Bug 2461071 - selinux breaks session dbus-broker when used with ssh ("fifo_file")
Summary: selinux breaks session dbus-broker when used with ssh ("fifo_file")
Keywords:
Status: ASSIGNED
Alias: None
Product: Fedora
Classification: Fedora
Component: selinux-policy
Version: 44
Hardware: Unspecified
OS: Linux
low
medium
Target Milestone: ---
Assignee: Zdenek Pytela
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-04-23 06:46 UTC by Marius Vollmer
Modified: 2026-04-23 11:03 UTC (History)
7 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Type: ---
Embargoed:
zpytela: mirror+


Attachments (Terms of Use)

Description Marius Vollmer 2026-04-23 06:46:21 UTC
With our current fedora-44 CI image, I can observe this:

    $ ssh c "systemctl --machine=admin@"
    Warning: Permanently added '[127.0.0.2]:2201' (ED25519) to the list of known hosts.
    Failed to start transient service unit: Connection reset by peer
    Failed to start transient service unit: Transport endpoint is not connected

Here "c" is a virtual machine running the fedora-44 CI image.  When I log into the machine normally and then execute the same command in the shell, it works:

    $ ssh c
    Warning: Permanently added '[127.0.0.2]:2201' (ED25519) to the list of known hosts.
    Web console: https://fedora-44-127-0-0-2-2201:9090/

    Last login: Thu Apr 23 06:03:01 2026 from 172.27.0.2
    [root@fedora-44-127-0-0-2-2201 ~]# systemctl --machine=admin@
      UNIT                                                                                LOAD   ACTIVE SUB       DESCRIPTION                                                                  
      proc-sys-fs-binfmt_misc.automount                                                   loaded active running   Arbitrary Executable File Formats File System Automount Point     
    [...]

Without the "--machine admin@" or with "--machine root@", it also works as expected.

Here are the details from sealert:

    # sealert -l 81ca8426-05fc-42fe-977e-07c7e19c8ee5
    SELinux is preventing dbus-broker from write access on the fifo_file fifo_file.

    *****  Plugin catchall (100. confidence) suggests   **************************

    If you believe that dbus-broker should be allowed write access on the fifo_file fifo_file 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 'dbus-broker' --raw | audit2allow -M my-dbusbroker
    # semodule -X 300 -i my-dbusbroker.pp


    Additional Information:
    Source Context                system_u:system_r:system_dbusd_t:s0-s0:c0.c1023
    Target Context                system_u:system_r:sshd_session_t:s0-s0:c0.c1023
    Target Objects                fifo_file [ fifo_file ]
    Source                        dbus-broker
    Source Path                   dbus-broker
    Port                          <Unknown>
    Host                          fedora-44-127-0-0-2-2201
    Source RPM Packages           
    Target RPM Packages           
    SELinux Policy RPM            selinux-policy-targeted-43.3-1.fc44.noarch
    Local Policy RPM              selinux-policy-targeted-43.3-1.fc44.noarch
    Selinux Enabled               True
    Policy Type                   targeted
    Enforcing Mode                Enforcing
    Host Name                     fedora-44-127-0-0-2-2201
    Platform                      Linux fedora-44-127-0-0-2-2201
                                  6.19.10-300.fc44.x86_64 #1 SMP PREEMPT_DYNAMIC Wed
                                  Mar 25 18:23:49 UTC 2026 x86_64
    Alert Count                   3
    First Seen                    2026-04-23 06:02:07 UTC
    Last Seen                     2026-04-23 06:03:06 UTC
    Local ID                      81ca8426-05fc-42fe-977e-07c7e19c8ee5

    Raw Audit Messages
    type=AVC msg=audit(1776924186.837:537): avc:  denied  { write } for  pid=753 comm="dbus-broker" path="pipe:[19809]" dev="pipefs" ino=19809 scontext=system_u:system_r:system_dbusd_t:s0-s0:c0.c1023 tcontext=system_u:system_r:sshd_session_t:s0-s0:c0.c1023 tclass=fifo_file permissive=0


    Hash: dbus-broker,system_dbusd_t,sshd_session_t,fifo_file,write

The PID 753 is the system dbus-broker.


Reproducible: Always

Comment 1 Marius Vollmer 2026-04-23 06:52:12 UTC
Ah, the versions.

selinux-policy-43.3-1.fc44.noarch

Comment 2 Marius Vollmer 2026-04-23 07:14:28 UTC
I can observe the same behavior with a VM running this image: https://download.fedoraproject.org/pub/fedora/linux/releases/test/44_Beta/Server/x86_64/images/Fedora-Server-Guest-Generic-44_Beta-1.2.x86_64.qcow2

It has selinux-policy-42.23-1.fc44.noarch

Comment 3 Marius Vollmer 2026-04-23 11:03:10 UTC
> $ ssh c "systemctl --machine=admin@"

I should say that this logs in as "root".


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