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From:   Russell Coker <russell@coker.com.au>
To:     Topi Miettinen <toiwoton@gmail.com>
Reply-To: russell@coker.com.au
Cc:     selinux-refpolicy@vger.kernel.org
Subject: Re: Access to raw memory: remove or make boolean?
Date:   Tue, 25 Feb 2020 02:42:58 +1100
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On Tuesday, 25 February 2020 2:11:46 AM AEDT Topi Miettinen wrote:
> Hi,
> 
> I made a PR 192 (https://github.com/SELinuxProject/refpolicy/pull/192)
> for introducing a new boolean to disable access to raw memory devices
> (/dev/mem, /dev/kmem, /dev/mergemem, dev/oldmem, /dev/port) because on
> modern systems, direct access shouldn't be needed anymore. Chris
> PeBenito asked to propose to this list whether instead of boolean, the
> access should be removed unconditionally if it's no longer needed. I
> think boolean could be useful for those systems where this is still
> needed but still use latest reference policy.

https://lwn.net/Articles/147901/

A quick search turned up the above article from 2005 debating whether /dev/
kmem was of any use then.

./admin/ddcprobe.te:dev_read_raw_memory(ddcprobe_t)
./admin/ddcprobe.te:dev_wx_raw_memory(ddcprobe_t)
./admin/dmidecode.te:dev_read_raw_memory(dmidecode_t)
./admin/kudzu.te:dev_rx_raw_memory(kudzu_t)
./admin/kudzu.te:dev_wx_raw_memory(kudzu_t)
./admin/mcelog.te:dev_read_raw_memory(mcelog_t)
./admin/rpm.te:dev_read_raw_memory(rpm_t)
./admin/sosreport.te:dev_read_raw_memory(sosreport_t)
./admin/tboot.te:dev_read_raw_memory(txtstat_t)
./admin/vbetool.te:dev_wx_raw_memory(vbetool_t)
./admin/vbetool.te:dev_read_raw_memory(vbetool_t)
./apps/vmware.te:dev_read_raw_memory(vmware_t)
./apps/vmware.te:dev_write_raw_memory(vmware_t)
./services/hal.te:dev_read_raw_memory(hald_t)
./services/hal.te:dev_read_raw_memory(hald_mac_t)
./services/hal.te:dev_write_raw_memory(hald_mac_t)
./services/devicekit.te:        dev_read_raw_memory(devicekit_disk_t)
./services/colord.te:dev_read_raw_memory(colord_t)
./services/colord.te:dev_write_raw_memory(colord_t)
./services/xserver.te:dev_read_raw_memory(xserver_t)
./services/xserver.te:dev_wx_raw_memory(xserver_t)
./system/iscsi.te:dev_read_raw_memory(iscsid_t)
./system/iscsi.te:dev_write_raw_memory(iscsid_t)
./system/raid.te:dev_read_raw_memory(mdadm_t)
./system/init.te:       dev_rx_raw_memory(initrc_t)
./system/init.te:       dev_wx_raw_memory(initrc_t)
./system/logging.te:dev_read_raw_memory(klogd_t)

A quick grep of the latest policy turned up the above access to /dev/mem.  Do 
ddcprobe_t, vbetool_t, and the X server still do that?  mcelog_t, and klogd_t 
might have good uses, as might sosreport_t (don't even know what it does but 
guessing it's like klogd_t).  rpm_t should maybe transition to a different 
domain for whatever it was doing and the same for kudzo_t.  Vmware  is a bit 
ugly, so vmware_t might actually do that.  iscsi_t, mdadm_t, colord_t, and 
initrc_t should never have needed that.  hald_t, hald_mac_t and 
devicekit_disk_t might have needed it, but hopefully that was fixed a long 
time ago.

Interestingly bootloader_t doesn't have such access even though a quick 
inspection of the LILO source code shows that it still probes the boot order 
by directly reading the BIOS memory.  I guess no-one uses LILO with SE Linux.

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