Fix GH-18173: ext/hash relies on implementation-defined malloc alignment#21668
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iliaal wants to merge 1 commit intophp:PHP-8.4from
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Fix GH-18173: ext/hash relies on implementation-defined malloc alignment#21668iliaal wants to merge 1 commit intophp:PHP-8.4from
iliaal wants to merge 1 commit intophp:PHP-8.4from
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…gnment XXH3_state_t requires 64-byte alignment for its acc, customSecret, and buffer members. php_hash_alloc_context() used ecalloc() which only guarantees alignof(max_align_t) alignment -- typically 16 bytes on x86_64. When heap layout broke that assumption, xxhash's aligned loads would segfault. Add a context_align field to php_hash_ops. When set, php_hash_alloc_context() over-allocates and manually aligns the returned pointer, storing the offset for php_hash_free_context() to recover the original allocation.
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Summary
XXH3_state_trequires 64-byte alignment for its internal buffers.php_hash_alloc_context()usedecalloc(), which only guaranteesalignof(max_align_t)(16 bytes on x86_64). When the allocator returned a pointer that wasn't 64-byte aligned, xxhash's aligned loads segfaulted.Adds a
context_alignfield tophp_hash_ops. When non-zero,php_hash_alloc_context()over-allocates and manually aligns the pointer, storing the offset byte sophp_hash_free_context()can recover the original allocation. Set to 64 for xxh3 and xxh128.Reproduce with
ZEND_MM_DEBUG=padding=8 TESTS=ext/hash make test.