[PATCH 4.4 153/158] media: cpia2_usb: first wake up, then free in disconnect

Greg Kroah-Hartman
2019-08-02T09:36:13Z

From: Oliver Neukum <oneukum@suse.com>

commit eff73de2b1600ad8230692f00bc0ab49b166512a upstream.

Kasan reported a use after free in cpia2_usb_disconnect()
It first freed everything and then woke up those waiting.
The reverse order is correct.

Fixes: 6c493f8b28c67 ("[media] cpia2: major overhaul to get it in a working state again")

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reported-by: syzbot+0c90fc937c84f97d0aa6@syzkaller.appspotmail.com
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/media/usb/cpia2/cpia2_usb.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/media/usb/cpia2/cpia2_usb.c
+++ b/drivers/media/usb/cpia2/cpia2_usb.c
@@ -884,7 +884,6 @@ static void cpia2_usb_disconnect(struct
cpia2_unregister_camera(cam);
v4l2_device_disconnect(&cam->v4l2_dev);
mutex_unlock(&cam->v4l2_lock);
- v4l2_device_put(&cam->v4l2_dev);

if(cam->buffers) {
DBG("Wakeup waiting processes\n");
@@ -897,6 +896,8 @@ static void cpia2_usb_disconnect(struct
DBG("Releasing interface\n");
usb_driver_release_interface(&cpia2_driver, intf);

+ v4l2_device_put(&cam->v4l2_dev);
+
LOG("CPiA2 camera disconnected.\n");
}