port-linux.c bug with oom_adjust_restore() - causes real bad oom_adj - which can cause DoS conditions.

[Darren Tucker]

On Tue, May 31, 2011 at 10:18 PM, Cal Leeming [Simplicity Media Ltd]
<cal.leeming at simplicitymedialtd.co.uk> wrote:
[...]
> Oh trust me, I looked *everywhere*. Even to the extent of running
> tripwire from a bare bones system, and looking manually at every
> change made. I also looked for loads of different keywords (-17, oom,
> proc, self) etc. Spent hours on it :/
>
> As for the comment about the modprobe, I already did all this (full
> debug can be found at
> http://www.debianhelp.org/content/cgroup-oom-killer-loop-causes-system-lockup-possible-fix-included
> ), and found that when the bnx2 module isn't loaded, the problem goes
> away.. When it is loaded, the problem comes back.

Did you check /proc/self/oom_adj before and after loading the module?
I don't see that in there, and it it *does* change it would eliminate
sshd as a variable.

As a workaround, you could add "echo 0 >/proc/self/oom_adj" to
/etc/default/ssh.  It's a bit ugly, but at least you wouldn't need to
recompile anything.

-- 
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.