From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Tom Rix <trix@redhat.com>,
        Tim Harvey <tharvey@gateworks.com>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 198/355] media: TDA1997x: handle short reads of hdmi info frame.
Date:   Mon, 15 Nov 2021 18:02:02 +0100
Message-Id: <20211115165320.167133991@linuxfoundation.org>
In-Reply-To: <20211115165313.549179499@linuxfoundation.org>
References: <20211115165313.549179499@linuxfoundation.org>
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From: Tom Rix <trix@redhat.com>

[ Upstream commit 48d219f9cc667bc6fbc3e3af0b1bfd75db94fce4 ]

Static analysis reports this representative problem

tda1997x.c:1939: warning: 7th function call argument is an uninitialized
value

The 7th argument is buffer[0], which is set in the earlier call to
io_readn().  When io_readn() call to io_read() fails with the first
read, buffer[0] is not set and 0 is returned and stored in len.

The later call to hdmi_infoframe_unpack()'s size parameter is the
static size of buffer, always 40, so a short read is not caught
in hdmi_infoframe_unpacks()'s checking.  The variable len should be
used instead.

Zero initialize buffer to 0 so it is in a known start state.

Fixes: 9ac0038db9a7 ("media: i2c: Add TDA1997x HDMI receiver driver")
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/media/i2c/tda1997x.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/media/i2c/tda1997x.c b/drivers/media/i2c/tda1997x.c
index 18a2027ba1450..5faffedb0feba 100644
--- a/drivers/media/i2c/tda1997x.c
+++ b/drivers/media/i2c/tda1997x.c
@@ -1247,13 +1247,13 @@ tda1997x_parse_infoframe(struct tda1997x_state *state, u16 addr)
 {
 	struct v4l2_subdev *sd = &state->sd;
 	union hdmi_infoframe frame;
-	u8 buffer[40];
+	u8 buffer[40] = { 0 };
 	u8 reg;
 	int len, err;
 
 	/* read data */
 	len = io_readn(sd, addr, sizeof(buffer), buffer);
-	err = hdmi_infoframe_unpack(&frame, buffer, sizeof(buffer));
+	err = hdmi_infoframe_unpack(&frame, buffer, len);
 	if (err) {
 		v4l_err(state->client,
 			"failed parsing %d byte infoframe: 0x%04x/0x%02x\n",
@@ -1927,13 +1927,13 @@ static int tda1997x_log_infoframe(struct v4l2_subdev *sd, int addr)
 {
 	struct tda1997x_state *state = to_state(sd);
 	union hdmi_infoframe frame;
-	u8 buffer[40];
+	u8 buffer[40] = { 0 };
 	int len, err;
 
 	/* read data */
 	len = io_readn(sd, addr, sizeof(buffer), buffer);
 	v4l2_dbg(1, debug, sd, "infoframe: addr=%d len=%d\n", addr, len);
-	err = hdmi_infoframe_unpack(&frame, buffer, sizeof(buffer));
+	err = hdmi_infoframe_unpack(&frame, buffer, len);
 	if (err) {
 		v4l_err(state->client,
 			"failed parsing %d byte infoframe: 0x%04x/0x%02x\n",
-- 
2.33.0