# Re: \[PATCH 0/4\] Fix use after free in HPT resizing code and related minor improvements

- From: David Gibson \<hidden\>
- Date: 2017-11-30 04:03:05 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2017/11/5145135
- Thread: https://ratatoskr.run/linuxppc-dev/2017/11/5144502/t.md

```text
On Wed, Nov 29, 2017 at 11:38:22AM -0500, Serhii Popovych wrote:
> It is possible to trigger use after free during HPT resize
> causing host kernel to crash. More details and analysis of
> the problem can be found in change with corresponding subject
> (KVM: PPC: Book3S HV: Fix use after free in case of multiple
> resize requests).
> 
> We need some changes to prepare for the fix, especially
> make ->error in HPT resize instance single point for
> tracking allocation state, improve kvmppc_allocate_hpt()
> and kvmppc_free_hpt() so they can be used more safely.
> 
> See individual commit description message to get more
> information on changes presented.
> 
> Serhii Popovych (4):
>   KVM: PPC: Book3S HV: Drop prepare_done from struct kvm_resize_hpt and
>     cleanups
>   KVM: PPC: Book3S HV: Improve kvmppc_allocate_hpt()/kvmppc_free_hpt()
>   KVM: PPC: Book3S HV: Fix use after free in case of multiple resize
>     requests
>   KVM: PPC: Book3S HV: Remove redundant parameter from
>     resize_hpt_release()
> 
>  arch/powerpc/kvm/book3s_64_mmu_hv.c | 139 +++++++++++++++++++++---------------
>  1 file changed, 82 insertions(+), 57 deletions(-)

Paul, these (at least 1-3) fix (another :() host crash bug which can
be triggered by guest and/or userspace actions.  Please merge ASAP.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
```

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