drm/amd/display: Add null pointer check for get_first_active_display()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Add null pointer check for get_first_active_display() The function mod_hdcp_hdcp1_enable_encryption() calls the function get_first_active_display(), but does not check its return value. The return value is a null pointer if the display list is empty. This will lead to a null pointer dereference in mod_hdcp_hdcp2_enable_encryption(). Add a null pointer check for get_first_active_display() and return MOD_HDCP_STATUS_DISPLAY_NOT_FOUND if the function return null.

References

• https://git.kernel.org/stable/c/34d3e10ab905f06445f8dbd8a3d9697095e71bae
• https://git.kernel.org/stable/c/1ebcdf38887949def1a553ff3e45c98ed95a3cd0
• https://git.kernel.org/stable/c/5148c7ea69e9c5bf2f05081190f45ba96d3d1e7a
• https://git.kernel.org/stable/c/4ce9f2dc9ff7cc410e8c5d936ec551e26b9599a9
• https://git.kernel.org/stable/c/b3005145eab98d36777660b8893466e4f630ae1c
• https://git.kernel.org/stable/c/c3e9826a22027a21d998d3e64882fa377b613006