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

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
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