From 0b91fda3a1f044141e1e615456ff62508c32b202 Mon Sep 17 00:00:00 2001 From: Paul Chaignon Date: Wed, 7 May 2025 13:31:58 +0200 Subject: [PATCH] xfrm: Sanitize marks before insert Prior to this patch, the mark is sanitized (applying the state's mask to the state's value) only on inserts when checking if a conflicting XFRM state or policy exists. We discovered in Cilium that this same sanitization does not occur in the hot-path __xfrm_state_lookup. In the hot-path, the sk_buff's mark is simply compared to the state's value: if ((mark & x->mark.m) != x->mark.v) continue; Therefore, users can define unsanitized marks (ex. 0xf42/0xf00) which will never match any packet. This commit updates __xfrm_state_insert and xfrm_policy_insert to store the sanitized marks, thus removing this footgun. This has the side effect of changing the ip output, as the returned mark will have the mask applied to it when printed. Fixes: 3d6acfa7641f ("xfrm: SA lookups with mark") Signed-off-by: Paul Chaignon Signed-off-by: Louis DeLosSantos Co-developed-by: Louis DeLosSantos Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_policy.c | 3 +++ net/xfrm/xfrm_state.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index 143ac3aa75374..f4bad8c895d66 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -1581,6 +1581,9 @@ int xfrm_policy_insert(int dir, struct xfrm_policy *policy, int excl) struct xfrm_policy *delpol; struct hlist_head *chain; + /* Sanitize mark before store */ + policy->mark.v &= policy->mark.m; + spin_lock_bh(&net->xfrm.xfrm_policy_lock); chain = policy_hash_bysel(net, &policy->selector, policy->family, dir); if (chain) diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index 2f57dabcc70b6..07fe8e5daa32b 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -1718,6 +1718,9 @@ static void __xfrm_state_insert(struct xfrm_state *x) list_add(&x->km.all, &net->xfrm.state_all); + /* Sanitize mark before store */ + x->mark.v &= x->mark.m; + h = xfrm_dst_hash(net, &x->id.daddr, &x->props.saddr, x->props.reqid, x->props.family); XFRM_STATE_INSERT(bydst, &x->bydst, net->xfrm.state_bydst + h, -- 2.47.2