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Commit 348badf1 authored by Haavard Skinnemoen's avatar Haavard Skinnemoen Committed by Linus Torvalds
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dmaengine: fix broken device refcounting 



When a DMA device is unregistered, its reference count is decremented twice
for each channel: Once dma_class_dev_release() and once in
dma_chan_cleanup().  This may result in the DMA device driver's remove()
function completing before all channels have been cleaned up, causing lots
of use-after-free fun.

Fix it by incrementing the device's reference count twice for each
channel during registration.

[dan.j.williams@intel.com: kill unnecessary client refcounting]
Signed-off-by: default avatarHaavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarShannon Nelson <shannon.nelson@intel.com>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 90d8dabf

drivers/dma/dmaengine.c

+6 −11
Original line number Diff line number Diff line
@@ -182,10 +182,9 @@ static void dma_client_chan_alloc(struct dma_client *client) 
				/* we are done once this client rejects

				 * an available resource

				 */

				if (ack == DMA_ACK) {

				if (ack == DMA_ACK)

					dma_chan_get(chan);

					kref_get(&device->refcount);

				} else if (ack == DMA_NAK)

				else if (ack == DMA_NAK)

					return;

			}

		}
@@ -272,11 +271,8 @@ static void dma_clients_notify_removed(struct dma_chan *chan) 
		/* client was holding resources for this channel so

		 * free it

		 */

		if (ack == DMA_ACK) {

		if (ack == DMA_ACK)

			dma_chan_put(chan);

			kref_put(&chan->device->refcount,

				dma_async_device_cleanup);

		}

	}



	mutex_unlock(&dma_list_mutex);
@@ -316,11 +312,8 @@ void dma_async_client_unregister(struct dma_client *client) 
			ack = client->event_callback(client, chan,

				DMA_RESOURCE_REMOVED);



			if (ack == DMA_ACK) {

			if (ack == DMA_ACK)

				dma_chan_put(chan);

				kref_put(&chan->device->refcount,

					dma_async_device_cleanup);

			}

		}



	list_del(&client->global_node);
@@ -397,6 +390,8 @@ int dma_async_device_register(struct dma_device *device) 
			goto err_out;

		}



		/* One for the channel, one of the class device */

		kref_get(&device->refcount);

		kref_get(&device->refcount);

		kref_init(&chan->refcount);

		chan->slow_ref = 0;