Description of problem:
I booted a Fedora 38 KDE Plasma installation with plymouth.debug=stream:/dev/null added to the 6.2.9 kernel command line as suggested by Hans de Goede at https://bugzilla.redhat.com/show_bug.cgi?id=2183743 to troubleshoot a problem with the boot splash screen showing a theme with three dots instead of the selected Spinner theme. plymouthd was denied reading cmdline repeatedly on each of a few boots with plymouth.debug=stream:/dev/null on the kernel command line.
type=AVC msg=audit(1680373014.556:258): avc:  denied  { read } for  pid=382 comm="plymouthd" name="stat" dev="proc" ino=20331 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:system_r:init_t:s0 tclass=file permissive=0

The denials didn't happen without that added to the kernel command line. I'm using the targeted policy from selinux-policy-38.9-1.fc38.noarch in enforcing mode. Hans mentioned denials like this at https://bugzilla.redhat.com/show_bug.cgi?id=1945585#c2

SELinux is preventing plymouthd from 'read' accesses on the file stat.

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

If you believe that plymouthd should be allowed read access on the stat 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 'plymouthd' --raw | audit2allow -M my-plymouthd
# semodule -X 300 -i my-plymouthd.pp

Additional Information:
Source Context                system_u:system_r:kernel_t:s0
Target Context                system_u:system_r:init_t:s0
Target Objects                stat [ file ]
Source                        plymouthd
Source Path                   plymouthd
Port                          <Unknown>
Host                          (removed)
Source RPM Packages           
Target RPM Packages           
SELinux Policy RPM            selinux-policy-targeted-38.9-1.fc38.noarch
Local Policy RPM              selinux-policy-targeted-38.9-1.fc38.noarch
Selinux Enabled               True
Policy Type                   targeted
Enforcing Mode                Enforcing
Host Name                     (removed)
Platform                      Linux (removed) 6.2.9-300.fc38.x86_64 #1 SMP
                              PREEMPT_DYNAMIC Thu Mar 30 22:32:58 UTC 2023
                              x86_64
Alert Count                   34
First Seen                    2023-04-01 14:16:52 EDT
Last Seen                     2023-04-01 14:16:54 EDT
Local ID                      12533528-3d83-4080-af55-597e0c2c9a22

Raw Audit Messages
type=AVC msg=audit(1680373014.556:258): avc:  denied  { read } for  pid=382 comm="plymouthd" name="stat" dev="proc" ino=20331 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:system_r:init_t:s0 tclass=file permissive=0


Hash: plymouthd,kernel_t,init_t,file,read

Version-Release number of selected component:
selinux-policy-targeted-38.9-1.fc38.noarch

Additional info:
reporter:       libreport-2.17.9
hashmarkername: setroubleshoot
type:           libreport
kernel:         6.2.9-300.fc38.x86_64
component:      selinux-policy
package:        selinux-policy-targeted-38.9-1.fc38.noarch
reason:         SELinux is preventing plymouthd from 'read' accesses on the file stat.
component:      selinux-policy