Allow xdm write to gnome-initial-setup fifo files

The commit addresses the following AVC denial:
type=PROCTITLE msg=audit(09/18/2024 16:14:09.301:217) : proctitle=/usr/bin/gnome-shell
type=SYSCALL msg=audit(09/18/2024 16:14:09.301:217) : arch=x86_64 syscall=recvmsg success=yes exit=52 a0=0xad a1=0x7ffcc3ba4450 a2=MSG_DONTWAIT|MSG_CMSG_CLOEXEC a3=0x0 items=0 ppid=1166 pid=1178 auid=unset uid=gnome-initial-setup gid=gnome-initial-setup euid=gnome-initial-setup suid=gnome-initial-setup fsuid=gnome-initial-setup egid=gnome-initial-setup sgid=gnome-initial-setup fsgid=gnome-initial-setup tty=tty1 ses=unset comm=gnome-shell exe=/usr/bin/gnome-shell subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 key=(null)
type=AVC msg=audit(09/18/2024 16:14:09.301:217) : avc:  denied  { write } for  pid=1178 comm=gnome-shell path=pipe:[19167] dev="pipefs" ino=19167 scontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tcontext=system_u:system_r:gnome_initial_setup_t:s0-s0:c0.c1023 tclass=fifo_file permissive=0

Resolves: rhbz#2278845

policy/modules/contrib/gnome.if

@@ -2207,6 +2207,25 @@ interface(`gnome_initial_setup_read_state',`
 	ps_process_pattern($1, gnome_initial_setup_t)
 ')
 
+########################################
+## <summary>
+##	Write/append gnome-initial-setup fifo files
+## </summary>
+## <param name="domain">
+##	<summary>
+##	Domain allowed access.
+##	</summary>
+## </param>
+#
+interface(`gnome_initial_setup_write_fifo_files',`
+	gen_require(`
+		type gnome_initial_setup_t;
+	')
+
+
+	allow $1 gnome_initial_setup_t:fifo_file write_fifo_file_perms;
+')
+
 ########################################
 ## <summary>
 ##	Transition to gnome-initial-setup named content

policy/modules/services/xserver.te

@@ -1067,6 +1067,7 @@ optional_policy(`
 	gnome_initial_setup_manage_var_run(xdm_t)
 	gnome_initial_setup_noatsecure(xdm_t)
 	gnome_initial_setup_read_state(xdm_t)
+	gnome_initial_setup_write_fifo_files(xdm_t)
 ')
 
 optional_policy(`