linux-kernel - [PATCH] drm/arm: fix unintentional integer overflow on left shift

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Message-Id: <20200618100400.11464-1-colin.king@canonical.com>
Date:   Thu, 18 Jun 2020 11:04:00 +0100
From:   Colin King <colin.king@...onical.com>
To:     Liviu Dudau <liviu.dudau@....com>,
        Brian Starkey <brian.starkey@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm/arm: fix unintentional integer overflow on left shift

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

Shifting the integer value 1 is evaluated using 32-bit arithmetic
and then used in an expression that expects a long value leads to
a potential integer overflow. Fix this by using the BIT macro to
perform the shift to avoid the overflow.

Addresses-Coverity: ("Unintentional integer overflow")
Fixes: ad49f8602fe8 ("drm/arm: Add support for Mali Display Processors")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/gpu/drm/arm/malidp_planes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/arm/malidp_planes.c b/drivers/gpu/drm/arm/malidp_planes.c
index 37715cc6064e..ab45ac445045 100644
--- a/drivers/gpu/drm/arm/malidp_planes.c
+++ b/drivers/gpu/drm/arm/malidp_planes.c
@@ -928,7 +928,7 @@ int malidp_de_planes_init(struct drm_device *drm)
 	const struct malidp_hw_regmap *map = &malidp->dev->hw->map;
 	struct malidp_plane *plane = NULL;
 	enum drm_plane_type plane_type;
-	unsigned long crtcs = 1 << drm->mode_config.num_crtc;
+	unsigned long crtcs = BIT(drm->mode_config.num_crtc);
 	unsigned long flags = DRM_MODE_ROTATE_0 | DRM_MODE_ROTATE_90 | DRM_MODE_ROTATE_180 |
 			      DRM_MODE_ROTATE_270 | DRM_MODE_REFLECT_X | DRM_MODE_REFLECT_Y;
 	unsigned int blend_caps = BIT(DRM_MODE_BLEND_PIXEL_NONE) |
-- 
2.27.0.rc0