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* [PATCH] dma: dma-jz4780: Fix race in jz4780_dma_tx_status
@ 2020-10-04 14:03 Paul Cercueil
  2020-10-05  4:27 ` Vinod Koul
  0 siblings, 1 reply; 2+ messages in thread
From: Paul Cercueil @ 2020-10-04 14:03 UTC (permalink / raw)
  To: Vinod Koul
  Cc: od, dmaengine, linux-kernel, Paul Cercueil, stable, Artur Rojek

The jz4780_dma_tx_status() function would check if a channel's cookie
state was set to 'completed', and if not, it would enter the critical
section. However, in that time frame, the jz4780_dma_chan_irq() function
was able to set the cookie to 'completed', and clear the jzchan->vchan
pointer, which was deferenced in the critical section of the first
function.

Fix this race by checking the channel's cookie state after entering the
critical function and not before.

Fixes: d894fc6046fe ("dmaengine: jz4780: add driver for the Ingenic JZ4780 DMA controller")
Cc: stable@vger.kernel.org # v4.0
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reported-by: Artur Rojek <contact@artur-rojek.eu>
Tested-by: Artur Rojek <contact@artur-rojek.eu>
---
 drivers/dma/dma-jz4780.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
index 8beed91428bd..a608efaa435f 100644
--- a/drivers/dma/dma-jz4780.c
+++ b/drivers/dma/dma-jz4780.c
@@ -639,11 +639,11 @@ static enum dma_status jz4780_dma_tx_status(struct dma_chan *chan,
 	unsigned long flags;
 	unsigned long residue = 0;
 
+	spin_lock_irqsave(&jzchan->vchan.lock, flags);
+
 	status = dma_cookie_status(chan, cookie, txstate);
 	if ((status == DMA_COMPLETE) || (txstate == NULL))
-		return status;
-
-	spin_lock_irqsave(&jzchan->vchan.lock, flags);
+		goto out_unlock_irqrestore;
 
 	vdesc = vchan_find_desc(&jzchan->vchan, cookie);
 	if (vdesc) {
@@ -660,6 +660,7 @@ static enum dma_status jz4780_dma_tx_status(struct dma_chan *chan,
 	    && jzchan->desc->status & (JZ_DMA_DCS_AR | JZ_DMA_DCS_HLT))
 		status = DMA_ERROR;
 
+out_unlock_irqrestore:
 	spin_unlock_irqrestore(&jzchan->vchan.lock, flags);
 	return status;
 }
-- 
2.28.0


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] dma: dma-jz4780: Fix race in jz4780_dma_tx_status
  2020-10-04 14:03 [PATCH] dma: dma-jz4780: Fix race in jz4780_dma_tx_status Paul Cercueil
@ 2020-10-05  4:27 ` Vinod Koul
  0 siblings, 0 replies; 2+ messages in thread
From: Vinod Koul @ 2020-10-05  4:27 UTC (permalink / raw)
  To: Paul Cercueil; +Cc: od, dmaengine, linux-kernel, stable, Artur Rojek

On 04-10-20, 16:03, Paul Cercueil wrote:
> The jz4780_dma_tx_status() function would check if a channel's cookie
> state was set to 'completed', and if not, it would enter the critical
> section. However, in that time frame, the jz4780_dma_chan_irq() function
> was able to set the cookie to 'completed', and clear the jzchan->vchan
> pointer, which was deferenced in the critical section of the first
> function.
> 
> Fix this race by checking the channel's cookie state after entering the
> critical function and not before.

Applied, thanks

-- 
~Vinod

^ permalink raw reply	[flat|nested] 2+ messages in thread

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2020-10-04 14:03 [PATCH] dma: dma-jz4780: Fix race in jz4780_dma_tx_status Paul Cercueil
2020-10-05  4:27 ` Vinod Koul

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