1
Commit Graph

221 Commits

Author SHA1 Message Date
James Chapman
510c0732fc l2tp: remove unneeded null check in l2tp_v2_session_get_next
Commit aa92c1cec9 ("l2tp: add tunnel/session get_next helpers") uses
idr_get_next APIs to iterate over l2tp session IDR lists.  Sessions in
l2tp_v2_session_idr always have a non-null session->tunnel pointer
since l2tp_session_register sets it before inserting the session into
the IDR. Therefore the null check on session->tunnel in
l2tp_v2_session_get_next is redundant and can be removed. Removing the
check avoids a warning from lkp.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202408111407.HtON8jqa-lkp@intel.com/
CC: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: James Chapman <jchapman@katalix.com>
Acked-by: Tom Parkin <tparkin@katalix.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240903113547.1261048-1-jchapman@katalix.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-09-04 16:39:32 -07:00
James Chapman
73d33bd063 l2tp: avoid using drain_workqueue in l2tp_pre_exit_net
Recent commit fc7ec7f554 ("l2tp: delete sessions using work queue")
incorrectly uses drain_workqueue. The use of drain_workqueue in
l2tp_pre_exit_net is flawed because the workqueue is shared by all
nets and it is therefore possible for new work items to be queued
for other nets while drain_workqueue runs.

Instead of using drain_workqueue, use __flush_workqueue twice. The
first one will run all tunnel delete work items and any work already
queued. When tunnel delete work items are run, they may queue
new session delete work items, which the second __flush_workqueue will
run.

In l2tp_exit_net, warn if any of the net's idr lists are not empty.

Fixes: fc7ec7f554 ("l2tp: delete sessions using work queue")
Signed-off-by: James Chapman <jchapman@katalix.com>
Link: https://patch.msgid.link/20240823142257.692667-1-jchapman@katalix.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-08-27 13:37:22 -07:00
Cong Wang
1461f5a3d8 l2tp: avoid overriding sk->sk_user_data
Although commit 4a4cd70369 ("l2tp: don't set sk_user_data in tunnel socket")
removed sk->sk_user_data usage, setup_udp_tunnel_sock() still touches
sk->sk_user_data, this conflicts with sockmap which also leverages
sk->sk_user_data to save psock.

Restore this sk->sk_user_data check to avoid such conflicts.

Fixes: 4a4cd70369 ("l2tp: don't set sk_user_data in tunnel socket")
Reported-by: syzbot+8dbe3133b840c470da0e@syzkaller.appspotmail.com
Cc: Tom Parkin <tparkin@katalix.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Tested-by: James Chapman <jchapman@katalix.com>
Reviewed-by: James Chapman <jchapman@katalix.com>
Link: https://patch.msgid.link/20240822182544.378169-1-xiyou.wangcong@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-08-26 09:55:40 -07:00
James Chapman
c1b2e36b87 l2tp: flush workqueue before draining it
syzbot exposes a race where a net used by l2tp is removed while an
existing pppol2tp socket is closed. In l2tp_pre_exit_net, l2tp queues
TUNNEL_DELETE work items to close each tunnel in the net. When these
are run, new SESSION_DELETE work items are queued to delete each
session in the tunnel. This all happens in drain_workqueue. However,
drain_workqueue allows only new work items if they are queued by other
work items which are already in the queue. If pppol2tp_release runs
after drain_workqueue has started, it may queue a SESSION_DELETE work
item, which results in the warning below in drain_workqueue.

Address this by flushing the workqueue before drain_workqueue such
that all queued TUNNEL_DELETE work items run before drain_workqueue is
started. This will queue SESSION_DELETE work items for each session in
the tunnel, hence pppol2tp_release or other API requests won't queue
SESSION_DELETE requests once drain_workqueue is started.

