Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757603AbZFZSCe (ORCPT ); Fri, 26 Jun 2009 14:02:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752611AbZFZSC1 (ORCPT ); Fri, 26 Jun 2009 14:02:27 -0400 Received: from charlotte.tuxdriver.com ([70.61.120.58]:51371 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751398AbZFZSC0 (ORCPT ); Fri, 26 Jun 2009 14:02:26 -0400 Date: Fri, 26 Jun 2009 14:02:22 -0400 From: Neil Horman To: Andrew Morton Cc: linux-kernel@vger.kernel.org, earl_chew@agilent.com, Oleg Nesterov , 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: <20090626180222.GD7337@hmsreliant.think-freely.org> References: <20090622172818.GB14673@hmsreliant.think-freely.org> <20090625163050.d6a71a13.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090625163050.d6a71a13.akpm@linux-foundation.org> 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: 2859 Lines: 71 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 | 32 +++++++++++++++++++------------- 1 file changed, 19 insertions(+), 13 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index ebe359f..163cfa7 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1802,22 +1802,28 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs) goto fail_unlock; if (ispipe) { - helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc); - /* 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"); + 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); + core_limit = RLIM_INFINITY; /* SIGPIPE can happen, but it's just never processed */ -- 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/