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Fix GH-20622: imagestring/imagestringup overflow/underflow. #20623

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Fix GH-20622: imagestring/imagestringup overflow/underflow. #20623

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b239154
Fix GH-20622: imagestring/imagestringup overflow/underflow.
devnexen Nov 29, 2025
c34cdbe
feedback + test
devnexen Nov 30, 2025
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9 changes: 5 additions & 4 deletions ext/gd/gd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2763,7 +2763,8 @@ static void php_imagechar(INTERNAL_FUNCTION_PARAMETERS, int mode)
char *C;
size_t C_len;
gdImagePtr im;
int ch = 0, col, x, y, i, l = 0;
int ch = 0, col, i, l = 0;
unsigned int x, y;
unsigned char *str = NULL;
zend_object *font_obj = NULL;
zend_long font_int = 0;
Expand Down Expand Up @@ -2795,21 +2796,21 @@ static void php_imagechar(INTERNAL_FUNCTION_PARAMETERS, int mode)

switch (mode) {
case 0:
gdImageChar(im, font, x, y, ch, col);
gdImageChar(im, font, (int)x, (int)y, ch, col);
break;
case 1:
php_gdimagecharup(im, font, x, y, ch, col);
break;
case 2:
for (i = 0; (i < l); i++) {
gdImageChar(im, font, x, y, (int) ((unsigned char) str[i]), col);
gdImageChar(im, font, (int)x, (int)y, (int) ((unsigned char) str[i]), col);
x += font->w;
}
break;
case 3: {
for (i = 0; (i < l); i++) {
/* php_gdimagecharup(im, font, x, y, (int) str[i], col); */
gdImageCharUp(im, font, x, y, (int) str[i], col);
gdImageCharUp(im, font, (int)x, (int)y, (int) str[i], col);
y -= font->w;
}
break;
Expand Down
13 changes: 13 additions & 0 deletions ext/gd/tests/gh20622.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
--TEST--
GH-20622: (imagestring/imagestringup overflow/underflow)
--EXTENSIONS--
gd
--FILE--
<?php
$im = imagecreate(64, 64);
imagestringup($im, 5, 0, -2147483648, 'STRINGUP', 0);
imagestring($im, 5, -2147483648, 0, 'STRING', 0);
echo "OK";
?>
--EXPECT--
OK
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