CVE-2021-47108 Information

Description

In the Linux kernel the following vulnerability has been resolved:

drm/mediatek: hdmi: Perform NULL pointer check for mtk_hdmi_conf

In commit 41ca9caaae0b (\drm/mediatek: hdmi: Add check for CEA modes only) a check for CEA modes was added to function mtk_hdmi_bridge_mode_valid() in order to address possible issues on MT8167; moreover with commit c91026a938c2 (\drm/mediatek: hdmi: Add optional limit on maximal HDMI mode clock) another similar check was introduced.

Unfortunately though at the time of writing MT8173 does not provide any mtk_hdmi_conf structure and this is crashing the kernel with NULL pointer upon entering mtk_hdmi_bridge_mode_valid() which happens as soon as a HDMI cable gets plugged in.

To fix this regression add a NULL pointer check for hdmi->conf in the said function restoring HDMI functionality and avoiding NULL pointer kernel panics.

Reference

https://git.kernel.org/stable/c/71d07ebc5000b9c1d140e99e7493b0bafa954776 https://git.kernel.org/stable/c/3b8e19a0aa3933a785be9f1541afd8d398c4ec69