[patch 09/29] dmaengine: fix broken device refcounting

Greg Kroah-Hartman
2007-11-20T18:28:59Z

[-- Attachment #1: dmaengine-fix-broken-device-refcounting.patch --]
[-- Type: text/plain, Size: 2452 bytes --]

2.6.23-stable review patch. If anyone has any objections, please let us
know.

------------------
From: Haavard Skinnemoen <hskinnemoen@atmel.com>

patch 348badf1e825323c419dd118f65783db0f7d2ec8 in mainline.

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: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/dma/dmaengine.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)

--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -182,10 +182,9 @@ static void dma_client_chan_alloc(struct
/* 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(s
/* 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
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
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;

--