From: Dongliang Mu mudongliangabcd@gmail.com

[ Upstream commit c08eadca1bdfa099e20a32f8fa4b52b2f672236d ]

The commit 47677e51e2a4("[media] em28xx: Only deallocate struct em28xx after finishing all extensions") adds kref_get to many init functions (e.g., em28xx_audio_init). However, kref_init is called too late in em28xx_usb_probe, since em28xx_init_dev before will invoke those init functions and call kref_get function. Then refcount bug occurs in my local syzkaller instance.

Fix it by moving kref_init before em28xx_init_dev. This issue occurs not only in dev but also dev->dev_next.

Fixes: 47677e51e2a4 ("[media] em28xx: Only deallocate struct em28xx after finishing all extensions") Reported-by: syzkaller syzkaller@googlegroups.com Signed-off-by: Dongliang Mu mudongliangabcd@gmail.com Signed-off-by: Hans Verkuil hverkuil-cisco@xs4all.nl [DP: drop changes related to dev->dev_next as second tuner functionality was added in 4.16] Signed-off-by: Dragos-Marian Panait dragos.panait@windriver.com --- drivers/media/usb/em28xx/em28xx-cards.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c index b736c027a0bd..23a9fe8d9d1e 100644 --- a/drivers/media/usb/em28xx/em28xx-cards.c +++ b/drivers/media/usb/em28xx/em28xx-cards.c @@ -3644,6 +3644,8 @@ static int em28xx_usb_probe(struct usb_interface *interface, goto err_free; }

+ kref_init(&dev->ref); + dev->devno = nr; dev->model = id->driver_info; dev->alt = -1; @@ -3730,8 +3732,6 @@ static int em28xx_usb_probe(struct usb_interface *interface, dev->dvb_xfer_bulk ? "bulk" : "isoc"); }

- kref_init(&dev->ref); - request_modules(dev);

/*