On Sat, Jul 02, 2022 at 10:56:51PM +0200, Florian Westphal wrote:
> > That would make sense, from further experiments I ran it somehow seems
> > to be related to the number of workers being spawned by stress-ng along
> > with the CPUs/cores involved.
> >
> > For instance, running the test with <=25 workers (--udp-flood 25 etc.)
> > results in the test running fine for at least 15 minutes.
>
> Ok. I will let it run for longer on the machines I have access to.
>
> In mean time, you could test attached patch, its simple s/refcount_/atomic_/
> in nf_conntrack.
>
> If mainline (patch vs. HEAD 69cb6c6556ad89620547318439) crashes for you
> but works with attached patch someone who understands aarch64 memory ordering
> would have to look more closely at refcount_XXX functions to see where they
> might differ from atomic_ ones.
I can confirm that the patch seems to solve the issue.
With it applied on top of the 5.19-rc5 tag the test runs fine for at
least 15 minutes which was not the case before so it looks like it is
that aarch64 memory ordering problem.
>
> If it still crashes, please try below hunk in addition, although I don't see
> how it would make a difference.
>
> This is the one spot where the original conversion replaced atomic_inc()
> with refcount_set(), this is on allocation, refcount is expected to be 0 so
> refcount_inc() triggers a warning hinting at a use-after free.
>
> diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
> --- a/net/netfilter/nf_conntrack_core.c
> +++ b/net/netfilter/nf_conntrack_core.c
> @@ -1776,7 +1776,7 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
> __nf_ct_try_assign_helper(ct, tmpl, GFP_ATOMIC);
>
> /* Now it is going to be associated with an sk_buff, set refcount to 1. */
> - atomic_set(&ct->ct_general.use, 1);
> + atomic_inc(&ct->ct_general.use);
>
> if (exp) {
> if (exp->expectfn)
> From 4234018dff486bdc30f4fe4625c8da1a8e30c2f6 Mon Sep 17 00:00:00 2001
> From: Florian Westphal <fw@xxxxxxxxx>
> Date: Sat, 2 Jul 2022 22:42:57 +0200
> Subject: [PATCH 1/1] netfilter: conntrack: revert to atomic_t api
>
> Just for testing.
> ---
> include/linux/netfilter/nf_conntrack_common.h | 6 ++---
> include/net/netfilter/nf_conntrack.h | 2 +-
> net/netfilter/nf_conntrack_core.c | 24 +++++++++----------
> net/netfilter/nf_conntrack_expect.c | 2 +-
> net/netfilter/nf_conntrack_netlink.c | 6 ++---
> net/netfilter/nf_conntrack_standalone.c | 4 ++--
> net/netfilter/nf_flow_table_core.c | 2 +-
> net/netfilter/nft_ct.c | 4 ++--
> net/netfilter/xt_CT.c | 2 +-
> 9 files changed, 26 insertions(+), 26 deletions(-)
>
> diff --git a/include/linux/netfilter/nf_conntrack_common.h b/include/linux/netfilter/nf_conntrack_common.h
> index 2770db2fa080..48a78944182d 100644
> --- a/include/linux/netfilter/nf_conntrack_common.h
> +++ b/include/linux/netfilter/nf_conntrack_common.h
> @@ -25,7 +25,7 @@ struct ip_conntrack_stat {
> #define NFCT_PTRMASK ~(NFCT_INFOMASK)
>
> struct nf_conntrack {
> - refcount_t use;
> + atomic_t use;
> };
>
> void nf_conntrack_destroy(struct nf_conntrack *nfct);
> @@ -33,13 +33,13 @@ void nf_conntrack_destroy(struct nf_conntrack *nfct);
> /* like nf_ct_put, but without module dependency on nf_conntrack */
> static inline void nf_conntrack_put(struct nf_conntrack *nfct)
> {
> - if (nfct && refcount_dec_and_test(&nfct->use))
> + if (nfct && atomic_dec_and_test(&nfct->use))
> nf_conntrack_destroy(nfct);
> }
> static inline void nf_conntrack_get(struct nf_conntrack *nfct)
> {
> if (nfct)
> - refcount_inc(&nfct->use);
