[ale] Permission hell question

[Geoffrey]

Stephan Uphoff wrote:

> The permissions of the covered mount point usually only come into play
> when accessing ".." from the root of the mounted fs.
> 
> This is true for Unix and BSD ... but I have never looked at this part 
> of the Linux sources.
> 
> As a normal user try to
> 	cd /mnt/memstick  #OK
> 	pwd               #Fails unless cached by shell
> 	ls ..             #Should fail
> 
> with /mnt/memstick permission set to 700 and user root.

I don't agree, note the following, all done as a normal user:

/home/esoteric> cd /mnt/memstick
ksh: cd: /mnt/memstick - Permission denied

rhws/home/esoteric> ls -l /mnt/memstick
ls: /mnt/memstick: Permission denied

rhws/home/esoteric> ls -ld /mnt/memstick
drwx------    2 root     root         4096 May 12 13:59 /mnt/memstick

rhws/home/esoteric> cd /mnt/memstick
ksh: cd: /mnt/memstick - Permission denied

rhws/home/esoteric> mount /mnt/memstick

rhws/home/esoteric> cd /mnt/memstick

rhws/mnt/memstick> pwd
/mnt/memstick

rhws/mnt/memstick> ls ..
cdrom  floppy  jump  memstick

So, I don't believe your point above is valid.

> It is not really necessary to have matching permissions - but the wrong set
> of permissions can cause interesting problems in a production environment.

If the mount options are correct, the permissions on the mount point do 
not matter.  I set the perms on /mnt/memstick to 000 as root:

d---------    2 root     root         4096 May 12 13:59 /mnt/memstick

I can still mount the partition as a normal user.  When I do, the perms are:

drwxr-xr-x    3 esoteric users       16384 Dec 31  1969 /mnt/memstick

-- 
Until later, Geoffrey                     Registered Linux User #108567
Building secure systems in spite of Microsoft