Commit 333e11bf authored by Joao Pinto's avatar Joao Pinto Committed by Vinod Koul
Browse files

Avoid hw_desc array overrun in dw-axi-dmac 



I have a use case where nr_buffers = 3 and in which each descriptor is composed by 3
segments, resulting in the DMA channel descs_allocated to be 9. Since axi_desc_put()
handles the hw_desc considering the descs_allocated, this scenario would result in a
kernel panic (hw_desc array will be overrun).

To fix this, the proposal is to add a new member to the axi_dma_desc structure,
where we keep the number of allocated hw_descs (axi_desc_alloc()) and use it in
axi_desc_put() to handle the hw_desc array correctly.

Additionally I propose to remove the axi_chan_start_first_queued() call after completing
the transfer, since it was identified that unbalance can occur (started descriptors can
be interrupted and transfer ignored due to DMA channel not being enabled).

Signed-off-by: default avatarJoao Pinto <jpinto@synopsys.com>
Link: https://lore.kernel.org/r/1711536564-12919-1-git-send-email-jpinto@synopsys.com


Signed-off-by: default avatarVinod Koul <vkoul@kernel.org>
parent 559a6690

drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c

+2 −4
Original line number Diff line number Diff line
@@ -302,6 +302,7 @@ static struct axi_dma_desc *axi_desc_alloc(u32 num) 
		kfree(desc);

		return NULL;

	}

	desc->nr_hw_descs = num;



	return desc;

}
@@ -328,7 +329,7 @@ static struct axi_dma_lli *axi_desc_get(struct axi_dma_chan *chan, 
static void axi_desc_put(struct axi_dma_desc *desc)

{

	struct axi_dma_chan *chan = desc->chan;

	int count = atomic_read(&chan->descs_allocated);

	int count = desc->nr_hw_descs;

	struct axi_dma_hw_desc *hw_desc;

	int descs_put;
@@ -1139,9 +1140,6 @@ static void axi_chan_block_xfer_complete(struct axi_dma_chan *chan) 
		/* Remove the completed descriptor from issued list before completing */

		list_del(&vd->node);

		vchan_cookie_complete(vd);



		/* Submit queued descriptors after processing the completed ones */

		axi_chan_start_first_queued(chan);

	}



out:

drivers/dma/dw-axi-dmac/dw-axi-dmac.h

+1 −0
Original line number Diff line number Diff line
@@ -104,6 +104,7 @@ struct axi_dma_desc { 
	u32				completed_blocks;

	u32				length;

	u32				period_len;

	u32				nr_hw_descs;

};



struct axi_dma_chan_config {