Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761385AbZFZUY1 (ORCPT ); Fri, 26 Jun 2009 16:24:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750899AbZFZUYU (ORCPT ); Fri, 26 Jun 2009 16:24:20 -0400 Received: from charlotte.tuxdriver.com ([70.61.120.58]:43052 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750803AbZFZUYT (ORCPT ); Fri, 26 Jun 2009 16:24:19 -0400 Date: Fri, 26 Jun 2009 16:24:11 -0400 From: Neil Horman To: Oleg Nesterov Cc: Andrew Morton , linux-kernel@vger.kernel.org, earl_chew@agilent.com, Alan Cox , Andi Kleen Subject: Re: [PATCH 1/2] exec: Make do_coredump more robust and safer when using pipes in core_pattern: recursive dump detection Message-ID: <20090626202411.GH7337@hmsreliant.think-freely.org> References: <20090622172818.GB14673@hmsreliant.think-freely.org> <20090625163050.d6a71a13.akpm@linux-foundation.org> <20090626180222.GD7337@hmsreliant.think-freely.org> <20090626165908.GB12063@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090626165908.GB12063@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-Spam-Score: -1.4 (-) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2046 Lines: 52 On Fri, Jun 26, 2009 at 06:59:08PM +0200, Oleg Nesterov wrote: > On 06/26, Neil Horman wrote: > > > > + if (core_limit == 0) { > > + /* > > + * Normally core limits are irrelevant to pipes, since > > + * we're not writing to the file system, but we use > > + * core_limit of 0 here as a speacial value. Any > > + * non-zero limit gets set to RLIM_INFINITY below, but > > + * a limit of 0 skips the dump. This is a consistent > > + * way to catch recursive crashes. We can still crash > > + * if the core_pattern binary sets RLIM_CORE = !0 > > + * but it runs as root, and can do lots of stupid things > > + * Note that we use task_tgid_vnr here to grab the pid of the > > + * process group leader. That way we get the right pid if a thread > > + * in a multi-threaded core_pattern process dies. > > + */ > > + printk(KERN_WARNING "Process %d(%s) has RLIMIT_CORE set to 0\n", > > + task_tgid_vnr(current), current->comm); > > + printk(KERN_WARNING "Aborting core\n"); > > Andrew has already pointed out this, unprivileged-user-triggerable > printk. > > Doesn't look good, if core_pattern starts with "|" any user can set > RLIMIT_CORE = 0 and then just do > > for (;;) > if (pid = fork()) > kill(pid, SIGQUIT); > > to DOS printk/syslog, no? > I don't think SIGQUIT will trigger this, but SIGSEGV will. Regardless, if you do that, I would think you have bigger problems on your system. I would be silent about this, but I'm not sure thats a better solution Neil > Oleg. > > -- > 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/ > -- 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/