Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756533AbZGCKuZ (ORCPT ); Fri, 3 Jul 2009 06:50:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755258AbZGCKuN (ORCPT ); Fri, 3 Jul 2009 06:50:13 -0400 Received: from charlotte.tuxdriver.com ([70.61.120.58]:50760 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754731AbZGCKuM (ORCPT ); Fri, 3 Jul 2009 06:50:12 -0400 Date: Fri, 3 Jul 2009 06:50:08 -0400 From: Neil Horman To: linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, earl_chew@agilent.com, alan@lxorguk.ukuu.org.uk, andi@firstfloor.org Subject: Re: [PATCH 1/3] exec: Make do_coredump more resilient to recursive crashes (v8) Message-ID: <20090703105008.GB19371@hmsreliant.think-freely.org> References: <20090622172818.GB14673@hmsreliant.think-freely.org> <20090703104447.GA19371@hmsreliant.think-freely.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090703104447.GA19371@hmsreliant.think-freely.org> User-Agent: Mutt/1.5.19 (2009-01-05) X-Spam-Score: -1.4 (-) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3374 Lines: 85 core_pattern: Change how we detect recursive dumps with core_pattern pipes Change how we detect recursive dumps. Currently we have a mechanism by which we try to compare pathnames of the crashing process to the core_pattern path. This is broken for a dozen reasons, and just doesn't work in any sort of robust way. I'm replacing it with the use of a 0 RLIMIT_CORE value. Since helper apps set RLIMIT_CORE to zero, we don't write out core files for any process with that particular limit set. It the core_pattern is a pipe, any non-zero limit is translated to RLIM_INFINITY. This allows complete dumps to be captured, but prevents infinite recursion in the event that the core_pattern process itself crashes. Signed-off-by: Neil Horman Reported-by: Earl Chew exec.c | 43 +++++++++++++++++++++---------------------- 1 file changed, 21 insertions(+), 22 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 9e05bd8..9defd20 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1776,35 +1776,34 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs) lock_kernel(); ispipe = format_corename(corename, signr); unlock_kernel(); - /* - * Don't bother to check the RLIMIT_CORE value if core_pattern points - * to a pipe. Since we're not writing directly to the filesystem - * RLIMIT_CORE doesn't really apply, as no actual core file will be - * created unless the pipe reader choses to write out the core file - * at which point file size limits and permissions will be imposed - * as it does with any other process - */ + if (ispipe) { + 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"); + goto fail_unlock; + } + helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc); if (!helper_argv) { printk(KERN_WARNING "%s failed to allocate memory\n", __func__); goto fail_unlock; } - /* Terminate the string before the first option */ - delimit = strchr(corename, ' '); - if (delimit) - *delimit = '\0'; - delimit = strrchr(helper_argv[0], '/'); - if (delimit) - delimit++; - else - delimit = helper_argv[0]; - if (!strcmp(delimit, current->comm)) { - printk(KERN_NOTICE "Recursive core dump detected, " - "aborting\n"); - goto fail_unlock; - } core_limit = RLIM_INFINITY; -- 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/