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Add ASan redzones between zone allocations (C) - #1195
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The zone carves many objects out of one malloc()ed chunk, so an overflow from one zone-allocated object into its neighbour stays inside a live heap block and AddressSanitizer cannot see it. When building with ASan, follow every allocation with a poisoned redzone, keep chunks of the configured size poisoned until handed out, and re-poison on msgpack_zone_clear(). Oversized chunks are not pre-poisoned, so a huge allocation costs no shadow updates proportional to its size. Builds without ASan are unchanged. Define MSGPACK_ZONE_NO_ASAN_ANNOTATIONS to opt out. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## c_master #1195 +/- ##
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+ Coverage 57.47% 58.19% +0.72%
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Files 10 10
Lines 1124 1141 +17
Branches 129 139 +10
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+ Hits 646 664 +18
+ Misses 478 477 -1 🚀 New features to boost your workflow:
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msgpack_zonecarves the unpacker's array/map element buffers out of onemalloc()ed chunk. An overflow from one into its neighbour stays inside a live heap block, so AddressSanitizer stays silent. This is detector hardening, not a bug fix, and the technique isn't new (manual allocator poisoning; see Trail of Bits, https://blog.trailofbits.com/2024/09/10/sanitize-your-c-containers-asan-annotations-step-by-step/).-DMSGPACK_ZONE_NO_ASAN_ANNOTATIONSopts out. Becausemsgpack_zone_malloc*are inline inzone.h, build the library and its users the same way.msgpack_zone_malloc/_no_alignplace each object on an 8-byte granule with a poisoned redzone after it. Chunks of the configured size are poisoned when created and re-poisoned bymsgpack_zone_clear(). Oversized chunks aren't pre-poisoned.msgpack_zone_malloc_expand()keeps its contract: the bytes it hands out are usable.Validation: unpacking
[[1],[2]]and writing one element past the first inner array is silent on stock and reportsuse-after-poisonwith the patch. All 6 tests pass under ASan with annotations on and off. The OSS-Fuzz public corpus plus about 16M executions of an unpack/pack harness show no reports. ASan overhead is about +4% time with unchanged peak memory on a corpus benchmark.Companion PR for the C++ zone on
cpp_master: #1194.🤖 Generated with Claude Code