How can I make an Ubuntu Samba Share **completely** writeable from Mavericks
Permission problems in Samba can be a bit tricky to diagnose.

What exactly is the command you are using to mount the share on the Mac?

At the command line could you go to the place where the share is mounted and do an ls -l@ so that the permissions there can be checked. Do the same in one of the directories that is giving you problems.

Are you sharing an ext3 volume and do you have Samba configured to use ACLs? If so then adding a line nt acl support = yes to your share definition will get them working and you get much nicer permission controls. They should be on by default but may not be.