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From:   Jim Mattson <jmattson@google.com>
Date:   Thu, 17 Jun 2021 17:25:04 -0700
Message-ID: <CALMp9eSFkRrWLjegJ5OC7kZ4oWtZypKRDjXFQD5=tFX4YLpUgw@mail.gmail.com>
Subject: Re: [PATCH] KVM: Use vmemdup_user()
To:     Denis Efremov <efremov@linux.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>, joe@perches.com,
        kvm list <kvm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, Jun 3, 2020 at 3:10 AM Denis Efremov <efremov@linux.com> wrote:
>
> Replace opencoded alloc and copy with vmemdup_user().
>
> Signed-off-by: Denis Efremov <efremov@linux.com>
> ---
> Looks like these are the only places in KVM that are suitable for
> vmemdup_user().
>
>  arch/x86/kvm/cpuid.c | 17 +++++++----------
>  virt/kvm/kvm_main.c  | 19 ++++++++-----------
>  2 files changed, 15 insertions(+), 21 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 901cd1fdecd9..27438a2bdb62 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -182,17 +182,14 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
>         r = -E2BIG;
>         if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)
>                 goto out;
> -       r = -ENOMEM;
>         if (cpuid->nent) {
> -               cpuid_entries =
> -                       vmalloc(array_size(sizeof(struct kvm_cpuid_entry),
> -                                          cpuid->nent));
> -               if (!cpuid_entries)
> -                       goto out;
> -               r = -EFAULT;
> -               if (copy_from_user(cpuid_entries, entries,
> -                                  cpuid->nent * sizeof(struct kvm_cpuid_entry)))
> +               cpuid_entries = vmemdup_user(entries,
> +                                            array_size(sizeof(struct kvm_cpuid_entry),
> +                                                       cpuid->nent));

Does this break memcg accounting? I ask, because I'm really not sure.