re: [PATCH ipsec-next 1/2] xfrm: introduce forwarding of ICMP Error messages

Dan Carpenter
2024-01-30T10:36:35Z

Hello Antony Antony,

The patch 63b21caba17e: "xfrm: introduce forwarding of ICMP Error
messages" from Jan 19, 2024 (linux-next), leads to the following
Smatch static checker warning:

net/xfrm/xfrm_policy.c:3708 __xfrm_policy_check()
error: testing array offset 'dir' after use.

net/xfrm/xfrm_policy.c
3689
3690 pol = NULL;
3691 sk = sk_to_full_sk(sk);
3692 if (sk && sk->sk_policy[dir]) {
^^^^^^^^^^^^^^^^
If dir is XFRM_POLICY_FWD (2) then it is one element beyond the end of
the ->sk_policy[] array.

3693 pol = xfrm_sk_policy_lookup(sk, dir, &fl, family, if_id);
3694 if (IS_ERR(pol)) {
3695 XFRM_INC_STATS(net, LINUX_MIB_XFRMINPOLERROR);
3696 return 0;
3697 }
3698 }
3699
3700 if (!pol)
3701 pol = xfrm_policy_lookup(net, &fl, family, dir, if_id);
3702
3703 if (IS_ERR(pol)) {
3704 XFRM_INC_STATS(net, LINUX_MIB_XFRMINPOLERROR);
3705 return 0;
3706 }
3707
3708 if (!pol && dir == XFRM_POLICY_FWD)
^^^^^^^^^^^^^^^^^^^^^^
This assumes that dir can be 2.

3709 pol = xfrm_in_fwd_icmp(skb, &fl, family, if_id);
3710
3711 if (!pol) {
3712 if (net->xfrm.policy_default[dir] == XFRM_USERPOLICY_BLOCK) {
3713 XFRM_INC_STATS(net, LINUX_MIB_XFRMINNOPOLS);
3714 return 0;
3715 }
3716
3717 if (sp && secpath_has_nontransport(sp, 0, &xerr_idx)) {
3718 xfrm_secpath_reject(xerr_idx, skb, &fl);
3719 XFRM_INC_STATS(net, LINUX_MIB_XFRMINNOPOLS);
3720 return 0;
3721 }
3722 return 1;

regards,
dan carpenter