ACK/CMNT: [PATCH 3/3] arm64: KVM: Sanitize PSTATE.M when being set from userspace

[Tyler Hicks]

On 2019-02-19 14:02:35, Paolo Pisati wrote:
> From: Marc Zyngier <marc.zyngier at arm.com>
> 
> Not all execution modes are valid for a guest, and some of them
> depend on what the HW actually supports. Let's verify that what
> userspace provides is compatible with both the VM settings and
> the HW capabilities.
> 
> Cc: <stable at vger.kernel.org>
> Fixes: 0d854a60b1d7 ("arm64: KVM: enable initialization of a 32bit vcpu")
> Reviewed-by: Christoffer Dall <christoffer.dall at arm.com>
> Reviewed-by: Mark Rutland <mark.rutland at arm.com>
> Reviewed-by: Dave Martin <Dave.Martin at arm.com>
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> Signed-off-by: Will Deacon <will.deacon at arm.com>

Needs the CVE id here:

CVE-2018-18021

> (cherry picked from commit 2a3f93459d689d990b3ecfbe782fec89b97d3279)

This technically isn't a cherry pick since you had to change
PSR_AA32_MODE_MASK to COMPAT_PSR_MODE_MASK. This line should be:

(backported from commit 2a3f93459d689d990b3ecfbe782fec89b97d3279)

> Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>

With those two changes:

Acked-by: Tyler Hicks <tyhicks at canonical.com>

Thanks for testing these patches.

Tyler

> ---
>  arch/arm64/kvm/guest.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 3f4817d..76d27ed 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -152,17 +152,25 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  	}
>  
>  	if (off == KVM_REG_ARM_CORE_REG(regs.pstate)) {
> -		u32 mode = (*(u32 *)valp) & COMPAT_PSR_MODE_MASK;
> +		u64 mode = (*(u64 *)valp) & COMPAT_PSR_MODE_MASK;
>  		switch (mode) {
>  		case COMPAT_PSR_MODE_USR:
> +			if (!system_supports_32bit_el0())
> +				return -EINVAL;
> +			break;
>  		case COMPAT_PSR_MODE_FIQ:
>  		case COMPAT_PSR_MODE_IRQ:
>  		case COMPAT_PSR_MODE_SVC:
>  		case COMPAT_PSR_MODE_ABT:
>  		case COMPAT_PSR_MODE_UND:
> +			if (!vcpu_el1_is_32bit(vcpu))
> +				return -EINVAL;
> +			break;
>  		case PSR_MODE_EL0t:
>  		case PSR_MODE_EL1t:
>  		case PSR_MODE_EL1h:
> +			if (vcpu_el1_is_32bit(vcpu))
> +				return -EINVAL;
>  			break;
>  		default:
>  			err = -EINVAL;
> -- 
> 2.7.4
> 
> 
> -- 
> kernel-team mailing list
> kernel-team at lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team