dmaengine: tegra-apb: Prevent race conditions of tasklet vs free list

commit c33ee1301c393a241d6424e36eff1071811b1064 upstream.

The interrupt handler puts a half-completed DMA descriptor on a free list
and then schedules tasklet to process bottom half of the descriptor that
executes client's callback, this creates possibility to pick up the busy
descriptor from the free list. Thus, let's disallow descriptor's re-use
until it is fully processed.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200209163356.6439-3-digetx@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
index 84d4d9eaf8da4694a89c408afc8b5e741c4125a3..4eaf92b2b8868a35ee8fda123b60a11372545d3c 100644 (file)
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -288,7 +288,7 @@ static struct tegra_dma_desc *tegra_dma_desc_get(
 
        /* Do not allocate if desc are waiting for ack */
        list_for_each_entry(dma_desc, &tdc->free_dma_desc, node) {
-               if (async_tx_test_ack(&dma_desc->txd)) {
+               if (async_tx_test_ack(&dma_desc->txd) && !dma_desc->cb_count) {
                        list_del(&dma_desc->node);
                        spin_unlock_irqrestore(&tdc->lock, flags);
                        dma_desc->txd.flags = 0;