linux-kernel - [PATCH AUTOSEL 4.9 36/60] media: ov9650: add a sanity check

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Message-Id: <20190922185934.4305-36-sashal@kernel.org>
Date:   Sun, 22 Sep 2019 14:59:09 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Sasha Levin <sashal@...nel.org>, linux-media@...r.kernel.org
Subject: [PATCH AUTOSEL 4.9 36/60] media: ov9650: add a sanity check

From: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>

[ Upstream commit 093347abc7a4e0490e3c962ecbde2dc272a8f708 ]

As pointed by cppcheck:

	[drivers/media/i2c/ov9650.c:706]: (error) Shifting by a negative value is undefined behaviour
	[drivers/media/i2c/ov9650.c:707]: (error) Shifting by a negative value is undefined behaviour
	[drivers/media/i2c/ov9650.c:721]: (error) Shifting by a negative value is undefined behaviour

Prevent mangling with gains with invalid values.

As pointed by Sylvester, this should never happen in practice,
as min value of V4L2_CID_GAIN control is 16 (gain is always >= 16
and m is always >= 0), but it is too hard for a static analyzer
to get this, as the logic with validates control min/max is
elsewhere inside V4L2 core.

Reviewed-by: Sylwester Nawrocki <s.nawrocki@...sung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/i2c/ov9650.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/media/i2c/ov9650.c b/drivers/media/i2c/ov9650.c
index 502c72238a4a5..db962e2108adf 100644
--- a/drivers/media/i2c/ov9650.c
+++ b/drivers/media/i2c/ov9650.c
@@ -708,6 +708,11 @@ static int ov965x_set_gain(struct ov965x *ov965x, int auto_gain)
 		for (m = 6; m >= 0; m--)
 			if (gain >= (1 << m) * 16)
 				break;
+
+		/* Sanity check: don't adjust the gain with a negative value */
+		if (m < 0)
+			return -EINVAL;
+
 		rgain = (gain - ((1 << m) * 16)) / (1 << m);
 		rgain |= (((1 << m) - 1) << 4);
 
-- 
2.20.1