linux-hardening - Re: [PATCH] dmaengine: stm32-dma3: Set lli

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Message-ID: <d1a9d59f-00cc-4878-9cf4-eb58e9dd1562@embeddedor.com>
Date: Tue, 16 Jul 2024 15:50:48 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Kees Cook <kees@...nel.org>, Amélie Delaunay
 <amelie.delaunay@...s.st.com>
Cc: Vinod Koul <vkoul@...nel.org>, Maxime Coquelin
 <mcoquelin.stm32@...il.com>, Alexandre Torgue
 <alexandre.torgue@...s.st.com>, dmaengine@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH] dmaengine: stm32-dma3: Set lli_size after allocation



On 16/07/24 15:38, Kees Cook wrote:
> With the new __counted_by annotation, the "lli_size" variable needs to
> valid for accesses to the "lli" array. This requirement is not met in
> stm32_dma3_chan_desc_alloc(), since "lli_size" starts at "0", so "lli"
> index "0" will not be considered valid during the initialization for loop.
> 
> Fix this by setting lli_size immediately after allocation (similar to
> how this is handled in stm32_mdma_alloc_desc() for the node/count
> relationship).
> 
> Fixes: f561ec8b2b33 ("dmaengine: Add STM32 DMA3 support")
> Signed-off-by: Kees Cook <kees@...nel.org>

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

Thanks
-- 
Gustavo

> ---
> Cc: "Amélie Delaunay" <amelie.delaunay@...s.st.com>
> Cc: Vinod Koul <vkoul@...nel.org>
> Cc: Maxime Coquelin <mcoquelin.stm32@...il.com>
> Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>
> Cc: dmaengine@...r.kernel.org
> Cc: linux-stm32@...md-mailman.stormreply.com
> Cc: linux-arm-kernel@...ts.infradead.org
> ---
>   drivers/dma/stm32/stm32-dma3.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/stm32/stm32-dma3.c b/drivers/dma/stm32/stm32-dma3.c
> index 4087e0263a48..0be6e944df6f 100644
> --- a/drivers/dma/stm32/stm32-dma3.c
> +++ b/drivers/dma/stm32/stm32-dma3.c
> @@ -403,6 +403,7 @@ static struct stm32_dma3_swdesc *stm32_dma3_chan_desc_alloc(struct stm32_dma3_ch
>   	swdesc = kzalloc(struct_size(swdesc, lli, count), GFP_NOWAIT);
>   	if (!swdesc)
>   		return NULL;
> +	swdesc->lli_size = count;
>   
>   	for (i = 0; i < count; i++) {
>   		swdesc->lli[i].hwdesc = dma_pool_zalloc(chan->lli_pool, GFP_NOWAIT,
> @@ -410,7 +411,6 @@ static struct stm32_dma3_swdesc *stm32_dma3_chan_desc_alloc(struct stm32_dma3_ch
>   		if (!swdesc->lli[i].hwdesc)
>   			goto err_pool_free;
>   	}
> -	swdesc->lli_size = count;
>   	swdesc->ccr = 0;
>   
>   	/* Set LL base address */