From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bryan Donlan Subject: Re: [resend][PATCH] Added PR_SET_PROCTITLE_AREA option for prctl() Date: Mon, 12 Oct 2009 15:33:11 -0400 Message-ID: <3e8340490910121233j17ebeb85m69e18566978b5ba2@mail.gmail.com> References: <2f11576a0910092332s6e0e3dcs35864e3a2164be0@mail.gmail.com> <3e8340490910100011u17497293o613334c64f1543c8@mail.gmail.com> <20091013031853.C744.A69D9226@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Return-path: In-Reply-To: <20091013031853.C744.A69D9226-+CUm20s59erQFUHtdCDX3A@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: KOSAKI Motohiro Cc: Andrew Morton , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Ulrich Drepper , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Timo Sirainen List-Id: linux-api@vger.kernel.org On Mon, Oct 12, 2009 at 3:03 PM, KOSAKI Motohiro wrote: > Hi > > Sorry for the delaying. > >> On Sat, Oct 10, 2009 at 2:32 AM, KOSAKI Motohiro >> wrote: >> >> >> It does seem like a maximum spin count should be put in there - and >> >> maybe a timeout as well (since with FUSE etc it's possible to engineer >> >> page faults that take arbitrarily long). >> >> Also, it occurs to me that: >> > >> > makes sense. >> > I like maximum spin rather than timeout. >> >> I'm worried about the scenario where process A sets its cmdline buffer >> to point to a page which will take a _VERY_ long time to pagein (maybe >> forever), and then process B goes to try to read its cmdline. What >> happens now? > > Honestly, I don't worry about so much. if attacker want DoS attack, fork bomb is > efficient than this way. then, attacker never use this. Fork bombs and etc can be mitigated by resource limits; but if the command line is placed on a page that will take a very long time to fault, then that cannot be mitigated... But again, this DoS already exists and isn't any easier with this patch, so I think it's a separate issue. >> Process A can arrange for this to happen by using a FUSE filesystem >> that sits on a read forever. And since the first thing the admin's >> likely to do to track down the problem is 'ps awux', this is liable to >> be a rather nasty DoS... > > Probably, I haven't understand this paragraph. Why is this FUSE related issue? Just an example of how one can create a page that will take a very long time to fault in.