> + atomic_inc(&nfct->use);
> }
>
> #endif /* _NF_CONNTRACK_COMMON_H */
> diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
> index a32be8aa7ed2..9fab0c8835bb 100644
> --- a/include/net/netfilter/nf_conntrack.h
> +++ b/include/net/netfilter/nf_conntrack.h
> @@ -180,7 +180,7 @@ void nf_ct_destroy(struct nf_conntrack *nfct);
> /* decrement reference count on a conntrack */
> static inline void nf_ct_put(struct nf_conn *ct)
> {
> - if (ct && refcount_dec_and_test(&ct->ct_general.use))
> + if (ct && atomic_dec_and_test(&ct->ct_general.use))
> nf_ct_destroy(&ct->ct_general);
> }
>
> diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
> index 082a2fd8d85b..4469e49d78a7 100644
> --- a/net/netfilter/nf_conntrack_core.c
> +++ b/net/netfilter/nf_conntrack_core.c
> @@ -554,7 +554,7 @@ struct nf_conn *nf_ct_tmpl_alloc(struct net *net,
> tmpl->status = IPS_TEMPLATE;
> write_pnet(&tmpl->ct_net, net);
> nf_ct_zone_add(tmpl, zone);
> - refcount_set(&tmpl->ct_general.use, 1);
> + atomic_set(&tmpl->ct_general.use, 1);
>
> return tmpl;
> }
> @@ -586,7 +586,7 @@ void nf_ct_destroy(struct nf_conntrack *nfct)
> struct nf_conn *ct = (struct nf_conn *)nfct;
>
> pr_debug("%s(%p)\n", __func__, ct);
> - WARN_ON(refcount_read(&nfct->use) != 0);
> + WARN_ON(atomic_read(&nfct->use) != 0);
>
> if (unlikely(nf_ct_is_template(ct))) {
> nf_ct_tmpl_free(ct);
> @@ -726,7 +726,7 @@ nf_ct_match(const struct nf_conn *ct1, const struct nf_conn *ct2)
> /* caller must hold rcu readlock and none of the nf_conntrack_locks */
> static void nf_ct_gc_expired(struct nf_conn *ct)
> {
> - if (!refcount_inc_not_zero(&ct->ct_general.use))
> + if (!atomic_inc_not_zero(&ct->ct_general.use))
> return;
>
> if (nf_ct_should_gc(ct))
> @@ -794,7 +794,7 @@ __nf_conntrack_find_get(struct net *net, const struct nf_conntrack_zone *zone,
> * in, try to obtain a reference and re-check tuple
> */
> ct = nf_ct_tuplehash_to_ctrack(h);
> - if (likely(refcount_inc_not_zero(&ct->ct_general.use))) {
> + if (likely(atomic_inc_not_zero(&ct->ct_general.use))) {
> if (likely(nf_ct_key_equal(h, tuple, zone, net)))
> goto found;
>
> @@ -923,7 +923,7 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct)
>
> smp_wmb();
> /* The caller holds a reference to this object */
> - refcount_set(&ct->ct_general.use, 2);
> + atomic_set(&ct->ct_general.use, 2);
> __nf_conntrack_hash_insert(ct, hash, reply_hash);
> nf_conntrack_double_unlock(hash, reply_hash);
> NF_CT_STAT_INC(net, insert);
> @@ -981,7 +981,7 @@ static void __nf_conntrack_insert_prepare(struct nf_conn *ct)
> {
> struct nf_conn_tstamp *tstamp;
>
> - refcount_inc(&ct->ct_general.use);
> + atomic_inc(&ct->ct_general.use);
>
> /* set conntrack timestamp, if enabled. */
> tstamp = nf_conn_tstamp_find(ct);
> @@ -1384,7 +1384,7 @@ static unsigned int early_drop_list(struct net *net,
> nf_ct_is_dying(tmp))
> continue;
>
> - if (!refcount_inc_not_zero(&tmp->ct_general.use))
> + if (!atomic_inc_not_zero(&tmp->ct_general.use))
> continue;
>
> /* kill only if still in same netns -- might have moved due to
> @@ -1533,7 +1533,7 @@ static void gc_worker(struct work_struct *work)
> continue;
>
> /* need to take reference to avoid possible races */
> - if (!refcount_inc_not_zero(&tmp->ct_general.use))
> + if (!atomic_inc_not_zero(&tmp->ct_general.use))
> continue;
>
> if (gc_worker_skip_ct(tmp)) {
> @@ -1640,7 +1640,7 @@ __nf_conntrack_alloc(struct net *net,
> /* Because we use RCU lookups, we set ct_general.use to zero before
> * this is inserted in any list.
