From patchwork Tue Nov 25 10:36:34 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luis Henriques X-Patchwork-Id: 414621 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id 0A3351401B1; Tue, 25 Nov 2014 22:02:30 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1XtDt4-00043j-SR; Tue, 25 Nov 2014 11:02:26 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1XtDY7-0002Gp-1N for kernel-team@lists.ubuntu.com; Tue, 25 Nov 2014 10:40:47 +0000 Received: from bl15-150-46.dsl.telepac.pt ([188.80.150.46] helo=localhost) by youngberry.canonical.com with esmtpsa (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1XtDY6-0001mp-Oj; Tue, 25 Nov 2014 10:40:46 +0000 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Subject: [PATCH 3.16.y-ckt 044/254] sysfs: driver core: Fix glue dir race condition by gdp_mutex Date: Tue, 25 Nov 2014 10:36:34 +0000 Message-Id: <1416912004-5928-45-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1416912004-5928-1-git-send-email-luis.henriques@canonical.com> References: <1416912004-5928-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Cc: Yijing Wang , Weng Meiling , Greg Kroah-Hartman X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: kernel-team-bounces@lists.ubuntu.com 3.16.7-ckt2 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Yijing Wang commit e4a60d139060975eb956717e4f63ae348d4d8cc5 upstream. There is a race condition when removing glue directory. It can be reproduced in following test: path 1: Add first child device device_add() get_device_parent() /*find parent from glue_dirs.list*/ list_for_each_entry(k, &dev->class->p->glue_dirs.list, entry) if (k->parent == parent_kobj) { kobj = kobject_get(k); break; } .... class_dir_create_and_add() path2: Remove last child device under glue dir device_del() cleanup_device_parent() cleanup_glue_dir() kobject_put(glue_dir); If path2 has been called cleanup_glue_dir(), but not call kobject_put(glue_dir), the glue dir is still in parent's kset list. Meanwhile, path1 find the glue dir from the glue_dirs.list. Path2 may release glue dir before path1 call kobject_get(). So kernel will report the warning and bug_on. This is a "classic" problem we have of a kref in a list that can be found while the last instance could be removed at the same time. This patch reuse gdp_mutex to fix this race condition. The following calltrace is captured in kernel 3.4, but the latest kernel still has this bug. ----------------------------------------------------- <4>[ 3965.441471] WARNING: at ...include/linux/kref.h:41 kobject_get+0x33/0x40() <4>[ 3965.441474] Hardware name: Romley <4>[ 3965.441475] Modules linked in: isd_iop(O) isd_xda(O)... ... <4>[ 3965.441605] Call Trace: <4>[ 3965.441611] [] warn_slowpath_common+0x7a/0xb0 <4>[ 3965.441615] [] warn_slowpath_null+0x15/0x20 <4>[ 3965.441618] [] kobject_get+0x33/0x40 <4>[ 3965.441624] [] get_device_parent.isra.11+0x135/0x1f0 <4>[ 3965.441627] [] device_add+0xd4/0x6d0 <4>[ 3965.441631] [] ? dev_set_name+0x3c/0x40 .... <2>[ 3965.441912] kernel BUG at ..../fs/sysfs/group.c:65! <4>[ 3965.441915] invalid opcode: 0000 [#1] SMP ... <4>[ 3965.686743] [] sysfs_create_group+0xe/0x10 <4>[ 3965.686748] [] blk_trace_init_sysfs+0x14/0x20 <4>[ 3965.686753] [] blk_register_queue+0x3b/0x120 <4>[ 3965.686756] [] add_disk+0x1cc/0x490 .... ------------------------------------------------------- Signed-off-by: Yijing Wang Signed-off-by: Weng Meiling Signed-off-by: Greg Kroah-Hartman Signed-off-by: Luis Henriques --- drivers/base/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index 20da3ad1696b..0e9468cb814f 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -724,12 +724,12 @@ class_dir_create_and_add(struct class *class, struct kobject *parent_kobj) return &dir->kobj; } +static DEFINE_MUTEX(gdp_mutex); static struct kobject *get_device_parent(struct device *dev, struct device *parent) { if (dev->class) { - static DEFINE_MUTEX(gdp_mutex); struct kobject *kobj = NULL; struct kobject *parent_kobj; struct kobject *k; @@ -793,7 +793,9 @@ static void cleanup_glue_dir(struct device *dev, struct kobject *glue_dir) glue_dir->kset != &dev->class->p->glue_dirs) return; + mutex_lock(&gdp_mutex); kobject_put(glue_dir); + mutex_unlock(&gdp_mutex); } static void cleanup_device_parent(struct device *dev)