[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/bcm3510.c:230:1: warning: 'bcm3510_do_hab_cmd' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/itd1000.c:69:1: warning: 'itd1000_write_regs.constprop.0' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/mt312.c:126:1: warning: 'mt312_write' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/nxt200x.c:111:1: warning: 'nxt200x_writebytes' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/stb6100.c:216:1: warning: 'stb6100_write_reg_range.constprop.3' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/stv6110.c:98:1: warning: 'stv6110_write_regs' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/stv6110x.c:85:1: warning: 'stv6110x_write_regs' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/tda18271c2dd.c:147:1: warning: 'WriteRegs' uses dynamic stack allocation [enabled by default]
	drivers/media/dvb-frontends/zl10039.c:119:1: warning: 'zl10039_write' 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>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/drivers/media/dvb-frontends/stv6110x.c b/drivers/media/dvb-frontends/stv6110x.c
index f36cab12bdc7..e66154e5c1d7 100644
--- a/drivers/media/dvb-frontends/stv6110x.c
+++ b/drivers/media/dvb-frontends/stv6110x.c
@@ -32,6 +32,9 @@
 #include "stv6110x.h"
 #include "stv6110x_priv.h"
 
+/* Max transfer size done by I2C transfer functions */
+#define MAX_XFER_SIZE  64
+
 static unsigned int verbose;
 module_param(verbose, int, 0644);
 MODULE_PARM_DESC(verbose, "Set Verbosity level");
@@ -61,7 +64,8 @@ static int stv6110x_write_regs(struct stv6110x_state *stv6110x, int start, u8 da
 {
 	int ret;
 	const struct stv6110x_config *config = stv6110x->config;
-	u8 buf[len + 1];
+	u8 buf[MAX_XFER_SIZE];
+
 	struct i2c_msg msg = {
 		.addr = config->addr,
 		.flags = 0,
@@ -69,6 +73,13 @@ static int stv6110x_write_regs(struct stv6110x_state *stv6110x, int start, u8 da
 		.len = len + 1
 	};
 
+	if (1 + len > sizeof(buf)) {
+		printk(KERN_WARNING
+		       "%s: i2c wr: len=%d is too big!\n",
+		       KBUILD_MODNAME, len);
+		return -EINVAL;
+	}
+
 	if (start + len > 8)
 		return -EINVAL;