Doublely-free in `remove_self_from_waiters()`

[vicLin8712]

Issue

In kernel/mutex.c, remove_self_from_waiters() calls list_remove() and free() at the same time, which free() has been called in the list_remove() may cause heap corruption or invalid free.

static bool remove_self_from_waiters(list_t *waiters)
{
 ...
    while (curr && curr != waiters->tail) {
        if (curr->data == self) {
            list_remove(waiters, curr);
            free(curr);
            return true;
        }
...
}