From 4bef1a1d32e29b68855616020dbff574b9cda08f Mon Sep 17 00:00:00 2001 From: Robin Watts Date: Thu, 29 Dec 2016 15:57:43 +0000 Subject: [PATCH] Bug 697453: Avoid divide by 0 in scan conversion code. Arithmetic overflow due to extreme values in the scan conversion code can cause a division by 0. Avoid this with a simple extra check. dx_old=cf814d81 endp->x_next=b0e859b9 alp->x_next=8069a73a leads to dx_den = 0 Upstream-Status: Backport CVE: CVE-2016-10219 Signed-off-by: Catalin Enache --- base/gxfill.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/base/gxfill.c b/base/gxfill.c index 99196c0..2f81bb0 100644 --- a/base/gxfill.c +++ b/base/gxfill.c @@ -1741,7 +1741,7 @@ intersect(active_line *endp, active_line *alp, fixed y, fixed y1, fixed *p_y_new fixed dx_old = alp->x_current - endp->x_current; fixed dx_den = dx_old + endp->x_next - alp->x_next; - if (dx_den <= dx_old) + if (dx_den <= dx_old || dx_den == 0) return false; /* Intersection isn't possible. */ dy = y1 - y; if_debug3('F', "[F]cross: dy=%g, dx_old=%g, dx_new=%g\n", @@ -1750,7 +1750,7 @@ intersect(active_line *endp, active_line *alp, fixed y, fixed y1, fixed *p_y_new /* Do the computation in single precision */ /* if the values are small enough. */ y_new = - ((dy | dx_old) < 1L << (size_of(fixed) * 4 - 1) ? + (((ufixed)(dy | dx_old)) < (1L << (size_of(fixed) * 4 - 1)) ? dy * dx_old / dx_den : (INCR_EXPR(mq_cross), fixed_mult_quo(dy, dx_old, dx_den))) + y; -- 2.10.2