Re: [PATCH 2/6] KVM MMU: fix kvm_mmu_zap_page() and its calling path

Xiao Guangrong
2010-04-12T09:22:28Z

Hi Avi,

Avi Kivity wrote:

> hlist_for_each_entry_safe() is supposed to be be safe against removal of
> the element that is pointed to by the iteration cursor.

If we destroyed the next point, hlist_for_each_entry_safe() is unsafe.

List hlist_for_each_entry_safe()'s code:

|#define hlist_for_each_entry_safe(tpos, pos, n, head, member) \
| for (pos = (head)->first; \
| pos && ({ n = pos->next; 1; }) && \
| ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
| pos = n)

if n is destroyed:
'pos = n, n = pos->next'
then it access n again, it's unsafe/illegal for us.

Xiao