kernel/linux.git/drivers/net/ovpn/socket.c, branch v6.19.11

ovpn: set sk_user_data before overriding callbacks

2026-02-26T23:01:29+00:00

[ Upstream commit 93686c472eb7b09a51b97a096449e7092fefcd1f ] During initialization, we override socket callbacks and set sk_user_data to an ovpn_socket instance. Currently, these two operations are decoupled: callbacks are overridden before sk_user_data is set. While existing callbacks perform safety checks for NULL or non-ovpn sk_user_data, this condition causes a "half-formed" state where valid packets arriving during attachment trigger error logs (e.g., "invoked on non ovpn socket"). Set sk_user_data before overriding the callbacks so that it can be accessed safely from them. Since we already check that the socket has no sk_user_data before setting it, this remains safe even if an interrupt accesses the socket after sk_user_data is set but before the callbacks are overridden. This also requires initializing all protocol-specific fields (such as tcp_tx_work and peer links) before calling ovpn_socket_attach, ensuring the ovpn_socket is fully formed before it becomes visible to any callback. Fixes: f6226ae7a0cd ("ovpn: introduce the ovpn_socket object") Signed-off-by: Ralf Lici Reviewed-by: Sabrina Dubroca Signed-off-by: Antonio Quartulli Signed-off-by: Sasha Levin

ovpn: ensure sk is still valid during cleanup

2025-06-03T11:08:15+00:00

Removing a peer while userspace attempts to close its transport socket triggers a race condition resulting in the following crash: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000077: 0000 [#1] SMP KASAN KASAN: null-ptr-deref in range [0x00000000000003b8-0x00000000000003bf] CPU: 12 UID: 0 PID: 162 Comm: kworker/12:1 Tainted: G O 6.15.0-rc2-00635-g521139ac3840 #272 PREEMPT(full) Tainted: [O]=OOT_MODULE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-20240910_120124-localhost 04/01/2014 Workqueue: events ovpn_peer_keepalive_work [ovpn] RIP: 0010:ovpn_socket_release+0x23c/0x500 [ovpn] Code: ea 03 80 3c 02 00 0f 85 71 02 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 64 24 18 49 8d bc 24 be 03 00 00 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 01 38 d0 7c 08 84 d2 0f 85 30 RSP: 0018:ffffc90000c9fb18 EFLAGS: 00010217 RAX: dffffc0000000000 RBX: ffff8881148d7940 RCX: ffffffff817787bb RDX: 0000000000000077 RSI: 0000000000000008 RDI: 00000000000003be RBP: ffffc90000c9fb30 R08: 0000000000000000 R09: fffffbfff0d3e840 R10: ffffffff869f4207 R11: 0000000000000000 R12: 0000000000000000 R13: ffff888115eb9300 R14: ffffc90000c9fbc8 R15: 000000000000000c FS: 0000000000000000(0000) GS:ffff8882b0151000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f37266b6114 CR3: 00000000054a8000 CR4: 0000000000750ef0 PKRU: 55555554 Call Trace: unlock_ovpn+0x8b/0xe0 [ovpn] ovpn_peer_keepalive_work+0xe3/0x540 [ovpn] ? ovpn_peers_free+0x780/0x780 [ovpn] ? lock_acquire+0x56/0x70 ? process_one_work+0x888/0x1740 process_one_work+0x933/0x1740 ? pwq_dec_nr_in_flight+0x10b0/0x10b0 ? move_linked_works+0x12d/0x2c0 ? assign_work+0x163/0x270 worker_thread+0x4d6/0xd90 ? preempt_count_sub+0x4c/0x70 ? process_one_work+0x1740/0x1740 kthread+0x36c/0x710 ? trace_preempt_on+0x8c/0x1e0 ? kthread_is_per_cpu+0xc0/0xc0 ? preempt_count_sub+0x4c/0x70 ? _raw_spin_unlock_irq+0x36/0x60 ? calculate_sigpending+0x7b/0xa0 ? kthread_is_per_cpu+0xc0/0xc0 ret_from_fork+0x3a/0x80 ? kthread_is_per_cpu+0xc0/0xc0 ret_from_fork_asm+0x11/0x20 Modules linked in: ovpn(O) This happens because the peer deletion operation reaches ovpn_socket_release() while ovpn_sock->sock (struct socket *) and its sk member (struct sock *) are still both valid. Here synchronize_rcu() is invoked, after which ovpn_sock->sock->sk becomes NULL, due to the concurrent socket closing triggered from userspace. After having invoked synchronize_rcu(), ovpn_socket_release() will attempt dereferencing ovpn_sock->sock->sk, triggering the crash reported above. The reason for accessing sk is that we need to retrieve its protocol and continue the cleanup routine accordingly. This crash can be easily produced by running openvpn userspace in client mode with `--keepalive 10 20`, while entirely omitting this option on the server side. After 20 seconds ovpn will assume the peer (server) to be dead, will start removing it and will notify userspace. The latter will receive the notification and close the transport socket, thus triggering the crash. To fix the race condition for good, we need to refactor struct ovpn_socket. Since ovpn is always only interested in the sock->sk member (struct sock *) we can directly hold a reference to it, raher than accessing it via its struct socket container. This means changing "struct socket *ovpn_socket->sock" to "struct sock *ovpn_socket->sk". While acquiring a reference to sk, we can increase its refcounter without affecting the socket close()/destroy() notification (which we rely on when userspace closes a socket we are using). By increasing sk's refcounter we know we can dereference it in ovpn_socket_release() without incurring in any race condition anymore. ovpn_socket_release() will ultimately decrease the reference counter. Cc: Oleksandr Natalenko Fixes: 11851cbd60ea ("ovpn: implement TCP transport") Reported-by: Qingfang Deng Closes: https://github.com/OpenVPN/ovpn-net-next/issues/1 Tested-by: Gert Doering Link: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg31575.html Reviewed-by: Michal Swiatkowski Signed-off-by: Antonio Quartulli

