Kajetan Puchalski <kajetan.puchalski@xxxxxxx> wrote:
> On Fri, Jul 01, 2022 at 10:01:10PM +0200, Florian Westphal wrote:
> > Kajetan Puchalski <kajetan.puchalski@xxxxxxx> wrote:
> > > While running the udp-flood test from stress-ng on Ampere Altra (Mt.
> > > Jade platform) I encountered a kernel panic caused by NULL pointer
> > > dereference within nf_conntrack.
> > >
> > > The issue is present in the latest mainline (5.19-rc4), latest stable
> > > (5.18.8), as well as multiple older stable versions. The last working
> > > stable version I found was 5.15.40.
> >
> > Do I need a special setup for conntrack?
>
> I don't think there was any special setup involved, the config I started
> from was a generic distribution config and I didn't change any
> networking-specific options. In case that's helpful here's the .config I
> used.
>
> https://pastebin.com/Bb2wttdx
>
> >
> > No crashes after more than one hour of stress-ng on
> > 1. 4 core amd64 Fedora 5.17 kernel
> > 2. 16 core amd64, linux stable 5.17.15
> > 3. 12 core intel, Fedora 5.18 kernel
> > 4. 3 core aarch64 vm, 5.18.7-200.fc36.aarch64
> >
>
> 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.
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
