pseudofs nodes store their name in a flexible array member, so the node
allocation is sized using the length of the name, including a nul
terminator. pfs_lookup() scans a directory of nodes, comparing names to
find a match. The comparison was incorrect and assumed that all node
names were at least as long as the name being looked up, which of course
isn't true.

I believe the bug is mostly harmless since it cannot result in false
positive or negative matches from the lookup, but it triggers a KASAN
check.

Reported by: pho