On Thu 17-06-21 17:25:04, Jim Mattson wrote:
> On Wed, Jun 3, 2020 at 3:10 AM Denis Efremov <efremov@xxxxxxxxx> wrote:
> >
> > Replace opencoded alloc and copy with vmemdup_user().
> >
> > Signed-off-by: Denis Efremov <efremov@xxxxxxxxx>
> > ---
> > 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.
What do you mean by that? The original code uses plain vmalloc so the
allocation is not memcg accounted (please note that __GFP_ACCOUNT needs
to be specified explicitly). vmemdup_user is the same in that regards.
--
Michal Hocko
SUSE Labs
