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From: Cornelia Huck <>
To: Alex Williamson <>
Subject: Re: [PATCH] vfio/type1: Limit DMA mappings per container
Date: Tue, 2 Apr 2019 16:58:35 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <155414977872.12780.13728555131525362206.stgit@gimli.home>

On Mon, 01 Apr 2019 14:16:52 -0600
Alex Williamson <> wrote:

> Memory backed DMA mappings are accounted against a user's locked
> memory limit, including multiple mappings of the same memory.  This
> accounting bounds the number of such mappings that a user can create.
> However, DMA mappings that are not backed by memory, such as DMA
> mappings of device MMIO via mmaps, do not make use of page pinning
> and therefore do not count against the user's locked memory limit.
> These mappings still consume memory, but the memory is not well
> associated to the process for the purpose of oom killing a task.
> To add bounding on this use case, we introduce a limit to the total
> number of concurrent DMA mappings that a user is allowed to create.
> This limit is exposed as a tunable module option where the default
> value of 64K is expected to be well in excess of any reasonable use
> case (a large virtual machine configuration would typically only make
> use of tens of concurrent mappings).
> This fixes CVE-2019-3882.
> Signed-off-by: Alex Williamson <>
> ---
>  drivers/vfio/vfio_iommu_type1.c |   14 ++++++++++++++
>  1 file changed, 14 insertions(+)

Reviewed-by: Cornelia Huck <>

      parent reply	other threads:[~2019-04-02 14:58 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-01 20:16 [PATCH] vfio/type1: Limit DMA mappings per container Alex Williamson
2019-04-02  2:41 ` Peter Xu
2019-04-02  4:34   ` Alex Williamson
2019-04-02  5:18     ` Peter Xu
2019-04-02 14:40       ` Alex Williamson
2019-04-02 14:58 ` Cornelia Huck [this message]

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