* FAILED: patch "[PATCH] smb: client: fix netns refcount leak after net_passive" failed to apply to 6.12-stable tree
@ 2025-08-12 11:52 gregkh
2025-08-12 18:32 ` [PATCH 6.12.y 1/3] net: Add net_passive_inc() and net_passive_dec() Sasha Levin
0 siblings, 1 reply; 4+ messages in thread
From: gregkh @ 2025-08-12 11:52 UTC (permalink / raw)
To: wangzhaolong, ematsumiya, kuniyu, stfrench; +Cc: stable
The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 59b33fab4ca4d7dacc03367082777627e05d0323
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025081230-dentist-cautious-7bb4@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 59b33fab4ca4d7dacc03367082777627e05d0323 Mon Sep 17 00:00:00 2001
From: Wang Zhaolong <wangzhaolong@huaweicloud.com>
Date: Thu, 17 Jul 2025 21:29:26 +0800
Subject: [PATCH] smb: client: fix netns refcount leak after net_passive
changes
After commit 5c70eb5c593d ("net: better track kernel sockets lifetime"),
kernel sockets now use net_passive reference counting. However, commit
95d2b9f693ff ("Revert "smb: client: fix TCP timers deadlock after rmmod"")
restored the manual socket refcount manipulation without adapting to this
new mechanism, causing a memory leak.
The issue can be reproduced by[1]:
1. Creating a network namespace
2. Mounting and Unmounting CIFS within the namespace
3. Deleting the namespace
Some memory leaks may appear after a period of time following step 3.
unreferenced object 0xffff9951419f6b00 (size 256):
comm "ip", pid 447, jiffies 4294692389 (age 14.730s)
hex dump (first 32 bytes):
1b 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 80 77 c2 44 51 99 ff ff .........w.DQ...
backtrace:
__kmem_cache_alloc_node+0x30e/0x3d0
__kmalloc+0x52/0x120
net_alloc_generic+0x1d/0x30
copy_net_ns+0x86/0x200
create_new_namespaces+0x117/0x300
unshare_nsproxy_namespaces+0x60/0xa0
ksys_unshare+0x148/0x360
__x64_sys_unshare+0x12/0x20
do_syscall_64+0x59/0x110
entry_SYSCALL_64_after_hwframe+0x78/0xe2
...
unreferenced object 0xffff9951442e7500 (size 32):
comm "mount.cifs", pid 475, jiffies 4294693782 (age 13.343s)
hex dump (first 32 bytes):
40 c5 38 46 51 99 ff ff 18 01 96 42 51 99 ff ff @.8FQ......BQ...
01 00 00 00 6f 00 c5 07 6f 00 d8 07 00 00 00 00 ....o...o.......
backtrace:
__kmem_cache_alloc_node+0x30e/0x3d0
kmalloc_trace+0x2a/0x90
ref_tracker_alloc+0x8e/0x1d0
sk_alloc+0x18c/0x1c0
inet_create+0xf1/0x370
__sock_create+0xd7/0x1e0
generic_ip_connect+0x1d4/0x5a0 [cifs]
cifs_get_tcp_session+0x5d0/0x8a0 [cifs]
cifs_mount_get_session+0x47/0x1b0 [cifs]
dfs_mount_share+0xfa/0xa10 [cifs]
cifs_mount+0x68/0x2b0 [cifs]
cifs_smb3_do_mount+0x10b/0x760 [cifs]
smb3_get_tree+0x112/0x2e0 [cifs]
vfs_get_tree+0x29/0xf0
path_mount+0x2d4/0xa00
__se_sys_mount+0x165/0x1d0
Root cause:
When creating kernel sockets, sk_alloc() calls net_passive_inc() for
sockets with sk_net_refcnt=0. The CIFS code manually converts kernel
sockets to user sockets by setting sk_net_refcnt=1, but doesn't call
the corresponding net_passive_dec(). This creates an imbalance in the
net_passive counter, which prevents the network namespace from being
destroyed when its last user reference is dropped. As a result, the
entire namespace and all its associated resources remain allocated.
