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

commit a6993af41b0ac74537613ab12a51ca819ec0af0e 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 319f31d270143a436527ce00a984fafd427f6f78..4a750e29bfb533953584bc101f6e5eec99cc0239 100644 (file)
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -281,7 +281,7 @@ 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;