Re: [PATCH v3] media: dvb-core: fix use-after-free in dvb_frontend_open()

["Zhou, Yun" <yun.zhou@windriver.com>]

Friendly ping

On 6/10/26 16:30, Yun Zhou wrote:
> dvb_frontend_open() calls dvb_generic_release() in its error path after
> dvb_generic_open() succeeds. dvb_generic_release() drops the device
> reference via dvb_device_put(), and then dvb_device_open() drops it again
> in its error handling, causing a use-after-free and refcount underflow.
>
> Fix this by incrementing the refcount before dvb_generic_release() in the
> error path, so that the put inside dvb_generic_release() is balanced and
> dvb_device_open() remains the sole effective put on open failure.
>
> Reported-by: syzbot+40339ea82afa8184ad5d@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=40339ea82afa8184ad5d
> Cc: stable@vger.kernel.org
> Fixes: 0fc044b2b5e2 ("media: dvbdev: adopts refcnt to avoid UAF")
> Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
> ---
> v3:
>   - Simplify fix: increment refcount before dvb_generic_release() instead
>     of introducing __dvb_generic_release()
>
> v2:
>   - Fix Fixes tag commit title
>   - Add Closes: link after Reported-by
>   - Cc stable@vger.kernel.org
>
>   drivers/media/dvb-core/dvb_frontend.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
> index d082b6c57c76..608525d08277 100644
> --- a/drivers/media/dvb-core/dvb_frontend.c
> +++ b/drivers/media/dvb-core/dvb_frontend.c
> @@ -2887,6 +2887,7 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
>   	mutex_unlock(&fe->dvb->mdev_lock);
>   err2:
>   #endif
> +	dvb_device_get(dvbdev);
>   	dvb_generic_release(inode, file);
>   err1:
>   	if (dvbdev->users == -1 && fe->ops.ts_bus_ctrl)