RE: [PATCH] firmware/sysfb: Fix device reference count leak in sysfb_disable()

[Deucher, Alexander]

Public

> -----Original Message-----
> From: Wentao Liang <vulab@xxxxxxxxxxx>
> Sent: Wednesday, September 16, 2026 3:38 AM
> To: Deucher, Alexander <Alexander.Deucher@xxxxxxx>
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx; javierm@xxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; tzimmermann@xxxxxxx; Wentao Liang
> <vulab@xxxxxxxxxxx>; stable@xxxxxxxxxxxxxxx
> Subject: [PATCH] firmware/sysfb: Fix device reference count leak in
> sysfb_disable()
>
> In sysfb_disable(), parent is obtained via sysfb_parent_dev(si), which calls
> screen_info_pci_dev(si) and returns a pointer to &pdev->dev with an acquired
> reference count. However, sysfb_disable() does not release this reference
> before returning, leading to a device reference leak.
>
> Fix this by checking if parent is not an ERR_PTR and calling
> put_device(parent) before releasing the mutex.
>
> Fixes: b49420d6a1ae ("video/aperture: optionally match the device in
> sysfb_disable()")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Wentao Liang <vulab@xxxxxxxxxxx>
> ---
>  drivers/firmware/sysfb.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/firmware/sysfb.c b/drivers/firmware/sysfb.c index
> 8833582c1883..11c5ce128a6c 100644
> --- a/drivers/firmware/sysfb.c
> +++ b/drivers/firmware/sysfb.c
> @@ -71,9 +71,12 @@ void sysfb_disable(struct device *dev)
>
>       mutex_lock(&disable_lock);
>       parent = sysfb_parent_dev(si);
> -     if (!dev || !parent || dev == parent) {
> -             sysfb_unregister();
> -             disabled = true;
> +     if (!IS_ERR(parent)) {

Are there cases where sysfb_unregister() would need to be called even if parent returns an error?

Alex

> +             if (!dev || !parent || dev == parent) {
> +                     sysfb_unregister();
> +                     disabled = true;
> +             }
> +             put_device(parent);
>       }
>       mutex_unlock(&disable_lock);
>  }
> --
> 2.34.1