Timeline of patches leading to this issue:
- commit ef7134c7fc48 ("smb: client: Fix use-after-free of network
namespace.") in v6.12 fixed the original netns UAF by manually
managing socket refcounts
- commit e9f2517a3e18 ("smb: client: fix TCP timers deadlock after
rmmod") in v6.13 attempted to use kernel sockets but introduced
TCP timer issues
- commit 5c70eb5c593d ("net: better track kernel sockets lifetime")
in v6.14-rc5 introduced the net_passive mechanism with
sk_net_refcnt_upgrade() for proper socket conversion
- commit 95d2b9f693ff ("Revert "smb: client: fix TCP timers deadlock
after rmmod"") in v6.15-rc3 reverted to manual refcount management
without adapting to the new net_passive changes
Fix this by using sk_net_refcnt_upgrade() which properly handles the
net_passive counter when converting kernel sockets to user sockets.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=220343 [1]
Fixes: 95d2b9f693ff ("Revert "smb: client: fix TCP timers deadlock after rmmod"")
Cc: stable@vger.kernel.org
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Wang Zhaolong <wangzhaolong@huaweicloud.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index 205f547ca49e..5eec8957f2a9 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -3362,18 +3362,15 @@ generic_ip_connect(struct TCP_Server_Info *server)
struct net *net = cifs_net_ns(server);
struct sock *sk;
- rc = __sock_create(net, sfamily, SOCK_STREAM,
- IPPROTO_TCP, &server->ssocket, 1);
+ rc = sock_create_kern(net, sfamily, SOCK_STREAM,
+ IPPROTO_TCP, &server->ssocket);
if (rc < 0) {
cifs_server_dbg(VFS, "Error %d creating socket\n", rc);
return rc;
}
sk = server->ssocket->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);
/* BB other socket options to set KEEPALIVE, NODELAY? */
cifs_dbg(FYI, "Socket created\n");
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH 6.12.y 1/3] net: Add net_passive_inc() and net_passive_dec().
2025-08-12 11:52 FAILED: patch "[PATCH] smb: client: fix netns refcount leak after net_passive" failed to apply to 6.12-stable tree gregkh
@ 2025-08-12 18:32 ` Sasha Levin
2025-08-12 18:32 ` [PATCH 6.12.y 2/3] net: better track kernel sockets lifetime Sasha Levin
2025-08-12 18:32 ` [PATCH 6.12.y 3/3] smb: client: fix netns refcount leak after net_passive changes Sasha Levin
0 siblings, 2 replies; 4+ messages in thread
From: Sasha Levin @ 2025-08-12 18:32 UTC (permalink / raw)
To: stable; +Cc: Kuniyuki Iwashima, Eric Dumazet, Jakub Kicinski, Sasha Levin
From: Kuniyuki Iwashima <kuniyu@amazon.com>
[ Upstream commit e57a6320215c3967f51ab0edeff87db2095440e4 ]
net_drop_ns() is NULL when CONFIG_NET_NS is disabled.
The next patch introduces a function that increments
and decrements net->passive.
As a prep, let's rename and export net_free() to
net_passive_dec() and add net_passive_inc().
Suggested-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/netdev/CANn89i+oUCt2VGvrbrweniTendZFEh+nwS=uonc004-aPkWy-Q@mail.gmail.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250217191129.19967-2-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 59b33fab4ca4 ("smb: client: fix netns refcount leak after net_passive changes")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/net_namespace.h | 16 ++++++++++++++++
net/core/net_namespace.c | 8 ++++----
2 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index da93873df4db..022ee2fc627c 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -291,6 +291,7 @@ static inline int check_net(const struct net *net)
}
void net_drop_ns(void *);
+void net_passive_dec(struct net *net);
#else
@@ -320,8 +321,23 @@ static inline int check_net(const struct net *net)
}
#define net_drop_ns NULL
+
+static inline void net_passive_dec(struct net *net)
+{
+ refcount_dec(&net->passive);
+}
#endif
+static inline void net_passive_inc(struct net *net)
+{
+ refcount_inc(&net->passive);
+}
+
+/* Returns true if the netns initialization is completed successfully */
+static inline bool net_initialized(const struct net *net)
+{
+ return READ_ONCE(net->list.next);
+}
static inline void __netns_tracker_alloc(struct net *net,
netns_tracker *tracker,
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 70fea7c1a4b0..ee3c1b37d06c 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -458,7 +458,7 @@ static void net_complete_free(void)
}
-static void net_free(struct net *net)
+void net_passive_dec(struct net *net)
{
if (refcount_dec_and_test(&net->passive)) {
kfree(rcu_access_pointer(net->gen));
@@ -476,7 +476,7 @@ void net_drop_ns(void *p)
struct net *net = (struct net *)p;
if (net)
- net_free(net);
+ net_passive_dec(net);
}
struct net *copy_net_ns(unsigned long flags,
@@ -517,7 +517,7 @@ struct net *copy_net_ns(unsigned long flags,
