[3/3] arm64: KVM: Sanitize PSTATE.M when being set from userspace
diff mbox series

Message ID 1550581355-7068-4-git-send-email-paolo.pisati@canonical.com
State New
Headers show
Series
  • CVE-2018-18021 - arm64 KVM DoS/privesc
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Commit Message

Paolo Pisati Feb. 19, 2019, 1:02 p.m. UTC
From: Marc Zyngier <marc.zyngier@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@vger.kernel.org>
Fixes: 0d854a60b1d7 ("arm64: KVM: enable initialization of a 32bit vcpu")
Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from commit 2a3f93459d689d990b3ecfbe782fec89b97d3279)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
---
 arch/arm64/kvm/guest.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

Comments

Tyler Hicks Feb. 20, 2019, 9:16 a.m. UTC | #1
On 2019-02-19 14:02:35, Paolo Pisati wrote:
> From: Marc Zyngier <marc.zyngier@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@vger.kernel.org>
> Fixes: 0d854a60b1d7 ("arm64: KVM: enable initialization of a 32bit vcpu")
> Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
> Reviewed-by: Mark Rutland <mark.rutland@arm.com>
> Reviewed-by: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Will Deacon <will.deacon@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@canonical.com>

With those two changes:

Acked-by: Tyler Hicks <tyhicks@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@lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team

Patch
diff mbox series

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;