linux-kernel - [PATCH][next][V3] media: vivid: fix potential integer overflow on left shift

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Message-Id: <20190627080541.11122-1-colin.king@canonical.com>
Date:   Thu, 27 Jun 2019 09:05:41 +0100
From:   Colin King <colin.king@...onical.com>
To:     Hans Verkuil <hverkuil@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next][V3] media: vivid: fix potential integer overflow on left shift

From: Colin Ian King <colin.king@...onical.com>

There is a potential integer overflow when int 2 is left shifted
as this is evaluated using 32 bit arithmetic but is being used in
a context that expects an expression of type s64.  Fix this by
generating a mask using GENMASK to avoid a 32 bit overflow.

Addresses-Coverity: ("Unintentional integer overflow")
Fixes: 8a99e9faa131 ("media: vivid: add HDMI (dis)connect RX emulation")
Fixes: 79a792dafac6 ("media: vivid: add HDMI (dis)connect TX emulation")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
V2: use intermediate variables for the shifted expression to make code
    a bit more readable.
V3: use GENMASK rather than shifting logic, rename variables adding
    _mask suffix.
---

Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/media/platform/vivid/vivid-ctrls.c | 24 +++++++++++-----------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/media/platform/vivid/vivid-ctrls.c b/drivers/media/platform/vivid/vivid-ctrls.c
index 3e916c8befb7..b04997569228 100644
--- a/drivers/media/platform/vivid/vivid-ctrls.c
+++ b/drivers/media/platform/vivid/vivid-ctrls.c
@@ -1613,6 +1613,8 @@ int vivid_create_controls(struct vivid_dev *dev, bool show_ccs_cap,
 	}
 
 	if (dev->num_hdmi_inputs) {
+		s64 hdmi_input_mask = GENMASK(dev->num_hdmi_inputs - 1, 0);
+
 		dev->ctrl_dv_timings_signal_mode = v4l2_ctrl_new_custom(hdl_vid_cap,
 					&vivid_ctrl_dv_timings_signal_mode, NULL);
 
@@ -1633,12 +1635,13 @@ int vivid_create_controls(struct vivid_dev *dev, bool show_ccs_cap,
 			V4L2_CID_DV_RX_RGB_RANGE, V4L2_DV_RGB_RANGE_FULL,
 			0, V4L2_DV_RGB_RANGE_AUTO);
 		dev->ctrl_rx_power_present = v4l2_ctrl_new_std(hdl_vid_cap,
-			NULL, V4L2_CID_DV_RX_POWER_PRESENT, 0,
-			(2 << (dev->num_hdmi_inputs - 1)) - 1, 0,
-			(2 << (dev->num_hdmi_inputs - 1)) - 1);
+			NULL, V4L2_CID_DV_RX_POWER_PRESENT, 0, hdmi_input_mask,
+			0, hdmi_input_mask);
 
 	}
 	if (dev->num_hdmi_outputs) {
+		s64 hdmi_output_mask = GENMASK(dev->num_hdmi_outputs - 1, 0);
+
 		/*
 		 * We aren't doing anything with this at the moment, but
 		 * HDMI outputs typically have this controls.
@@ -1652,17 +1655,14 @@ int vivid_create_controls(struct vivid_dev *dev, bool show_ccs_cap,
 		dev->ctrl_display_present = v4l2_ctrl_new_custom(hdl_vid_out,
 			&vivid_ctrl_display_present, NULL);
 		dev->ctrl_tx_hotplug = v4l2_ctrl_new_std(hdl_vid_out,
-			NULL, V4L2_CID_DV_TX_HOTPLUG, 0,
-			(2 << (dev->num_hdmi_outputs - 1)) - 1, 0,
-			(2 << (dev->num_hdmi_outputs - 1)) - 1);
+			NULL, V4L2_CID_DV_TX_HOTPLUG, 0, hdmi_output_mask,
+			0, hdmi_output_mask);
 		dev->ctrl_tx_rxsense = v4l2_ctrl_new_std(hdl_vid_out,
-			NULL, V4L2_CID_DV_TX_RXSENSE, 0,
-			(2 << (dev->num_hdmi_outputs - 1)) - 1, 0,
-			(2 << (dev->num_hdmi_outputs - 1)) - 1);
+			NULL, V4L2_CID_DV_TX_RXSENSE, 0, hdmi_output_mask,
+			0, hdmi_output_mask);
 		dev->ctrl_tx_edid_present = v4l2_ctrl_new_std(hdl_vid_out,
-			NULL, V4L2_CID_DV_TX_EDID_PRESENT, 0,
-			(2 << (dev->num_hdmi_outputs - 1)) - 1, 0,
-			(2 << (dev->num_hdmi_outputs - 1)) - 1);
+			NULL, V4L2_CID_DV_TX_EDID_PRESENT, 0, hdmi_output_mask,
+			0, hdmi_output_mask);
 	}
 	if ((dev->has_vid_cap && dev->has_vid_out) ||
 	    (dev->has_vbi_cap && dev->has_vbi_out))
-- 
2.20.1