Commit 2f42e05b authored Dec 18, 2019 by John Stultz Committed by Vinod Koul Dec 23, 2019

dmaengine: k3dma: Avoid null pointer traversal



In some cases we seem to submit two transactions in a row, which
causes us to lose track of the first. If we then cancel the
request, we may still get an interrupt, which traverses a null
ds_run value.

So try to avoid starting a new transaction if the ds_run value
is set.

While this patch avoids the null pointer crash, I've had some
reports of the k3dma driver still getting confused, which
suggests the ds_run/ds_done value handling still isn't quite
right. However, I've not run into an issue recently with it
so I think this patch is worth pushing upstream to avoid the
crash.

Signed-off-by: John Stultz <john.stultz@linaro.org>
[add ss tag]
Link: https://lore.kernel.org/r/20191218190906.6641-1-john.stultz@linaro.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>

parent a40c94be

drivers/dma/k3dma.c

+9 −3

Original line number	Diff line number	Diff line
		@@ -229,9 +229,11 @@ static irqreturn_t k3_dma_int_handler(int irq, void *dev_id)
		c = p->vchan;
		if (c && (tc1 & BIT(i))) {
		spin_lock_irqsave(&c->vc.lock, flags);
		if (p->ds_run != NULL) {
		vchan_cookie_complete(&p->ds_run->vd);
		p->ds_done = p->ds_run;
		p->ds_run = NULL;
		}
		spin_unlock_irqrestore(&c->vc.lock, flags);
		}
		if (c && (tc2 & BIT(i))) {
		@@ -271,6 +273,10 @@ static int k3_dma_start_txd(struct k3_dma_chan *c)
		if (BIT(c->phy->idx) & k3_dma_get_chan_stat(d))
		return -EAGAIN;

		/* Avoid losing track of ds_run if a transaction is in flight */
		if (c->phy->ds_run)
		return -EAGAIN;

		if (vd) {
		struct k3_dma_desc_sw *ds =
		container_of(vd, struct k3_dma_desc_sw, vd);

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