Re: [PATCH 06/21] dmaengine: moxart-dma: Annotate struct moxart_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 moxart_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: dmaengine@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>

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

Thanks
--
Gustavo

> ---
>   drivers/dma/moxart-dma.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/dma/moxart-dma.c b/drivers/dma/moxart-dma.c
> index 7565ad98ba66..c1dd5716a46d 100644
> --- a/drivers/dma/moxart-dma.c
> +++ b/drivers/dma/moxart-dma.c
> @@ -124,7 +124,7 @@ struct moxart_desc {
>   	unsigned int			dma_cycles;
>   	struct virt_dma_desc		vd;
>   	uint8_t				es;
> -	struct moxart_sg		sg[];
> +	struct moxart_sg		sg[] __counted_by(sglen);
>   };
>   
>   struct moxart_chan {
> @@ -309,6 +309,7 @@ static struct dma_async_tx_descriptor *moxart_prep_slave_sg(
>   	d = kzalloc(struct_size(d, sg, sg_len), GFP_ATOMIC);
>   	if (!d)
>   		return NULL;
> +	d->sglen = sg_len;
>   
>   	d->dma_dir = dir;
>   	d->dev_addr = dev_addr;
> @@ -319,8 +320,6 @@ static struct dma_async_tx_descriptor *moxart_prep_slave_sg(
>   		d->sg[i].len = sg_dma_len(sgent);
>   	}
>   
> -	d->sglen = sg_len;
> -
>   	ch->error = 0;
>   
>   	return vchan_tx_prep(&ch->vc, &d->vd, tx_flags);