Description of problem:
SELinux is preventing lightdm from using the 'dac_override' capabilities.

*****  Plugin dac_override (91.4 confidence) suggests   **********************

If if you want to help identify if domain needs this access or you have a file with the wrong permissions on your system
Then turn on full auditing to get path information about the offending file and generate the error again.
Do

Turn on full auditing
# auditctl -w /etc/shadow -p w
Try to recreate AVC. Then execute
# ausearch -m avc -ts recent
If you see PATH record check ownership/permissions on file, and fix it,
otherwise report as a bugzilla.

*****  Plugin catchall (9.59 confidence) suggests   **************************

If if you believe that lightdm should have the dac_override capability by default.
Then you should report this as a bug.
You can generate a local policy module to allow this access.
Do
allow this access for now by executing:
# ausearch -c 'lightdm' --raw | audit2allow -M my-lightdm
# semodule -X 300 -i my-lightdm.pp

Additional Information:
Source Context                system_u:system_r:xdm_t:s0-s0:c0.c1023
Target Context                system_u:system_r:xdm_t:s0-s0:c0.c1023
Target Objects                Unknown [ capability ]
Source                        lightdm
Source Path                   lightdm
Port                          <Unknown>
Host                          (removed)
Source RPM Packages           
Target RPM Packages           
Policy RPM                    selinux-policy-3.13.1-288.fc28.noarch
Selinux Enabled               True
Policy Type                   targeted
Enforcing Mode                Permissive
Host Name                     (removed)
Platform                      Linux (removed) 4.14.0-0.rc2.git0.1.fc28.x86_64 #1
                              SMP Mon Sep 25 12:59:54 UTC 2017 x86_64 x86_64
Alert Count                   1
First Seen                    2017-09-27 12:01:24 PDT
Last Seen                     2017-09-27 12:01:24 PDT
Local ID                      8aab5604-a458-4952-a8a4-21544212d891

Raw Audit Messages
type=AVC msg=audit(1506538884.60:188): avc:  denied  { dac_override } for  pid=609 comm="lightdm" capability=1  scontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tcontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tclass=capability permissive=1


Hash: lightdm,xdm_t,xdm_t,capability,dac_override

Version-Release number of selected component:
selinux-policy-3.13.1-288.fc28.noarch

Additional info:
component:      selinux-policy
reporter:       libreport-2.9.2
hashmarkername: setroubleshoot
kernel:         4.14.0-0.rc2.git0.1.fc28.x86_64
type:           libreport