From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934318AbbCPP1g (ORCPT ); Mon, 16 Mar 2015 11:27:36 -0400 Received: from cantor2.suse.de ([195.135.220.15]:48687 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932646AbbCPP1c (ORCPT ); Mon, 16 Mar 2015 11:27:32 -0400 From: Petr Mladek To: Masami Hiramatsu , "David S. Miller" , Anil S Keshavamurthy , Ananth NMavinakayanahalli , Frederic Weisbecker Cc: Ingo Molnar , Steven Rostedt , Jiri Kosina , linux-kernel@vger.kernel.org, Petr Mladek Subject: [PATCH v2] kprobes: Disable Kprobe when ftrace arming fails Date: Mon, 16 Mar 2015 16:27:47 +0100 Message-Id: <1426519667-7321-1-git-send-email-pmladek@suse.cz> X-Mailer: git-send-email 1.8.5.6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org arm_kprobe_ftrace() could fail, especially after introducing ftrace IPMODIFY flag and LifePatching. But this situation is not properly handled. This patch adds the most important changes. First, it does not make sense to register "kprobe_ftrace_ops" if the filter was not set. Second, we should remove the filter if the registration of "kprobe_ftrace_ops" fails. The failure might be caused by conflict between the Kprobe and a life patch via the IPMODIFY flag. If we remove the filter, we will allow to register "kprobe_ftrace_ops" for another non-conflicting Kprobe later. Third, we need to make sure that "kprobe_ftrace_enabled" is incremented only when "kprobe_ftrace_ops" is successfully registered. Otherwise, another Kprobe will not try to register it again. Note that we could move the manipulation with this counter because it is accessed only under "kprobe_mutex". Four, we should mark the probe as disabled if the ftrace stuff is not usable. It will be the correct status. Also it will prevent the unregistration code from producing another failure. It looks more safe to disable the Kprobe directly in "kprobe_ftrace_ops". Note that we need to disable also all listed Kprobes in case of an aggregated probe. It would be enough to disable only the new one but we do not know which one it was. They should be in sync anyway. Signed-off-by: Petr Mladek Acked-by: Masami Hiramatsu --- Hi, I resend this patch separately and have just added the acked by Masami. Best Regards, Petr kernel/kprobes.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index c90e417bb963..54b22db084f3 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -932,16 +932,33 @@ static int prepare_kprobe(struct kprobe *p) /* Caller must lock kprobe_mutex */ static void arm_kprobe_ftrace(struct kprobe *p) { + struct kprobe *kp; int ret; ret = ftrace_set_filter_ip(&kprobe_ftrace_ops, (unsigned long)p->addr, 0, 0); - WARN(ret < 0, "Failed to arm kprobe-ftrace at %p (%d)\n", p->addr, ret); - kprobe_ftrace_enabled++; - if (kprobe_ftrace_enabled == 1) { + if (WARN(ret < 0, + "Failed to arm kprobe-ftrace at %p (%d). The kprobe gets disabled.\n", + p->addr, ret)) + goto err_filter; + + if (!kprobe_ftrace_enabled) { ret = register_ftrace_function(&kprobe_ftrace_ops); - WARN(ret < 0, "Failed to init kprobe-ftrace (%d)\n", ret); + if (WARN(ret < 0, + "Failed to init kprobe-ftrace (%d). The probe at %p gets disabled\n", + ret, p->addr)) + goto err_function; } + kprobe_ftrace_enabled++; + return; + +err_function: + ftrace_set_filter_ip(&kprobe_ftrace_ops, (unsigned long)p->addr, 1, 0); +err_filter: + p->flags |= KPROBE_FLAG_DISABLED; + if (kprobe_aggrprobe(p)) + list_for_each_entry_rcu(kp, &p->list, list) + kp->flags |= KPROBE_FLAG_DISABLED; } /* Caller must lock kprobe_mutex */ -- 1.8.5.6