  WARNING: CPU: 1 PID: 5467 at kernel/workqueue.c:2259 __queue_work+0xcd3/0xf50 kernel/workqueue.c:2258
  Modules linked in:
  CPU: 1 UID: 0 PID: 5467 Comm: syz.3.43 Not tainted 6.11.0-rc1-syzkaller-00247-g3608d6aca5e7 #0
  Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
  RIP: 0010:__queue_work+0xcd3/0xf50 kernel/workqueue.c:2258
  Code: ff e8 11 84 36 00 90 0f 0b 90 e9 1e fd ff ff e8 03 84 36 00 eb 13 e8 fc 83 36 00 eb 0c e8 f5 83 36 00 eb 05 e8 ee 83 36 00 90 <0f> 0b 90 48 83 c4 60 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc
  RSP: 0018:ffffc90004607b48 EFLAGS: 00010093
  RAX: ffffffff815ce274 RBX: ffff8880661fda00 RCX: ffff8880661fda00
  RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
  RBP: 0000000000000000 R08: ffffffff815cd6d4 R09: 0000000000000000
  R10: ffffc90004607c20 R11: fffff520008c0f85 R12: ffff88802ac33800
  R13: ffff88802ac339c0 R14: dffffc0000000000 R15: 0000000000000008
  FS:  00005555713eb500(0000) GS:ffff8880b9300000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000000008 CR3: 000000001eda6000 CR4: 00000000003506f0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   <TASK>
   queue_work_on+0x1c2/0x380 kernel/workqueue.c:2392
   pppol2tp_release+0x163/0x230 net/l2tp/l2tp_ppp.c:445
   __sock_release net/socket.c:659 [inline]
   sock_close+0xbc/0x240 net/socket.c:1421
   __fput+0x24a/0x8a0 fs/file_table.c:422
   task_work_run+0x24f/0x310 kernel/task_work.c:228
   resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
   exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
   exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
   __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
   syscall_exit_to_user_mode+0x168/0x370 kernel/entry/common.c:218
   do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
   entry_SYSCALL_64_after_hwframe+0x77/0x7f
  RIP: 0033:0x7f061e9779f9
  Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
  RSP: 002b:00007ffff1c1fce8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
  RAX: 0000000000000000 RBX: 000000000001017d RCX: 00007f061e9779f9
  RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
  RBP: 00007ffff1c1fdc0 R08: 0000000000000001 R09: 00007ffff1c1ffcf
  R10: 00007f061e800000 R11: 0000000000000246 R12: 0000000000000032
  R13: 00007ffff1c1fde0 R14: 00007ffff1c1fe00 R15: ffffffffffffffff
  </TASK>

Fixes: fc7ec7f554 ("l2tp: delete sessions using work queue")
Reported-by: syzbot+0e85b10481d2f5478053@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=0e85b10481d2f5478053
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-08-11 04:38:50 +01:00
James Chapman
abe7a1a7d0 l2tp: improve tunnel/session refcount helpers
l2tp_tunnel_inc_refcount and l2tp_session_inc_refcount wrap
refcount_inc. They add no value so just use the refcount APIs directly
and drop l2tp's helpers. l2tp already uses refcount_inc_not_zero
anyway.

Rename l2tp_tunnel_dec_refcount and l2tp_session_dec_refcount to
l2tp_tunnel_put and l2tp_session_put to better match their use pairing
various _get getters.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-08-11 04:38:50 +01:00
James Chapman
1f4c3dce91 l2tp: use get_next APIs for management requests and procfs/debugfs
l2tp netlink and procfs/debugfs iterate over tunnel and session lists
to obtain data. They currently use very inefficient get_nth functions
to do so. Replace these with get_next.

For netlink, use nl cb->ctx[] for passing state instead of the
obsolete cb->args[].

l2tp_tunnel_get_nth and l2tp_session_get_nth are no longer used so
they can be removed.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-08-11 04:38:49 +01:00
James Chapman
aa92c1cec9 l2tp: add tunnel/session get_next helpers
l2tp management APIs and procfs/debugfs iterate over l2tp tunnel and
session lists. Since these lists are now implemented using IDR, we can
use IDR get_next APIs to iterate them. Add tunnel/session get_next
functions to do so.

The session get_next functions get the next session in a given tunnel
and need to account for l2tpv2 and l2tpv3 differences:

 * l2tpv2 sessions are keyed by tunnel ID / session ID. Iteration for
   a given tunnel ID, TID, can therefore start with a key given by
   TID/0 and finish when the next entry's tunnel ID is not TID. This
   is possible only because the tunnel ID part of the key is the upper
   16 bits and the session ID part the lower 16 bits; when idr_next
   increments the key value, it therefore finds the next sessions of
   the current tunnel before those of the next tunnel. Entries with
   session ID 0 are always skipped because they are used internally by
   pppol2tp.

 * l2tpv3 sessions are keyed by session ID. Iteration starts at the
   first IDR entry and skips entries where the tunnel does not
   match. Iteration must also consider session ID collisions and walk
   the list of colliding sessions (if any) for one which matches the
   supplied tunnel.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-08-11 04:38:49 +01:00
James Chapman
b0a8deda06 l2tp: handle hash key collisions in l2tp_v3_session_get
To handle colliding l2tpv3 session IDs, l2tp_v3_session_get searches a
hashed list keyed by ID and sk. Although unlikely, if hash keys
collide, it is possible that hash_for_each_possible loops over a
session which doesn't have the ID that we are searching for. So check
for session ID match when looping over possible hash key matches.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-08-11 04:38:49 +01:00
James Chapman
168464c19e l2tp: remove inline from functions in c sources
Update l2tp to remove the inline keyword from several functions in C
sources, since this is now discouraged.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-08-11 04:38:49 +01:00
Jakub Kicinski
e47fd9beb1 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Cross-merge networking fixes after downstream PR.

