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Message-ID: <20250220131854.4048077-1-edumazet@google.com>
Date: Thu, 20 Feb 2025 13:18:54 +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, Kuniyuki Iwashima <kuniyu@...zon.com>, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>, syzbot+30a19e01a97420719891@...kaller.appspotmail.com
Subject: [PATCH net] net: better track kernel sockets lifetime
While kernel sockets are dismantled during pernet_operations->exit(),
their freeing can be delayed by any tx packets still held in qdisc
or device queues, due to skb_set_owner_w() prior calls.
This then trigger the following warning from ref_tracker_dir_exit() [1]
To fix this, make sure that kernel sockets own a reference on net->passive.
Add sk_net_refcnt_upgrade() helper, used whenever a kernel socket
is converted to a refcounted one.
[1]
[ 136.263918][ T35] ref_tracker: net notrefcnt@...f8880638f01e0 has 1/2 users at
[ 136.263918][ T35] sk_alloc+0x2b3/0x370
[ 136.263918][ T35] inet6_create+0x6ce/0x10f0
[ 136.263918][ T35] __sock_create+0x4c0/0xa30
[ 136.263918][ T35] inet_ctl_sock_create+0xc2/0x250
[ 136.263918][ T35] igmp6_net_init+0x39/0x390
[ 136.263918][ T35] ops_init+0x31e/0x590
[ 136.263918][ T35] setup_net+0x287/0x9e0
[ 136.263918][ T35] copy_net_ns+0x33f/0x570
[ 136.263918][ T35] create_new_namespaces+0x425/0x7b0
[ 136.263918][ T35] unshare_nsproxy_namespaces+0x124/0x180
[ 136.263918][ T35] ksys_unshare+0x57d/0xa70
[ 136.263918][ T35] __x64_sys_unshare+0x38/0x40
[ 136.263918][ T35] do_syscall_64+0xf3/0x230
[ 136.263918][ T35] entry_SYSCALL_64_after_hwframe+0x77/0x7f
[ 136.263918][ T35]
[ 136.343488][ T35] ref_tracker: net notrefcnt@...f8880638f01e0 has 1/2 users at
[ 136.343488][ T35] sk_alloc+0x2b3/0x370
[ 136.343488][ T35] inet6_create+0x6ce/0x10f0
[ 136.343488][ T35] __sock_create+0x4c0/0xa30
[ 136.343488][ T35] inet_ctl_sock_create+0xc2/0x250
[ 136.343488][ T35] ndisc_net_init+0xa7/0x2b0
[ 136.343488][ T35] ops_init+0x31e/0x590
[ 136.343488][ T35] setup_net+0x287/0x9e0
[ 136.343488][ T35] copy_net_ns+0x33f/0x570
[ 136.343488][ T35] create_new_namespaces+0x425/0x7b0
[ 136.343488][ T35] unshare_nsproxy_namespaces+0x124/0x180
[ 136.343488][ T35] ksys_unshare+0x57d/0xa70
[ 136.343488][ T35] __x64_sys_unshare+0x38/0x40
[ 136.343488][ T35] do_syscall_64+0xf3/0x230
[ 136.343488][ T35] entry_SYSCALL_64_after_hwframe+0x77/0x7f
Fixes: 0cafd77dcd03 ("net: add a refcount tracker for kernel sockets")
Reported-by: syzbot+30a19e01a97420719891@...kaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/67b72aeb.050a0220.14d86d.0283.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/net/sock.h | 1 +
net/core/sock.c | 27 ++++++++++++++++++++++-----
net/mptcp/subflow.c | 5 +----
net/netlink/af_netlink.c | 10 ----------
net/rds/tcp.c | 8 ++------
net/smc/af_smc.c | 5 +----
net/sunrpc/svcsock.c | 5 +----
net/sunrpc/xprtsock.c | 8 ++------
8 files changed, 30 insertions(+), 39 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index 8036b3b79cd8be64550dcfd6ce213039460acb1f..7ef728324e4e7e6e9cfa7aad56d4f46b29de2e06 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1751,6 +1751,7 @@ static inline bool sock_allow_reclassification(const struct sock *csk)
struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
struct proto *prot, int kern);
void sk_free(struct sock *sk);
+void sk_net_refcnt_upgrade(struct sock *sk);
void sk_destruct(struct sock *sk);
struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority);
void sk_free_unlock_clone(struct sock *sk);
diff --git a/net/core/sock.c b/net/core/sock.c
index eae2ae70a2e03df370d8ef7750a7bb13cc3b8d8f..6c0e87f97fa4a7220950ff576b10291e3e55731d 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2246,6 +2246,7 @@ struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
get_net_track(net, &sk->ns_tracker, priority);
sock_inuse_add(net, 1);
} else {
+ net_passive_inc(net);
__netns_tracker_alloc(net, &sk->ns_tracker,
false, priority);
}
@@ -2270,6 +2271,7 @@ EXPORT_SYMBOL(sk_alloc);
static void __sk_destruct(struct rcu_head *head)
{
struct sock *sk = container_of(head, struct sock, sk_rcu);
+ struct net *net = sock_net(sk);
struct sk_filter *filter;
if (sk->sk_destruct)
@@ -2301,14 +2303,28 @@ static void __sk_destruct(struct rcu_head *head)
put_cred(sk->sk_peer_cred);
put_pid(sk->sk_peer_pid);
- 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);
-
+ if (likely(sk->sk_net_refcnt)) {
+ put_net_track(net, &sk->ns_tracker);
+ } else {
+ __netns_tracker_free(net, &sk->ns_tracker, false);
+ net_passive_dec(net);
+ }
sk_prot_free(sk->sk_prot_creator, sk);
}
+void sk_net_refcnt_upgrade(struct sock *sk)
+{
+ struct net *net = sock_net(sk);
+
+ WARN_ON_ONCE(sk->sk_net_refcnt);
+ __netns_tracker_free(net, &sk->ns_tracker, false);
+ net_passive_dec(net);
+ sk->sk_net_refcnt = 1;
+ get_net_track(net, &sk->ns_tracker, GFP_KERNEL);
+ sock_inuse_add(net, 1);
+}
+EXPORT_SYMBOL_GPL(sk_net_refcnt_upgrade);
+
void sk_destruct(struct sock *sk)
{
bool use_call_rcu = sock_flag(sk, SOCK_RCU_FREE);
@@ -2405,6 +2421,7 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
* is not properly dismantling its kernel sockets at netns
* destroy time.
