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-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20071015230729.53fcbaf7.pj@sgi.com>
Date:	Mon, 15 Oct 2007 23:07:29 -0700
From:	Paul Jackson <pj@....com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	menage@...gle.com, nickpiggin@...oo.com.au, a.p.zijlstra@...llo.nl,
	balbir@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	clg@...ibm.com, ebiederm@...ssion.com, containers@...ts.osdl.org,
	serue@...ibm.com, svaidy@...ux.vnet.ibm.com,
	akpm@...ux-foundation.org, xemul@...nvz.org
Subject: Re: [RFC] cpuset update_cgroup_cpus_allowed

> > +			if (cpus_equal(*cpus, t->cpus_allowed))
> > +				continue;
> > ...
> > +		for (q = tasks; q < p; q++) {
> > +			set_cpus_allowed(*q, *cpus);
> > +			put_task_struct(*q);
> > +		}
> > +	}
> > +}
> 
> Yet by not doing any locking here to prevent a cpu from being 
> hot-unplugged, you can race and allow the hot-unplug event to happen 
> before calling set_cpus_allowed().  That makes this entire function a 
> no-op with set_cpus_allowed() returning -EINVAL for every call, which 
> isn't caught, and no error is reported to userspace.
> 
> Now all the tasks in the cpuset have an inconsistent state with respect to 
> their p->cpuset->cpus_allowed, because that was already updated in 
> update_cpumask().

My solution may be worse than that.  Because set_cpus_allowed() will
fail if asked to set a non-overlapping cpumask, my solution could never
terminate.  If asked to set a cpusets cpus to something that went off
line right then, this I'd guess this code could keep looping forever,
looking for cpumasks that didn't match, and then not noticing that it
was failing to set them so as they would match.

... it needs work ... or the alternative solution from Paul M.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@....com> 1.925.600.0401
-
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/

Powered by blists - more mailing lists