Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754743AbZINKFF (ORCPT ); Mon, 14 Sep 2009 06:05:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753314AbZINKFE (ORCPT ); Mon, 14 Sep 2009 06:05:04 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:46601 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752318AbZINKFC (ORCPT ); Mon, 14 Sep 2009 06:05:02 -0400 Date: Mon, 14 Sep 2009 15:34:59 +0530 From: Ananth N Mavinakayanahalli To: Masami Hiramatsu Cc: Frederic Weisbecker , Steven Rostedt , Ingo Molnar , lkml , systemtap , DLE , Jim Keniston , Andi Kleen , Christoph Hellwig , "Frank Ch. Eigler" , "H. Peter Anvin" , Jason Baron , "K.Prasad" , Lai Jiangshan , Li Zefan , Peter Zijlstra , Srikar Dronamraju , Tom Zanussi Subject: Re: [BUGFIX] kprobes: prevent re-registration of the same kprobe - take2 Message-ID: <20090914100459.GA4446@in.ibm.com> Reply-To: ananth@in.ibm.com References: <20090910235258.22412.29317.stgit@dhcp-100-2-132.bos.redhat.com> <20090910235329.22412.94731.stgit@dhcp-100-2-132.bos.redhat.com> <20090911031253.GD16396@nowhere> <20090913100713.GB14251@in.ibm.com> <4AADA0BB.4030307@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4AADA0BB.4030307@redhat.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3715 Lines: 127 On Sun, Sep 13, 2009 at 09:47:39PM -0400, Masami Hiramatsu wrote: > Ananth N Mavinakayanahalli wrote: > > On Fri, Sep 11, 2009 at 05:12:54AM +0200, Frederic Weisbecker wrote: > >> On Thu, Sep 10, 2009 at 07:53:30PM -0400, Masami Hiramatsu wrote: ... > Hmm, if we catch the second registration here, it's too late. At > register_kprobe(), we initialized some field of kprobe before calling > register_aggr_kprobe(). Especially kprobe.list is cleared. > > And this can't check the case that 'p' is already registered on > an aggr kprobe. Agreed. I thought of this case after sending out the earlier patch... > Thus, I think some initialization paths should be changed (kp.flag > field is initialized too early, yearh, that's my mistake), > and also, you will need to use get_valid_kprobe() to check the kprobe > has not been registered. __get_valid_kprobe() makes the task easy. We should just prevent re-registration whether or not the earlier probe is disabled. How does this patch look? --- Prevent re-registration of the same kprobe. This situation, though unlikely, needs to be flagged since it can lead to a system crash if its not handled. The core change itself is small, but the helper routine needed to be moved around a bit; hence the diffstat. Signed-off-by: Ananth N Mavinakayanahalli --- kernel/kprobes.c | 58 ++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 38 insertions(+), 20 deletions(-) Index: linux-2.6.31/kernel/kprobes.c =================================================================== --- linux-2.6.31.orig/kernel/kprobes.c +++ linux-2.6.31/kernel/kprobes.c @@ -681,6 +681,40 @@ static kprobe_opcode_t __kprobes *kprobe return (kprobe_opcode_t *)(((char *)addr) + p->offset); } +/* Check passed kprobe is valid and return kprobe in kprobe_table. */ +static struct kprobe * __kprobes __get_valid_kprobe(struct kprobe *p) +{ + struct kprobe *old_p, *list_p; + + old_p = get_kprobe(p->addr); + if (unlikely(!old_p)) + return NULL; + + if (p != old_p) { + list_for_each_entry_rcu(list_p, &old_p->list, list) + if (list_p == p) + /* kprobe p is a valid probe */ + goto valid; + return NULL; + } +valid: + return old_p; +} + +/* Return error if the kprobe is being re-registered */ +static inline int check_kprobe_rereg(struct kprobe *p) +{ + int ret = 0; + struct kprobe *old_p; + + mutex_lock(&kprobe_mutex); + old_p = __get_valid_kprobe(p); + if (old_p == p) + ret = -EINVAL; + mutex_unlock(&kprobe_mutex); + return ret; +} + int __kprobes register_kprobe(struct kprobe *p) { int ret = 0; @@ -693,6 +727,10 @@ int __kprobes register_kprobe(struct kpr return -EINVAL; p->addr = addr; + ret = check_kprobe_rereg(p); + if (ret) + return ret; + preempt_disable(); if (!kernel_text_address((unsigned long) p->addr) || in_kprobes_functions((unsigned long) p->addr)) { @@ -762,26 +800,6 @@ out: } EXPORT_SYMBOL_GPL(register_kprobe); -/* Check passed kprobe is valid and return kprobe in kprobe_table. */ -static struct kprobe * __kprobes __get_valid_kprobe(struct kprobe *p) -{ - struct kprobe *old_p, *list_p; - - old_p = get_kprobe(p->addr); - if (unlikely(!old_p)) - return NULL; - - if (p != old_p) { - list_for_each_entry_rcu(list_p, &old_p->list, list) - if (list_p == p) - /* kprobe p is a valid probe */ - goto valid; - return NULL; - } -valid: - return old_p; -} - /* * Unregister a kprobe without a scheduler synchronization. */ -- 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/