Why does the filesystem think /selinux/enforce is an empty file?

openSauce · 12-17-2008, 06:58 AM

The file /selinux/enforce contains 1 character, according to cat, but apparently it has zero size. What's going on here?

Code:

$ cat /selinux/enforce
1$ ls -l /selinux/enforce
-rw-r--r-- 1 root root 0 2008-12-17 12:36 /selinux/enforce
$ du -b /selinux/enforce
0       /selinux/enforce
$ file /selinux/enforce
/selinux/enforce: empty
$

PTrenholme · 12-17-2008, 08:07 AM

Yes, that's strange. Perhaps you should ask he moderators to move his thread to the security forum. I suspect that it's a security issue. Speaking of zero length files with content, look at this:

Code:

$ ls -l /selinux/
total 0
-rw-rw-rw-  1 root root    0 2008-12-16 21:33 access
dr-xr-xr-x  2 root root    0 2008-12-16 21:33 avc
dr-xr-xr-x  2 root root    0 2008-12-16 21:33 booleans
-rw-r--r--  1 root root    0 2008-12-16 21:33 checkreqprot
dr-xr-xr-x 75 root root    0 2008-12-16 21:33 class
--w-------  1 root root    0 2008-12-16 21:33 commit_pending_bools
-rw-r--r--  1 root root    0 2008-12-16 21:33 compat_net
-rw-rw-rw-  1 root root    0 2008-12-16 21:33 context
-rw-rw-rw-  1 root root    0 2008-12-16 21:33 create
-r--r--r--  1 root root    0 2008-12-16 21:33 deny_unknown
--w-------  1 root root    0 2008-12-16 21:33 disable
-rw-r--r--  1 root root    0 2008-12-16 21:33 enforce
dr-xr-xr-x  2 root root    0 2008-12-16 21:33 initial_contexts
-rw-------  1 root root    0 2008-12-16 21:33 load
-rw-rw-rw-  1 root root    0 2008-12-16 21:33 member
-r--r--r--  1 root root    0 2008-12-16 21:33 mls
crw-rw-rw-  1 root root 1, 3 2008-12-16 21:33 null
dr-xr-xr-x  2 root root    0 2008-12-16 21:33 policy_capabilities
-r--r--r--  1 root root    0 2008-12-16 21:33 policyvers
-r--r--r--  1 root root    0 2008-12-16 21:33 reject_unknown
-rw-rw-rw-  1 root root    0 2008-12-16 21:33 relabel
-rw-rw-rw-  1 root root    0 2008-12-16 21:33 user

Note the date/time is the time I last turned off the system . . .

Valery Reznic · 12-18-2008, 02:58 AM

It's not only /slinux but /proc too.
All files but links has zero size.
Looks like kernel doesn't bother to export correct file size for stat