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dmaengine: k3dma: Avoid null pointer traversal

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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>
This commit is contained in:
John Stultz 2019-12-18 19:09:06 +00:00 committed by Vinod Koul
parent a40c94be23
commit 2f42e05b94
1 changed files with 9 additions and 3 deletions
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12
drivers/dma/k3dma.c
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@ -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);
vchan_cookie_complete(&p->ds_run->vd);
p->ds_done = p->ds_run;
p->ds_run = NULL;
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);