Does it happen when selinux-policy >= 3.13 is installed ?

Could you add following line to /etc/audit/rules.d/audit.rules and restart audit daemon?

-w /etc/shadow -p w

From now on, the AVCs will contain more information.

(In reply to Milos Malik from comment #2)
> Does it happen when selinux-policy >= 3.13 is installed ?

That's bad ... I don't have RHEL-7 on my computer anymore, but I probably will have it sometime later this month (with new computer). Keeping the needinfo alive.

Actually, I can reproduce it even with Fedora 21:

SELinux is preventing /usr/sbin/ModemManager from connectto access on the unix_stream_socket @qmi-proxy.

*****  Plugin catchall_boolean (89.3 confidence) suggests   ******************

If you want to enable cluster mode for daemons.
Then you must tell SELinux about this by enabling the 'daemons_enable_cluster_mode' boolean.
You can read 'modemmanager_selinux' man page for more details.
Do
setsebool -P daemons_enable_cluster_mode 1

*****  Plugin catchall (11.6 confidence) suggests   **************************

If you believe that ModemManager should be allowed connectto access on the @qmi-proxy unix_stream_socket 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:
# grep ModemManager /var/log/audit/audit.log | audit2allow -M mypol
# semodule -i mypol.pp

Additional Information:
Source Context                system_u:system_r:modemmanager_t:s0
Target Context                system_u:system_r:modemmanager_t:s0
Target Objects                @qmi-proxy [ unix_stream_socket ]
Source                        ModemManager
Source Path                   /usr/sbin/ModemManager
Port                          <Unknown>
Host                          wycliff
Source RPM Packages           ModemManager-1.4.0-1.fc21.x86_64
Target RPM Packages           
Policy RPM                    selinux-policy-3.13.1-90.fc21.noarch
Selinux Enabled               True
Policy Type                   targeted
Enforcing Mode                Permissive
Host Name                     wycliff
Platform                      Linux wycliff 3.17.1-302.fc21.x86_64 #1 SMP Fri
                              Oct 17 20:05:46 UTC 2014 x86_64 x86_64
Alert Count                   1153
First Seen                    2014-10-06 20:53:09 CEST
Last Seen                     2014-10-24 13:56:39 CEST
Local ID                      bad6634e-2940-4e4c-b342-fca770e8e3f1

Raw Audit Messages
type=AVC msg=audit(1414151799.918:3443): avc:  denied  { connectto } for  pid=1020 comm="ModemManager" path=00716D692D70726F7879 scontext=system_u:system_r:modemmanager_t:s0 tcontext=system_u:system_r:modemmanager_t:s0 tclass=unix_stream_socket permissive=1


type=SYSCALL msg=audit(1414151799.918:3443): arch=x86_64 syscall=connect success=yes exit=0 a0=9 a1=7ffff0bc5e90 a2=c a3=10 items=0 ppid=1 pid=1020 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm=ModemManager exe=/usr/sbin/ModemManager subj=system_u:system_r:modemmanager_t:s0 key=(null)

Hash: ModemManager,modemmanager_t,modemmanager_t,unix_stream_socket,connectto

commit 5ba54f3dd852dea537fb6c64fa63af7e2629fb12
Author: Dan Walsh <dwalsh>
Date:   Sat Oct 25 06:52:23 2014 -0400

    Allow modemmanger to connectto itself

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-0458.html