关于c双向链表的插入问题

bool _inser(int index, const char* name)
{
NODE* p = (NODE*)malloc(sizeof(NODE));
memset(p,0,sizeof(NODE));
p->index = index;
strcpy_s(p->name, name);
if (head == NULL)
{
head = p;
return true;
}
if (head->index > index)
{
p->next = head;
head->prev = p;
head = p;
return true;
}
NODE* buffer = head;
for (;buffer!=NULL;buffer=buffer->next)
{
if (buffer->next == NULL)
{
buffer->next = p;
p->prev = buffer;
return true;
}
if (buffer->next->index > p->index)
{
/*p->next = buffer->next;
p->prev = buffer;
buffer->next->prev = p;
p->prev = buffer;*/
p->next = buffer->next;
buffer->next->prev = p;
buffer->next = p;
p->prev = buffer;
return true;
}

}

return false;

}

为什么会发生部分数据的丢失？如1 9 4 8 10