[media] af9035: Don't use dynamic static allocation

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>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

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 @@ static int af9035_ctrl_msg(struct dvb_usb_device *d, struct usb_req *req)
 /* 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;