[Samba] Changes in share permissions lead to disruption of service

[Viktor Trojanovic]

I just had something very strange happening, I'm curious if someone can
understand what it was in spite of the limited available information.

I'm running Samba 4.11.6 as an AD file server. Rowland checked my config
recently and could not find any issue with it, it's really very standard,
using the idmap backend. Only 2 users in the AD. Linux access is not a
topic, the shares are only accessed by Windows users, and all security
permissions are set from Windows.

This all worked perfectly until when I decided today to disable security
permissions inheritance on two of three shares and converted inherited
permissions into explicit permissions. I then changed the permissions for
user2 on the share to read only, giving him write access to the underlying
folder.

Somehow, this broke everything. User2 suddenly could not even browse the
server anymore, let alone the share in question. The smbd log filled up
with:


[2020/06/09 09:48:19.746725,  0]
../../source3/smbd/uid.c:448(change_to_user_internal)
  change_to_user_internal: chdir_current_service() failed!

Since I needed this solved quickly, I logged out user2 from all devices,
restarted the member server. This didn't change anything yet. Then, I
removed the permissions and set them again. The exact same permissions as
they were before removing them. Now user2 could access the shares again.

Any idea what happened here?

Viktor