kern/42513: permission denied to "cd .."

[Bernd Ernesti <pr200915%veego.de@localhost>]

>Number:         42513
>Category:       kern
>Synopsis:       permission denied to "cd .."
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Dec 23 21:20:00 +0000 2009
>Originator:     Bernd Ernesti
>Release:        NetBSD 5.0_STABLE 20092312 1200UTC
>Organization:
        
>Environment:
        
        
System: NetBSD 5.0_STABLE 20092312 1200UTC
Architecture: i386
Machine: i386
>Description:
        I had a problem to build a kernel and was flooded with
                cd: can't cd to ..
        lines until i did a ctrl-c.

        The kernel obj directory was outside of the source tree and the obj
        dir (below /x/y) was not on the root filesystem:

                /dev/wd0a   /
                /dev/wd0e   /x
                /dev/wd1e   /x/y

        Changing to /x/y works but going one directory up cause an error:

        $ /x/y> cd ..
        ..: Permission denied.

        A ls -lad from /x showed this:
                drwxr-xr-x  28 xx xx 1024 Dec 23 17:03 y
        So it should be fine but looking again after unmounting /x/y
        showed this for the same directory:
                drwx------  2 xx xx  512 Oct 12  2008 y

        Now to the question: Is this a bug or intentional?

        IMHO is this a bug and the cd should use the permissions of the
        mounted filesystem and not the one from the underlying fs.

>How-To-Repeat:
        Alan Barrett suggested this:

        replication recipe (run as non-root user with permission to sudo):
        ( set -x ; sudo mkdir -p /foo/tmp ; sudo chmod 700 /foo/tmp ; ls -ld 
/foo/tmp ;
        sudo mount_tmpfs -s 10m tmpfs /foo/tmp ; sudo chown "$(id -u)" /foo/tmp 
;
        ls -ld /foo/tmp ; cd /foo/tmp ; ls -la ; cd .. ; cd / ; sudo umount 
/foo/tmp )

>Fix:

>Unformatted: