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protect against double-free in multi-threaded free list

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daan 2019-10-30 14:53:21 -07:00
parent 6cf16b1201
commit 4a4d74927c
1 changed files with 9 additions and 2 deletions
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11
src/page.c
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@ -161,14 +161,21 @@ static void _mi_page_thread_free_collect(mi_page_t* page)
// return if the list is empty
if (head == NULL) return;
// find the tail
// find the tail -- also to get a proper count (without data races)
uintptr_t max_count = page->capacity; // cannot collect more than capacity
uintptr_t count = 1;
mi_block_t* tail = head;
mi_block_t* next;
while ((next = mi_block_next(page,tail)) != NULL) {
while ((next = mi_block_next(page,tail)) != NULL && count <= max_count) {
count++;
tail = next;
}
// if `count > max_count` there was a memory corruption (possibly infinite list due to double multi-threaded free)
if (count > max_count) {
_mi_fatal_error("corrupted thread-free list\n");
return; // the thread-free items cannot be freed
}
// and append the current local free list
mi_block_set_next(page,tail, page->local_free);
page->local_free = head;