UBUNTU-CVE-2021-47108

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UBUNTU-CVE-2021-47108

Summary:

Details: 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.

References: https://ubuntu.com/security/CVE-2021-47108, https://git.kernel.org/linus/3b8e19a0aa3933a785be9f1541afd8d398c4ec69, https://git.kernel.org/stable/c/71d07ebc5000b9c1d140e99e7493b0bafa954776, https://git.kernel.org/stable/c/3b8e19a0aa3933a785be9f1541afd8d398c4ec69, https://www.cve.org/CVERecord?id=CVE-2021-47108