2015-12-07 11:00:54

by M'boumba Cedric Madianga

Subject: [PATCH v2] dmaengine: stm32-dma: Fix unchecked deference of chan->desc

'commit d8b468394fb7 ("dmaengine: Add STM32 DMA driver")' leads to the
following Smatch complaint:

drivers/dma/stm32-dma.c:562 stm32_dma_issue_pending()
error: we previously assumed 'chan->desc' could be null (see line 560)

So, this patch fixes the unchecked dereference of chan->desc by returning
operation not permitted error when stm32_dma_start_transfer() does not
succeed to allocate a virtual channel descriptor.

Reported-by: Dan Carpenter <[email protected]>
Signed-off-by: M'boumba Cedric Madianga <[email protected]>

---
Changes since v1:
Explain what the patch fixes in the title (Vinod)
Add Dan as reporter using Reported-by tag (Vinod)
---
---
drivers/dma/stm32-dma.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c
index 12f3a3e..047476a 100644
--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -437,7 +437,7 @@ static int stm32_dma_start_transfer(struct stm32_dma_chan *chan)
if (!chan->desc) {
vdesc = vchan_next_desc(&chan->vchan);
if (!vdesc)
- return 0;
+ return -EPERM;

chan->desc = to_stm32_dma_desc(vdesc);
chan->next_sg = 0;
@@ -559,7 +559,7 @@ static void stm32_dma_issue_pending(struct dma_chan *c)
if (!chan->busy) {
if (vchan_issue_pending(&chan->vchan) && !chan->desc) {
ret = stm32_dma_start_transfer(chan);
- if ((chan->desc->cyclic) && (!ret))
+ if ((!ret) && (chan->desc->cyclic))
stm32_dma_configure_next_sg(chan);
}
}
--
1.9.1

2015-12-10 04:12:46

by Vinod Koul

Subject: Re: [PATCH v2] dmaengine: stm32-dma: Fix unchecked deference of chan->desc

On Mon, Dec 07, 2015 at 12:00:28PM +0100, M'boumba Cedric Madianga wrote:
> 'commit d8b468394fb7 ("dmaengine: Add STM32 DMA driver")' leads to the
> following Smatch complaint:
>
> drivers/dma/stm32-dma.c:562 stm32_dma_issue_pending()
> error: we previously assumed 'chan->desc' could be null (see line 560)
>
> So, this patch fixes the unchecked dereference of chan->desc by returning
> operation not permitted error when stm32_dma_start_transfer() does not
> succeed to allocate a virtual channel descriptor.

Applied, thanks

--
~Vinod