cx24116: fix a buffer overflow when checking userspace params

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@osg.samsung.com>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
(cherry picked from commit 729c8c5e3700410e3436573abfa5b68e8d3c89d6)

Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/drivers/media/dvb/frontends/cx24116.c b/drivers/media/dvb/frontends/cx24116.c
index 2410d8b59b6b428aa7621ed8b71839bef23282a8..b7d484759aaf38c106d57c3462ad00c265ccfeb4 100644 (file)
--- a/drivers/media/dvb/frontends/cx24116.c
+++ b/drivers/media/dvb/frontends/cx24116.c
@@ -950,6 +950,10 @@ static int cx24116_send_diseqc_msg(struct dvb_frontend *fe,
        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__);
@@ -961,10 +965,6 @@ static int cx24116_send_diseqc_msg(struct dvb_frontend *fe,
                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];