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Fix Use-After-Free in NumPy/df #478

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Merged
merged 1 commit into from
Sep 18, 2025
Merged

Fix Use-After-Free in NumPy/df #478

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12 changes: 8 additions & 4 deletions src/amrex/extensions/ArrayOfStructs.py
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Original file line number Diff line number Diff line change
Expand Up @@ -32,10 +32,14 @@ def aos_to_numpy(self, copy=False):
if copy:
# This supports a device-to-host copy.
#
# todo: validate of the to_host() returned object
# lifetime is always managed correctly by
# Python's GC - otherwise copy twice via copy=True
return np.array(self.to_host(), copy=False)
# The to_host() returned object is a temporary, and
# np.array using the __array_interface__ protocol does
# not keep it alive automatically unless it is stored
# in an actual variable (tmp).
tmp = self.to_host()
ret = np.array(tmp, copy=False)
assert ret.base is tmp
return ret
else:
return np.array(self, copy=False)

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12 changes: 8 additions & 4 deletions src/amrex/extensions/PODVector.py
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Expand Up @@ -29,10 +29,14 @@ def podvector_to_numpy(self, copy=False):
if copy:
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@ax3l ax3l Sep 17, 2025 •
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We can generally make this a bit more explicit by checking if self is on GPU and otherwise just copying from it directly, with another if/else branch. But the logic here should have the same effect and amount of copies involved...

The only difference is that here we will always end up with pinned memory, while we might be sometimes interested using regular host memory. But seems niche.

# This supports a device-to-host copy.
#
# todo: validate of the to_host() returned object
# lifetime is always managed correctly by
# Python's GC - otherwise copy twice via copy=True
return np.array(self.to_host(), copy=False)
# The to_host() returned object is a temporary, and
# np.array using the __array_interface__ protocol does
# not keep it alive automatically unless it is stored
# in an actual variable (tmp).
tmp = self.to_host()
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@ax3l ax3l Sep 18, 2025 •
edited
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Hm, looks like there is more / this is not a sufficient fix (at least for some SP tests on conda-forge):
conda-forge/impactx-feedstock#56 (comment)

It already has an issue here, so the problem could be in the implementation of to_host()...
https://github.com/AMReX-Codes/pyamrex/blob/25.09/src/Base/PODVector.cpp#L79-L87

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@ax3l ax3l Sep 23, 2025

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Very hard to reproduce locally... also cannot spot anything in valgrind yet.

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@ax3l ax3l Sep 23, 2025

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seems to be fixed by BLAST-ImpactX/impactx#1156 o.0

ret = np.array(tmp, copy=False)
assert ret.base is tmp
return ret
else:
return np.array(self, copy=False)
else:
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