linux-kernel - Re: [alsa-devel] [PATCH 1/7 v2] dmaengine: add a simple dma library

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Message-ID: <20120126173444.GM5446@pengutronix.de>
Date:	Thu, 26 Jan 2012 18:34:44 +0100
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Guennadi Liakhovetski <g.liakhovetski@....de>
Cc:	linux-kernel@...r.kernel.org, alsa-devel@...a-project.org,
	linux-sh@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	Magnus Damm <magnus.damm@...il.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	linux-mmc@...r.kernel.org, Paul Mundt <lethal@...ux-sh.org>,
	linux-serial@...r.kernel.org
Subject: Re: [alsa-devel] [PATCH 1/7 v2] dmaengine: add a simple dma library

Hi Guennadi,

On Thu, Jan 26, 2012 at 03:56:18PM +0100, Guennadi Liakhovetski wrote:
> This patch adds a library of functions, helping to implement dmaengine
> drivers for hardware, unable to handle scatter-gather lists natively.
> The first version of this driver only supports memcpy and slave DMA
> operation.
> 
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@....de>
> ---
> 

[...]

> +
> +/*
> + * For slave DMA we assume, that there is a finite number of DMA slaves in the
> + * system, and that each such slave can only use a finite number of channels.
> + * We use slave channel IDs to make sure, that no such slave channel ID is
> + * allocated more than once.
> + */
> +static unsigned int slave_num = 256;
> +module_param(slave_num, uint, 0444);
> +
> +/* A bitmask with slave_num bits */
> +static unsigned long *simple_slave_used;

You never check that the slave ids passed into this code are
within the range of slave_num. Given that this is a user changeable
value this is a bit flawy.

Sascha

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