All communication between auditdistd senders and receivers and
internally between auditdistd and its worker children passes through the
same pair of send / receive functions. The receive function uses
recv(2) with the MSG_WAITALL flag, which in theory means we should never
get a short read. However, when handing off a socket to a worker child,
we also pass a variable-length string identifying the type of socket
we're passing, and reading this string relies on a short read. This
used to work because the arrival of the descriptor would interrupt the
recv(2) call, but this bug was fixed when the AF_UNIX code was rewritten
a while ago and auditdistd has been broken ever since.
Fixing the length of the protocol name to four characters including the
terminating null solves the short-read bug by never requiring a short
read (nothing else in auditdistd requires one).
MFC after: 3 days
Event: EuroBSDcon DevSummit 2026