Re: [PATCH 18/21] dmaengine: ti: omap-dma: Annotate struct omap_desc with __counted_by

Gustavo A. R. Silva
2023-08-18T03:56:19Z

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@kernel.org>
> Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
> 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/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++) {