From: Sebastian von Ohr <vonohr@xxxxxxxxxxx> [ Upstream commit b269426011bcfd97b7c3101abfe1a99147b6f40b ] The DMA transfer might finish just after checking the state with dma_cookie_status, but before the lock is acquired. Not checking for an empty list in xilinx_dma_tx_status may result in reading random data or data corruption when desc is written to. This can be reliably triggered by using dma_sync_wait to wait for DMA completion. Signed-off-by: Sebastian von Ohr <vonohr@xxxxxxxxxxx> Tested-by: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxxxxx> Link: https://lore.kernel.org/r/20200303130518.333-1-vonohr@xxxxxxxxxxx Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/dma/xilinx/xilinx_dma.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c index a9c5d5cc9f2bd..5d5f1d0ce16cb 100644 --- a/drivers/dma/xilinx/xilinx_dma.c +++ b/drivers/dma/xilinx/xilinx_dma.c @@ -1229,16 +1229,16 @@ static enum dma_status xilinx_dma_tx_status(struct dma_chan *dchan, return ret; spin_lock_irqsave(&chan->lock, flags); - - desc = list_last_entry(&chan->active_list, - struct xilinx_dma_tx_descriptor, node); - /* - * VDMA and simple mode do not support residue reporting, so the - * residue field will always be 0. - */ - if (chan->has_sg && chan->xdev->dma_config->dmatype != XDMA_TYPE_VDMA) - residue = xilinx_dma_get_residue(chan, desc); - + if (!list_empty(&chan->active_list)) { + desc = list_last_entry(&chan->active_list, + struct xilinx_dma_tx_descriptor, node); + /* + * VDMA and simple mode do not support residue reporting, so the + * residue field will always be 0. + */ + if (chan->has_sg && chan->xdev->dma_config->dmatype != XDMA_TYPE_VDMA) + residue = xilinx_dma_get_residue(chan, desc); + } spin_unlock_irqrestore(&chan->lock, flags); dma_set_residue(txstate, residue); -- 2.20.1
