Check the OPTIONS directive in /etc/default/saslauthd and set it to within your postfix chroot.
OPTIONS=”-c -r -m /var/spool/postfix/var/run/saslauthd”
Then run;
dpkg-statoverride –add root sasl 710 /var/spool/postfix/var/run/saslauthd
adduser postfix sasl
Restart both postfix and saslauthd for the changes to take effect.