From: Jason Gunthorpe <jgg@ziepe.ca>
To: Joao Martins <joao.m.martins@oracle.com>
Cc: linux-nvdimm@lists.01.org,
Dan Williams <dan.j.williams@intel.com>,
Vishal Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Ira Weiny <ira.weiny@intel.com>,
Alex Williamson <alex.williamson@redhat.com>,
Cornelia Huck <cohuck@redhat.com>,
kvm@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H . Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Liran Alon <liran.alon@oracle.com>,
Nikita Leshenko <nikita.leshchenko@oracle.com>,
Barret Rhoden <brho@google.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Matthew Wilcox <willy@infradead.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [PATCH RFC 09/10] vfio/type1: Use follow_pfn for VM_FPNMAP VMAs
Date: Fri, 7 Feb 2020 17:08:31 -0400 [thread overview]
Message-ID: <20200207210831.GA31015@ziepe.ca> (raw)
In-Reply-To: <20200110190313.17144-10-joao.m.martins@oracle.com>
On Fri, Jan 10, 2020 at 07:03:12PM +0000, Joao Martins wrote:
> From: Nikita Leshenko <nikita.leshchenko@oracle.com>
>
> Unconditionally interpreting vm_pgoff as a PFN is incorrect.
>
> VMAs created by /dev/mem do this, but in general VM_PFNMAP just means
> that the VMA doesn't have an associated struct page and is being managed
> directly by something other than the core mmu.
>
> Use follow_pfn like KVM does to find the PFN.
>
> Signed-off-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
> drivers/vfio/vfio_iommu_type1.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 2ada8e6cdb88..1e43581f95ea 100644
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -362,9 +362,9 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
> vma = find_vma_intersection(mm, vaddr, vaddr + 1);
>
> if (vma && vma->vm_flags & VM_PFNMAP) {
> - *pfn = ((vaddr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
> - if (is_invalid_reserved_pfn(*pfn))
> - ret = 0;
> + ret = follow_pfn(vma, vaddr, pfn);
> + if (!ret && !is_invalid_reserved_pfn(*pfn))
> + ret = -EOPNOTSUPP;
> }
FWIW this existing code is a huge hack and a security problem.
I'm not sure how you could be successfully using this path on actual
memory without hitting bad bugs?
Fudamentally VFIO can't retain a reference to a page from within a VMA
without some kind of recount/locking/etc to allow the thing that put
the page there to know it is still being used (ie programmed in a
IOMMU) by VFIO.
Otherwise it creates use-after-free style security problems on the
page.
This code needs to be deleted, not extended :(
Jason
next prev parent reply other threads:[~2020-02-07 21:08 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 19:03 [PATCH RFC 00/10] device-dax: Support devices without PFN metadata Joao Martins
2020-01-10 19:03 ` [PATCH RFC 01/10] mm: Add pmd support for _PAGE_SPECIAL Joao Martins
2020-02-03 21:34 ` Matthew Wilcox
2020-02-04 16:14 ` Joao Martins
2020-01-10 19:03 ` [PATCH RFC 02/10] mm: Handle pmd entries in follow_pfn() Joao Martins
2020-02-03 21:37 ` Matthew Wilcox
2020-02-04 16:17 ` Joao Martins
2020-01-10 19:03 ` [PATCH RFC 03/10] mm: Add pud support for _PAGE_SPECIAL Joao Martins
2020-01-10 19:03 ` [PATCH RFC 04/10] mm: Handle pud entries in follow_pfn() Joao Martins
2020-01-10 19:03 ` [PATCH RFC 05/10] device-dax: Do not enforce MADV_DONTFORK on mmap() Joao Martins
2020-01-10 19:03 ` [PATCH RFC 06/10] device-dax: Introduce pfn_flags helper Joao Martins
2020-01-10 19:03 ` [PATCH RFC 07/10] device-dax: Add support for PFN_SPECIAL flags Joao Martins
2020-01-10 19:03 ` [PATCH RFC 08/10] dax/pmem: Add device-dax support for PFN_MODE_NONE Joao Martins
2020-01-10 19:03 ` [PATCH RFC 09/10] vfio/type1: Use follow_pfn for VM_FPNMAP VMAs Joao Martins
2020-02-07 21:08 ` Jason Gunthorpe [this message]
2020-02-11 16:23 ` Joao Martins
2020-02-11 16:50 ` Jason Gunthorpe
2020-01-10 19:03 ` [PATCH RFC 10/10] nvdimm/e820: add multiple namespaces support Joao Martins
2020-02-04 15:28 ` Barret Rhoden
2020-02-04 16:44 ` Dan Williams
2020-02-04 18:20 ` Barret Rhoden
2020-02-04 19:24 ` Joao Martins
2020-02-04 21:43 ` Dan Williams
2020-02-04 21:57 ` Barret Rhoden
2020-02-04 1:24 ` [PATCH RFC 00/10] device-dax: Support devices without PFN metadata Dan Williams
2020-02-04 19:07 ` Joao Martins
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