Linus Torvalds wrote:
quoted text
> And it would be perfectly ok for O_DIRECTORY to open such a file, as long
> as it opens the directory branch, not the special device.

What about:

    cd /dev/into_directory_branch/
    run_setuid_program

        -> calls pwd
           pwd opens("."), (".."), ("../..") etc.
 
        -> the setuid program thus ends up opening a device or fifo,
           when it does pwd's path walk.  Yes it could use the getcwd
           syscall, but some programs do their own path walk.

quoted text
> I advocated (long ago) something like this for /dev handling, just because
> I think it would make sense to have
> 
> 	/dev/hda	<- special file
> 	/dev/hda/part1	<- partition 1 (aka /dev/hda1)
> 
> which just seems like a very obvious and intuitive interface to me. Of 
> course, we have so much legacy in /dev that there's no real point to doing 
> this, but it's still an appealing approach, I think.

It also fits the container idea very well:

        /dev/hda/part1/ <- the filesystem inside partition 1

That's not a contrivance, it's what I'd expect to happen if
/dev/hda is an ordinary file containing a disk image:

 	image.bin	 <- hard disk image (a regular file)
 	image.bin/part1	 <- partition 1
 	image.bin/part1/ <- the filesystem inside partition 1

That's assuming there's a format handler which recognises that image.

-- Jamie