dmaengine: dw-axi-dmac: Do not dereference NULL structure

[PATCH] dmaengine: dw-axi-dmac: Do not dereference NULL structure

Posted by Kees Cook 2 years, 7 months ago

If "vdesc" is NULL, it cannot be used with vd_to_axi_desc(). Leave
"bytes" unchanged at 0. Seen under GCC 13 with -Warray-bounds:

../drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c: In function 'dma_chan_tx_status':
../drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c:329:46: warning: array subscript 0 is outside array bounds of 'struct
virt_dma_desc[46116860184273879]' [-Warray-bounds=]
  329 |                 bytes = vd_to_axi_desc(vdesc)->length;
      |                                              ^~

Fixes: 8e55444da65c ("dmaengine: dw-axi-dmac: Support burst residue granularity")
Cc: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: dmaengine@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
index 08af483331fd..4169e1d7d5ca 100644
--- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
+++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
@@ -325,8 +325,6 @@ dma_chan_tx_status(struct dma_chan *dchan, dma_cookie_t cookie,
 		len = vd_to_axi_desc(vdesc)->hw_desc[0].len;
 		completed_length = completed_blocks * len;
 		bytes = length - completed_length;
-	} else {
-		bytes = vd_to_axi_desc(vdesc)->length;
 	}
 
 	spin_unlock_irqrestore(&chan->vc.lock, flags);
-- 
2.34.1

Re: [PATCH] dmaengine: dw-axi-dmac: Do not dereference NULL structure

Posted by Vinod Koul 2 years, 7 months ago

On 27-01-23, 14:36, Kees Cook wrote:
> If "vdesc" is NULL, it cannot be used with vd_to_axi_desc(). Leave
> "bytes" unchanged at 0. Seen under GCC 13 with -Warray-bounds:
> 
> ../drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c: In function 'dma_chan_tx_status':
> ../drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c:329:46: warning: array subscript 0 is outside array bounds of 'struct
> virt_dma_desc[46116860184273879]' [-Warray-bounds=]
>   329 |                 bytes = vd_to_axi_desc(vdesc)->length;
>       |                                              ^~
> 

Applied, thanks

-- 
~Vinod

Re: [PATCH] dmaengine: dw-axi-dmac: Do not dereference NULL structure

Posted by Andy Shevchenko 2 years, 7 months ago

On Fri, Jan 27, 2023 at 02:36:27PM -0800, Kees Cook wrote:
> If "vdesc" is NULL, it cannot be used with vd_to_axi_desc(). Leave
> "bytes" unchanged at 0. Seen under GCC 13 with -Warray-bounds:
> 
> ../drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c: In function 'dma_chan_tx_status':
> ../drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c:329:46: warning: array subscript 0 is outside array bounds of 'struct
> virt_dma_desc[46116860184273879]' [-Warray-bounds=]
>   329 |                 bytes = vd_to_axi_desc(vdesc)->length;
>       |                                              ^~

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Fixes: 8e55444da65c ("dmaengine: dw-axi-dmac: Support burst residue granularity")
> Cc: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> Cc: Vinod Koul <vkoul@kernel.org>
> Cc: dmaengine@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> index 08af483331fd..4169e1d7d5ca 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> @@ -325,8 +325,6 @@ dma_chan_tx_status(struct dma_chan *dchan, dma_cookie_t cookie,
>  		len = vd_to_axi_desc(vdesc)->hw_desc[0].len;
>  		completed_length = completed_blocks * len;
>  		bytes = length - completed_length;
> -	} else {
> -		bytes = vd_to_axi_desc(vdesc)->length;
>  	}
>  
>  	spin_unlock_irqrestore(&chan->vc.lock, flags);
> -- 
> 2.34.1
> 

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] dmaengine: dw-axi-dmac: Do not dereference NULL structure

Posted by Andy Shevchenko 2 years, 7 months ago

On Fri, Jan 27, 2023 at 02:36:27PM -0800, Kees Cook wrote:
> If "vdesc" is NULL, it cannot be used with vd_to_axi_desc(). Leave
> "bytes" unchanged at 0. Seen under GCC 13 with -Warray-bounds:
> 
> ../drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c: In function 'dma_chan_tx_status':
> ../drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c:329:46: warning: array subscript 0 is outside array bounds of 'struct
> virt_dma_desc[46116860184273879]' [-Warray-bounds=]
>   329 |                 bytes = vd_to_axi_desc(vdesc)->length;
>       |                                              ^~
> 
> Fixes: 8e55444da65c ("dmaengine: dw-axi-dmac: Support burst residue granularity")
> Cc: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> Cc: Vinod Koul <vkoul@kernel.org>
> Cc: dmaengine@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> index 08af483331fd..4169e1d7d5ca 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> @@ -325,8 +325,6 @@ dma_chan_tx_status(struct dma_chan *dchan, dma_cookie_t cookie,
>  		len = vd_to_axi_desc(vdesc)->hw_desc[0].len;
>  		completed_length = completed_blocks * len;
>  		bytes = length - completed_length;
> -	} else {
> -		bytes = vd_to_axi_desc(vdesc)->length;
>  	}
>  
>  	spin_unlock_irqrestore(&chan->vc.lock, flags);

If you want to fix it properly, the code should be modified like

	status = dma_cookie_status(dchan, cookie, txstate);
	if (status == DMA_COMPLETE || !txstate) {
		if (txstate)
			goto out;
		return status;
	}

	...

out:
	dma_set_residue(txstate, bytes);

	return status;

to be in accordance with the Documentation.

**OR**

the Documentation should be fixed to tell that if status is DMA_COMPLETE,
residue is undefined and assumed to be 0.

Vinod?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] dmaengine: dw-axi-dmac: Do not dereference NULL structure

Posted by Andy Shevchenko 2 years, 7 months ago

On Mon, Jan 30, 2023 at 12:46:26PM +0200, Andy Shevchenko wrote:
> On Fri, Jan 27, 2023 at 02:36:27PM -0800, Kees Cook wrote:

...

> If you want to fix it properly, the code should be modified like
> 
> 	status = dma_cookie_status(dchan, cookie, txstate);
> 	if (status == DMA_COMPLETE || !txstate) {
> 		if (txstate)
> 			goto out;
> 		return status;
> 	}
> 
> 	...
> 
> out:
> 	dma_set_residue(txstate, bytes);
> 
> 	return status;
> 
> to be in accordance with the Documentation.
> 
> **OR**
> 
> the Documentation should be fixed to tell that if status is DMA_COMPLETE,
> residue is undefined and assumed to be 0.
> 
> Vinod?

Disregard my message. The dma_cookie_status() makes sure it's 0.
Sorry for the noise.

-- 
With Best Regards,
Andy Shevchenko