Re: [PATCH 08/21] dmaengine: sa11x0: Annotate struct sa11x0_dma_desc with __counted_by

Gustavo A. R. Silva
2023-08-18T01:25:30Z

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 sa11x0_dma_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@kernel.org>
> Cc: dmaengine@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
--
Gustavo

> ---
> drivers/dma/sa11x0-dma.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/dma/sa11x0-dma.c b/drivers/dma/sa11x0-dma.c
> index a29c13cae716..e5849622f198 100644
> --- a/drivers/dma/sa11x0-dma.c
> +++ b/drivers/dma/sa11x0-dma.c
> @@ -78,7 +78,7 @@ struct sa11x0_dma_desc {
> bool cyclic;
>
> unsigned sglen;
> - struct sa11x0_dma_sg sg[];
> + struct sa11x0_dma_sg sg[] __counted_by(sglen);
> };
>
> struct sa11x0_dma_phy;
> @@ -558,6 +558,7 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_slave_sg(
> dev_dbg(chan->device->dev, "vchan %p: kzalloc failed\n", &c->vc);
> return NULL;
> }
> + txd->sglen = j;
>
> j = 0;
> for_each_sg(sg, sgent, sglen, i) {
> @@ -593,7 +594,6 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_slave_sg(
>
> txd->ddar = c->ddar;
> txd->size = size;
> - txd->sglen = j;
>
> dev_dbg(chan->device->dev, "vchan %p: txd %p: size %zu nr %u\n",
> &c->vc, &txd->vd, txd->size, txd->sglen);
> @@ -628,6 +628,7 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_dma_cyclic(
> dev_dbg(chan->device->dev, "vchan %p: kzalloc failed\n", &c->vc);
> return NULL;
> }
> + txd->sglen = sglen;
>
> for (i = k = 0; i < size / period; i++) {
> size_t tlen, len = period;
> @@ -653,7 +654,6 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_dma_cyclic(
>
> txd->ddar = c->ddar;
> txd->size = size;
> - txd->sglen = sglen;
> txd->cyclic = 1;
> txd->period = sgperiod;
>