linux-kernel - Re: [PATCH] KVM: Use vmemdup

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Date:   Fri, 18 Jun 2021 19:32:21 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Michal Hocko <mhocko@...e.com>, Jim Mattson <jmattson@...gle.com>
Cc:     Denis Efremov <efremov@...ux.com>, joe@...ches.com,
        kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: Use vmemdup_user()

On 18/06/21 19:04, Michal Hocko wrote:
> On Fri 18-06-21 09:53:53, Jim Mattson wrote:
>> In any case, these allocations *should* be accounted, shouldn't they?
> 
> This is more of a question to maintainers. Are these objects easy to
> request by userspace without any bounds?

This particular one need not be accounted because the allocation only 
lasts for the duration of the ioctl. The allocation below in 
kvm_vcpu_ioctl_set_cpuid

      e2 = kvmalloc_array(cpuid->nent, sizeof(*e2), GFP_KERNEL_ACCOUNT);

is long term and is already accounted for.

kvm_vcpu_ioctl_set_cpuid2 should also use kvmalloc_array and 
GFP_KERNEL_ACCOUNT.  However, it wasn't doing so before this patch went 
in, either.

Paolo