Re: [PATCH 18/21] dmaengine: ti: omap-dma: Annotate struct omap_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 omap_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: Peter Ujfalusi <peter.ujfalusi@xxxxxxxxx>
> Cc: dmaengine@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>

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

Thanks
--
Gustavo

> ---
>   drivers/dma/ti/omap-dma.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/dma/ti/omap-dma.c b/drivers/dma/ti/omap-dma.c
> index cf96cf915c0c..11ac3fc0a52a 100644
> --- a/drivers/dma/ti/omap-dma.c
> +++ b/drivers/dma/ti/omap-dma.c
> @@ -124,7 +124,7 @@ struct omap_desc {
>   	uint32_t csdp;		/* CSDP value */
>   
>   	unsigned sglen;
> -	struct omap_sg sg[];
> +	struct omap_sg sg[] __counted_by(sglen);
>   };
>   
>   enum {
> @@ -1005,6 +1005,7 @@ static struct dma_async_tx_descriptor *omap_dma_prep_slave_sg(
>   	d = kzalloc(struct_size(d, sg, sglen), GFP_ATOMIC);
>   	if (!d)
>   		return NULL;
> +	d->sglen = sglen;
>   
>   	d->dir = dir;
>   	d->dev_addr = dev_addr;
> @@ -1120,8 +1121,6 @@ static struct dma_async_tx_descriptor *omap_dma_prep_slave_sg(
>   		}
>   	}
>   
> -	d->sglen = sglen;
> -
>   	/* Release the dma_pool entries if one allocation failed */
>   	if (ll_failed) {
>   		for (i = 0; i < d->sglen; i++) {