media: ov9650: add a sanity check

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>

diff --git a/drivers/media/i2c/ov9650.c b/drivers/media/i2c/ov9650.c
index 8b56011446a92e735bce8eb6977fda65441209dc..4fe68aa5578993e81644cc7cbc85e607d0b2cbd9 100644 (file)
--- a/drivers/media/i2c/ov9650.c
+++ b/drivers/media/i2c/ov9650.c
@@ -703,6 +703,11 @@ 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);