[Leaplist] major bug found in Linux to give root access to untrusted users...

[Edward Guldemond]

On Wed, Nov 04, 2009 at 12:26:49PM -0500, Ray Brunkow wrote:
> is this as bad as it sounds?

Check to see if your vm.mmap_min_addr sysctl is set to a value above
0.  On my system (Debian), it's as simple as:

        $ sudo sysctl -n vm.mmap_min_addr
        4096

So my system is safe.  Check yours.  If it's not greater than zero,
then use sysctl to set it to something greater than zero:

        $ sudo sysctl -w vm.mmap_min_addr=4096

And put that in a startup script until your disto fixes it or you're
using a patched kernel (though 4096 is a safe default setting).

vm.mmap_min_addr, as the name implies, is the minimum memory address
that a process can mmap(), and it's tunable.  What this means is that
a process will not be allowed to mmap() at 0, thus preventing the NULL
pointer dereference attack.

-- 
Ed
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