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

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: improve 'no route to host' debug message

2025-05-15T11:09:36+00:00

When debugging a 'no route to host' error it can be beneficial to know the address of the unreachable destination. Print it along the debugging text. While at it, add a missing parenthesis in a different debugging message inside ovpn_peer_endpoints_update(). Signed-off-by: Antonio Quartulli

ovpn: drop useless reg_state check in keepalive worker

2025-05-15T11:09:36+00:00

The keepalive worker is cancelled before calling unregister_netdevice_queue(), therefore it will never hit a situation where the reg_state can be different than NETDEV_REGISTERED. For this reason, checking reg_state is useless and the condition can be removed. Signed-off-by: Antonio Quartulli

ovpn: notify userspace when a peer is deleted

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

Whenever a peer is deleted, send a notification to userspace so that it can react accordingly. This is most important when a peer is deleted due to ping timeout, because it all happens in kernelspace and thus userspace has no direct way to learn about it. Signed-off-by: Antonio Quartulli Link: https://patch.msgid.link/20250415-b4-ovpn-v26-21-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Abeni

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: add support for updating local or remote UDP endpoint

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

In case of UDP links, the local or remote endpoint used to communicate with a given peer may change without a connection restart. Add support for learning the new address in case of change. Signed-off-by: Antonio Quartulli Link: https://patch.msgid.link/20250415-b4-ovpn-v26-17-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Abeni

ovpn: implement keepalive mechanism

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

OpenVPN supports configuring a periodic keepalive packet. message to allow the remote endpoint detect link failures. This change implements the keepalive sending and timer expiring logic. Signed-off-by: Antonio Quartulli Link: https://patch.msgid.link/20250415-b4-ovpn-v26-16-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Abeni

ovpn: implement peer lookup logic

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

In a multi-peer scenario there are a number of situations when a specific peer needs to be looked up. We may want to lookup a peer by: 1. its ID 2. its VPN destination IP 3. its transport IP/port couple For each of the above, there is a specific routing table referencing all peers for fast look up. Case 2. is a bit special in the sense that an outgoing packet may not be sent to the peer VPN IP directly, but rather to a network behind it. For this reason we first perform a nexthop lookup in the system routing table and then we use the retrieved nexthop as peer search key. Signed-off-by: Antonio Quartulli Link: https://patch.msgid.link/20250415-b4-ovpn-v26-15-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Abeni

ovpn: implement multi-peer support

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

With this change an ovpn instance will be able to stay connected to multiple remote endpoints. This functionality is strictly required when running ovpn on an OpenVPN server. Signed-off-by: Antonio Quartulli Link: https://patch.msgid.link/20250415-b4-ovpn-v26-14-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Abeni

ovpn: store tunnel and transport statistics

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

Byte/packet counters for in-tunnel and transport streams are now initialized and updated as needed. To be exported via netlink. Signed-off-by: Antonio Quartulli Link: https://patch.msgid.link/20250415-b4-ovpn-v26-10-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Abeni