Permissions on ps

Midnight Oil jamie at
Tue Jun 7 04:52:29 GMT 2005

   I'm having difficulty understanding just how it is a regular
with simple priviliges is able to run ps.

ps accesses /dev/kmem to get a process list.

floyd% ls -al /dev/kmem
crw-r-----  1 root  kmem    2,   1 Jan 16  2004 /dev/kmem

 -- /dev/kmem is read/write accessable to root, and read accessable to
anyone in group kmem.

floyd% ls -al /bin/ps
-r-xr-xr-x  1 root  wheel  215368 Oct 27  2003 /bin/ps*

 -- /bin/ps is owned by root:wheel, no suid or sgid, so it should run as
whoever starts it (world executable).

  Million $$ question:
  How is it that anyone can run ps if ps accesses /dev/kmem? It shouldn't
be able to open that device. Any idea?

   - Jme

The Moon is New

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