[PATCH 14/33] dmaengine: at_hdmac: Fix concurrency over descriptor

Tudor Ambarus
2022-08-20T12:59:08Z

The descriptor was added to the free_list before calling the callback,
which could result in reissuing of the same descriptor and calling of a
single callback for both. Move the decriptor to the free list after the
callback is invoked.

Fixes: dc78baa2b90b ("dmaengine: at_hdmac: new driver for the Atmel AHB DMA Controller")
Reported-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/lkml/13c6c9a2-6db5-c3bf-349b-4c127ad3496a@axentia.se/
---
drivers/dma/at_hdmac.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index 10424a6fcbbf..b3184da7ced4 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -904,11 +904,8 @@ atc_chain_complete(struct at_dma_chan *atchan, struct at_desc *desc)
desc->memset_buffer = false;
}

- /* move children to free_list */
- list_splice_init(&desc->tx_list, &atchan->free_list);
- /* move myself to free_list */
- list_move(&desc->desc_node, &atchan->free_list);
-
+ /* Remove transfer node from the active list. */
+ list_del_init(&desc->desc_node);
spin_unlock_irqrestore(&atchan->lock, flags);

dma_descriptor_unmap(txd);
@@ -918,6 +915,13 @@ atc_chain_complete(struct at_dma_chan *atchan, struct at_desc *desc)
dmaengine_desc_get_callback_invoke(txd, NULL);

dma_run_dependencies(txd);
+
+ spin_lock_irqsave(&atchan->lock, flags);
+ /* move children to free_list */
+ list_splice_init(&desc->tx_list, &atchan->free_list);
+ /* add myself to free_list */
+ list_add(&desc->desc_node, &atchan->free_list);
+ spin_unlock_irqrestore(&atchan->lock, flags);
}

/**
--
2.25.1