Re: Debian 4.0 and mmap_min_addr null pointer dereference flaw

[Rick Moen <rick@linuxmafia.com>]

Quoting john (lists.john@gmail.com):

> I see that there is another null pointer dereference flaw being talked about.
> http://www.theregister.co.uk/2009/11/03/linux_kernel_vulnerability/
> 
> It looks like we can take step in Debian 5.0 to mitigate this threat by setting
> echvm.mmap_min_addr = 4096
> 
> per http://wiki.debian.org/mmap_min_addr
> 
> I am running some servers running Debian 4.0. I doesn't look like
> there is a /etc/sysctl.d/mmap_min_addr.conf to edit. Where are these
> values stored
> under Debian 4.0.

John, I believe you can/should just put 

  vm.mmap_min_addr = 4096

at the bottom of /etc/sysctl.conf, and then re-run (as root) "sysctl -p"
to load values from that file.  You can verify that the appropriate
/proc value has been set by doing

  cat /proc/sys/vm/mmap_min_addr

Should now be "4096", rather than the distro default of "0".

As you know, BitBake, dosemu (run by non-root users), WINE (if running
Win16 apps), and qemu are the applications thus far identified that need
to be able to mmap to low memory addresses, necessitating low
vm.mmap_min_addr AKA /proc/sys/vm/mmap_min_addr values.