linux-kernel - Re: [PATCH v5 3/3] drm: protect drm_master pointers in drm

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Date:   Wed, 30 Jun 2021 01:16:10 +0100
From:   Emil Velikov <emil.l.velikov@...il.com>
To:     Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Dave Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
        skhan@...uxfoundation.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Daniel Vetter <daniel.vetter@...ll.ch>
Subject: Re: [PATCH v5 3/3] drm: protect drm_master pointers in drm_lease.c

Hi Desmond,

Couple of small suggestions, with those the series is:
Reviewed-by: Emil Velikov <emil.l.velikov@...il.com>

On Tue, 29 Jun 2021 at 04:38, Desmond Cheong Zhi Xi
<desmondcheongzx@...il.com> wrote:

> @@ -128,13 +137,20 @@ bool drm_lease_held(struct drm_file *file_priv, int id)
>         struct drm_master *master;
>         bool ret;
>
> -       if (!file_priv || !file_priv->master || !file_priv->master->lessor)
> +       if (!file_priv)
>                 return true;
>
> -       master = file_priv->master;
> +       master = drm_file_get_master(file_priv);
> +       if (master == NULL)
> +               return true;
> +       if (!master->lessor) {
> +               drm_master_put(&master);
> +               return true;

Let's add a "ret = true; goto unlock;" here, so we can have a single
drm_master_put() in the function.
Nearly all code paths touched by this patch already follow this approach.

> @@ -154,10 +170,16 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in)
>         int count_in, count_out;
>         uint32_t crtcs_out = 0;
>
> -       if (!file_priv || !file_priv->master || !file_priv->master->lessor)
> +       if (!file_priv)
>                 return crtcs_in;
>
> -       master = file_priv->master;
> +       master = drm_file_get_master(file_priv);
> +       if (master == NULL)
> +               return crtcs_in;
> +       if (!master->lessor) {
> +               drm_master_put(&master);
> +               return crtcs_in;

Ditto

Thanks
Emil