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BUG: non integer overlap might lead to corrupt memory access in as_strided [backport 1.4.x] #3845

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Merged
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Nov 26, 2014
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BUG: non integer overlap might lead to corrupt memory access in as_strided [backport 1.4.x] #3845

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9 changes: 9 additions & 0 deletions lib/matplotlib/mlab.py
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Original file line number Diff line number Diff line change
Expand Up @@ -590,6 +590,11 @@ def stride_windows(x, n, noverlap=None, axis=0):
if n > x.size:
raise ValueError('n cannot be greater than the length of x')

# np.lib.stride_tricks.as_strided easily leads to memory corruption for
# non integer shape and strides, i.e. noverlap or n. See #3845.
noverlap = int(noverlap)
n = int(n)

step = n - noverlap
if axis == 0:
shape = (n, (x.shape[-1]-noverlap)//step)
Expand Down Expand Up @@ -642,6 +647,10 @@ def stride_repeat(x, n, axis=0):
if n < 1:
raise ValueError('n cannot be less than 1')

# np.lib.stride_tricks.as_strided easily leads to memory corruption for
# non integer shape and strides, i.e. n. See #3845.
n = int(n)

if axis == 0:
shape = (n, x.size)
strides = (0, x.strides[0])
Expand Down
18 changes: 18 additions & 0 deletions lib/matplotlib/tests/test_mlab.py
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Expand Up @@ -283,6 +283,24 @@ def test_stride_windows_n32_noverlap0_axis1_unflatten(self):
assert_equal(y.shape, x1.shape)
assert_array_equal(y, x1)

def test_stride_ensure_integer_type(self):
N = 100
x = np.empty(N + 20, dtype='>f4')
x.fill(np.NaN)
y = x[10:-10]
y.fill(0.3)
# previous to #3845 lead to corrupt access
y_strided = mlab.stride_windows(y, n=33, noverlap=0.6)
assert_array_equal(y_strided, 0.3)
# previous to #3845 lead to corrupt access
y_strided = mlab.stride_windows(y, n=33.3, noverlap=0)
assert_array_equal(y_strided, 0.3)
# even previous to #3845 could not find any problematic
# configuration however, let's be sure it's not accidentally
# introduced
y_strided = mlab.stride_repeat(y, n=33.815)
assert_array_equal(y_strided, 0.3)


class csv_testcase(CleanupTestCase):
def setUp(self):
Expand Down