*/
+ net_passive_inc(sock_net(newsk));
__netns_tracker_alloc(sock_net(newsk), &newsk->ns_tracker,
false, priority);
}
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index fd021cf8286eff9234b950a4d4c083ea7756eba3..dfcbef9c46246983d21c827d9551d4eb2c95430e 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1772,10 +1772,7 @@ int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
* needs it.
* Update ns_tracker to current stack trace and refcounted tracker.
*/
- __netns_tracker_free(net, &sf->sk->ns_tracker, false);
- sf->sk->sk_net_refcnt = 1;
- get_net_track(net, &sf->sk->ns_tracker, GFP_KERNEL);
- sock_inuse_add(net, 1);
+ sk_net_refcnt_upgrade(sf->sk);
err = tcp_set_ulp(sf->sk, "mptcp");
if (err)
goto err_free;
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 85311226183a259574c64643eae9e906ccc9c1da..a53ea60d0a78d1b739ab392b16d383686c613d7f 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -795,16 +795,6 @@ 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 0581c53e6517043ad6c2ad4207b26ab169989ed8..3cc2f303bf786579a77b8b67ddc77468e085a3d3 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -504,12 +504,8 @@ 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);
+ sk_net_refcnt_upgrade(sk);
+ put_net(net);
}
rtn = net_generic(net, rds_tcp_netid);
if (rtn->sndbuf_size > 0) {
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index ca6984541edbda33a3539a48ed7c2aefecfa690e..3e6cb35baf25aff51518fe98a0bcbf1c3cec1629 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -3337,10 +3337,7 @@ int smc_create_clcsk(struct net *net, struct sock *sk, int family)
* which need net ref.
*/
sk = smc->clcsock->sk;
- __netns_tracker_free(net, &sk->ns_tracker, false);
- sk->sk_net_refcnt = 1;
- get_net_track(net, &sk->ns_tracker, GFP_KERNEL);
- sock_inuse_add(net, 1);
+ sk_net_refcnt_upgrade(sk);
return 0;
}
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index cb3bd12f5818bad13226d9b91be2881c55f56bc2..72e5a01df3d352582a5c25e0b8081a041e3792ee 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1541,10 +1541,7 @@ static struct svc_xprt *svc_create_socket(struct svc_serv *serv,
newlen = error;
if (protocol == IPPROTO_TCP) {
- __netns_tracker_free(net, &sock->sk->ns_tracker, false);
- sock->sk->sk_net_refcnt = 1;
- get_net_track(net, &sock->sk->ns_tracker, GFP_KERNEL);
- sock_inuse_add(net, 1);
+ sk_net_refcnt_upgrade(sock->sk);
if ((error = kernel_listen(sock, 64)) < 0)
goto bummer;
}
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index c60936d8cef71b3eb7937a3ec8dd8a4edbaaff10..940fe65b2a3511933a3f87465cdee1095ec096c6 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1941,12 +1941,8 @@ static struct socket *xs_create_sock(struct rpc_xprt *xprt,
goto out;
}
- if (protocol == IPPROTO_TCP) {
- __netns_tracker_free(xprt->xprt_net, &sock->sk->ns_tracker, false);
- sock->sk->sk_net_refcnt = 1;
- get_net_track(xprt->xprt_net, &sock->sk->ns_tracker, GFP_KERNEL);
- sock_inuse_add(xprt->xprt_net, 1);
- }
+ if (protocol == IPPROTO_TCP)
+ sk_net_refcnt_upgrade(sock->sk);
filp = sock_alloc_file(sock, O_NONBLOCK, NULL);
if (IS_ERR(filp))
--
2.48.1.601.g30ceb7b040-goog
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