[PATCH 5.4 307/320] dmaengine: at_xdmac: Fix concurrency over xfers_list

[Greg Kroah-Hartman]

From: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>

commit 18deddea9184b62941395889ff7659529c877326 upstream.

Since tx_submit can be called from a hard IRQ, xfers_list must be
protected with a lock to avoid concurency on the list's elements.
Since at_xdmac_handle_cyclic() is called from a tasklet, spin_lock_irq
is enough to protect from a hard IRQ.

Fixes: e1f7c9eee707 ("dmaengine: at_xdmac: creation of the atmel eXtended DMA Controller driver")
Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20211215110115.191749-8-tudor.ambarus@xxxxxxxxxxxxx
Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/dma/at_xdmac.c |   17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -1564,14 +1564,17 @@ static void at_xdmac_handle_cyclic(struc
 	struct at_xdmac_desc		*desc;
 	struct dma_async_tx_descriptor	*txd;
 
-	if (!list_empty(&atchan->xfers_list)) {
-		desc = list_first_entry(&atchan->xfers_list,
-					struct at_xdmac_desc, xfer_node);
-		txd = &desc->tx_dma_desc;
-
-		if (txd->flags & DMA_PREP_INTERRUPT)
-			dmaengine_desc_get_callback_invoke(txd, NULL);
+	spin_lock_irq(&atchan->lock);
+	if (list_empty(&atchan->xfers_list)) {
+		spin_unlock_irq(&atchan->lock);
+		return;
 	}
+	desc = list_first_entry(&atchan->xfers_list, struct at_xdmac_desc,
+				xfer_node);
+	spin_unlock_irq(&atchan->lock);
+	txd = &desc->tx_dma_desc;
+	if (txd->flags & DMA_PREP_INTERRUPT)
+		dmaengine_desc_get_callback_invoke(txd, NULL);
 }
 
 static void at_xdmac_handle_error(struct at_xdmac_chan *atchan)