> */
> - refcount_set(&ct->ct_general.use, 0);
> + atomic_set(&ct->ct_general.use, 0);
> return ct;
> out:
> atomic_dec(&cnet->count);
> @@ -1665,7 +1665,7 @@ void nf_conntrack_free(struct nf_conn *ct)
> /* A freed object has refcnt == 0, that's
> * the golden rule for SLAB_TYPESAFE_BY_RCU
> */
> - WARN_ON(refcount_read(&ct->ct_general.use) != 0);
> + WARN_ON(atomic_read(&ct->ct_general.use) != 0);
>
> if (ct->status & IPS_SRC_NAT_DONE) {
> const struct nf_nat_hook *nat_hook;
> @@ -1776,7 +1776,7 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
> __nf_ct_try_assign_helper(ct, tmpl, GFP_ATOMIC);
>
> /* Now it is going to be associated with an sk_buff, set refcount to 1. */
> - refcount_set(&ct->ct_general.use, 1);
> + atomic_set(&ct->ct_general.use, 1);
>
> if (exp) {
> if (exp->expectfn)
> @@ -2390,7 +2390,7 @@ get_next_corpse(int (*iter)(struct nf_conn *i, void *data),
>
> return NULL;
> found:
> - refcount_inc(&ct->ct_general.use);
> + atomic_inc(&ct->ct_general.use);
> spin_unlock(lockp);
> local_bh_enable();
> return ct;
> diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
> index 96948e98ec53..84cb05eae410 100644
> --- a/net/netfilter/nf_conntrack_expect.c
> +++ b/net/netfilter/nf_conntrack_expect.c
> @@ -208,7 +208,7 @@ nf_ct_find_expectation(struct net *net,
> * can be sure the ct cannot disappear underneath.
> */
> if (unlikely(nf_ct_is_dying(exp->master) ||
> - !refcount_inc_not_zero(&exp->master->ct_general.use)))
> + !atomic_inc_not_zero(&exp->master->ct_general.use)))
> return NULL;
>
> if (exp->flags & NF_CT_EXPECT_PERMANENT) {
> diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
> index 722af5e309ba..d5de0e580e6c 100644
> --- a/net/netfilter/nf_conntrack_netlink.c
> +++ b/net/netfilter/nf_conntrack_netlink.c
> @@ -514,7 +514,7 @@ static int ctnetlink_dump_id(struct sk_buff *skb, const struct nf_conn *ct)
>
> static int ctnetlink_dump_use(struct sk_buff *skb, const struct nf_conn *ct)
> {
> - if (nla_put_be32(skb, CTA_USE, htonl(refcount_read(&ct->ct_general.use))))
> + if (nla_put_be32(skb, CTA_USE, htonl(atomic_read(&ct->ct_general.use))))
> goto nla_put_failure;
> return 0;
>
> @@ -1204,7 +1204,7 @@ ctnetlink_dump_table(struct sk_buff *skb, struct netlink_callback *cb)
> ct = nf_ct_tuplehash_to_ctrack(h);
> if (nf_ct_is_expired(ct)) {
> if (i < ARRAY_SIZE(nf_ct_evict) &&
> - refcount_inc_not_zero(&ct->ct_general.use))
> + atomic_inc_not_zero(&ct->ct_general.use))
> nf_ct_evict[i++] = ct;
> continue;
> }
> @@ -1747,7 +1747,7 @@ static int ctnetlink_dump_one_entry(struct sk_buff *skb,
