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prevent UB in arena reservation

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daanx 2024-06-01 12:29:48 -07:00
parent 87d088b7e0
commit 616db104a9
2 changed files with 15 additions and 1 deletions
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8
include/mimalloc/internal.h
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@ -329,6 +329,14 @@ static inline uintptr_t _mi_divide_up(uintptr_t size, size_t divider) {
return (divider == 0 ? size : ((size + divider - 1) / divider));
}
// clamp an integer
static inline size_t _mi_clamp(size_t sz, size_t min, size_t max) {
if (sz < min) return min;
else if (sz > max) return max;
else return sz;
}
// Is memory zero initialized?
static inline bool mi_mem_is_zero(const void* p, size_t size) {
for (size_t i = 0; i < size; i++) {

8
src/arena.c
View File

@ -358,8 +358,14 @@ static bool mi_arena_reserve(size_t req_size, bool allow_large, mi_arena_id_t re
arena_reserve = arena_reserve/4; // be conservative if virtual reserve is not supported (for WASM for example)
}
arena_reserve = _mi_align_up(arena_reserve, MI_ARENA_BLOCK_SIZE);
arena_reserve = _mi_align_up(arena_reserve, MI_SEGMENT_SIZE);
if (arena_count >= 8 && arena_count <= 128) {
arena_reserve = ((size_t)1<<(arena_count/8)) * arena_reserve; // scale up the arena sizes exponentially
// scale up the arena sizes exponentially every 8 entries (128 entries get to 589TiB)
const size_t multiplier = (size_t)1 << _mi_clamp(arena_count/8, 0, 16 );
size_t reserve = 0;
if (!mi_mul_overflow(multiplier, arena_reserve, &reserve)) {
arena_reserve = reserve;
}
}
if (arena_reserve < req_size) return false; // should be able to at least handle the current allocation size