Under the hood, the NamedProcessIterator class tries to access /proc/<pid>/exe for every <pid> on the system. With shill running as a non-root user, this generates an EACCESS error for every process on the system that isn't
owned by shill. This doesn't affect correctness of execution (since shill can still access /proc/<pid>/exe for processes it spawns, and in first iteration of dropping shill privs we give it CAP_KILL so it can kill children after they've switched UID/GID to a different user), but does produce a
bunch of syscall errors that were not seen before. There is already a TODO in the NamedProcessIterator code (https://cs.corp.google.com/chromeos_public/src/aosp/external/libchrome/base/process/process_iterator_linux.cc?rcl=0b087f9dcf23367a24f0bacc738abe9ec8ed6506&l=79) to skip trying to access /proc/<pid>/exe for "processes owned by different UID", so not much more we can do here.