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Fixed GH-18241: imagefilledpolygon underflow with poly coordinates. #18248

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Fixed GH-18241: imagefilledpolygon underflow with poly coordinates. #18248

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9abb472
Fixed GH-18241: imagefilledpolygon underflow with poly coordinates.
devnexen Apr 4, 2025
85701cc
doing overflow check ourselves, it s meant for mem allocation anyway ..
devnexen Apr 4, 2025
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37 changes: 26 additions & 11 deletions ext/gd/libgd/gd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2688,18 +2688,20 @@ void gdImageFilledPolygon (gdImagePtr im, gdPointPtr p, int n, int c)
return;
}

if (overflow2(sizeof(int), n)) {
return;
}

if (c == gdAntiAliased) {
fill_color = im->AA_color;
} else {
fill_color = c;
}

if (!im->polyAllocated) {
if (overflow2(sizeof(int), n)) {
return;
}
im->polyInts = (int *) gdMalloc(sizeof(int) * n);
if (!im->polyInts) {
return;
}
im->polyAllocated = n;
}
if (im->polyAllocated < n) {
Expand All @@ -2710,6 +2712,9 @@ void gdImageFilledPolygon (gdImagePtr im, gdPointPtr p, int n, int c)
return;
}
im->polyInts = (int *) gdRealloc(im->polyInts, sizeof(int) * im->polyAllocated);
if (!im->polyInts) {
return;
}
}
miny = p[0].y;
maxy = p[0].y;
Expand All @@ -2736,11 +2741,12 @@ void gdImageFilledPolygon (gdImagePtr im, gdPointPtr p, int n, int c)
}
pmaxy = maxy;
/* 2.0.16: Optimization by Ilia Chipitsine -- don't waste time offscreen */
if (miny < 0) {
miny = 0;
/* 2.0.26: clipping rectangle is even better */
if (miny < im->cy1) {
miny = im->cy1;
}
if (maxy >= gdImageSY(im)) {
maxy = gdImageSY(im) - 1;
if (maxy > im->cy2) {
maxy = im->cy2;
}

/* Fix in 1.3: count a vertex only once */
Expand Down Expand Up @@ -2774,9 +2780,18 @@ void gdImageFilledPolygon (gdImagePtr im, gdPointPtr p, int n, int c)
* that Polygon and FilledPolygon for the same set of points have the
* same footprint.
*/
if (y >= y1 && y < y2) {
im->polyInts[ints++] = (float) ((y - y1) * (x2 - x1)) / (float) (y2 - y1) + 0.5 + x1;
} else if (y == pmaxy && y == y2) {
if ((y >= y1) && (y < y2)) {
if ((y1 > 0 && y < INT_MIN + y1) ||
(y1 < 0 && y > INT_MAX + y1) ||
(x1 > 0 && x2 < INT_MIN + x1) ||
(x1 < 0 && x2 > INT_MAX + x1) ||
(((y - y1) <= 0 || (x2 - x1) <= 0)) ||
((y - y1) > INT_MAX / (x2 - x1))) {
return;
}
im->polyInts[ints++] = (int) ((float) ((y - y1) * (x2 - x1)) /
(float) (y2 - y1) + 0.5 + x1);
} else if ((y == pmaxy) && (y == y2)) {
im->polyInts[ints++] = x2;
}
}
Expand Down
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