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Subject: media: edia: dvbdev: fix a use-after-free
Author: Zhipeng Lu <alexi...@zju.edu.cn>
Date: Sat Feb 3 14:40:43 2024 +0100
In dvb_register_device, *pdvbdev is set equal to dvbdev, which is freed
in several error-handling paths. However, *pdvbdev is not set to NULL
after dvbdev's deallocation, causing use-after-frees in many places,
for example, in the following call chain:
budget_register
|-> dvb_dmxdev_init
|-> dvb_register_device
|-> dvb_dmxdev_release
|-> dvb_unregister_device
|-> dvb_remove_device
|-> dvb_device_put
|-> kref_put
When calling dvb_unregister_device, dmxdev->dvbdev (i.e. *pdvbdev in
dvb_register_device) could point to memory that had been freed in
dvb_register_device. Thereafter, this pointer is transferred to
kref_put and triggering a use-after-free.
Link:
https://lore.kernel.org/linux-media/20240203134046.3120099-1-alexi...@zju.edu.cn
Fixes: b61901024776 ("V4L/DVB (5244): Dvbdev: fix illegal re-usage of
fileoperations struct")
Signed-off-by: Zhipeng Lu <alexi...@zju.edu.cn>
Signed-off-by: Mauro Carvalho Chehab <mche...@kernel.org>
drivers/media/dvb-core/dvbdev.c | 5 +++++
1 file changed, 5 insertions(+)
---
diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
index 49f0eb7d0b9d..733d0bc4b4cc 100644
--- a/drivers/media/dvb-core/dvbdev.c
+++ b/drivers/media/dvb-core/dvbdev.c
@@ -490,6 +490,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct
dvb_device **pdvbdev,
dvbdevfops = kmemdup(template->fops, sizeof(*dvbdevfops),
GFP_KERNEL);
if (!dvbdevfops) {
kfree(dvbdev);
+ *pdvbdev = NULL;
mutex_unlock(&dvbdev_register_lock);
return -ENOMEM;
}
@@ -498,6 +499,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct
dvb_device **pdvbdev,
if (!new_node) {
kfree(dvbdevfops);
kfree(dvbdev);
+ *pdvbdev = NULL;
mutex_unlock(&dvbdev_register_lock);
return -ENOMEM;
}
@@ -531,6 +533,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct
dvb_device **pdvbdev,
}
list_del(&dvbdev->list_head);
kfree(dvbdev);
+ *pdvbdev = NULL;
up_write(&minor_rwsem);
mutex_unlock(&dvbdev_register_lock);
return -EINVAL;
@@ -553,6 +556,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct
dvb_device **pdvbdev,
dvb_media_device_free(dvbdev);
list_del(&dvbdev->list_head);
kfree(dvbdev);
+ *pdvbdev = NULL;
mutex_unlock(&dvbdev_register_lock);
return ret;
}
@@ -571,6 +575,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct
dvb_device **pdvbdev,
dvb_media_device_free(dvbdev);
list_del(&dvbdev->list_head);
kfree(dvbdev);
+ *pdvbdev = NULL;
mutex_unlock(&dvbdev_register_lock);
return PTR_ERR(clsdev);
}
