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media: dvbdev: adopts refcnt to avoid UAF

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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 <linma@zju.edu.cn>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
This commit is contained in:
Lin Ma
2022-08-07 15:59:52 +01:00
committed by Mauro Carvalho Chehab
parent 9b7de3c2da
commit 0fc044b2b5
4 changed files with 44 additions and 23 deletions
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drivers/media/dvb-core/dvbdev.c
+25 -7
View File
@@ -97,7 +97,7 @@ static int dvb_device_open(struct inode *inode, struct file *file)
new_fops = fops_get(dvbdev->fops);
if (!new_fops)
goto fail;
file->private_data = dvbdev;
file->private_data = dvb_device_get(dvbdev);
replace_fops(file, new_fops);
if (file->f_op->open)
err = file->f_op->open(inode, file);
@@ -161,6 +161,9 @@ int dvb_generic_release(struct inode *inode, struct file *file)
}
dvbdev->users++;
dvb_device_put(dvbdev);
return 0;
}
EXPORT_SYMBOL(dvb_generic_release);
@@ -479,6 +482,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
return -ENOMEM;
}
kref_init(&dvbdev->ref);
memcpy(dvbdev, template, sizeof(struct dvb_device));
dvbdev->type = type;
dvbdev->id = id;
@@ -510,7 +514,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
#endif
dvbdev->minor = minor;
dvb_minors[minor] = dvbdev;
dvb_minors[minor] = dvb_device_get(dvbdev);
up_write(&minor_rwsem);
ret = dvb_register_media_device(dvbdev, type, minor, demux_sink_pads);
@@ -555,6 +559,7 @@ void dvb_remove_device(struct dvb_device *dvbdev)
down_write(&minor_rwsem);
dvb_minors[dvbdev->minor] = NULL;
dvb_device_put(dvbdev);
up_write(&minor_rwsem);
dvb_media_device_free(dvbdev);
@@ -566,21 +571,34 @@ void dvb_remove_device(struct dvb_device *dvbdev)
EXPORT_SYMBOL(dvb_remove_device);
void dvb_free_device(struct dvb_device *dvbdev)
static void dvb_free_device(struct kref *ref)
{
if (!dvbdev)
return;
struct dvb_device *dvbdev = container_of(ref, struct dvb_device, ref);
kfree (dvbdev->fops);
kfree (dvbdev);
}
EXPORT_SYMBOL(dvb_free_device);
struct dvb_device *dvb_device_get(struct dvb_device *dvbdev)
{
kref_get(&dvbdev->ref);
return dvbdev;
}
EXPORT_SYMBOL(dvb_device_get);
void dvb_device_put(struct dvb_device *dvbdev)
{
if (dvbdev)
kref_put(&dvbdev->ref, dvb_free_device);
}
void dvb_unregister_device(struct dvb_device *dvbdev)
{
dvb_remove_device(dvbdev);
dvb_free_device(dvbdev);
dvb_device_put(dvbdev);
}
EXPORT_SYMBOL(dvb_unregister_device);