I added book keeping of whether or not the 8250-dma driver has an RX
transfer pending or not so we don't BUG here if it calls
dmaengine_pause() on a channel which has not a pending transfer. Guess
what, this is not enough.
The following can be triggered with a busy RX channel and hackbench in
background:
- DMA transfer completes. The callback is delayed via
vchan_cookie_complete() into a tasklet so it das not happen asap.
- hackbench keeps the system busy so the tasklet does not run "soon".
- the UART collected enough data and generates an "timeout"-interrupt.
Since 8250-dma *thinks* the DMA-transfer is still pending it tries to
cancel it via invoking dmaengine_pause() first. This causes the segfault
because echan->edesc is NULL now that the transfer completed (however
the callback did not run yet).
With this patch we don't BUG in the scenario described.
Cc: vinod.koul@xxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
drivers/dma/edma.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c
index 7b65633f495e..123f578d6dd3 100644
--- a/drivers/dma/edma.c
+++ b/drivers/dma/edma.c
@@ -288,7 +288,7 @@ static int edma_slave_config(struct edma_chan *echan,
static int edma_dma_pause(struct edma_chan *echan)
{
/* Pause/Resume only allowed with cyclic mode */
- if (!echan->edesc->cyclic)
+ if (!echan->edesc || !echan->edesc->cyclic)
return -EINVAL;
edma_pause(echan->ch_num);
--
2.1.0
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