drm/mediatek: Fix device use-after-free on unbind

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: drm/mediatek: Fix device use-after-free on unbind A recent change fixed device reference leaks when looking up drm platform device driver data during bind() but failed to remove a partial fix which had been added by commit 80805b62ea5b ("drm/mediatek: Fix kobject put for component sub-drivers"). This results in a reference imbalance on component bind() failures and on unbind() which could lead to a user-after-free. Make sure to only drop the references after retrieving the driver data by effectively reverting the previous partial fix. Note that holding a reference to a device does not prevent its driver data from going away so there is no point in keeping the reference.

References

• https://git.kernel.org/stable/c/a5a896f8315de358a2932e2c23c42d550256046a
• https://git.kernel.org/stable/c/0142fe895986addf35885b43440718e567121155
• https://git.kernel.org/stable/c/8ba827e09eb586e952d10e39406fa02d10bb591e
• https://git.kernel.org/stable/c/926d002e6d7e2f1fd5c1b53cf6208153ee7d380d