linux-kernel - [PATCH 09/13] media: cx24116: prevent overflows on SNR calculus

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Message-ID: <644e1a8c55b7cabad791c398e488e2a825fdefb9.1729074076.git.mchehab+huawei@kernel.org>
Date: Wed, 16 Oct 2024 12:22:25 +0200
From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To: 
Cc: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
	Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
	Steven Toth <stoth@...uxtv.org>,
	linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org,
	stable@...r.kernel.org
Subject: [PATCH 09/13] media: cx24116: prevent overflows on SNR calculus

If reading SNR registers fail, a negative number will be
returned, causing an underflow when reading SNR registers.

Prevent that.

Fixes: 8953db793d5b ("V4L/DVB (9178): cx24116: Add module parameter to return SNR as ESNO.")
Cc: stable@...r.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
---
 drivers/media/dvb-frontends/cx24116.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/media/dvb-frontends/cx24116.c b/drivers/media/dvb-frontends/cx24116.c
index 8b978a9f74a4..f5dd3a81725a 100644
--- a/drivers/media/dvb-frontends/cx24116.c
+++ b/drivers/media/dvb-frontends/cx24116.c
@@ -741,6 +741,7 @@ static int cx24116_read_snr_pct(struct dvb_frontend *fe, u16 *snr)
 {
 	struct cx24116_state *state = fe->demodulator_priv;
 	u8 snr_reading;
+	int ret;
 	static const u32 snr_tab[] = { /* 10 x Table (rounded up) */
 		0x00000, 0x0199A, 0x03333, 0x04ccD, 0x06667,
 		0x08000, 0x0999A, 0x0b333, 0x0cccD, 0x0e667,
@@ -749,7 +750,11 @@ static int cx24116_read_snr_pct(struct dvb_frontend *fe, u16 *snr)
 
 	dprintk("%s()\n", __func__);
 
-	snr_reading = cx24116_readreg(state, CX24116_REG_QUALITY0);
+	ret = cx24116_readreg(state, CX24116_REG_QUALITY0);
+	if (ret  < 0)
+		return ret;
+
+	snr_reading = ret;
 
 	if (snr_reading >= 0xa0 /* 100% */)
 		*snr = 0xffff;
-- 
2.47.0