[PATCH 3.2 003/110] [media] cx24116: fix a buffer overflow when checking userspace params

[Ben Hutchings]

3.2.71-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>

commit 1fa2337a315a2448c5434f41e00d56b01a22283c upstream.

The maximum size for a DiSEqC command is 6, according to the
userspace API. However, the code allows to write up much more values:
	drivers/media/dvb-frontends/cx24116.c:983 cx24116_send_diseqc_msg() error: buffer overflow 'd->msg' 6 <= 23

Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/media/dvb/frontends/cx24116.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/media/dvb/frontends/cx24116.c
+++ b/drivers/media/dvb/frontends/cx24116.c
@@ -963,6 +963,10 @@ static int cx24116_send_diseqc_msg(struc
 	struct cx24116_state *state = fe->demodulator_priv;
 	int i, ret;
 
+	/* Validate length */
+	if (d->msg_len > sizeof(d->msg))
+                return -EINVAL;
+
 	/* Dump DiSEqC message */
 	if (debug) {
 		printk(KERN_INFO "cx24116: %s(", __func__);
@@ -974,10 +978,6 @@ static int cx24116_send_diseqc_msg(struc
 		printk(") toneburst=%d\n", toneburst);
 	}
 
-	/* Validate length */
-	if (d->msg_len > (CX24116_ARGLEN - CX24116_DISEQC_MSGOFS))
-		return -EINVAL;
-
 	/* DiSEqC message */
 	for (i = 0; i < d->msg_len; i++)
 		state->dsec_cmd.args[CX24116_DISEQC_MSGOFS + i] = d->msg[i];

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