On Thu, Apr 1, 2021 at 2:56 PM Yufen Yu <yuyufen@xxxxxxxxxx> wrote: > > 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. The patch looks reasonable to me, but the above is not what it does. It causes device_del() to be a no-op for devices that have not been successfully added. > 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); > --
