Re: [PATCH v3 26/29] [media] af9035: Don't use dynamic static allocation

[Antti Palosaari <crope@iki.fi>]

Acked-by: Antti Palosaari <crope@iki.fi>
Reviewed-by: Antti Palosaari <crope@iki.fi>

Antti

On 05.11.2013 12:01, Mauro Carvalho Chehab wrote:
> Dynamic static allocation is evil, as Kernel stack is too low, and
> compilation complains about it on some archs:
> 	drivers/media/usb/dvb-usb-v2/af9035.c:142:1: warning: 'af9035_wr_regs' uses dynamic stack allocation [enabled by default]
> 	drivers/media/usb/dvb-usb-v2/af9035.c:305:1: warning: 'af9035_i2c_master_xfer' uses dynamic stack allocation [enabled by default]
>
> Instead, let's enforce a limit for the buffer to be the max size of
> a control URB payload data (64 bytes).
>
> Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
> ---
>   drivers/media/usb/dvb-usb-v2/af9035.c | 29 ++++++++++++++++++++++++++---
>   1 file changed, 26 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/usb/dvb-usb-v2/af9035.c b/drivers/media/usb/dvb-usb-v2/af9035.c
> index 1ea17dc2a76e..c8fcd78425bd 100644
> --- a/drivers/media/usb/dvb-usb-v2/af9035.c
> +++ b/drivers/media/usb/dvb-usb-v2/af9035.c
> @@ -21,6 +21,9 @@
>
>   #include "af9035.h"
>
> +/* Max transfer size done by I2C transfer functions */
> +#define MAX_XFER_SIZE  64
> +
>   DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
>
>   static u16 af9035_checksum(const u8 *buf, size_t len)
> @@ -126,10 +129,16 @@ exit:
>   /* write multiple registers */
>   static int af9035_wr_regs(struct dvb_usb_device *d, u32 reg, u8 *val, int len)
>   {
> -	u8 wbuf[6 + len];
> +	u8 wbuf[MAX_XFER_SIZE];
>   	u8 mbox = (reg >> 16) & 0xff;
>   	struct usb_req req = { CMD_MEM_WR, mbox, sizeof(wbuf), wbuf, 0, NULL };
>
> +	if (6 + len > sizeof(wbuf)) {
> +		dev_warn(&d->udev->dev, "%s: i2c wr: len=%d is too big!\n",
> +			 KBUILD_MODNAME, len);
> +		return -EOPNOTSUPP;
> +	}
> +
>   	wbuf[0] = len;
>   	wbuf[1] = 2;
>   	wbuf[2] = 0;
> @@ -228,9 +237,16 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
>   					msg[1].len);
>   		} else {
>   			/* I2C */
> -			u8 buf[5 + msg[0].len];
> +			u8 buf[MAX_XFER_SIZE];
>   			struct usb_req req = { CMD_I2C_RD, 0, sizeof(buf),
>   					buf, msg[1].len, msg[1].buf };
> +
> +			if (5 + msg[0].len > sizeof(buf)) {
> +				dev_warn(&d->udev->dev,
> +					 "%s: i2c xfer: len=%d is too big!\n",
> +					 KBUILD_MODNAME, msg[0].len);
> +				return -EOPNOTSUPP;
> +			}
>   			req.mbox |= ((msg[0].addr & 0x80)  >>  3);
>   			buf[0] = msg[1].len;
>   			buf[1] = msg[0].addr << 1;
> @@ -257,9 +273,16 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
>   					msg[0].len - 3);
>   		} else {
>   			/* I2C */
> -			u8 buf[5 + msg[0].len];
> +			u8 buf[MAX_XFER_SIZE];
>   			struct usb_req req = { CMD_I2C_WR, 0, sizeof(buf), buf,
>   					0, NULL };
> +
> +			if (5 + msg[0].len > sizeof(buf)) {
> +				dev_warn(&d->udev->dev,
> +					 "%s: i2c xfer: len=%d is too big!\n",
> +					 KBUILD_MODNAME, msg[0].len);
> +				return -EOPNOTSUPP;
> +			}
>   			req.mbox |= ((msg[0].addr & 0x80)  >>  3);
>   			buf[0] = msg[0].len;
>   			buf[1] = msg[0].addr << 1;
>


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