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Wed, 17 Jun 2020 11:47:42 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 17 Jun 2020 11:47:41 +0100 From: Marc Zyngier To: Steven Price Cc: Catalin Marinas , Will Deacon , James Morse , Julien Thierry , Suzuki K Poulose , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave Martin Subject: Re: [PATCH] KVM: arm64: kvm_reset_vcpu() return code incorrect with SVE In-Reply-To: <20200617104339.35094-1-steven.price@arm.com> References: <20200617104339.35094-1-steven.price@arm.com> User-Agent: Roundcube Webmail/1.4.5 Message-ID: X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: steven.price@arm.com, catalin.marinas@arm.com, will@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave.Martin@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steven, On 2020-06-17 11:43, Steven Price wrote: > 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") > Reported-by: James Morse > Signed-off-by: Steven Price > --- > The problematic chunk isn't visible in the diff, so reproduced here: > > if (!kvm_arm_vcpu_sve_finalized(vcpu)) { > if (test_bit(KVM_ARM_VCPU_SVE, vcpu->arch.features)) { > ret = kvm_vcpu_enable_sve(vcpu); > if (ret) > goto out; > } > } else { > kvm_vcpu_reset_sve(vcpu); > } > > arch/arm64/kvm/reset.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c > index d3b209023727..f1057603b756 100644 > --- a/arch/arm64/kvm/reset.c > +++ b/arch/arm64/kvm/reset.c > @@ -245,7 +245,7 @@ static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu > *vcpu) > */ > int kvm_reset_vcpu(struct kvm_vcpu *vcpu) > { > - int ret = -EINVAL; > + int ret; > bool loaded; > u32 pstate; > > @@ -269,15 +269,19 @@ 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 (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1)) > + if (cpus_have_const_cap(ARM64_HAS_32BIT_EL1)) { Do you really mean this? Seems counter-productive... :-( > + ret = -EINVAL; > goto out; > + } > pstate = VCPU_RESET_PSTATE_SVC; > } else { > pstate = VCPU_RESET_PSTATE_EL1; Thanks, M. -- Jazz is not dead. It just smells funny...