linux-kernel - [PATCH 5.4 086/109] KVM: arm64: Fix kvm_reset_vcpu() return code being incorrect with SVE

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Message-Id: <20200714184109.668790444@linuxfoundation.org>
Date:   Tue, 14 Jul 2020 20:44:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, James Morse <james.morse@....com>,
        Steven Price <steven.price@....com>,
        Marc Zyngier <maz@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 086/109] KVM: arm64: Fix kvm_reset_vcpu() return code being incorrect with SVE

From: Steven Price <steven.price@....com>

If SVE is enabled then 'ret' can be assigned the return value of
kvm_vcpu_enable_sve() which may be 0 causing future "goto out" sites to
erroneously return 0 on failure rather than -EINVAL as expected.

Remove the initialisation of 'ret' and make setting the return value
explicit to avoid this situation in the future.

Fixes: 9a3cdf26e336 ("KVM: arm64/sve: Allow userspace to enable SVE for vcpus")
Cc: stable@...r.kernel.org
Reported-by: James Morse <james.morse@....com>
Signed-off-by: Steven Price <steven.price@....com>
Signed-off-by: Marc Zyngier <maz@...nel.org>
Link: https://lore.kernel.org/r/20200617105456.28245-1-steven.price@arm.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm64/kvm/reset.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -258,7 +258,7 @@ static int kvm_vcpu_enable_ptrauth(struc
 int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 {
 	const struct kvm_regs *cpu_reset;
-	int ret = -EINVAL;
+	int ret;
 	bool loaded;
 
 	/* Reset PMU outside of the non-preemptible section */
@@ -281,15 +281,19 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu
 
 	if (test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, vcpu->arch.features) ||
 	    test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features)) {
-		if (kvm_vcpu_enable_ptrauth(vcpu))
+		if (kvm_vcpu_enable_ptrauth(vcpu)) {
+			ret = -EINVAL;
 			goto out;
+		}
 	}
 
 	switch (vcpu->arch.target) {
 	default:
 		if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) {
-			if (!cpu_has_32bit_el1())
+			if (!cpu_has_32bit_el1()) {
+				ret = -EINVAL;
 				goto out;
+			}
 			cpu_reset = &default_regs_reset32;
 		} else {
 			cpu_reset = &default_regs_reset;