Re: [PATCH 19/21] dmaengine: uniphier-xdmac: Annotate struct uniphier_xdmac_desc with __counted_by

[Gustavo A. R. Silva]

On 8/17/23 17:58, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> As found with Coccinelle[1], add __counted_by for struct uniphier_xdmac_desc.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
>
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>
> Cc: Vinod Koul <vkoul@xxxxxxxxxx>
> Cc: Kunihiko Hayashi <hayashi.kunihiko@xxxxxxxxxxxxx>
> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Cc: dmaengine@xxxxxxxxxxxxxxx
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>

Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>

Thanks
--
Gustavo

> ---
>   drivers/dma/uniphier-xdmac.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/dma/uniphier-xdmac.c b/drivers/dma/uniphier-xdmac.c
> index 290836b7e1be..dd51522879a7 100644
> --- a/drivers/dma/uniphier-xdmac.c
> +++ b/drivers/dma/uniphier-xdmac.c
> @@ -80,7 +80,7 @@ struct uniphier_xdmac_desc {
>   	unsigned int nr_node;
>   	unsigned int cur_node;
>   	enum dma_transfer_direction dir;
> -	struct uniphier_xdmac_desc_node nodes[];
> +	struct uniphier_xdmac_desc_node nodes[] __counted_by(nr_node);
>   };
>   
>   struct uniphier_xdmac_chan {
> @@ -295,6 +295,7 @@ uniphier_xdmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dst,
>   	xd = kzalloc(struct_size(xd, nodes, nr), GFP_NOWAIT);
>   	if (!xd)
>   		return NULL;
> +	xd->nr_node = nr;
>   
>   	for (i = 0; i < nr; i++) {
>   		burst_size = min_t(size_t, len, XDMAC_MAX_WORD_SIZE);
> @@ -309,7 +310,6 @@ uniphier_xdmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dst,
>   	}
>   
>   	xd->dir = DMA_MEM_TO_MEM;
> -	xd->nr_node = nr;
>   	xd->cur_node = 0;
>   
>   	return vchan_tx_prep(vc, &xd->vd, flags);
> @@ -351,6 +351,7 @@ uniphier_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
>   	xd = kzalloc(struct_size(xd, nodes, sg_len), GFP_NOWAIT);
>   	if (!xd)
>   		return NULL;
> +	xd->nr_node = sg_len;
>   
>   	for_each_sg(sgl, sg, sg_len, i) {
>   		xd->nodes[i].src = (direction == DMA_DEV_TO_MEM)
> @@ -385,7 +386,6 @@ uniphier_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
>   	}
>   
>   	xd->dir = direction;
> -	xd->nr_node = sg_len;
>   	xd->cur_node = 0;
>   
>   	return vchan_tx_prep(vc, &xd->vd, flags);