[PATCH] drivers core: don't do anything in device_del() when device_add() fail

[Yufen Yu]

Recently, our syzbot test reported NULL pointer dereference in
device_del() by injecting memory allocation fail in device_add().

For now, callers of device_add(), such as add_disk(), may ignore
device_add()'s fail and go on working. In unregister path, it will
call device_del() from del_gendisk(). That can cause various NULL
pointer dereference, including dev->p is NULL in kill_device(),
'name' is NULL in sysfs_remove_link(), kobj->sd is 'NULL' when call
dpm_sysfs_remove(), and so on.

To avoid these kernel panic, we call device_del() only when device_add()
is success.

Signed-off-by: Yufen Yu <yuyufen@xxxxxxxxxx>
---
 drivers/base/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index f29839382f81..a10ec5dbc577 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3380,6 +3380,9 @@ void device_del(struct device *dev)
 	struct class_interface *class_intf;
 	unsigned int noio_flag;
 
+	if (!dev->p)
+		return;
+
 	device_lock(dev);
 	kill_device(dev);
 	device_unlock(dev);
-- 
2.25.4