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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/media/usb/em28xx/em28xx-cards.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c index 06da08f8efdb..c7f79d0f3883 100644 --- a/drivers/media/usb/em28xx/em28xx-cards.c +++ b/drivers/media/usb/em28xx/em28xx-cards.c @@ -3822,6 +3822,8 @@ static int em28xx_usb_probe(struct usb_interface *intf, goto err_free; }
+ kref_init(&dev->ref); + dev->devno = nr; dev->model = id->driver_info; dev->alt = -1; @@ -3922,6 +3924,8 @@ static int em28xx_usb_probe(struct usb_interface *intf, }
if (dev->board.has_dual_ts && em28xx_duplicate_dev(dev) == 0) { + kref_init(&dev->dev_next->ref); + dev->dev_next->ts = SECONDARY_TS; dev->dev_next->alt = -1; dev->dev_next->is_audio_only = has_vendor_audio && @@ -3976,12 +3980,8 @@ static int em28xx_usb_probe(struct usb_interface *intf, em28xx_write_reg(dev, 0x0b, 0x82); mdelay(100); } - - kref_init(&dev->dev_next->ref); }
- kref_init(&dev->ref); - request_modules(dev);
/*