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; }