Re: [PATCH resend RFC 5/9] s390/uv: fully validate the VMA before calling follow_page()

Liam Howlett
2021-09-14T22:41:24Z

Reviwed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

* David Hildenbrand <david@redhat.com> [210909 12:23]:
> 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").
>
> find_vma() does not check if the address is >= the VMA start address;
> use vma_lookup() instead.
>
> Fixes: 214d9bbcd3a6 ("s390/mm: provide memory management functions for protected KVM guests")
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> arch/s390/kernel/uv.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
> index aeb0a15bcbb7..193205fb2777 100644
> --- a/arch/s390/kernel/uv.c
> +++ b/arch/s390/kernel/uv.c
> @@ -227,7 +227,7 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb)
> uaddr = __gmap_translate(gmap, gaddr);
> if (IS_ERR_VALUE(uaddr))
> goto out;
> - vma = find_vma(gmap->mm, uaddr);
> + vma = vma_lookup(gmap->mm, uaddr);
> if (!vma)
> goto out;
> /*
> --
> 2.31.1
>
>