linux-kernel - Re: [PATCH for 4.14-stable] s390/mm: validate VMA in PGSTE manipulation functions

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Message-ID: <YaTIAiR9NVQBPUBE@kroah.com>
Date:   Mon, 29 Nov 2021 13:30:58 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     stable@...r.kernel.org, linux-kernel@...r.kernel.org,
        borntraeger@...ibm.com, hca@...ux.ibm.com, imbrenda@...ux.ibm.com
Subject: Re: [PATCH for 4.14-stable] s390/mm: validate VMA in PGSTE
 manipulation functions

On Mon, Nov 29, 2021 at 09:40:32AM +0100, David Hildenbrand wrote:
> On 28.11.21 12:54, Greg KH wrote:
> > On Fri, Nov 26, 2021 at 06:15:36PM +0100, David Hildenbrand wrote:
> >> commit fe3d10024073f06f04c74b9674bd71ccc1d787cf upstream.
> >>
> >> We should not walk/touch page tables outside of VMA boundaries when
> >> holding only the mmap sem in read mode. Evil user space can modify the
> >> VMA layout just before this function runs and e.g., trigger races with
> >> page table removal code since commit dd2283f2605e ("mm: mmap: zap pages
> >> with read mmap_sem in munmap"). gfn_to_hva() will only translate using
> >> KVM memory regions, but won't validate the VMA.
> >>
> >> Further, we should not allocate page tables outside of VMA boundaries: if
> >> evil user space decides to map hugetlbfs to these ranges, bad things will
> >> happen because we suddenly have PTE or PMD page tables where we
> >> shouldn't have them.
> >>
> >> Similarly, we have to check if we suddenly find a hugetlbfs VMA, before
> >> calling get_locked_pte().
> >>
> >> Fixes: 2d42f9477320 ("s390/kvm: Add PGSTE manipulation functions")
> >> Signed-off-by: David Hildenbrand <david@...hat.com>
> >> Reviewed-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
> >> Acked-by: Heiko Carstens <hca@...ux.ibm.com>
> >> Link: https://lore.kernel.org/r/20210909162248.14969-4-david@redhat.com
> >> Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
> >> Signed-off-by: David Hildenbrand <david@...hat.com>
> >> ---
> >>  arch/s390/mm/pgtable.c | 13 +++++++++++++
> >>  1 file changed, 13 insertions(+)
> > 
> > What about for 5.10-stable and 5.4-stable and 4.19-stable?  Will this
> > commit work there as well?
> 
> Good point, I only have "FAILED: patch "[PATCH] s390/mm: validate VMA in
> PGSTE manipulation functions" failed to apply to 4.14-stable tree" in my
> inbox ... but maybe I accidentally deleted the others.

No, odd, I did not send those out, sorry about that.

> This commit can also be used for:
> - 4.19-stable
> - 5.4-stable
> - 5.10-stable

Thanks, will go take this now for all of those.

greg k-h