linux-kernel - [PATCH 2/7] KVM: x86: Improve return type handling in kvm_vm_ioctl_get_nr_mmu

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Date:   Fri,  3 Feb 2023 10:42:25 +0100
From:   Thomas Huth <thuth@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kvm-riscv@...ts.infradead.org, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 2/7] KVM: x86: Improve return type handling in kvm_vm_ioctl_get_nr_mmu_pages()

kvm_vm_ioctl_get_nr_mmu_pages() tries to return a "unsigned long" value,
but its caller only stores ther return value in an "int" - which is also
what all the other kvm_vm_ioctl_*() functions are returning. So returning
values that do not fit into a 32-bit integer anymore does not work here.
It's better to adjust the return type, add a sanity check and return an
error instead if the value is too big.

Signed-off-by: Thomas Huth <thuth@...hat.com>
---
 arch/x86/kvm/x86.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index da4bbd043a7b..caa2541833dd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6007,8 +6007,11 @@ static int kvm_vm_ioctl_set_nr_mmu_pages(struct kvm *kvm,
 	return 0;
 }
 
-static unsigned long kvm_vm_ioctl_get_nr_mmu_pages(struct kvm *kvm)
+static int kvm_vm_ioctl_get_nr_mmu_pages(struct kvm *kvm)
 {
+	if (kvm->arch.n_max_mmu_pages > INT_MAX)
+		return -EOVERFLOW;
+
 	return kvm->arch.n_max_mmu_pages;
 }
 
-- 
2.31.1