linux-kernel - [PATCH 5.5 215/367] drm/rect: Avoid division by zero

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Message-Id: <20200210122444.083805445@linuxfoundation.org>
Date:   Mon, 10 Feb 2020 04:32:08 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Benjamin Gaignard <benjamin.gaignard@...com>,
        Daniel Vetter <daniel@...ll.ch>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>
Subject: [PATCH 5.5 215/367] drm/rect: Avoid division by zero

From: Ville Syrjälä <ville.syrjala@...ux.intel.com>

commit 433480c1afd44f3e1e664b85063d98cefeefa0ed upstream.

Check for zero width/height destination rectangle in
drm_rect_clip_scaled() to avoid a division by zero.

Cc: stable@...r.kernel.org
Fixes: f96bdf564f3e ("drm/rect: Handle rounding errors in drm_rect_clip_scaled, v3.")
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Cc: Benjamin Gaignard <benjamin.gaignard@...com>
Cc: Daniel Vetter <daniel@...ll.ch>
Testcase: igt/kms_selftest/drm_rect_clip_scaled_div_by_zero
Signed-off-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191122175623.13565-2-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@...com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/drm_rect.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_rect.c
+++ b/drivers/gpu/drm/drm_rect.c
@@ -54,7 +54,12 @@ EXPORT_SYMBOL(drm_rect_intersect);
 
 static u32 clip_scaled(u32 src, u32 dst, u32 clip)
 {
-	u64 tmp = mul_u32_u32(src, dst - clip);
+	u64 tmp;
+
+	if (dst == 0)
+		return 0;
+
+	tmp = mul_u32_u32(src, dst - clip);
 
 	/*
 	 * Round toward 1.0 when clipping so that we don't accidentally