Re: [PATCH] drm/gma500: Add NULL check for pci_gfx_root in mid_get_vbt_data()

[Patrik Jakobsson]

On Wed, Mar 5, 2025 at 12:20 PM Ivan Abramov
<i.abramov@xxxxxxxxxxxxxxxxx> wrote:
>
> Since pci_get_domain_bus_and_slot() can return NULL, add NULL check for
> pci_gfx_root in the mid_get_vbt_data().
>
> This change is similar to the checks implemented in mid_get_fuse_settings()
> and mid_get_pci_revID(), which were introduced by commit 0cecdd818cd7
> ("gma500: Final enables for Oaktrail") as "additional minor
> bulletproofing".
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Fixes: ba99d8348864 ("drm/gma500: Deprecate pci_get_bus_and_slot()")

Patch looks good but pci_get_bus_and_slot() also returned a struct
pci_dev so the issue was present before ba99d8348864.
The correct fixes tag should be:
Fixes: f910b411053f ("gma500: Add the glue to the various BIOS and
firmware interfaces")

-Patrik

>
> Signed-off-by: Ivan Abramov <i.abramov@xxxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/gma500/mid_bios.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/gma500/mid_bios.c b/drivers/gpu/drm/gma500/mid_bios.c
> index 7e76790c6a81..cba97d7db131 100644
> --- a/drivers/gpu/drm/gma500/mid_bios.c
> +++ b/drivers/gpu/drm/gma500/mid_bios.c
> @@ -279,6 +279,11 @@ static void mid_get_vbt_data(struct drm_psb_private *dev_priv)
>                                             0, PCI_DEVFN(2, 0));
>         int ret = -1;
>
> +       if (pci_gfx_root == NULL) {
> +               WARN_ON(1);
> +               return;
> +       }
> +
>         /* Get the address of the platform config vbt */
>         pci_read_config_dword(pci_gfx_root, 0xFC, &addr);
>         pci_dev_put(pci_gfx_root);
> --
> 2.48.1
>