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authorYijing Wang <wangyijing@huawei.com>2014-11-07 12:05:49 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-11-07 08:17:43 -0800
commite4a60d139060975eb956717e4f63ae348d4d8cc5 (patch)
tree2535a5d665bf81e7ddcf253caf5c4ca8b4b8f8e4
parent0df1f2487d2f0d04703f142813d53615d62a1da4 (diff)
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sysfs: driver core: Fix glue dir race condition by gdp_mutex
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] [<ffffffff8103717a>] warn_slowpath_common+0x7a/0xb0 <4>[ 3965.441615] [<ffffffff810371c5>] warn_slowpath_null+0x15/0x20 <4>[ 3965.441618] [<ffffffff81215963>] kobject_get+0x33/0x40 <4>[ 3965.441624] [<ffffffff812d1e45>] get_device_parent.isra.11+0x135/0x1f0 <4>[ 3965.441627] [<ffffffff812d22d4>] device_add+0xd4/0x6d0 <4>[ 3965.441631] [<ffffffff812d0dbc>] ? 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] [<ffffffff811a677e>] sysfs_create_group+0xe/0x10 <4>[ 3965.686748] [<ffffffff810cfb04>] blk_trace_init_sysfs+0x14/0x20 <4>[ 3965.686753] [<ffffffff811fcabb>] blk_register_queue+0x3b/0x120 <4>[ 3965.686756] [<ffffffff812030bc>] add_disk+0x1cc/0x490 .... ------------------------------------------------------- Signed-off-by: Yijing Wang <wangyijing@huawei.com> Signed-off-by: Weng Meiling <wengmeiling.weng@huawei.com> Cc: <stable@vger.kernel.org> #3.4+ Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/base/core.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 14d162952c3b..842d04707de6 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)