[PATCH] xfrm: use list_for_each_entry_safe in xfrm_policy_flush

[Li RongQing]

The iterated pol maybe be freed since it is not protected
by RCU or spinlock when put it, lead to UAF, so use _safe
function to iterate over it against removal

Signed-off-by: Li RongQing <lirongq...@baidu.com>
---
 net/xfrm/xfrm_policy.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 3235562f6588..87d770dab1f5 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1772,7 +1772,7 @@ xfrm_policy_flush_secctx_check(struct net *net, u8 type, 
bool task_valid)
 int xfrm_policy_flush(struct net *net, u8 type, bool task_valid)
 {
        int dir, err = 0, cnt = 0;
-       struct xfrm_policy *pol;
+       struct xfrm_policy *pol, *tmp;
 
        spin_lock_bh(&net->xfrm.xfrm_policy_lock);
 
@@ -1781,7 +1781,7 @@ int xfrm_policy_flush(struct net *net, u8 type, bool 
task_valid)
                goto out;
 
 again:
-       list_for_each_entry(pol, &net->xfrm.policy_all, walk.all) {
+       list_for_each_entry_safe(pol, tmp, &net->xfrm.policy_all, walk.all) {
                dir = xfrm_policy_id2dir(pol->index);
                if (pol->walk.dead ||
                    dir >= XFRM_POLICY_MAX ||
-- 
2.16.2