[PATCH] driver core: fix resource leak in device_add()

[Zhengchao Shao]

When calling kobject_add() failed in device_add(), it will call
cleanup_glue_dir() to free resource. But in kobject_add(),
dev->kobj.parent has been set to NULL. This will cause resource leak.

The process is as follows:
device_add()
	get_device_parent()
		class_dir_create_and_add()
			kobject_add()		//kobject_get()
	...
	dev->kobj.parent = kobj;
	...
	kobject_add()		//failed, but set dev->kobj.parent = NULL
	...
	glue_dir = get_glue_dir(dev)	//glue_dir = NULL, and goto
					//"Error" label
	...
	cleanup_glue_dir()	//becaues glue_dir is NULL, not call
				//kobject_put()

The preceding problem may cause insmod mac80211_hwsim.ko to failed.
sysfs: cannot create duplicate filename '/devices/virtual/mac80211_hwsim'
Call Trace:
<TASK>
dump_stack_lvl+0x8e/0xd1
sysfs_warn_dup.cold+0x1c/0x29
sysfs_create_dir_ns+0x224/0x280
kobject_add_internal+0x2aa/0x880
kobject_add+0x135/0x1a0
get_device_parent+0x3d7/0x590
device_add+0x2aa/0x1cb0
device_create_groups_vargs+0x1eb/0x260
device_create+0xdc/0x110
mac80211_hwsim_new_radio+0x31e/0x4790 [mac80211_hwsim]
init_mac80211_hwsim+0x48d/0x1000 [mac80211_hwsim]
do_one_initcall+0x10f/0x630
do_init_module+0x19f/0x5e0
load_module+0x64b7/0x6eb0
__do_sys_finit_module+0x140/0x200
do_syscall_64+0x35/0x80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
</TASK>
kobject_add_internal failed for mac80211_hwsim with -EEXIST, don't try to
register things with the same name in the same directory.

Fixes: cebf8fd16900 ("driver core: fix race between creating/querying glue dir and its cleanup")
Signed-off-by: Zhengchao Shao <shaozhengchao@xxxxxxxxxx>
---
 drivers/base/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index d02501933467..1a7e74840dad 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3451,7 +3451,7 @@ int device_add(struct device *dev)
 	/* we require the name to be set before, and pass NULL */
 	error = kobject_add(&dev->kobj, dev->kobj.parent, NULL);
 	if (error) {
-		glue_dir = get_glue_dir(dev);
+		glue_dir = kobj;
 		goto Error;
 	}
 
-- 
2.17.1