From: Thomas Huth Date: Wed, 8 Feb 2023 14:01:03 +0000 (+0100) Subject: KVM: arm64: Limit length in kvm_vm_ioctl_mte_copy_tags() to INT_MAX X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=2def950c63e3f976af87a2606dabe0c9e21c605b;p=linux.git KVM: arm64: Limit length in kvm_vm_ioctl_mte_copy_tags() to INT_MAX 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 Reviewed-by: Cornelia Huck Reviewed-by: Gavin Shan Reviewed-by: Steven Price Message-Id: <20230208140105.655814-5-thuth@redhat.com> Signed-off-by: Paolo Bonzini --- diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 62de0768d6aa5..48fad65568227 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -5645,7 +5645,8 @@ 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 bcd774d74f349..6f7b218a681f0 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -1005,8 +1005,8 @@ 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 07444fa228888..26a2ebc465ea7 100644 --- a/arch/arm64/kvm/guest.c +++ b/arch/arm64/kvm/guest.c @@ -1019,8 +1019,8 @@ 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; @@ -1041,6 +1041,10 @@ 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);