linux-kernel - Re: [PATCH] ums_realtek: do not use stack memory for DMA

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Date:	Thu, 25 Aug 2011 14:51:51 +0400
From:	Sergei Shtylyov <sshtylyov@...sta.com>
To:	Adam Cozzette <acozzette@...hmc.edu>
CC:	Greg Kroah-Hartman <gregkh@...e.de>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, Josh Boyer <jwboyer@...hat.com>,
	edwin_rong <edwin_rong@...lsil.com.cn>,
	wwang <wei_wang@...lsil.com.cn>
Subject: Re: [PATCH] ums_realtek: do not use stack memory for DMA

Hello.

On 24-08-2011 22:22, Adam Cozzette wrote:

> This patch changes rts51x_read_mem, rts51x_write_mem, and rts51x_read_status to
> allocate temporary buffers with kmalloc. This way stack addresses are not used
> for DMA when these functions call rts51x_bulk_transport.

> Signed-off-by: Adam Cozzette<acozzette@...hmc.edu>
> ---
>   realtek_cr.c |   35 ++++++++++++++++++++++++++++++-----
>   1 file changed, 30 insertions(+), 5 deletions(-)

> diff --git a/drivers/usb/storage/realtek_cr.c b/drivers/usb/storage/realtek_cr.c
> index 34adc4b..232167a 100644
> --- a/drivers/usb/storage/realtek_cr.c
> +++ b/drivers/usb/storage/realtek_cr.c
[...]
> @@ -342,6 +351,12 @@ static int rts51x_write_mem(struct us_data *us, u16 addr, u8 *data, u16 len)
>   {
>   	int retval;
>   	u8 cmnd[12] = { 0 };
> +	u8 *buf;
> +
> +	buf = kmalloc(len, GFP_NOIO);
> +	if (buf == NULL)
> +		return USB_STOR_TRANSPORT_ERROR;
> +	memcpy(buf, data, len);

    You could use kmemdup() instead of kmalloc()/memcpy()...

WBR, Sergei
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