key_remove_domain(net->key_domain);
#endif
put_user_ns(user_ns);
- net_free(net);
+ net_passive_dec(net);
dec_ucounts:
dec_net_namespaces(ucounts);
return ERR_PTR(rv);
@@ -662,7 +662,7 @@ static void cleanup_net(struct work_struct *work)
key_remove_domain(net->key_domain);
#endif
put_user_ns(net->user_ns);
- net_free(net);
+ net_passive_dec(net);
}
}
--
2.39.5
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH 6.12.y 2/3] net: better track kernel sockets lifetime
2025-08-12 18:32 ` [PATCH 6.12.y 1/3] net: Add net_passive_inc() and net_passive_dec() Sasha Levin
@ 2025-08-12 18:32 ` Sasha Levin
2025-08-12 18:32 ` [PATCH 6.12.y 3/3] smb: client: fix netns refcount leak after net_passive changes Sasha Levin
1 sibling, 0 replies; 4+ messages in thread
From: Sasha Levin @ 2025-08-12 18:32 UTC (permalink / raw)
To: stable
Cc: Eric Dumazet, syzbot+30a19e01a97420719891, Kuniyuki Iwashima,
Jakub Kicinski, Sasha Levin
From: Eric Dumazet <edumazet@google.com>
[ Upstream commit 5c70eb5c593d64d93b178905da215a9fd288a4b5 ]
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@ffff8880638f01e0 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@ffff8880638f01e0 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@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/67b72aeb.050a0220.14d86d.0283.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250220131854.4048077-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 b7270b6b9e9c..722f409cccd3 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1780,6 +1780,7 @@ 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 9c63da2829f6..d392cb37a864 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2243,6 +2243,7 @@ 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);
}
@@ -2267,6 +2268,7 @@ 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)
@@ -2298,14 +2300,28 @@ 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);
@@ -2402,6 +2418,7 @@ 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 0253a863a621..a05f201d194c 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1768,10 +1768,7 @@ 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 b02fb75f8d4f..2290d14b0932 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -794,16 +794,6 @@ 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 0581c53e6517..3cc2f303bf78 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 3c43239f09d3..cdd445d40b94 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -3353,10 +3353,7 @@ 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 3bfbb789c4be..780a54548372 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 67d099c7c662..acae53d74230 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1940,12 +1940,8 @@ 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))
--
2.39.5
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH 6.12.y 3/3] smb: client: fix netns refcount leak after net_passive changes
2025-08-12 18:32 ` [PATCH 6.12.y 1/3] net: Add net_passive_inc() and net_passive_dec() Sasha Levin
2025-08-12 18:32 ` [PATCH 6.12.y 2/3] net: better track kernel sockets lifetime Sasha Levin
@ 2025-08-12 18:32 ` Sasha Levin
1 sibling, 0 replies; 4+ messages in thread
From: Sasha Levin @ 2025-08-12 18:32 UTC (permalink / raw)
To: stable
Cc: Wang Zhaolong, Kuniyuki Iwashima, Enzo Matsumiya, Steve French,
Sasha Levin
From: Wang Zhaolong <wangzhaolong@huaweicloud.com>
[ Upstream commit 59b33fab4ca4d7dacc03367082777627e05d0323 ]
After commit 5c70eb5c593d ("net: better track kernel sockets lifetime"),
kernel sockets now use net_passive reference counting. However, commit
95d2b9f693ff ("Revert "smb: client: fix TCP timers deadlock after rmmod"")
restored the manual socket refcount manipulation without adapting to this
new mechanism, causing a memory leak.
The issue can be reproduced by[1]:
1. Creating a network namespace
2. Mounting and Unmounting CIFS within the namespace
3. Deleting the namespace
Some memory leaks may appear after a period of time following step 3.
unreferenced object 0xffff9951419f6b00 (size 256):
comm "ip", pid 447, jiffies 4294692389 (age 14.730s)
hex dump (first 32 bytes):
1b 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 80 77 c2 44 51 99 ff ff .........w.DQ...
backtrace:
__kmem_cache_alloc_node+0x30e/0x3d0
__kmalloc+0x52/0x120
net_alloc_generic+0x1d/0x30
copy_net_ns+0x86/0x200
create_new_namespaces+0x117/0x300
unshare_nsproxy_namespaces+0x60/0xa0
ksys_unshare+0x148/0x360
__x64_sys_unshare+0x12/0x20
do_syscall_64+0x59/0x110
entry_SYSCALL_64_after_hwframe+0x78/0xe2
...
unreferenced object 0xffff9951442e7500 (size 32):
comm "mount.cifs", pid 475, jiffies 4294693782 (age 13.343s)
hex dump (first 32 bytes):
40 c5 38 46 51 99 ff ff 18 01 96 42 51 99 ff ff @.8FQ......BQ...
