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Date: Thu, 20 Oct 2022 23:20:18 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next] net: add a refcount tracker for kernel sockets
Commit ffa84b5ffb37 ("net: add netns refcount tracker to struct sock")
added a tracker to sockets, but did not track kernel sockets.
We still have syzbot reports hinting about netns being destroyed
while some kernel TCP sockets had not been dismantled.
This patch tracks kernel sockets, and adds a ref_tracker_dir_print()
call to net_free() right before the netns is freed.
Normally, each layer is responsible for properly releasing its
kernel sockets before last call to net_free().
This debugging facility is enabled with CONFIG_NET_NS_REFCNT_TRACKER=y
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/net/net_namespace.h | 30 ++++++++++++++++++++++--------
net/core/net_namespace.c | 5 +++++
net/core/sock.c | 14 ++++++++++++++
net/netlink/af_netlink.c | 11 +++++++++++
net/rds/tcp.c | 3 +++
5 files changed, 55 insertions(+), 8 deletions(-)
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 8c3587d5c308f048a3fbd681125f40ec86a00eb4..78beaa765c733665c035e99c5923334740a18770 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -92,7 +92,9 @@ struct net {
struct ns_common ns;
struct ref_tracker_dir refcnt_tracker;
-
+ struct ref_tracker_dir notrefcnt_tracker; /* tracker for objects not
+ * refcounted against netns
+ */
struct list_head dev_base_head;
struct proc_dir_entry *proc_net;
struct proc_dir_entry *proc_net_stat;
@@ -320,19 +322,31 @@ static inline int check_net(const struct net *net)
#endif
-static inline void netns_tracker_alloc(struct net *net,
- netns_tracker *tracker, gfp_t gfp)
+static inline void __netns_tracker_alloc(struct net *net,
+ netns_tracker *tracker,
+ bool refcounted,
+ gfp_t gfp)
{
#ifdef CONFIG_NET_NS_REFCNT_TRACKER
- ref_tracker_alloc(&net->refcnt_tracker, tracker, gfp);
+ ref_tracker_alloc(refcounted ? &net->refcnt_tracker :
+ &net->notrefcnt_tracker,
+ tracker, gfp);
#endif
}
-static inline void netns_tracker_free(struct net *net,
- netns_tracker *tracker)
+static inline void netns_tracker_alloc(struct net *net, netns_tracker *tracker,
+ gfp_t gfp)
+{
+ __netns_tracker_alloc(net, tracker, true, gfp);
+}
+
+static inline void __netns_tracker_free(struct net *net,
+ netns_tracker *tracker,
+ bool refcounted)
{
#ifdef CONFIG_NET_NS_REFCNT_TRACKER
- ref_tracker_free(&net->refcnt_tracker, tracker);
+ ref_tracker_free(refcounted ? &net->refcnt_tracker :
+ &net->notrefcnt_tracker, tracker);
#endif
}
@@ -346,7 +360,7 @@ static inline struct net *get_net_track(struct net *net,
static inline void put_net_track(struct net *net, netns_tracker *tracker)
{
- netns_tracker_free(net, tracker);
+ __netns_tracker_free(net, tracker, true);
put_net(net);
}
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 0ec2f5906a27c7f930e832835682d69a32e3c8e1..12c68edf768283e4f3ba74f0818618766c8f8d67 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -309,6 +309,7 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
refcount_set(&net->ns.count, 1);
ref_tracker_dir_init(&net->refcnt_tracker, 128);
+ ref_tracker_dir_init(&net->notrefcnt_tracker, 128);
refcount_set(&net->passive, 1);
get_random_bytes(&net->hash_mix, sizeof(u32));
@@ -429,6 +430,10 @@ static void net_free(struct net *net)
{
if (refcount_dec_and_test(&net->passive)) {
kfree(rcu_access_pointer(net->gen));
+
+ /* There should not be any trackers left there. */
+ ref_tracker_dir_exit(&net->notrefcnt_tracker);
+
kmem_cache_free(net_cachep, net);
}
}
diff --git a/net/core/sock.c b/net/core/sock.c
index a3ba0358c77c0e44db1cfbaeb420f8b80ad7cf98..aa608dc0930b51ced01af4ff59ae5430da84dd9a 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2094,6 +2094,9 @@ struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
if (likely(sk->sk_net_refcnt)) {
get_net_track(net, &sk->ns_tracker, priority);
sock_inuse_add(net, 1);
+ } else {
+ __netns_tracker_alloc(net, &sk->ns_tracker,
+ false, priority);
}
sock_net_set(sk, net);
@@ -2149,6 +2152,9 @@ static void __sk_destruct(struct rcu_head *head)
if (likely(sk->sk_net_refcnt))
put_net_track(sock_net(sk), &sk->ns_tracker);
+ else
+ __netns_tracker_free(sock_net(sk), &sk->ns_tracker, false);
+
sk_prot_free(sk->sk_prot_creator, sk);
}
@@ -2237,6 +2243,14 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
if (likely(newsk->sk_net_refcnt)) {
get_net_track(sock_net(newsk), &newsk->ns_tracker, priority);
sock_inuse_add(sock_net(newsk), 1);
+ } else {
+ /* Kernel sockets are not elevating the struct net refcount.
+ * Instead, use a tracker to more easily detect if a layer
+ * is not properly dismantling its kernel sockets at netns
+ * destroy time.
+ */
+ __netns_tracker_alloc(sock_net(newsk), &newsk->ns_tracker,
+ false, priority);
}
sk_node_init(&newsk->sk_node);
sock_lock_init(newsk);
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index a662e8a5ff84a658e51d165e3a6da1e182ad6b38..f0c94d394ab194193a6c67b15ae6e700a6ffdf2d 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -812,6 +812,17 @@ static int netlink_release(struct socket *sock)
}
sock_prot_inuse_add(sock_net(sk), &netlink_proto, -1);
+
+ /* Because struct net might disappear soon, do not keep a pointer. */
+ if (!sk->sk_net_refcnt && sock_net(sk) != &init_net) {
+ __netns_tracker_free(sock_net(sk), &sk->ns_tracker, false);
+ /* Because of deferred_put_nlk_sk and use of work queue,
+ * it is possible netns will be freed before this socket.
+ */
+ sock_net_set(sk, &init_net);
+ __netns_tracker_alloc(&init_net, &sk->ns_tracker,
+ false, GFP_KERNEL);
+ }
call_rcu(&nlk->rcu, deferred_put_nlk_sk);
return 0;
}
diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index 4444fd82b66df7d54065893dc3d1aa02c3e2ef7c..c5b86066ff663f4250f2646b1eee80f9c7f30821 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -503,6 +503,9 @@ bool rds_tcp_tune(struct socket *sock)
release_sock(sk);
return false;
}
+ /* Update ns_tracker to current stack trace and refcounted tracker */
+ __netns_tracker_free(net, &sk->ns_tracker, false);
+
sk->sk_net_refcnt = 1;
netns_tracker_alloc(net, &sk->ns_tracker, GFP_KERNEL);
sock_inuse_add(net, 1);
--
2.38.0.135.g90850a2211-goog
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