Anton Volkov noticed that engine->dev is NULL before
of_dma_controller_register() in probe.
Thus there might be a NULL pointer dereference in
rcar_dmac_chan_start_xfer while accessing chan->chan.device->dev which
is equal to (&dmac->engine)->dev.
To be more safety code, this patch initialize dmac->engine before it.

Reported-by: Anton Volkov <avol...@ispras.ru>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto...@renesas.com>
---
> Anton, Laurent

I created this patch because noone posted it yesterday.
Anton, you can use this patch and replace Author to you if you want.
Thus, I used [RFC] on this patch

 drivers/dma/sh/rcar-dmac.c | 51 +++++++++++++++++++++++-----------------------
 1 file changed, 26 insertions(+), 25 deletions(-)

diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index ffcadca..6d60628 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1818,8 +1818,32 @@ static int rcar_dmac_probe(struct platform_device *pdev)
                goto error;
        }
 
-       /* Initialize the channels. */
-       INIT_LIST_HEAD(&dmac->engine.channels);
+       /* Initialize engine */
+       engine = &dmac->engine;
+
+       dma_cap_set(DMA_MEMCPY, engine->cap_mask);
+       dma_cap_set(DMA_SLAVE, engine->cap_mask);
+
+       engine->dev             = &pdev->dev;
+       engine->copy_align      = ilog2(RCAR_DMAC_MEMCPY_XFER_SIZE);
+
+       engine->src_addr_widths = widths;
+       engine->dst_addr_widths = widths;
+       engine->directions      = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM);
+       engine->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
+
+       engine->device_alloc_chan_resources     = 
rcar_dmac_alloc_chan_resources;
+       engine->device_free_chan_resources      = rcar_dmac_free_chan_resources;
+       engine->device_prep_dma_memcpy          = rcar_dmac_prep_dma_memcpy;
+       engine->device_prep_slave_sg            = rcar_dmac_prep_slave_sg;
+       engine->device_prep_dma_cyclic          = rcar_dmac_prep_dma_cyclic;
+       engine->device_config                   = rcar_dmac_device_config;
+       engine->device_terminate_all            = rcar_dmac_chan_terminate_all;
+       engine->device_tx_status                = rcar_dmac_tx_status;
+       engine->device_issue_pending            = rcar_dmac_issue_pending;
+       engine->device_synchronize              = rcar_dmac_device_synchronize;
+
+       INIT_LIST_HEAD(&engine->channels);
 
        for (i = 0; i < dmac->n_channels; ++i) {
                ret = rcar_dmac_chan_probe(dmac, &dmac->channels[i],
@@ -1839,29 +1863,6 @@ static int rcar_dmac_probe(struct platform_device *pdev)
         *
         * Default transfer size of 32 bytes requires 32-byte alignment.
         */
-       engine = &dmac->engine;
-       dma_cap_set(DMA_MEMCPY, engine->cap_mask);
-       dma_cap_set(DMA_SLAVE, engine->cap_mask);
-
-       engine->dev = &pdev->dev;
-       engine->copy_align = ilog2(RCAR_DMAC_MEMCPY_XFER_SIZE);
-
-       engine->src_addr_widths = widths;
-       engine->dst_addr_widths = widths;
-       engine->directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM);
-       engine->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
-
-       engine->device_alloc_chan_resources = rcar_dmac_alloc_chan_resources;
-       engine->device_free_chan_resources = rcar_dmac_free_chan_resources;
-       engine->device_prep_dma_memcpy = rcar_dmac_prep_dma_memcpy;
-       engine->device_prep_slave_sg = rcar_dmac_prep_slave_sg;
-       engine->device_prep_dma_cyclic = rcar_dmac_prep_dma_cyclic;
-       engine->device_config = rcar_dmac_device_config;
-       engine->device_terminate_all = rcar_dmac_chan_terminate_all;
-       engine->device_tx_status = rcar_dmac_tx_status;
-       engine->device_issue_pending = rcar_dmac_issue_pending;
-       engine->device_synchronize = rcar_dmac_device_synchronize;
-
        ret = dma_async_device_register(engine);
        if (ret < 0)
                goto error;
-- 
1.9.1

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