[PATCH nf,v1 4/4] netfilter: nf_conntrack_helper: cap maximum number of expectation at helper registration

[Pablo Neira Ayuso <pablo@netfilter.org>]

On helper registration, the maximum number of expectations cannot go over
NF_CT_EXPECT_MAX_CNT (255), but zero can be specified then
nf_conntrack_expect_max applies. Turn zero into NF_CT_EXPECT_MAX_CNT
otherwise, expectation LRU eviction on insertion is disabled.

Moreover, expand this sanity check all expectation classes.

This max_expecy policy is only tunable since userspace helpers are
available, set Fixes: tag to the commit that adds such infrastructure.

Remove the check for p->max_expected given this field must always
be non-zero after this patch.

Fixes: 12f7a505331e ("netfilter: add user-space connection tracking helper infrastructure")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
v1: resend to let sashiko pick in with this batch.

 net/netfilter/nf_conntrack_expect.c | 3 +--
 net/netfilter/nf_conntrack_helper.c | 9 +++++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
index 113bb1cb1683..38630c5e006f 100644
--- a/net/netfilter/nf_conntrack_expect.c
+++ b/net/netfilter/nf_conntrack_expect.c
@@ -496,8 +496,7 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect,
 					   lockdep_is_held(&nf_conntrack_expect_lock));
 	if (helper) {
 		p = &helper->expect_policy[expect->class];
-		if (p->max_expected &&
-		    master_help->expecting[expect->class] >= p->max_expected)
+		if (master_help->expecting[expect->class] >= p->max_expected)
 			evict_oldest_expect(master_help, expect, p);
 	} else {
 		const struct nf_conntrack_expect_policy default_exp_policy = {
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index 8b94001c2430..a7fffe26b830 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -374,8 +374,13 @@ int __nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 	if (!nf_ct_helper_hash)
 		return -ENOENT;
 
-	if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
-		return -EINVAL;
+	for (i = 0; i < me->expect_class_max; i++) {
+		if (!me->expect_policy[i].max_expected)
+			me->expect_policy[i].max_expected = NF_CT_EXPECT_MAX_CNT;
+
+		if (me->expect_policy[i].max_expected > NF_CT_EXPECT_MAX_CNT)
+			return -EINVAL;
+	}
 
 	mutex_lock(&nf_ct_helper_mutex);
 	for (i = 0; i < nf_ct_helper_hsize; i++) {
-- 
2.47.3