Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752649AbXJZKo7 (ORCPT ); Fri, 26 Oct 2007 06:44:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751301AbXJZKow (ORCPT ); Fri, 26 Oct 2007 06:44:52 -0400 Received: from twin.jikos.cz ([213.151.79.26]:53870 "EHLO twin.jikos.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751312AbXJZKov (ORCPT ); Fri, 26 Oct 2007 06:44:51 -0400 Date: Fri, 26 Oct 2007 12:44:23 +0200 (CEST) From: Jiri Kosina To: Sami Farin , Andrew Morton cc: Linux kernel Mailing List , Jiri Kosina , Arjan van de Ven Subject: [PATCH] [RFC] brk randomization: compute RLIMIT_DATA properly (was Re: x86: randomize brk() and RLIMIT_DATA) In-Reply-To: <20071025171942.pjff7jbpempfcuri@m.safari.iki.fi> Message-ID: References: <20071025134124.wc44gdud7ixghfxv@m.safari.iki.fi> <20071025071324.2eac21d6@laptopd505.fenrus.org> <20071025171942.pjff7jbpempfcuri@m.safari.iki.fi> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2189 Lines: 52 On Thu, 25 Oct 2007, Sami Farin wrote: > > > > Would be neat if randomized brk and setrlimit(RLIMIT_DATA, ...) > > > > worked in a predictable way: > > > this isn't a valid case afaics; even on "traditional x86" (before we > > > changed the address space layout, or even today if you have an > > > unlimited stack rlimit) this isn't going to work. applications > > > really shouldn't use (s)brk() but malloc(); you have to be able to > > > fall back to mmap regardless of what you do. > > I tend to agree here with Arjan. However it probably would make no > > harm to make at least a little bit consisten behavior of setrlimit(), > > though it has a little use in such cases. > > Sami, does the patch below work for you? > Thanks, Jiri, now RLIMIT_DATA works as expected. Using only RLIMIT_AS to > limit processes' memory usage is not very easy. It includes also > libraries mapped read-only, I have to check/modify the limits when I > update/add libraries,... This patch is [RFC] as I am not sure whether it is worth it (see Arjan's comment above). From: Jiri Kosina brk randomization: compute RLIMIT_DATA properly In cases of heap area placed at randomly-generated offset from mm->end_data (arch_randomize_brk()), we need to subtract the value of the offset for setrlimit(RLIMIT_DATA) to work properly -- otherwise we count the unoccupied memory between mm->end_data and mm->start_brk as occupied. Signed-off-by: Jiri Kosina diff --git a/mm/mmap.c b/mm/mmap.c index facc1a7..c7ade18 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -251,7 +251,8 @@ asmlinkage unsigned long sys_brk(unsigned long brk) * not page aligned -Ram Gupta */ rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur; - if (rlim < RLIM_INFINITY && brk - mm->start_data > rlim) + if (rlim < RLIM_INFINITY && brk - mm->start_data - + (mm->start_brk - mm->end_data) > rlim) goto out; newbrk = PAGE_ALIGN(brk); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/