Mdadm allows to change the name of the volume to empty and not trim whitespaces.

[Impact]

 * Due to a lack of input checking mdadm could program the IMSM
   with empty "" names for the storage devices causing issues
   later on.

 * Fix by backporting a fix that was committed shortly after what made
   it into Bionic/Disco

[Test Case]

 * This needs a Intel(R) Matrix Storage Hardware which limits the
   systems this can be tested. Below in the original report is example
   output of these commands.
   $ mdadm --create /dev/md/imsm0 --metadata=imsm --raid-devices=2 /dev/nvme11n1 /dev/nvme12n1 --run
   $ mdadm --create /dev/md/r0d2 --level=0 --chunk=128 --raid-devices=2 /dev/nvme11n1 /dev/nvme12n1 --run
   $ mdadm -D /dev/md/imsm0
   $ mdadm --stop /dev/md/r0d2
   $ mdadm --update-subarray=0 --update=name -N "" /dev/md/imsm0
   # the command above should not be allowed, empty of non-trimmed names cause issues down the road.
   $ mdadm --assemble --scan
   $ mdadm -D /dev/md/imsm0

[Regression Potential]

 * The fixes are local to the support of the Intel(R) Matrix Storage
   Manager through mdadm. As much as that makes testing harder it also
   limits the fallout of regressions to other components.
   The one regression I could think of is automation/scripts that
   expects to work with whitespaces, but since that is known to
   fail it is better to force them off of that.

[Other Info]

 * n/a

---

Description:
Mdadm allows to change the name of the volume to any, including empty, too short and too long.
White spaces in the begin or end of the correct name are not trimmed properly.

Steps to reproduce:
1. Create the volume:
# mdadm --create /dev/md/imsm0 --metadata=imsm --raid-devices=2 /dev/nvme11n1 /dev/nvme12n1 --run
# mdadm --create /dev/md/r0d2 --level=0 --chunk=128 --raid-devices=2 /dev/nvme11n1 /dev/nvme12n1 --run

2. Check if volume name is correct:
# mdadm -D /dev/md/imsm0
/dev/md/imsm0:
           Version : imsm
        Raid Level : container
     Total Devices : 2

   Working Devices : 2

              UUID : 6dce006b:086ce0fa:bdcf4f9e:d8bd68c4
     Member Arrays : /dev/md/r0d2

    Number Major Minor RaidDevice

       - 259 13 - /dev/nvme12n1
       - 259 12 - /dev/nvme11n1
root@gklab-94-128:~# mdadm -D /dev/md/r0d2
/dev/md/r0d2:
         Container : /dev/md/imsm0, member 0
        Raid Level : raid0
        Array Size : 781412352 (745.21 GiB 800.17 GB)
      Raid Devices : 2
     Total Devices : 2

             State : clean
    Active Devices : 2
   Working Devices : 2
    Failed Devices : 0
     Spare Devices : 0

        Chunk Size : 128K

Consistency Policy : none

              UUID : 9608dbcd:e4668ab4:015e7469:a263e5e0
    Number Major Minor RaidDevice State
       0 259 12 0 active sync /dev/nvme11n1
       1 259 13 1 active sync /dev/nvme12n1

3. Stop the volume:
# mdadm --stop /dev/md/r0d2

4. Try to change the name of the volume. New name should not be allowed by mdadm (ex. empty), or shuld start or end with whitespaces:
# mdadm --update-subarray=0 --update=name -N "" /dev/md/imsm0

5. Assembly the volume:
# mdadm --assemble --scan
mdadm: Started /dev/md126 with 2 devices

6. Check the volume name.

Expected result:
Mdam should not allow to change name to incorrect. The volume with wrong name should not be assembled. If volume name is correct, eventual whitespaces should be trimmed.

Current result:
Mdadm allows to change the name of the volume to any and assemble the volume with wrong name.
If name is correct and starts/ends with whitespace, it is not trimmed.

# mdadm -D /dev/md/imsm0
/dev/md/imsm0:
           Version : imsm
        Raid Level : container
     Total Devices : 2

   Working Devices : 2

              UUID : 6dce006b:086ce0fa:bdcf4f9e:d8bd68c4
     Member Arrays : /dev/md126

    Number Major Minor RaidDevice

       - 259 13 - /dev/nvme12n1
       - 259 12 - /dev/nvme11n1

# mdadm -E /dev/nvme12n1
/dev/nvme12n1:
          Magic : Intel Raid ISM Cfg Sig.
        Version : 1.0.00
    Orig Family : 3292ee00
         Family : 3292ee00
     Generation : 00000003
     Attributes : All supported
           UUID : 6dce006b:086ce0fa:bdcf4f9e:d8bd68c4
       Checksum : 88845429 correct
    MPB Sectors : 1
          Disks : 2
   RAID Devices : 1

  Disk01 Serial : FT641000CH400BGN
          State : active
             Id : 00000000
    Usable Size : 97676545 (372.61 GiB 400.08 GB)

[]:
           UUID : f4d7bd6c:34479c57:2583d3f6:7247c93e
     RAID Level : 0
        Members : 2
          Slots : [UU]
    Failed disk : none
      This Slot : 1
    Sector Size : 4096
     Array Size : 195353088 (745.21 GiB 800.17 GB)
   Per Dev Size : 97676800 (372.61 GiB 400.08 GB)
  Sector Offset : 0
    Num Stripes : 3052392
     Chunk Size : 128 KiB
       Reserved : 0
  Migrate State : idle
      Map State : normal
    Dirty State : clean
     RWH Policy : off

  Disk00 Serial : FT62040052400GGN
          State : active
             Id : 00000000
    Usable Size : 97676545 (372.61 GiB 400.08 GB)