From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933561AbcBABv4 (ORCPT ); Sun, 31 Jan 2016 20:51:56 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:56668 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933350AbcBABvz (ORCPT ); Sun, 31 Jan 2016 20:51:55 -0500 From: Weilong Chen To: , , Subject: [PATCH v2] Race between cat /proc/kallsyms and rmmod Date: Mon, 1 Feb 2016 09:51:32 +0800 Message-ID: <1454291492-105918-1-git-send-email-chenweilong@huawei.com> X-Mailer: git-send-email 2.5.0 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.101.78] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020205.56AEBA34.00BA,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 09fe2a82f5fdb25abdf16dab904539da Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Iterating code of /proc/kallsyms calls module_get_kallsym() which grabs and drops module_mutex internally and returns "struct module *", module is removed, aforementioned "struct module *" is used in non-trivial way. So, grab module_mutex for entire operation like /proc/modules does. Steps to reproduce: while true; do modprobe xfs; rmmod xfs; done vs while true; do cat /proc/kallsyms >/dev/null; done Signed-off-by: Weilong Chen --- kernel/kallsyms.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 5c5987f..e09df60 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -516,6 +516,9 @@ static void *s_next(struct seq_file *m, void *p, loff_t *pos) static void *s_start(struct seq_file *m, loff_t *pos) { +#ifdef CONFIG_MODULES + mutex_lock(&module_mutex); +#endif if (!update_iter(m->private, *pos)) return NULL; return m->private; @@ -523,6 +526,9 @@ static void *s_start(struct seq_file *m, loff_t *pos) static void s_stop(struct seq_file *m, void *p) { +#ifdef CONFIG_MODULES + mutex_unlock(&module_mutex); +#endif } static int s_show(struct seq_file *m, void *p) -- 1.8.3.1