dmaengine: ti-dma-crossbar: Fix possible race condition with dma_inuse

commit 2ccb483 upstream.

When looking for unused xbar_out lane we should also protect the set_bit()
call with the same mutex to protect against concurrent threads picking the
same ID.

Fixes: ec9bfa1 ("dmaengine: ti-dma-crossbar: dra7: Use bitops instead of idr")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Peter Ujfalusi

drivers/dma/ti-dma-crossbar.c

@@ -262,13 +262,14 @@ static void *ti_dra7_xbar_route_allocate(struct of_phandle_args *dma_spec,
 	mutex_lock(&xbar->mutex);
 	map->xbar_out = find_first_zero_bit(xbar->dma_inuse,
 					    xbar->dma_requests);
-	mutex_unlock(&xbar->mutex);
 	if (map->xbar_out == xbar->dma_requests) {
+		mutex_unlock(&xbar->mutex);
 		dev_err(&pdev->dev, "Run out of free DMA requests\n");
 		kfree(map);
 		return ERR_PTR(-ENOMEM);
 	}
 	set_bit(map->xbar_out, xbar->dma_inuse);
+	mutex_unlock(&xbar->mutex);
 
 	map->xbar_in = (u16)dma_spec->args[0];