Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22E0AC636CC for ; Wed, 8 Feb 2023 14:06:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231182AbjBHOF4 (ORCPT ); Wed, 8 Feb 2023 09:05:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57422 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230011AbjBHOFw (ORCPT ); Wed, 8 Feb 2023 09:05:52 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7D9065FF7; Wed, 8 Feb 2023 06:05:50 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 820751042; Wed, 8 Feb 2023 06:06:32 -0800 (PST) Received: from [10.57.12.246] (unknown [10.57.12.246]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AE2293F8C6; Wed, 8 Feb 2023 06:05:47 -0800 (PST) Message-ID: <0f6690ec-8b33-866f-536e-3d111523b203@arm.com> Date: Wed, 8 Feb 2023 14:05:46 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [PATCH v2 4/6] KVM: arm64: Limit length in kvm_vm_ioctl_mte_copy_tags() to INT_MAX Content-Language: en-GB To: Thomas Huth , kvm@vger.kernel.org, Paolo Bonzini , Sean Christopherson Cc: kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, kvm-riscv@lists.infradead.org, Marc Zyngier , James Morse , Suzuki K Poulose , Oliver Upton , Zenghui Yu , Christian Borntraeger , Janosch Frank , David Hildenbrand , Gavin Shan , Cornelia Huck References: <20230208140105.655814-1-thuth@redhat.com> <20230208140105.655814-5-thuth@redhat.com> From: Steven Price In-Reply-To: <20230208140105.655814-5-thuth@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/02/2023 14:01, Thomas Huth wrote: > In case of success, this function returns the amount of handled bytes. > However, this does not work for large values: The function is called > from kvm_arch_vm_ioctl() (which still returns a long), which in turn > is called from kvm_vm_ioctl() in virt/kvm/kvm_main.c. And that function > stores the return value in an "int r" variable. So the upper 32-bits > of the "long" return value are lost there. > > KVM ioctl functions should only return "int" values, so let's limit > the amount of bytes that can be requested here to INT_MAX to avoid > the problem with the truncated return value. We can then also change > the return type of the function to "int" to make it clearer that it > is not possible to return a "long" here. > > Fixes: f0376edb1ddc ("KVM: arm64: Add ioctl to fetch/store tags in a guest") > Signed-off-by: Thomas Huth Thanks for fixing this. Reviewed-by: Steven Price > --- > Documentation/virt/kvm/api.rst | 3 ++- > arch/arm64/include/asm/kvm_host.h | 4 ++-- > arch/arm64/kvm/guest.c | 8 ++++++-- > 3 files changed, 10 insertions(+), 5 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 0a67cb738013..f184427931fa 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -5553,7 +5553,8 @@ with the KVM_XEN_VCPU_GET_ATTR ioctl. > }; > > Copies Memory Tagging Extension (MTE) tags to/from guest tag memory. The > -``guest_ipa`` and ``length`` fields must be ``PAGE_SIZE`` aligned. The ``addr`` > +``guest_ipa`` and ``length`` fields must be ``PAGE_SIZE`` aligned. > +``length`` must not be bigger than 2^31 - PAGE_SIZE bytes. The ``addr`` > field must point to a buffer which the tags will be copied to or from. > > ``flags`` specifies the direction of copy, either ``KVM_ARM_TAGS_TO_GUEST`` or > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 35a159d131b5..b1a16343767f 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -963,8 +963,8 @@ int kvm_arm_vcpu_arch_get_attr(struct kvm_vcpu *vcpu, > int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu, > struct kvm_device_attr *attr); > > -long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm, > - struct kvm_arm_copy_mte_tags *copy_tags); > +int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm, > + struct kvm_arm_copy_mte_tags *copy_tags); > > /* Guest/host FPSIMD coordination helpers */ > int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu); > diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c > index cf4c495a4321..cadef953046f 100644 > --- a/arch/arm64/kvm/guest.c > +++ b/arch/arm64/kvm/guest.c > @@ -1013,8 +1013,8 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu, > return ret; > } > > -long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm, > - struct kvm_arm_copy_mte_tags *copy_tags) > +int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm, > + struct kvm_arm_copy_mte_tags *copy_tags) > { > gpa_t guest_ipa = copy_tags->guest_ipa; > size_t length = copy_tags->length; > @@ -1035,6 +1035,10 @@ long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm, > if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK) > return -EINVAL; > > + /* Lengths above INT_MAX cannot be represented in the return value */ > + if (length > INT_MAX) > + return -EINVAL; > + > gfn = gpa_to_gfn(guest_ipa); > > mutex_lock(&kvm->slots_lock);