linux-kernel - Re: [PATCH] drm/rockchip: Fix suspend crash when drm is not bound

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Date:   Wed, 9 Aug 2017 14:09:56 -0400
From:   Sean Paul <seanpaul@...omium.org>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark yao <mark.yao@...k-chips.com>,
        Brian Norris <briannorris@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/rockchip: Fix suspend crash when drm is not bound

On Wed, Aug 9, 2017 at 6:41 AM, Jeffy Chen <jeffy.chen@...k-chips.com> wrote:
> Currently we are allocating drm_device in rockchip_drm_bind, so if the
> suspend/resume code access it when drm is not bound, we would hit this
> crash:
>
> [  253.402836] Unable to handle kernel NULL pointer dereference at virtual address 00000028
> [  253.402837] pgd = ffffffc06c9b0000
> [  253.402841] [00000028] *pgd=0000000000000000, *pud=0000000000000000
> [  253.402844] Internal error: Oops: 96000005 [#1] PREEMPT SMP
> [  253.402859] Modules linked in: btusb btrtl btbcm btintel bluetooth ath10k_pci ath10k_core ar10k_ath ar10k_mac80211 cfg80211 ip6table_filter asix usbnet mii
> [  253.402864] CPU: 4 PID: 1331 Comm: cat Not tainted 4.4.70 #15
> [  253.402865] Hardware name: Google Scarlet (DT)
> [  253.402867] task: ffffffc076c0ce00 ti: ffffffc06c2c8000 task.ti: ffffffc06c2c8000
> [  253.402871] PC is at rockchip_drm_sys_suspend+0x20/0x5c
>
> Add sanity checks to prevent that.
>
> Reported-by: Brian Norris <briannorris@...omium.com>
> Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
>

Hi Jeffy,
Thank you for the patch. In future, please also Cc dri-devel for more
visibility (I've added them to this reply).

I've applied the patch to drm-misc-fixes.

Sean



> ---
>
>  drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> index c41f48a..ff3d0f5 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> @@ -270,11 +270,15 @@ static void rockchip_drm_fb_resume(struct drm_device *drm)
>  static int rockchip_drm_sys_suspend(struct device *dev)
>  {
>         struct drm_device *drm = dev_get_drvdata(dev);
> -       struct rockchip_drm_private *priv = drm->dev_private;
> +       struct rockchip_drm_private *priv;
> +
> +       if (!drm)
> +               return 0;
>
>         drm_kms_helper_poll_disable(drm);
>         rockchip_drm_fb_suspend(drm);
>
> +       priv = drm->dev_private;
>         priv->state = drm_atomic_helper_suspend(drm);
>         if (IS_ERR(priv->state)) {
>                 rockchip_drm_fb_resume(drm);
> @@ -288,8 +292,12 @@ static int rockchip_drm_sys_suspend(struct device *dev)
>  static int rockchip_drm_sys_resume(struct device *dev)
>  {
>         struct drm_device *drm = dev_get_drvdata(dev);
> -       struct rockchip_drm_private *priv = drm->dev_private;
> +       struct rockchip_drm_private *priv;
> +
> +       if (!drm)
> +               return 0;
>
> +       priv = drm->dev_private;
>         drm_atomic_helper_resume(drm, priv->state);
>         rockchip_drm_fb_resume(drm);
>         drm_kms_helper_poll_enable(drm);
> --
> 2.1.4
>
>