kern/44657: rmdir of cwd in tmpfs causes kassert in lookup

[Taylor R Campbell <campbell+netbsd%mumble.net@localhost>]

>Number:         44657
>Category:       kern
>Synopsis:       rmdir of cwd in tmpfs causes kassert in lookup
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Mar 01 15:20:00 +0000 2011
>Originator:     Taylor R Campbell <campbell+netbsd%mumble.net@localhost>
>Release:        NetBSD 5.99.47
>Organization:
>Environment:
System: NetBSD oberon.local 5.99.47 NetBSD 5.99.47 (RIAMONODEBUG) #31: Mon Feb 
28 05:14:15 UTC 2011 
riastradh@smalltalk.local:/home/riastradh/netbsd/current/obj/sys/arch/i386/compile/RIAMONODEBUG
 i386
Architecture: i386
Machine: i386
>Description:

        If my cwd is in a tmpfs, and I rmdir the cwd, then `cd ..'
        triggers the KASSERT(0) in tmpfs_alloc_vp.

>How-To-Repeat:

        % rump_tmpfs -s10m ~/tmp
        % cd ~/tmp
        % mkdir -p lose/foo
        % cd lose/foo
        % rm -r ~/tmp/lose
        % cd ..
        panic: kernel diagnostic assertion "0" failed: file 
"/home/riastradh/netbsd/current/src/sys/rump/fs/lib/libtmpfs/../../../../fs/tmpfs/tmpfs_subr.c",
 line 404
        rump kernel halting...
        halted
        cd: device not configured: ..

>Fix:

        Not sure yet.