linux-kernel - [PATCH 12/33] dmaengine: at_hdmac: Protect atchan->status with the channel lock

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Date:   Sat, 20 Aug 2022 15:56:56 +0300
From:   Tudor Ambarus <tudor.ambarus@...rochip.com>
To:     <vkoul@...nel.org>, <peda@...ntia.se>, <du@...ntia.se>,
        <regressions@...mhuis.info>
CC:     <ludovic.desroches@...rochip.com>, <maciej.sosnowski@...el.com>,
        <tudor.ambarus@...rochip.com>, <dan.j.williams@...el.com>,
        <nicolas.ferre@...rochip.com>, <mripard@...nel.org>,
        <torfl6749@...il.com>, <linux-kernel@...r.kernel.org>,
        <dmaengine@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <stable@...r.kernel.org>
Subject: [PATCH 12/33] dmaengine: at_hdmac: Protect atchan->status with the channel lock

Now that the complete callback call was removed from
device_terminate_all(), we can protect the atchan->status with the channel
lock. The atomic bitops on atchan->status do not substitute proper locking
on the status, as one could still modify the status after the lock was
dropped in atc_terminate_all() but before the atomic bitops were executed.

Fixes: 078a6506141a ("dmaengine: at_hdmac: Fix deadlocks")
Reported-by: Peter Rosin <peda@...ntia.se>
Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/lkml/13c6c9a2-6db5-c3bf-349b-4c127ad3496a@axentia.se/
---
 drivers/dma/at_hdmac.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index b3895e5d2ae9..aeb241832c52 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -1902,12 +1902,12 @@ static int atc_terminate_all(struct dma_chan *chan)
 	list_splice_tail_init(&atchan->queue, &atchan->free_list);
 	list_splice_tail_init(&atchan->active_list, &atchan->free_list);
 
-	spin_unlock_irqrestore(&atchan->lock, flags);
-
 	clear_bit(ATC_IS_PAUSED, &atchan->status);
 	/* if channel dedicated to cyclic operations, free it */
 	clear_bit(ATC_IS_CYCLIC, &atchan->status);
 
+	spin_unlock_irqrestore(&atchan->lock, flags);
+
 	return 0;
 }
 
-- 
2.25.1