[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, 11 insertions, 1 deletions

diff --git a/drivers/media/dvb-frontends/zl10039.c b/drivers/media/dvb-frontends/zl10039.c
index eff9c5fde50a..91b6b2e9b792 100644
--- a/drivers/media/dvb-frontends/zl10039.c
+++ b/drivers/media/dvb-frontends/zl10039.c
@@ -30,6 +30,9 @@
 
 static int debug;
 
+/* Max transfer size done by I2C transfer functions */
+#define MAX_XFER_SIZE  64
+
 #define dprintk(args...) \
 	do { \
 		if (debug) \
@@ -98,7 +101,7 @@ static int zl10039_write(struct zl10039_state *state,
 			const enum zl10039_reg_addr reg, const u8 *src,
 			const size_t count)
 {
-	u8 buf[count + 1];
+	u8 buf[MAX_XFER_SIZE];
 	struct i2c_msg msg = {
 		.addr = state->i2c_addr,
 		.flags = 0,
@@ -106,6 +109,13 @@ static int zl10039_write(struct zl10039_state *state,
 		.len = count + 1,
 	};
 
+	if (1 + count > sizeof(buf)) {
+		printk(KERN_WARNING
+		       "%s: i2c wr reg=%04x: len=%zd is too big!\n",
+		       KBUILD_MODNAME, reg, count);
+		return -EINVAL;
+	}
+
 	dprintk("%s\n", __func__);
 	/* Write register address and data in one go */
 	buf[0] = reg;