util: check for trailing characters in partition names

util: check for trailing characters in partition names

The function which maps partition names to partition ids currently
ignores trailing characters in the partition names. For example, the
partition name "/vicepbogus" is currently considered a valid partition
name ("/vicepbogus" maps to "bo" which is id 66). Although this is not a
regression, it is problematic for several reasons.

Firstly, this can lead to duplicate partition ids on the server, for
example "/vicepbad" and "/vicepbar" both map to the same partition id
("ba" is id 52).

Second, partitions are internally tracked by numeric id. The partition
names are generated from numeric ids when reporting partition names.
This means the trailing characters are lost when reporting the partition
names. For example, vos reports the attached partition "/vicepbad" as
"/vicepba".

Third, it could be possible (but perhaps unlikely) in the future to
extend the range of partition ids, so the trailing characters could
become significant at that time.

Finally, it could be confusing to admins that such partition names are
attached by the fileserver. For example, "/vicepaa-backup" is attached
and is used by the fileserver as partition id 26.

This change adds a check for trailing characters in partition names in
the volutil_GetPartitionID function, so it is more strict in what it
accepts as a valid partition name.  That function will now return -1
(illegal partition name) when trailing characters are found in
partition names.

Change-Id: Iad9aee05fcf439cac9afcd89cf367be693261fbd
Reviewed-on: https://gerrit.openafs.org/13039
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>