linux-kernel - Re: [PATCH] drm/radeon:avoid null pointer dereference when dev is not bound

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Date:   Mon, 4 Jan 2021 12:00:27 -0500
From:   Alex Deucher <alexdeucher@...il.com>
To:     Defang Bo <bodefang@....com>
Cc:     Dave Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        "Deucher, Alexander" <alexander.deucher@....com>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/radeon:avoid null pointer dereference when dev is not bound

On Sun, Dec 27, 2020 at 3:56 PM Defang Bo <bodefang@....com> wrote:
>
> [Why]
> Similar to commit<0fa375e6>. If the set_state/can_switch code access the drm_device when dev is not bound,
> a null pointer dereference can happen.
>
> [How]
> Add sanity checks to prevent it.
>
> Signed-off-by: Defang Bo <bodefang@....com>

Are you actually hitting this or is this just defensive?  I don't
think we can actually get into a state where this would be a problem.

Alex

> ---
>  drivers/gpu/drm/radeon/radeon_device.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
> index 266e3cb..50a1a60 100644
> --- a/drivers/gpu/drm/radeon/radeon_device.c
> +++ b/drivers/gpu/drm/radeon/radeon_device.c
> @@ -1224,6 +1224,9 @@ static void radeon_switcheroo_set_state(struct pci_dev *pdev, enum vga_switchero
>  {
>         struct drm_device *dev = pci_get_drvdata(pdev);
>
> +       if (!dev)
> +               return;
> +
>         if (radeon_is_px(dev) && state == VGA_SWITCHEROO_OFF)
>                 return;
>
> @@ -1257,6 +1260,9 @@ static void radeon_switcheroo_set_state(struct pci_dev *pdev, enum vga_switchero
>  static bool radeon_switcheroo_can_switch(struct pci_dev *pdev)
>  {
>         struct drm_device *dev = pci_get_drvdata(pdev);
> +
> +       if (!dev)
> +               return false;
>
>         /*
>          * FIXME: open_count is protected by drm_global_mutex but that would lead to
> --
> 2.7.4
>
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx

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