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

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Message-ID: <Y9e9gyARKf1nrmgG@smile.fi.intel.com>
Date:   Mon, 30 Jan 2023 14:52:19 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>, dmaengine@...r.kernel.org,
        Sia Jee Heng <jee.heng.sia@...el.com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] dmaengine: dw-axi-dmac: Do not dereference NULL structure

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