Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 14 Sep 2021 18:54:33 +0200
From:   Claudio Imbrenda <imbrenda@linux.ibm.com>
To:     David Hildenbrand <david@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
        kvm@vger.kernel.org, linux-mm@kvack.org,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        Cornelia Huck <cohuck@redhat.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()
Message-ID: <20210914185433.41f0a0b9@p-imbrenda>
In-Reply-To: <20210909162248.14969-7-david@redhat.com>
References: <20210909162248.14969-1-david@redhat.com>
 <20210909162248.14969-7-david@redhat.com>
Organization: IBM
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Thu,  9 Sep 2021 18:22:45 +0200
David Hildenbrand <david@redhat.com> wrote:

> 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: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap")
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  arch/s390/pci/pci_mmio.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> 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, mmio_addr, 
>  	mmap_read_lock(current->mm);
>  	ret = -EINVAL;
> -	vma = find_vma(current->mm, mmio_addr);
> +	vma = 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, mmio_addr, 
>  	mmap_read_lock(current->mm);
>  	ret = -EINVAL;
> -	vma = find_vma(current->mm, mmio_addr);
> +	vma = vma_lookup(current->mm, mmio_addr);
>  	if (!vma)
>  		goto out_unlock_mmap;
>  	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))