[media] dvb-frontends: 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/dvb-frontends/af9013.c:77:1: warning: 'af9013_wr_regs_i2c' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/af9033.c:188:1: warning: 'af9033_wr_reg_val_tab' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/af9033.c:68:1: warning: 'af9033_wr_regs' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/bcm3510.c:230:1: warning: 'bcm3510_do_hab_cmd' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/cxd2820r_core.c:84:1: warning: 'cxd2820r_rd_regs_i2c.isra.1' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/rtl2830.c:56:1: warning: 'rtl2830_wr' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/rtl2832.c:187:1: warning: 'rtl2832_wr' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/tda10071.c:52:1: warning: 'tda10071_wr_regs' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/tda10071.c:84:1: warning: 'tda10071_rd_regs' uses dynamic stack allocation [enabled by default]
Instead, let's enforce a limit for the buffer. Considering that I2C
transfers are generally limited, and that devices used on USB has a
max data length of 64 bytes for	the control URBs.
So, it seem safe to use 64 bytes as the hard limit for all those devices.
 On most cases, the limit is a way lower than that, but	this limit
is small enough to not affect the Kernel stack, and it is a no brain
limit, as using smaller ones would require to either carefully each
driver or to take a look on each datasheet.

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>

1 files changed, 20 insertions, 3 deletions

diff --git a/drivers/media/dvb-frontends/af9033.c b/drivers/media/dvb-frontends/af9033.c
index a777b4b944eb..30ee59052157 100644
--- a/drivers/media/dvb-frontends/af9033.c
+++ b/drivers/media/dvb-frontends/af9033.c
@@ -21,6 +21,9 @@
 
 #include "af9033_priv.h"
 
+/* Max transfer size done by I2C transfer functions */
+#define MAX_XFER_SIZE  64
+
 struct af9033_state {
 	struct i2c_adapter *i2c;
 	struct dvb_frontend fe;
@@ -40,16 +43,23 @@ static int af9033_wr_regs(struct af9033_state *state, u32 reg, const u8 *val,
 		int len)
 {
 	int ret;
-	u8 buf[3 + len];
+	u8 buf[MAX_XFER_SIZE];
 	struct i2c_msg msg[1] = {
 		{
 			.addr = state->cfg.i2c_addr,
 			.flags = 0,
-			.len = sizeof(buf),
+			.len = 3 + len,
 			.buf = buf,
 		}
 	};
 
+	if (3 + len > sizeof(buf)) {
+		dev_warn(&state->i2c->dev,
+			 "%s: i2c wr reg=%04x: len=%d is too big!\n",
+			 KBUILD_MODNAME, reg, len);
+		return -EINVAL;
+	}
+
 	buf[0] = (reg >> 16) & 0xff;
 	buf[1] = (reg >>  8) & 0xff;
 	buf[2] = (reg >>  0) & 0xff;
@@ -161,7 +171,14 @@ static int af9033_wr_reg_val_tab(struct af9033_state *state,
 		const struct reg_val *tab, int tab_len)
 {
 	int ret, i, j;
-	u8 buf[tab_len];
+	u8 buf[MAX_XFER_SIZE];
+
+	if (tab_len > sizeof(buf)) {
+		dev_warn(&state->i2c->dev,
+			 "%s: i2c wr len=%d is too big!\n",
+			 KBUILD_MODNAME, tab_len);
+		return -EINVAL;
+	}
 
 	dev_dbg(&state->i2c->dev, "%s: tab_len=%d\n", __func__, tab_len);