media: adv7604: Prevent out of bounds access

These can only be accessed with CAP_SYS_ADMIN so it's not a critical
security issue.  The problem is that "page" is controlled by the user in
the ioctl().  The test to see if the bit is set in state->info->page_mask
is not sufficient because "page" can be very high and shift wrap around
to a bit which is set.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/i2c/adv7604.c

@@ -618,7 +618,7 @@ static int adv76xx_read_reg(struct v4l2_subdev *sd, unsigned int reg)
 	unsigned int val;
 	int err;
 
-	if (!(BIT(page) & state->info->page_mask))
+	if (page >= ADV76XX_PAGE_MAX || !(BIT(page) & state->info->page_mask))
 		return -EINVAL;
 
 	reg &= 0xff;
@@ -633,7 +633,7 @@ static int adv76xx_write_reg(struct v4l2_subdev *sd, unsigned int reg, u8 val)
 	struct adv76xx_state *state = to_state(sd);
 	unsigned int page = reg >> 8;
 
-	if (!(BIT(page) & state->info->page_mask))
+	if (page >= ADV76XX_PAGE_MAX || !(BIT(page) & state->info->page_mask))
 		return -EINVAL;
 
 	reg &= 0xff;