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From:   Liam Howlett <liam.howlett@oracle.com>
To:     David Hildenbrand <david@redhat.com>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        Cornelia Huck <cohuck@redhat.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Niklas Schnelle <schnelle@linux.ibm.com>,
        Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
        Ulrich Weigand <Ulrich.Weigand@de.ibm.com>
Subject: Re: [PATCH resend RFC 6/9] s390/pci_mmio: fully validate the VMA
 before calling follow_pte()
Thread-Topic: [PATCH resend RFC 6/9] s390/pci_mmio: fully validate the VMA
 before calling follow_pte()
Thread-Index: AQHXpZcbJLTjiRrwCkuHdXeigSfj7KukKDqA
Date:   Tue, 14 Sep 2021 22:41:54 +0000
Message-ID: <20210914224149.pet5qov4233sg5nw@revolver>
References: <20210909162248.14969-1-david@redhat.com>
 <20210909162248.14969-7-david@redhat.com>
In-Reply-To: <20210909162248.14969-7-david@redhat.com>
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Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

* David Hildenbrand <david@redhat.com> [210909 12:24]:
> 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").
>=20
> find_vma() does not check if the address is >=3D the VMA start address;
> use vma_lookup() instead.
>=20
> Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap")
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  arch/s390/pci/pci_mmio.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>=20
> diff --git a/arch/s390/pci/pci_mmio.c b/arch/s390/pci/pci_mmio.c
> index ae683aa623ac..c5b35ea129cf 100644
> --- a/arch/s390/pci/pci_mmio.c
> +++ b/arch/s390/pci/pci_mmio.c
> @@ -159,7 +159,7 @@ SYSCALL_DEFINE3(s390_pci_mmio_write, unsigned long, m=
mio_addr,
> =20
>  	mmap_read_lock(current->mm);
>  	ret =3D -EINVAL;
> -	vma =3D find_vma(current->mm, mmio_addr);
> +	vma =3D vma_lookup(current->mm, mmio_addr);
>  	if (!vma)
>  		goto out_unlock_mmap;
>  	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
> @@ -298,7 +298,7 @@ SYSCALL_DEFINE3(s390_pci_mmio_read, unsigned long, mm=
io_addr,
> =20
>  	mmap_read_lock(current->mm);
>  	ret =3D -EINVAL;
> -	vma =3D find_vma(current->mm, mmio_addr);
> +	vma =3D vma_lookup(current->mm, mmio_addr);
>  	if (!vma)
>  		goto out_unlock_mmap;
>  	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
> --=20
> 2.31.1
>=20
> =