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From: Colin King <colin.king@canonical.com>
To: Liviu Dudau <liviu.dudau@arm.com>,
	Brian Starkey <brian.starkey@arm.com>,
	David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	dri-devel@lists.freedesktop.org
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] drm/arm: fix unintentional integer overflow on left shift
Date: Thu, 18 Jun 2020 10:04:00 +0000	[thread overview]
Message-ID: <20200618100400.11464-1-colin.king@canonical.com> (raw)

From: Colin Ian King <colin.king@canonical.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@canonical.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

             reply	other threads:[~2020-06-18 10:04 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-18 10:04 Colin King [this message]
2020-06-18 12:14 ` [PATCH] drm/arm: fix unintentional integer overflow on left shift Liviu Dudau
2020-06-18 12:50   ` Colin Ian King
2020-06-18 14:21     ` Liviu Dudau
2020-06-18 14:36       ` Garrit Franke
2020-06-18 14:38         ` Colin Ian King
2020-06-18 15:22         ` Dan Carpenter

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