ovpn: implement peer add/get/dump/delete via netlink

2025-04-17T10:30:03+00:00

This change introduces the netlink command needed to add, delete and retrieve/dump known peers. Userspace is expected to use these commands to handle known peer lifecycles. Signed-off-by: Antonio Quartulli Link: https://patch.msgid.link/20250415-b4-ovpn-v26-18-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Abeni

ovpn: implement TCP transport

2025-04-17T10:30:03+00:00

With this change ovpn is allowed to communicate to peers also via TCP. Parsing of incoming messages is implemented through the strparser API. Note that ovpn redefines sk_prot and sk_socket->ops for the TCP socket used to communicate with the peer. For this reason it needs to access inet6_stream_ops, which is declared as extern in the IPv6 module, but it is not fully exported. Therefore this patch is also adding EXPORT_SYMBOL_GPL(inet6_stream_ops) to net/ipv6/af_inet6.c. Cc: David Ahern Cc: Eric Dumazet Cc: Jakub Kicinski Cc: Paolo Abeni Cc: Simon Horman Signed-off-by: Antonio Quartulli Link: https://patch.msgid.link/20250415-b4-ovpn-v26-11-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Abeni

ovpn: implement basic RX path (UDP)

2025-04-17T10:30:02+00:00

Packets received over the socket are forwarded to the user device. Implementation is UDP only. TCP will be added by a later patch. Note: no decryption/decapsulation exists yet, packets are forwarded as they arrive without much processing. Signed-off-by: Antonio Quartulli Link: https://patch.msgid.link/20250415-b4-ovpn-v26-8-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Abeni

ovpn: introduce the ovpn_socket object

2025-04-17T10:30:02+00:00

This specific structure is used in the ovpn kernel module to wrap and carry around a standard kernel socket. ovpn takes ownership of passed sockets and therefore an ovpn specific objects is attached to them for status tracking purposes. Initially only UDP support is introduced. TCP will come in a later patch. Cc: willemdebruijn.kernel@gmail.com Signed-off-by: Antonio Quartulli Link: https://patch.msgid.link/20250415-b4-ovpn-v26-6-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Abeni