linux-kernel - evading ulimits

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 22 Dec 2006 16:23:59 -0500
From:	John Richard Moser <nigelenki@...cast.net>
To:	linux-kernel@...r.kernel.org
Subject: evading ulimits

I've set up some stuff on my box where /etc/security/limits.conf
contains the following:

@users          soft    nproc           3072
@users          hard    nproc           4096

I'm in group users, and a simple fork bomb is easily quashed by this:

bluefox@...box:~$ :(){ :|:; };:
bash: fork: Resource temporarily unavailable
Terminated

Oddly enough, trying this again and again yields the same results; but,
I can kill the box (eventually; about 1 minute in I managed to `/exec
killall -9 bash` from x-chat, since I couldn't get a new shell open)
with the below:

bluefox@...box:~$ :(){ :|:|:; };:

How exactly does the ulimit work?  Why do I seem to be able to evade
limits on maximum number of processes by doing a bigger fork bomb?  I
would have thought that the above would have terminated much sooner,
since it was spawning x^3 processes instead of x^2 for iteration x and
should have hit 4096 a lot sooner.

-- 
    We will enslave their women, eat their children and rape their
    cattle!
             -- Bosc, Evil alien overlord from the fifth dimension
Anti-Spam:  https://bugzilla.mozilla.org/show_bug.cgi?id=229686
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/