I had a hell of a time trying to figure out why after upgrading the CentOS Samba package the samba shares quit working. Every time someone tried to access the share, the smb service would crash. I had this system configured to use active directory credentials and it worked well for a time, but no longer.
After much digging I found my problem to be the lack of a krb5.keytab file. This is due to my using PowerBroker Open instead of kerberos for authentication.
The solution was to add this line to my samba config:
kerberos method = system keytab
That one bit made all the difference. My current samba config is as follows with no more crashing:
[global] security = ADS passdb backend = tdbsam realm = DOMAIN encrypt passwords = yes lanman auth = no ntlm auth = no kerberos method = system keytab obey pam restrictions = yes winbind enum users = yes winbind enum groups = yes