Re: [PATCH 14/21] dmaengine: stm32-mdma: Annotate struct stm32_mdma_device with __counted_by

Gustavo A. R. Silva
2023-08-18T01:28:41Z

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 stm32_mdma_device.
> 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: Maxime Coquelin <mcoquelin.stm32@gmail.com>
> Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
> Cc: dmaengine@vger.kernel.org
> Cc: linux-stm32@st-md-mailman.stormreply.com
> Cc: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
--
Gustavo

> ---
> drivers/dma/stm32-mdma.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma/stm32-mdma.c b/drivers/dma/stm32-mdma.c
> index 926d6ecf1274..0c7d2295856e 100644
> --- a/drivers/dma/stm32-mdma.c
> +++ b/drivers/dma/stm32-mdma.c
> @@ -256,7 +256,7 @@ struct stm32_mdma_device {
> u32 nr_ahb_addr_masks;
> u32 chan_reserved;
> struct stm32_mdma_chan chan[STM32_MDMA_MAX_CHANNELS];
> - u32 ahb_addr_masks[];
> + u32 ahb_addr_masks[] __counted_by(nr_ahb_addr_masks);
> };
>
> static struct stm32_mdma_device *stm32_mdma_get_dev(
> @@ -1611,13 +1611,13 @@ static int stm32_mdma_probe(struct platform_device *pdev)
> GFP_KERNEL);
> if (!dmadev)
> return -ENOMEM;
> + dmadev->nr_ahb_addr_masks = count;
>
> dmadev->nr_channels = nr_channels;
> dmadev->nr_requests = nr_requests;
> device_property_read_u32_array(&pdev->dev, "st,ahb-addr-masks",
> dmadev->ahb_addr_masks,
> count);
> - dmadev->nr_ahb_addr_masks = count;
>
> dmadev->base = devm_platform_ioremap_resource(pdev, 0);
> if (IS_ERR(dmadev->base))