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Subject[PATCH 4.9 038/109] dmaengine: stm32-dma: Fix null pointer dereference in stm32_dma_tx_status
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: M'boumba Cedric Madianga <cedric.madianga@gmail.com>


[ Upstream commit 57b5a32135c813f2ab669039fb4ec16b30cb3305 ]

chan->desc is always set to NULL when a DMA transfer is complete.
As a DMA transfer could be complete during the call of stm32_dma_tx_status,
we need to be sure that chan->desc is not NULL before using this variable
to avoid a null pointer deference issue.

Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
Reviewed-by: Ludovic BARRE <ludovic.barre@st.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/dma/stm32-dma.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -884,7 +884,7 @@ static enum dma_status stm32_dma_tx_stat
struct virt_dma_desc *vdesc;
enum dma_status status;
unsigned long flags;
- u32 residue;
+ u32 residue = 0;

status = dma_cookie_status(c, cookie, state);
if ((status == DMA_COMPLETE) || (!state))
@@ -892,16 +892,12 @@ static enum dma_status stm32_dma_tx_stat

spin_lock_irqsave(&chan->vchan.lock, flags);
vdesc = vchan_find_desc(&chan->vchan, cookie);
- if (cookie == chan->desc->vdesc.tx.cookie) {
+ if (chan->desc && cookie == chan->desc->vdesc.tx.cookie)
residue = stm32_dma_desc_residue(chan, chan->desc,
chan->next_sg);
- } else if (vdesc) {
+ else if (vdesc)
residue = stm32_dma_desc_residue(chan,
to_stm32_dma_desc(vdesc), 0);
- } else {
- residue = 0;
- }
-
dma_set_residue(state, residue);

spin_unlock_irqrestore(&chan->vchan.lock, flags);

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