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Message-ID: <87pmakmc79.fsf@redhat.com>
Date: Wed, 08 Feb 2023 16:03:22 +0100
From: Cornelia Huck <cohuck@...hat.com>
To: Thomas Huth <thuth@...hat.com>, 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>,
David Hildenbrand <david@...hat.com>,
Gavin Shan <gshan@...hat.com>,
Steven Price <steven.price@....com>
Subject: Re: [PATCH v2 4/6] KVM: arm64: Limit length in
kvm_vm_ioctl_mte_copy_tags() to INT_MAX
On Wed, Feb 08 2023, Thomas Huth <thuth@...hat.com> 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 <thuth@...hat.com>
> ---
> 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(-)
Reviewed-by: Cornelia Huck <cohuck@...hat.com>
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