linux-kernel - Re: [PATCH v2] drm/panfrost: Prevent race when handling page fault

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Date:   Thu, 19 Sep 2019 11:53:31 -0500
From:   Rob Herring <robh@...nel.org>
To:     Steven Price <steven.price@....com>
Cc:     Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/panfrost: Prevent race when handling page fault

On Fri, Sep 13, 2019 at 11:03 AM Steven Price <steven.price@....com> wrote:
>
> When handling a GPU page fault addr_to_drm_mm_node() is used to
> translate the GPU address to a buffer object. However it is possible for
> the buffer object to be freed after the function has returned resulting
> in a use-after-free of the BO.
>
> Change addr_to_drm_mm_node to return the panfrost_gem_object with an
> extra reference on it, preventing the BO from being freed until after
> the page fault has been handled.
>
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> Changes since v1:
>  * Hold the mm_lock around drm_mm_for_each_node()
>
> I've also posted a new IGT test for this:
> https://patchwork.freedesktop.org/patch/330513/
>
>  drivers/gpu/drm/panfrost/panfrost_mmu.c | 55 ++++++++++++++++---------
>  1 file changed, 36 insertions(+), 19 deletions(-)

Applied.

Rob