Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756307AbYKEVlp (ORCPT ); Wed, 5 Nov 2008 16:41:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751954AbYKEVlh (ORCPT ); Wed, 5 Nov 2008 16:41:37 -0500 Received: from mx2.redhat.com ([66.187.237.31]:52032 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751363AbYKEVlg (ORCPT ); Wed, 5 Nov 2008 16:41:36 -0500 Message-ID: <491212C0.4030900@redhat.com> Date: Wed, 05 Nov 2008 16:40:16 -0500 From: Masami Hiramatsu User-Agent: Thunderbird 2.0.0.16 (X11/20080723) MIME-Version: 1.0 To: Lai Jiangshan , Andrew Morton , ananth@in.ibm.com CC: David Miller , Linux Kernel Mailing List , h-shimamoto@ct.jp.nec.com Subject: Re: [PATCH] kprobes: disable preempt for module_text_address() References: <490FE405.1000105@cn.fujitsu.com> <4910F697.2050203@redhat.com> <4910FB3D.4020805@cn.fujitsu.com> In-Reply-To: <4910FB3D.4020805@cn.fujitsu.com> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3281 Lines: 105 Lai Jiangshan wrote: > actually, calling __module_text_address() in __register_kprobe() is > better after my fix applied. but I found that a line have exceed > 80 characters, so I don't use __module_text_address(). I don't think that coding style is a good reason not to fix it...:( Anyway, I think the issue that you pointed must be fixed. I found there were same kind of issues in kprobes and updated your patch. This includes fixes which Hiroshi pointed out. Thanks a lot! :) __register_kprobe() can be preempted after checking probing address but before try_module_get() or module_put(), and in this interval the module can be unloaded. In that case, try_module_get(probed_mod) or module_put(mod) will access to invalid address, or kprobe will probe invalid address. this patch uses preempt_disable() to protect it and use __module_text_address() and __kernel_text_address(). Signed-off-by: Lai Jiangshan Signed-off-by: Masami Hiramatsu --- kernel/kprobes.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) Index: 2.6.28-rc3/kernel/kprobes.c =================================================================== --- 2.6.28-rc3.orig/kernel/kprobes.c +++ 2.6.28-rc3/kernel/kprobes.c @@ -613,30 +613,37 @@ static int __kprobes __register_kprobe(s return -EINVAL; p->addr = addr; - if (!kernel_text_address((unsigned long) p->addr) || - in_kprobes_functions((unsigned long) p->addr)) + preempt_disable(); + if (!__kernel_text_address((unsigned long) p->addr) || + in_kprobes_functions((unsigned long) p->addr)) { + preempt_enable(); return -EINVAL; + } p->mod_refcounted = 0; /* * Check if are we probing a module. */ - probed_mod = module_text_address((unsigned long) p->addr); + probed_mod = __module_text_address((unsigned long) p->addr); if (probed_mod) { - struct module *calling_mod = module_text_address(called_from); + struct module *calling_mod; + calling_mod = __module_text_address(called_from); /* * We must allow modules to probe themself and in this case * avoid incrementing the module refcount, so as to allow * unloading of self probing modules. */ if (calling_mod && calling_mod != probed_mod) { - if (unlikely(!try_module_get(probed_mod))) + if (unlikely(!try_module_get(probed_mod))) { + preempt_enable(); return -EINVAL; + } p->mod_refcounted = 1; } else probed_mod = NULL; } + preempt_enable(); p->nmissed = 0; INIT_LIST_HEAD(&p->list); @@ -718,9 +725,11 @@ static void __kprobes __unregister_kprob struct kprobe *old_p; if (p->mod_refcounted) { - mod = module_text_address((unsigned long)p->addr); + preempt_disable(); + mod = __module_text_address((unsigned long)p->addr); if (mod) module_put(mod); + preempt_enable(); } if (list_empty(&p->list) || list_is_singular(&p->list)) { -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America) Inc. Software Solutions Division e-mail: mhiramat@redhat.com -- 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/