On Sat, 2007-10-27 at 06:49 -0700, Haavard Skinnemoen wrote:
> On Fri, 26 Oct 2007 09:36:17 -0700
> Dan Williams <[EMAIL PROTECTED]> wrote:
>
> > @@ -221,7 +220,6 @@ void dma_chan_cleanup(struct kref *kref)
> > {
> > struct dma_chan *chan = container_of(kref, struct dma_chan, refcount);
> > chan->device->device_free_chan_resources(chan);
> > - kref_put(&chan->device->refcount, dma_async_device_cleanup);
> > }
> > EXPORT_SYMBOL(dma_chan_cleanup);
>
> While I can't see any problems with the rest of the patch, I think this
> part is wrong for the same reasons removing the kref_put() from the
> class device cleanup function is. I don't see any constraint that
> guarantees that dma_chan_cleanup() will always be called before
> dma_dev_release(), which means that "chan" may have been freed before
> this function gets a chance to run. Please correct me if I'm wrong.
Absolutely right, the driver, not dmaengine, frees the memory so there
must be a per channel reference on the device to hold off the driver's
remove routine.
>
> Håvard
So how about this...
---snip---
dmaengine: Fix broken device refcounting
From: Haavard Skinnemoen <[EMAIL PROTECTED]>
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 <[EMAIL PROTECTED]>
[EMAIL PROTECTED]: kill unnecessary client refcounting]
Signed-off-by: Dan Williams <[EMAIL PROTECTED]>
---
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;
-
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