linux-hardening - Re: [PATCH 06/21] dmaengine: moxart-dma: Annotate struct moxart_desc with __counted

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Date:   Thu, 17 Aug 2023 19:23:47 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Kees Cook <keescook@...omium.org>, Vinod Koul <vkoul@...nel.org>
Cc:     dmaengine@...r.kernel.org, Hector Martin <marcan@...can.st>,
        Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Tudor Ambarus <tudor.ambarus@...aro.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Zhou Wang <wangzhou1@...ilicon.com>,
        Jie Hai <haijie1@...wei.com>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Green Wan <green.wan@...ive.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Patrice Chotard <patrice.chotard@...s.st.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Jon Hunter <jonathanh@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Peter Ujfalusi <peter.ujfalusi@...il.com>,
        Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Yu Kuai <yukuai3@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jordy Zomer <jordy@...ing.systems>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        asahi@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-tegra@...r.kernel.org, llvm@...ts.linux.dev,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH 06/21] dmaengine: moxart-dma: Annotate struct moxart_desc
 with __counted_by



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@...nel.org>
> Cc: dmaengine@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

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

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);