Created attachment 2432 [details]
proposed fix

ssh-agent sometimes forks child processes.  For example,
ask_permission() may fork a child process to execute an askpass program.
If it fails to execute, the child process exits using fatal(), which in
turn calls cleanup_exit(), and the latter calls cleanup_socket().  As
result, an error in child process causes unintended UNIX-domain socket
removal.  The fix is to record pid of the process that is responsible
for socket cleanup, and skip this cleanup for other processes.