From e407fd655bf9b40c38cba29aa7d38149989798bb Mon Sep 17 00:00:00 2001 From: Lars-Peter Clausen Date: Mon, 4 Jun 2012 10:41:42 +0200 Subject: iio: Fix potential use after free There is no guarantee that the last reference to the iio device has already been dropped when iio_device_free is called. This means that we can up calling iio_dev_release after iio_device_free which will lead to a use after free. As the general rule the struct containing the device should always be freed in the release callback. This is what this patch does, it moves freeing the iio device struct as well as releasing the idr reference to the release callback. To ensure that the device is not freed before calling iio_device_free the device_unregister call in iio_device_unregister is broken apart. iio_device_unregister will now only call device_del to remove the device from the system and iio_device_free will call put_device to drop the reference we obtained in iio_devce_alloc. We also have to take care that calling iio_device_free without having called iio_device_register still works (i.e. this can happen if something failed during device initialization). For this to work properly two minor changes were necessary: channel_attr_list needs to be initialized in iio_device_alloc and we have to check whether the chrdev has been registered before releasing it in iio_device_release. This change also brings iio_device_unregister and iio_device_free more in sync with iio_device_register and iio_device_alloc which call device_add and device_initialize respectively. Signed-off-by: Lars-Peter Clausen Acked-by: Jonathan Cameron Signed-off-by: Greg Kroah-Hartman --- drivers/iio/industrialio-core.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) (limited to 'drivers/iio') diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c index 1ddd8861c71b..4f947e4377ef 100644 --- a/drivers/iio/industrialio-core.c +++ b/drivers/iio/industrialio-core.c @@ -661,7 +661,6 @@ static int iio_device_register_sysfs(struct iio_dev *indio_dev) * New channel registration method - relies on the fact a group does * not need to be initialized if it is name is NULL. */ - INIT_LIST_HEAD(&indio_dev->channel_attr_list); if (indio_dev->channels) for (i = 0; i < indio_dev->num_channels; i++) { ret = iio_device_add_channel_sysfs(indio_dev, @@ -725,12 +724,16 @@ static void iio_device_unregister_sysfs(struct iio_dev *indio_dev) static void iio_dev_release(struct device *device) { struct iio_dev *indio_dev = dev_to_iio_dev(device); - cdev_del(&indio_dev->chrdev); + if (indio_dev->chrdev.dev) + cdev_del(&indio_dev->chrdev); if (indio_dev->modes & INDIO_BUFFER_TRIGGERED) iio_device_unregister_trigger_consumer(indio_dev); iio_device_unregister_eventset(indio_dev); iio_device_unregister_sysfs(indio_dev); iio_device_unregister_debugfs(indio_dev); + + ida_simple_remove(&iio_ida, indio_dev->id); + kfree(indio_dev); } static struct device_type iio_dev_type = { @@ -761,6 +764,7 @@ struct iio_dev *iio_device_alloc(int sizeof_priv) dev_set_drvdata(&dev->dev, (void *)dev); mutex_init(&dev->mlock); mutex_init(&dev->info_exist_lock); + INIT_LIST_HEAD(&dev->channel_attr_list); dev->id = ida_simple_get(&iio_ida, 0, 0, GFP_KERNEL); if (dev->id < 0) { @@ -778,10 +782,8 @@ EXPORT_SYMBOL(iio_device_alloc); void iio_device_free(struct iio_dev *dev) { - if (dev) { - ida_simple_remove(&iio_ida, dev->id); - kfree(dev); - } + if (dev) + put_device(&dev->dev); } EXPORT_SYMBOL(iio_device_free); @@ -902,7 +904,7 @@ void iio_device_unregister(struct iio_dev *indio_dev) mutex_lock(&indio_dev->info_exist_lock); indio_dev->info = NULL; mutex_unlock(&indio_dev->info_exist_lock); - device_unregister(&indio_dev->dev); + device_del(&indio_dev->dev); } EXPORT_SYMBOL(iio_device_unregister); subsys_initcall(iio_init); -- cgit v1.2.3