/lib/udev/rules.d/60-drm.rules is in udev 232-25+deb9u8.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | # do not edit this file, it will be overwritten on update
ACTION!="remove", SUBSYSTEM=="drm", SUBSYSTEMS=="pci|usb|platform", IMPORT{builtin}="path_id"
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