys_reg(vcpu, ESR_EL1);
esr &= ~GENMASK_ULL(5, 0);
vcpu_write_sys_reg(vcpu, esr, ESR_EL1);
}
/**
* kvm_inject_undefined - inject an undefined instruction into the guest
* @vcpu: The vCPU in which to inject the exception

19
arch/arm64/kvm/mmu.c
View file

@ -1337,6 +1337,25 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
is_iabt = kvm_vcpu_trap_is_iabt(vcpu);
if (fault_status == FSC_FAULT) {
/* Beyond sanitised PARange (which is the IPA limit) */
if (fault_ipa >= BIT_ULL(get_kvm_ipa_limit())) {
kvm_inject_size_fault(vcpu);
return 1;
}
/* Falls between the IPA range and the PARange? */
if (fault_ipa >= BIT_ULL(vcpu->arch.hw_mmu->pgt->ia_bits)) {
fault_ipa |= kvm_vcpu_get_hfar(vcpu) & GENMASK(11, 0);
if (is_iabt)
kvm_inject_pabt(vcpu, fault_ipa);
else
kvm_inject_dabt(vcpu, fault_ipa);
return 1;
}
}
/* Synchronous External Abort? */
if (kvm_vcpu_abt_issea(vcpu)) {
/*