This issue exists in RHEL9 as well

Multipath now has improved checking of multipath.conf values.  However, this error checking is still more limited than what you are testing for.  For numeric values with ranges, multipath.conf will now cap the values to the range. For values with keywords, multipath will now print a  message if the keyword is invalid. There are a couple of other checks.  However, for values that are arbitrary strings, multipath does not do any checking, since it doesn't know which values will be accepted. This depends on things like which kernel modules exist on the system. For instance, if the service-time path selector module exists, then

path_selector "service-time 0"

is valid. If that module doesn't exist, it isn't.

This amount of error checking is what is acceptable upstream.

Verified on device-mapper-multipath-0.8.7-3.el9
[root@storageqe-25 ~]# rpm -qa | grep multipath
device-mapper-multipath-libs-0.8.7-3.el9.x86_64
device-mapper-multipath-0.8.7-3.el9.x86_64


[root@storageqe-25 ~]# man multipath.conf
defaults section
       The defaults section recognizes the following keywords:

       verbosity        Default  verbosity.  Higher  values  increase the ver‐
                        bosity level. Valid levels are between 0 and 6.

                        The default is: 2


Edit /etc/multipath.conf
[root@storageqe-25 ~]# cat /etc/multipath.conf
defaults {
	user_friendly_names yes
	find_multipaths yes
        verbosity 8 <--------------------------------
}

[root@storageqe-25 ~]# multipath -ll
53929.624073 | /etc/multipath.conf line 14, value for verbosity too large, capping at 4


Test result: For numeric values with ranges, multipath.conf will now cap the values to the range.




Edit /etc/multipath.conf
[root@storageqe-25 ~]# cat /etc/multipath.conf
defaults {
	user_friendly_names yes
	find_multipaths yes
        #verbosity 8
        foo 2 <-----------------------------
}



[root@storageqe-25 ~]# service multipathd reload
Redirecting to /bin/systemctl reload multipathd.service


[root@storageqe-25 ~]# multipath -ll
54170.516702 | /etc/multipath.conf line 15, invalid keyword in the defaults section: foo  <-----------------------------
360a98000324669436c2b45666c567858 dm-3 NETAPP,LUN
size=2.0G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 alua' wp=rw
|-+- policy='service-time 0' prio=50 status=active
| |- 6:0:1:0 sdf 8:80  active ready running
| `- 8:0:1:0 sdn 8:208 active ready running
`-+- policy='service-time 0' prio=10 status=enabled
  |- 6:0:0:0 sdb 8:16  active ready running
  `- 8:0:0:0 sdj 8:144 active ready running


Test result:For values with keywords, multipath will now print a  message if the keyword is invalid.

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 (new packages: device-mapper-multipath), 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://access.redhat.com/errata/RHBA-2022:3971