[3.13] gh-154258: Fix mmap.resize() crash on NetBSD growing a shared anonymous mapping (GH-154259) (GH-154264)
serhiy-storchaka <[email protected]>
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https://github.com/python/cpython/commit/1ef605cf7e54093ab6870471a8a86e9980fd98ec commit: 1ef605cf7e54093ab6870471a8a86e9980fd98ec branch: 3.13 author: Miss Islington (bot) <[email protected]> committer: serhiy-storchaka <[email protected]> date: 2026-07-20T14:30:40Z summary: [3.13] gh-154258: Fix mmap.resize() crash on NetBSD growing a shared anonymous mapping (GH-154259) (GH-154264) NetBSD mremap() returns a mapping whose grown region is not backed when growing a shared anonymous mapping, so accessing it crashes. Reject it with ValueError, as is already done on Linux. (cherry picked from commit 542b98293108a84fa5d904fb6dcf8bfb5080ec93) Co-authored-by: Serhiy Storchaka <[email protected]> Co-authored-by: Claude Fable 5 <[email protected]> files: A Misc/NEWS.d/next/Library/2026-07-20-18-30-00.gh-issue-154258.mmapresize.rst M Lib/test/test_mmap.py M Modules/mmapmodule.c diff --git a/Lib/test/test_mmap.py b/Lib/test/test_mmap.py index 7f33db5c8efccc..1d91cee994ef10 100644 --- a/Lib/test/test_mmap.py +++ b/Lib/test/test_mmap.py @@ -909,9 +909,10 @@ def test_resize_up_anonymous_mapping(self): with mmap.mmap(-1, start_size) as m: m[:] = data - if sys.platform.startswith(('linux', 'android')): - # Can't expand a shared anonymous mapping on Linux. - # See https://bugzilla.kernel.org/show_bug.cgi?id=8691 + if sys.platform.startswith(('linux', 'android', 'netbsd')): + # Can't expand a shared anonymous mapping on Linux + # (see https://bugzilla.kernel.org/show_bug.cgi?id=8691) + # or NetBSD. with self.assertRaises(ValueError): m.resize(new_size) else: diff --git a/Misc/NEWS.d/next/Library/2026-07-20-18-30-00.gh-issue-154258.mmapresize.rst b/Misc/NEWS.d/next/Library/2026-07-20-18-30-00.gh-issue-154258.mmapresize.rst new file mode 100644 index 00000000000000..4c33336e0bbdca --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-07-20-18-30-00.gh-issue-154258.mmapresize.rst @@ -0,0 +1,3 @@ +Fix a crash in :meth:`mmap.mmap.resize` on NetBSD when growing a shared +anonymous mapping. :meth:`!resize` now raises :exc:`ValueError` in this +case, as it already did on Linux. diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c index 0e1a709835e328..060f60c666964b 100644 --- a/Modules/mmapmodule.c +++ b/Modules/mmapmodule.c @@ -872,10 +872,13 @@ mmap_resize_method(mmap_object *self, #else void *newmap; -#ifdef __linux__ +#if defined(__linux__) || defined(__NetBSD__) + // Linux mremap() refuses to grow a shared anonymous mapping, and + // NetBSD mremap() returns a mapping whose grown region is not backed, + // so accessing it crashes. Reject it here in both cases. if (self->fd == -1 && !(self->flags & MAP_PRIVATE) && new_size > self->size) { PyErr_Format(PyExc_ValueError, - "mmap: can't expand a shared anonymous mapping on Linux"); + "mmap: can't expand a shared anonymous mapping"); return NULL; } #endif _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]