media: ov9650: add a sanity check

BugLink: https://bugs.launchpad.net/bugs/1847155
[ 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@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/media/i2c/ov9650.c b/drivers/media/i2c/ov9650.c
index 69433e1e25335b263140e8a131a8a184d441573c..2d789be2ad15f0f09a6c379c87971965ca6be3dc 100644 (file)
--- a/drivers/media/i2c/ov9650.c
+++ b/drivers/media/i2c/ov9650.c
@@ -710,6 +710,11 @@ 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);