01 00 00 00 6f 00 c5 07 6f 00 d8 07 00 00 00 00 ....o...o.......
backtrace:
__kmem_cache_alloc_node+0x30e/0x3d0
kmalloc_trace+0x2a/0x90
ref_tracker_alloc+0x8e/0x1d0
sk_alloc+0x18c/0x1c0
inet_create+0xf1/0x370
__sock_create+0xd7/0x1e0
generic_ip_connect+0x1d4/0x5a0 [cifs]
cifs_get_tcp_session+0x5d0/0x8a0 [cifs]
cifs_mount_get_session+0x47/0x1b0 [cifs]
dfs_mount_share+0xfa/0xa10 [cifs]
cifs_mount+0x68/0x2b0 [cifs]
cifs_smb3_do_mount+0x10b/0x760 [cifs]
smb3_get_tree+0x112/0x2e0 [cifs]
vfs_get_tree+0x29/0xf0
path_mount+0x2d4/0xa00
__se_sys_mount+0x165/0x1d0
Root cause:
When creating kernel sockets, sk_alloc() calls net_passive_inc() for
sockets with sk_net_refcnt=0. The CIFS code manually converts kernel
sockets to user sockets by setting sk_net_refcnt=1, but doesn't call
the corresponding net_passive_dec(). This creates an imbalance in the
net_passive counter, which prevents the network namespace from being
destroyed when its last user reference is dropped. As a result, the
entire namespace and all its associated resources remain allocated.
Timeline of patches leading to this issue:
- commit ef7134c7fc48 ("smb: client: Fix use-after-free of network
namespace.") in v6.12 fixed the original netns UAF by manually
managing socket refcounts
- commit e9f2517a3e18 ("smb: client: fix TCP timers deadlock after
rmmod") in v6.13 attempted to use kernel sockets but introduced
TCP timer issues
- commit 5c70eb5c593d ("net: better track kernel sockets lifetime")
in v6.14-rc5 introduced the net_passive mechanism with
sk_net_refcnt_upgrade() for proper socket conversion
- commit 95d2b9f693ff ("Revert "smb: client: fix TCP timers deadlock
after rmmod"") in v6.15-rc3 reverted to manual refcount management
without adapting to the new net_passive changes
Fix this by using sk_net_refcnt_upgrade() which properly handles the
net_passive counter when converting kernel sockets to user sockets.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=220343 [1]
Fixes: 95d2b9f693ff ("Revert "smb: client: fix TCP timers deadlock after rmmod"")
Cc: stable@vger.kernel.org
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Wang Zhaolong <wangzhaolong@huaweicloud.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/smb/client/connect.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index ebc380b18da7..9d93794e9c50 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -3165,18 +3165,15 @@ generic_ip_connect(struct TCP_Server_Info *server)
struct net *net = cifs_net_ns(server);
struct sock *sk;
- rc = __sock_create(net, sfamily, SOCK_STREAM,
- IPPROTO_TCP, &server->ssocket, 1);
+ rc = sock_create_kern(net, sfamily, SOCK_STREAM,
+ IPPROTO_TCP, &server->ssocket);
if (rc < 0) {
cifs_server_dbg(VFS, "Error %d creating socket\n", rc);
return rc;
}
sk = server->ssocket->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);
/* BB other socket options to set KEEPALIVE, NODELAY? */
cifs_dbg(FYI, "Socket created\n");
--
2.39.5
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2025-08-12 11:52 FAILED: patch "[PATCH] smb: client: fix netns refcount leak after net_passive" failed to apply to 6.12-stable tree gregkh
2025-08-12 18:32 ` [PATCH 6.12.y 1/3] net: Add net_passive_inc() and net_passive_dec() Sasha Levin
2025-08-12 18:32 ` [PATCH 6.12.y 2/3] net: better track kernel sockets lifetime Sasha Levin
2025-08-12 18:32 ` [PATCH 6.12.y 3/3] smb: client: fix netns refcount leak after net_passive changes Sasha Levin
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