Messages in this thread Patch in this message | | | Subject | [PATCH] dmaengine: Fix broken device refcounting | From | Dan Williams <> | Date | Wed, 07 Nov 2007 11:46:07 -0700 |
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From: Haavard Skinnemoen <hskinnemoen@atmel.com>
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.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com> [dan.j.williams@intel.com: kill unnecessary client refcounting] Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Shannon Nelson <shannon.nelson@intel.com> Cc: stable@kernel.org ---
This fixes dmaengine refcounting in 2.6.23.y and 2.6.24-rc.
drivers/dma/dmaengine.c | 17 ++++++----------- 1 files changed, 6 insertions(+), 11 deletions(-)
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 84257f7..ec7e871 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -186,10 +186,9 @@ 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; } } @@ -276,11 +275,8 @@ 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); @@ -320,11 +316,8 @@ 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); @@ -401,6 +394,8 @@ 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; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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