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dmaengine: rcar-dmac: Reject zero-length slave DMA requests 

While the .device_prep_slave_sg() callback rejects empty scatterlists,
it still accepts single-entry scatterlists with a zero-length segment.
These may happen if a driver calls dmaengine_prep_slave_single() with a
zero len parameter.  The corresponding DMA request will never complete,
leading to messages like:

    rcar-dmac e7300000.dma-controller: Channel Address Error happen

and DMA timeouts.

Although requesting a zero-length DMA request is a driver bug, rejecting
it early eases debugging.  Note that the .device_prep_dma_memcpy()
callback already rejects requests to copy zero bytes.

Reported-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Analyzed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Geert Uytterhoeven 2019-06-24 14:38:18 +02:00 committed by Vinod Koul
parent 9e5ab0655e
commit 78efb76ab4
1 changed files with 1 additions and 1 deletions
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2
drivers/dma/sh/rcar-dmac.c
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@ -1165,7 +1165,7 @@ rcar_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
/* Someone calling slave DMA on a generic channel? */
if (rchan->mid_rid < 0 || !sg_len) {
if (rchan->mid_rid < 0 || !sg_len || !sg_dma_len(sgl)) {
dev_warn(chan->device->dev,
"%s: bad parameter: len=%d, id=%d\n",
__func__, sg_len, rchan->mid_rid);