| Message ID | 20210818085047.1005285-4-oupton@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: arm64: Fix some races in CPU_ON PSCI call | expand |
On Wed, 18 Aug 2021 09:50:46 +0100, Oliver Upton <oupton@google.com> wrote: > > Some calls in PSCI take a target affinity argument, defined to be > bit-compatible with the affinity fields in MPIDR_EL1. All other bits in > the parameter are reserved and must be 0. For future reference, it may be worth quoting the spec (ARM DEN 0022D, 5.1.4 "CPU_ON"). > Return INVALID_PARAMETERS if the guest incorrectly sets a reserved > bit. > > Signed-off-by: Oliver Upton <oupton@google.com> > --- > arch/arm64/kvm/psci.c | 20 +++++++++++++++++--- > 1 file changed, 17 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c > index db4056ecccfd..bb76be01abd2 100644 > --- a/arch/arm64/kvm/psci.c > +++ b/arch/arm64/kvm/psci.c > @@ -59,6 +59,17 @@ static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu) > kvm_vcpu_kick(vcpu); > } > > +static inline bool kvm_psci_valid_affinity(struct kvm_vcpu *vcpu, > + unsigned long affinity) > +{ > + unsigned long mask = MPIDR_HWID_BITMASK; > + > + if (vcpu_mode_is_32bit(vcpu)) > + mask &= ~((u32) 0); I don't think we need this anymore since 5.7: - fdc9999e20cd ("KVM: arm64: PSCI: Forbid 64bit functions for 32bit guests") guarantees that the guest can't trick KVM into using the SMC64 functions. - with 2890ac993daa ("KVM: arm64: PSCI: Narrow input registers when using 32bit functions"), the registers are always narrowed down to 32bit Put the two together, and you can't have a 32bit guest issuing a PSCI operation with crap in the upper 32bits. > + > + return !(affinity & ~mask); So the whole helper can now be rewritten as return !(affinity & ~MPIDR_HWID_BITMASK); > +} > + > static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu) > { > struct vcpu_reset_state *reset_state; > @@ -66,9 +77,9 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu) > struct kvm_vcpu *vcpu = NULL; > unsigned long cpu_id; > > - cpu_id = smccc_get_arg1(source_vcpu) & MPIDR_HWID_BITMASK; > - if (vcpu_mode_is_32bit(source_vcpu)) > - cpu_id &= ~((u32) 0); > + cpu_id = smccc_get_arg1(source_vcpu); > + if (!kvm_psci_valid_affinity(source_vcpu, cpu_id)) > + return PSCI_RET_INVALID_PARAMS; > > vcpu = kvm_mpidr_to_vcpu(kvm, cpu_id); > > @@ -126,6 +137,9 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu) > target_affinity = smccc_get_arg1(vcpu); > lowest_affinity_level = smccc_get_arg2(vcpu); > > + if (!kvm_psci_valid_affinity(vcpu, target_affinity)) > + return PSCI_RET_INVALID_PARAMS; > + > /* Determine target affinity mask */ > target_affinity_mask = psci_affinity_mask(lowest_affinity_level); > if (!target_affinity_mask) Otherwise, looks good to me. Thanks, M.
diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c index db4056ecccfd..bb76be01abd2 100644 --- a/arch/arm64/kvm/psci.c +++ b/arch/arm64/kvm/psci.c @@ -59,6 +59,17 @@ static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu) kvm_vcpu_kick(vcpu); } +static inline bool kvm_psci_valid_affinity(struct kvm_vcpu *vcpu, + unsigned long affinity) +{ + unsigned long mask = MPIDR_HWID_BITMASK; + + if (vcpu_mode_is_32bit(vcpu)) + mask &= ~((u32) 0); + + return !(affinity & ~mask); +} + static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu) { struct vcpu_reset_state *reset_state; @@ -66,9 +77,9 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu) struct kvm_vcpu *vcpu = NULL; unsigned long cpu_id; - cpu_id = smccc_get_arg1(source_vcpu) & MPIDR_HWID_BITMASK; - if (vcpu_mode_is_32bit(source_vcpu)) - cpu_id &= ~((u32) 0); + cpu_id = smccc_get_arg1(source_vcpu); + if (!kvm_psci_valid_affinity(source_vcpu, cpu_id)) + return PSCI_RET_INVALID_PARAMS; vcpu = kvm_mpidr_to_vcpu(kvm, cpu_id); @@ -126,6 +137,9 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu) target_affinity = smccc_get_arg1(vcpu); lowest_affinity_level = smccc_get_arg2(vcpu); + if (!kvm_psci_valid_affinity(vcpu, target_affinity)) + return PSCI_RET_INVALID_PARAMS; + /* Determine target affinity mask */ target_affinity_mask = psci_affinity_mask(lowest_affinity_level); if (!target_affinity_mask)
Some calls in PSCI take a target affinity argument, defined to be bit-compatible with the affinity fields in MPIDR_EL1. All other bits in the parameter are reserved and must be 0. Return INVALID_PARAMETERS if the guest incorrectly sets a reserved bit. Signed-off-by: Oliver Upton <oupton@google.com> --- arch/arm64/kvm/psci.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-)