Message ID | 20210401130138.2164928-1-yuyufen@huawei.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | drivers core: don't do anything in device_del() when device_add() fail | expand |
On Thu, Apr 1, 2021 at 2:56 PM Yufen Yu <yuyufen@huawei.com> 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@huawei.com> > --- > 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); > --
On Thu, Apr 01, 2021 at 09:01:38AM -0400, Yufen Yu wrote: > Recently, our syzbot test reported NULL pointer dereference in > device_del() by injecting memory allocation fail in device_add(). Don't do that :) > For now, callers of device_add(), such as add_disk(), may ignore > device_add()'s fail and go on working. Please fix up those users, if device_add() fails there is no need to call device_del(). > 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. As Rafael said, that's not what you are doing here, so even if I wanted to take this patch, I can't. > > Signed-off-by: Yufen Yu <yuyufen@huawei.com> > --- > 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; Also, this isn't a good test as it's not obvious what you are trying to check for here. thanks, greg k-h
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);
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@huawei.com> --- drivers/base/core.c | 3 +++ 1 file changed, 3 insertions(+)