xfrm: Sanitize marks before insert

[ Upstream commit 0b91fda3a1f044141e1e615456ff62508c32b202 ]

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 <paul.chaignon@gmail.com>
Signed-off-by: Louis DeLosSantos <louis.delos.devel@gmail.com>
Co-developed-by: Louis DeLosSantos <louis.delos.devel@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index a022f49846879f96c99898a0c54e27ca87775664..e015ff225b27a7ac46c4e667b8e9646937fb3b90 100644 (file)
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1597,6 +1597,9 @@ 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 b5047a94c7d0147ecb4617f4a5afa07bc0c07918..58c53bb1c58381d6b4c48990e06cf346d48a19f6 100644 (file)
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -1275,6 +1275,9 @@ 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);
        hlist_add_head_rcu(&x->bydst, net->xfrm.state_bydst + h);