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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Christoffer Dall <christoffer.dall@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Dave Martin <Dave.Martin@arm.com>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Will Deacon <will.deacon@arm.com>
Subject: [PATCH 4.4 072/113] arm64: KVM: Sanitize PSTATE.M when being set from userspace
Date:   Mon,  8 Oct 2018 20:31:13 +0200
Message-Id: <20181008175534.926850701@linuxfoundation.org>
In-Reply-To: <20181008175530.864641368@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marc Zyngier <marc.zyngier@arm.com>

commit 2a3f93459d689d990b3ecfbe782fec89b97d3279 upstream.

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>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/arm64/include/asm/kvm_emulate.h |    5 +++++
 arch/arm64/kvm/guest.c               |   10 +++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -41,6 +41,11 @@ void kvm_inject_undefined(struct kvm_vcp
 void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr);
 void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);
 
+static inline bool vcpu_el1_is_32bit(struct kvm_vcpu *vcpu)
+{
+	return !(vcpu->arch.hcr_el2 & HCR_RW);
+}
+
 static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.hcr_el2 = HCR_GUEST_FLAGS;
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -143,17 +143,25 @@ static int set_core_reg(struct kvm_vcpu
 	}
 
 	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;