From 2abd73433872194bccdf1432a0980e4ec5273c2a Mon Sep 17 00:00:00 2001 From: Lin Ma Date: Sun, 7 Aug 2022 15:59:52 +0100 Subject: media: dvbdev: adopts refcnt to avoid UAF [ Upstream commit 0fc044b2b5e2d05a1fa1fb0d7f270367a7855d79 ] dvb_unregister_device() is known that prone to use-after-free. That is, the cleanup from dvb_unregister_device() releases the dvb_device even if there are pointers stored in file->private_data still refer to it. This patch adds a reference counter into struct dvb_device and delays its deallocation until no pointer refers to the object. Link: https://lore.kernel.org/linux-media/20220807145952.10368-1-linma@zju.edu.cn Signed-off-by: Lin Ma Reported-by: kernel test robot Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Sasha Levin --- include/media/dvbdev.h | 31 +++++++++++++++++-------------- 1 file changed, 17 insertions(+), 14 deletions(-) (limited to 'include/media') diff --git a/include/media/dvbdev.h b/include/media/dvbdev.h index e547cbeee431..6e736587aa1f 100644 --- a/include/media/dvbdev.h +++ b/include/media/dvbdev.h @@ -156,6 +156,7 @@ struct dvb_adapter { */ struct dvb_device { struct list_head list_head; + struct kref ref; const struct file_operations *fops; struct dvb_adapter *adapter; enum dvb_device_type type; @@ -187,6 +188,20 @@ struct dvb_device { void *priv; }; +/** + * dvb_device_get - Increase dvb_device reference + * + * @dvbdev: pointer to struct dvb_device + */ +struct dvb_device *dvb_device_get(struct dvb_device *dvbdev); + +/** + * dvb_device_get - Decrease dvb_device reference + * + * @dvbdev: pointer to struct dvb_device + */ +void dvb_device_put(struct dvb_device *dvbdev); + /** * dvb_register_adapter - Registers a new DVB adapter * @@ -231,29 +246,17 @@ int dvb_register_device(struct dvb_adapter *adap, /** * dvb_remove_device - Remove a registered DVB device * - * This does not free memory. To do that, call dvb_free_device(). + * This does not free memory. dvb_free_device() will do that when + * reference counter is empty * * @dvbdev: pointer to struct dvb_device */ void dvb_remove_device(struct dvb_device *dvbdev); -/** - * dvb_free_device - Free memory occupied by a DVB device. - * - * Call dvb_unregister_device() before calling this function. - * - * @dvbdev: pointer to struct dvb_device - */ -void dvb_free_device(struct dvb_device *dvbdev); /** * dvb_unregister_device - Unregisters a DVB device * - * This is a combination of dvb_remove_device() and dvb_free_device(). - * Using this function is usually a mistake, and is often an indicator - * for a use-after-free bug (when a userspace process keeps a file - * handle to a detached device). - * * @dvbdev: pointer to struct dvb_device */ void dvb_unregister_device(struct dvb_device *dvbdev); -- cgit v1.2.3