From 093347abc7a4e0490e3c962ecbde2dc272a8f708 Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Thu, 22 Aug 2019 11:55:07 -0300
Subject: [PATCH] media: ov9650: add a sanity check
Git-commit: 093347abc7a4e0490e3c962ecbde2dc272a8f708
Patch-mainline: v5.4-rc1
References: bsc#1051510

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 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 8b56011446a9..4fe68aa55789 100644
--- 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);
 
-- 
2.16.4