45 lines
1.5 KiB
Diff
45 lines
1.5 KiB
Diff
From 4bef1a1d32e29b68855616020dbff574b9cda08f Mon Sep 17 00:00:00 2001
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From: Robin Watts <Robin.Watts@artifex.com>
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Date: Thu, 29 Dec 2016 15:57:43 +0000
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Subject: [PATCH] Bug 697453: Avoid divide by 0 in scan conversion code.
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Arithmetic overflow due to extreme values in the scan conversion
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code can cause a division by 0.
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Avoid this with a simple extra check.
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dx_old=cf814d81
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endp->x_next=b0e859b9
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alp->x_next=8069a73a
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leads to dx_den = 0
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---
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base/gxfill.c | 4 ++--
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1 file changed, 2 insertions(+), 2 deletions(-)
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diff --git a/base/gxfill.c b/base/gxfill.c
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index 99196c0..2f81bb0 100644
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--- a/base/gxfill.c
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+++ b/base/gxfill.c
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@@ -1741,7 +1741,7 @@ intersect(active_line *endp, active_line *alp, fixed y, fixed y1, fixed *p_y_new
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fixed dx_old = alp->x_current - endp->x_current;
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fixed dx_den = dx_old + endp->x_next - alp->x_next;
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- if (dx_den <= dx_old)
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+ if (dx_den <= dx_old || dx_den == 0)
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return false; /* Intersection isn't possible. */
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dy = y1 - y;
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if_debug3('F', "[F]cross: dy=%g, dx_old=%g, dx_new=%g\n",
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@@ -1750,7 +1750,7 @@ intersect(active_line *endp, active_line *alp, fixed y, fixed y1, fixed *p_y_new
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/* Do the computation in single precision */
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/* if the values are small enough. */
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y_new =
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- ((dy | dx_old) < 1L << (size_of(fixed) * 4 - 1) ?
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+ (((ufixed)(dy | dx_old)) < (1L << (size_of(fixed) * 4 - 1)) ?
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dy * dx_old / dx_den :
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(INCR_EXPR(mq_cross), fixed_mult_quo(dy, dx_old, dx_den)))
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+ y;
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--
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2.9.3
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