> NFNL_MSG_TYPE(cb->nlh->nlmsg_type),
> ct, dying, 0);
> if (res < 0) {
> - if (!refcount_inc_not_zero(&ct->ct_general.use))
> + if (!atomic_inc_not_zero(&ct->ct_general.use))
> return 0;
>
> ctx->last = ct;
> diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
> index 6ad7bbc90d38..badd3f219533 100644
> --- a/net/netfilter/nf_conntrack_standalone.c
> +++ b/net/netfilter/nf_conntrack_standalone.c
> @@ -303,7 +303,7 @@ static int ct_seq_show(struct seq_file *s, void *v)
> int ret = 0;
>
> WARN_ON(!ct);
> - if (unlikely(!refcount_inc_not_zero(&ct->ct_general.use)))
> + if (unlikely(!atomic_inc_not_zero(&ct->ct_general.use)))
> return 0;
>
> if (nf_ct_should_gc(ct)) {
> @@ -370,7 +370,7 @@ static int ct_seq_show(struct seq_file *s, void *v)
> ct_show_zone(s, ct, NF_CT_DEFAULT_ZONE_DIR);
> ct_show_delta_time(s, ct);
>
> - seq_printf(s, "use=%u\n", refcount_read(&ct->ct_general.use));
> + seq_printf(s, "use=%u\n", atomic_read(&ct->ct_general.use));
>
> if (seq_has_overflowed(s))
> goto release;
> diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
> index f2def06d1070..8b3f91a60ba2 100644
> --- a/net/netfilter/nf_flow_table_core.c
> +++ b/net/netfilter/nf_flow_table_core.c
> @@ -54,7 +54,7 @@ struct flow_offload *flow_offload_alloc(struct nf_conn *ct)
> struct flow_offload *flow;
>
> if (unlikely(nf_ct_is_dying(ct) ||
> - !refcount_inc_not_zero(&ct->ct_general.use)))
> + !atomic_inc_not_zero(&ct->ct_general.use)))
> return NULL;
>
> flow = kzalloc(sizeof(*flow), GFP_ATOMIC);
> diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c
> index d8e1614918a1..1b6ead61a8f1 100644
> --- a/net/netfilter/nft_ct.c
> +++ b/net/netfilter/nft_ct.c
> @@ -260,8 +260,8 @@ static void nft_ct_set_zone_eval(const struct nft_expr *expr,
>
> ct = this_cpu_read(nft_ct_pcpu_template);
>
> - if (likely(refcount_read(&ct->ct_general.use) == 1)) {
> - refcount_inc(&ct->ct_general.use);
> + if (likely(atomic_read(&ct->ct_general.use) == 1)) {
> + atomic_inc(&ct->ct_general.use);
> nf_ct_zone_add(ct, &zone);
> } else {
> /* previous skb got queued to userspace, allocate temporary
> diff --git a/net/netfilter/xt_CT.c b/net/netfilter/xt_CT.c
> index 267757b0392a..cf2f8c1d4fb5 100644
> --- a/net/netfilter/xt_CT.c
> +++ b/net/netfilter/xt_CT.c
> @@ -24,7 +24,7 @@ static inline int xt_ct_target(struct sk_buff *skb, struct nf_conn *ct)
> return XT_CONTINUE;
>
> if (ct) {
> - refcount_inc(&ct->ct_general.use);
> + atomic_inc(&ct->ct_general.use);
> nf_ct_set(skb, ct, IP_CT_NEW);
> } else {
> nf_ct_set(skb, ct, IP_CT_UNTRACKED);
> --
> 2.35.1
>
