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

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Kees Cook <keescook@chromium.org>, Vinod Koul <vkoul@kernel.org>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	dmaengine@vger.kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org,
	Hector Martin <marcan@marcan.st>, Sven Peter <sven@svenpeter.dev>,
	Alyssa Rosenzweig <alyssa@rosenzweig.io>,
	Ludovic Desroches <ludovic.desroches@microchip.com>,
	Tudor Ambarus <tudor.ambarus@linaro.org>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Zhou Wang <wangzhou1@hisilicon.com>, Jie Hai <haijie1@huawei.com>,
	Andy Gross <agross@kernel.org>,
	Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	Green Wan <green.wan@sifive.com>,
	Orson Zhai <orsonzhai@gmail.com>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	Chunyan Zhang <zhang.lyra@gmail.com>,
	Patrice Chotard <patrice.chotard@foss.st.com>,
	Laxman Dewangan <ldewangan@nvidia.com>,
	Jon Hunter <jonathanh@nvidia.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Peter Ujfalusi <peter.ujfalusi@gmail.com>,
	Kunihiko Hayashi <hayashi.kunihiko@socionext.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Yu Kuai <yukuai3@huawei.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jordy Zomer <jordy@pwning.systems>,
	Jernej Skrabec <jernej.skrabec@gmail.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Tom Rix <trix@redhat.com>,
	linux-kernel@vger.kernel.org, asahi@lists.linux.dev,
	linux-arm-msm@vger.kernel.org, linux-tegra@vger.kernel.org,
	llvm@lists.linux.dev, linux-hardening@vger.kernel.org
Subject: Re: [PATCH 14/21] dmaengine: stm32-mdma: Annotate struct stm32_mdma_device with __counted_by
Date: Thu, 17 Aug 2023 19:26:02 -0600	[thread overview]
Message-ID: <1f6873bb-e6d3-fdff-5e20-72332469def2@embeddedor.com> (raw)
In-Reply-To: <20230817235859.49846-14-keescook@chromium.org>


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))