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FIX: guard against integer overflow in FT2Image dimensions #31860

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FIX: guard against integer overflow in FT2Image dimensions #31860

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12 changes: 12 additions & 0 deletions lib/matplotlib/tests/test_ft2font.py
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,18 @@ def test_ft2image_draw_rect_filled():
assert np.sum(a) == 255 * filled


def test_ft2image_dimension_overflow():
import ctypes
# Pick width == height such that width * height overflows the C `unsigned
# long` used to size the buffer (2**32 on LP64, 2**16 on a 32-bit long).
# Without the overflow guard, calloc would under-allocate and
# draw_rect_filled would write out of bounds.
n = 1 << (ctypes.sizeof(ctypes.c_ulong) * 8 // 2)
with pytest.warns(mpl.MatplotlibDeprecationWarning):
with pytest.raises((OverflowError, MemoryError)):
ft2font.FT2Image(n, n)


def test_ft2font_dejavu_attrs():
file = fm.findfont('DejaVu Sans')
font = ft2font.FT2Font(file)
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14 changes: 13 additions & 1 deletion src/ft2font.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,9 @@
#include <algorithm>
#include <cstdio>
#include <iterator>
#include <limits>
#include <map>
#include <new>
#include <set>
#include <stdexcept>
#include <string>
Expand All @@ -19,8 +21,18 @@
FT_Library _ft2Library;

FT2Image::FT2Image(unsigned long width, unsigned long height)
: m_buffer((unsigned char *)calloc(width * height, 1)), m_width(width), m_height(height)
: m_buffer(nullptr), m_width(width), m_height(height)
{
// Guard against width * height overflowing unsigned long, which would make
// calloc allocate a buffer far smaller than m_width * m_height and let
// draw_rect_filled write out of bounds.
if (width != 0 && height > std::numeric_limits<unsigned long>::max() / width) {
throw std::overflow_error("FT2Image dimensions are too large");
}
m_buffer = (unsigned char *)calloc(width * height, 1);
if (m_buffer == nullptr && width != 0 && height != 0) {
throw std::bad_alloc();
}
}

FT2Image::~FT2Image()
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