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From:   Tudor Ambarus <tudor.ambarus@microchip.com>
To:     <vkoul@kernel.org>, <peda@axentia.se>, <du@axentia.se>
CC:     <maciej.sosnowski@intel.com>, <nicolas.ferre@microchip.com>,
        <mripard@kernel.org>, <torfl6749@gmail.com>,
        <linux-kernel@vger.kernel.org>, <dmaengine@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        "Tudor Ambarus" <tudor.ambarus@microchip.com>,
        <stable@vger.kernel.org>
Subject: [PATCH v2 08/32] dmaengine: at_hdmac: Fix concurrency over descriptor
Date:   Tue, 25 Oct 2022 12:02:42 +0300
Message-ID: <20221025090306.297886-9-tudor.ambarus@microchip.com>
In-Reply-To: <20221025090306.297886-1-tudor.ambarus@microchip.com>
References: <20221025090306.297886-1-tudor.ambarus@microchip.com>
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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 f1e6fa6af6c2..2012ecc57826 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -469,11 +469,8 @@ 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);
@@ -483,6 +480,13 @@ 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