Re: procfs permissions on 2.6.x

[bert hubert <ahu@ds9a.nl>]

On Sat, Jul 03, 2004 at 01:35:56PM -0700, Andrew Morton wrote:

> Why is it "extremely bogus"?  I assume Olaf had a reason for wanting chmod
> on procfs files?

On a related note:
ahu@d800:/sys/devices/system/cpu/cpu0/cpufreq$ ls -l
total 0
-r--------    1 ahu      ahu          4096 2004-07-04 03:18 cpuinfo_cur_freq
-r--r--r--    1 ahu      ahu          4096 2004-07-04 03:18 cpuinfo_max_freq

..

I'm not entirely sure why the current CPU frequency has suddenly become a
state secret, nor why the ownership of these files appears to be uid 1000.

-r--r--r--    1 ahu      ahu          4096 2004-07-04 03:18 cpuinfo_min_freq
-r--r--r--    1 ahu      ahu          4096 2004-07-04 03:18 scaling_available_frequencies
-r--r--r--    1 ahu      ahu          4096 2004-07-04 03:18 scaling_available_governors
-r--r--r--    1 ahu      ahu          4096 2004-07-04 03:18 scaling_cur_freq
-r--r--r--    1 ahu      ahu          4096 2004-07-04 03:18 scaling_driver
-rw-r--r--    1 ahu      ahu          4096 2004-07-04 03:18 scaling_governor
-rw-r--r--    1 ahu      ahu          4096 2004-07-04 03:18 scaling_max_freq
-rw-r--r--    1 ahu      ahu          4096 2004-07-04 03:18 scaling_min_freq

This appears to be even more bogus - uid 1000 can write to the scaling
governor. It looks like the uid that mounted /sys owns these files. Not
entirely sure what happens.

Fixes appear trivial but I wonder about the reasons.

Regards,

bert

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