Hi Dan,
Thank you for the report. Your analysis is right, I'll send a patch to fix the
problem.
On Wednesday 07 January 2015 15:45:13 Dan Carpenter wrote:
> Hello Laurent Pinchart,
>
> The patch 87244fe5abdf: "dmaengine: rcar-dmac: Add Renesas R-Car Gen2
> DMA Controller (DMAC) driver" from Jul 9, 2014, leads to the
> following static checker warning:
>
> drivers/dma/sh/rcar-dmac.c:571 rcar_dmac_desc_get()
> error: potentially using uninitialized 'desc'.
>
> drivers/dma/sh/rcar-dmac.c
> 542 static struct rcar_dmac_desc *rcar_dmac_desc_get(struct
> rcar_dmac_chan *chan) 543 {
> 544 struct rcar_dmac_desc *desc;
> ^^^^
> Not initialized.
>
> 545 int ret;
> 546
> 547 /* Recycle acked descriptors before attempting allocation.
> */ 548 rcar_dmac_desc_recycle_acked(chan);
> 549
> 550 spin_lock_irq(&chan->lock);
> 551
> 552 do {
> 553 if (list_empty(&chan->desc.free)) {
> 554 /*
> 555 * No free descriptors, allocate a page
> worth of them 556 * and try again, as someone
> else could race us to get 557 * the newly
> allocated descriptors. If the allocation 558 *
> fails return an error.
> 559 */
> 560 spin_unlock_irq(&chan->lock);
> 561 ret = rcar_dmac_desc_alloc(chan,
> GFP_NOWAIT); 562 if (ret < 0)
> 563 return NULL;
> 564 spin_lock_irq(&chan->lock);
> 565 continue;
> ^^^^^^^^
> Let's assume that the list is empty on the first iteration through the
> loop so we hit this continue.
>
> 566 }
> 567
> 568 desc = list_first_entry(&chan->desc.free, struct
> rcar_dmac_desc, 569 node);
> 570 list_del(&desc->node);
> 571 } while (!desc);
> ^^^^
> Then we don't know if 'desc' is NULL or not because it wasn't
> initialized.
>
> 572
> 573 spin_unlock_irq(&chan->lock);
> 574
> 575 return desc;
> 576 }
--
Regards,
Laurent Pinchart
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