No conflicts or adjacent changes.

Link: https://patch.msgid.link/20240808170148.3629934-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-08-08 14:04:17 -07:00
James Chapman
86a41ea9fd l2tp: fix lockdep splat
When l2tp tunnels use a socket provided by userspace, we can hit
lockdep splats like the below when data is transmitted through another
(unrelated) userspace socket which then gets routed over l2tp.

This issue was previously discussed here:
https://lore.kernel.org/netdev/87sfialu2n.fsf@cloudflare.com/

The solution is to have lockdep treat socket locks of l2tp tunnel
sockets separately than those of standard INET sockets. To do so, use
a different lockdep subclass where lock nesting is possible.

  ============================================
  WARNING: possible recursive locking detected
  6.10.0+ #34 Not tainted
  --------------------------------------------
  iperf3/771 is trying to acquire lock:
  ffff8881027601d8 (slock-AF_INET/1){+.-.}-{2:2}, at: l2tp_xmit_skb+0x243/0x9d0

  but task is already holding lock:
  ffff888102650d98 (slock-AF_INET/1){+.-.}-{2:2}, at: tcp_v4_rcv+0x1848/0x1e10

  other info that might help us debug this:
   Possible unsafe locking scenario:

         CPU0
         ----
    lock(slock-AF_INET/1);
    lock(slock-AF_INET/1);

   *** DEADLOCK ***

   May be due to missing lock nesting notation

  10 locks held by iperf3/771:
   #0: ffff888102650258 (sk_lock-AF_INET){+.+.}-{0:0}, at: tcp_sendmsg+0x1a/0x40
   #1: ffffffff822ac220 (rcu_read_lock){....}-{1:2}, at: __ip_queue_xmit+0x4b/0xbc0
   #2: ffffffff822ac220 (rcu_read_lock){....}-{1:2}, at: ip_finish_output2+0x17a/0x1130
   #3: ffffffff822ac220 (rcu_read_lock){....}-{1:2}, at: process_backlog+0x28b/0x9f0
   #4: ffffffff822ac220 (rcu_read_lock){....}-{1:2}, at: ip_local_deliver_finish+0xf9/0x260
   #5: ffff888102650d98 (slock-AF_INET/1){+.-.}-{2:2}, at: tcp_v4_rcv+0x1848/0x1e10
   #6: ffffffff822ac220 (rcu_read_lock){....}-{1:2}, at: __ip_queue_xmit+0x4b/0xbc0
   #7: ffffffff822ac220 (rcu_read_lock){....}-{1:2}, at: ip_finish_output2+0x17a/0x1130
   #8: ffffffff822ac1e0 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0xcc/0x1450
   #9: ffff888101f33258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2){+...}-{2:2}, at: __dev_queue_xmit+0x513/0x1450

  stack backtrace:
  CPU: 2 UID: 0 PID: 771 Comm: iperf3 Not tainted 6.10.0+ #34
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
  Call Trace:
   <IRQ>
   dump_stack_lvl+0x69/0xa0
   dump_stack+0xc/0x20
   __lock_acquire+0x135d/0x2600
   ? srso_alias_return_thunk+0x5/0xfbef5
   lock_acquire+0xc4/0x2a0
   ? l2tp_xmit_skb+0x243/0x9d0
   ? __skb_checksum+0xa3/0x540
   _raw_spin_lock_nested+0x35/0x50
   ? l2tp_xmit_skb+0x243/0x9d0
   l2tp_xmit_skb+0x243/0x9d0
   l2tp_eth_dev_xmit+0x3c/0xc0
   dev_hard_start_xmit+0x11e/0x420
   sch_direct_xmit+0xc3/0x640
   __dev_queue_xmit+0x61c/0x1450
   ? ip_finish_output2+0xf4c/0x1130
   ip_finish_output2+0x6b6/0x1130
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? __ip_finish_output+0x217/0x380
   ? srso_alias_return_thunk+0x5/0xfbef5
   __ip_finish_output+0x217/0x380
   ip_output+0x99/0x120
   __ip_queue_xmit+0xae4/0xbc0
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? tcp_options_write.constprop.0+0xcb/0x3e0
   ip_queue_xmit+0x34/0x40
   __tcp_transmit_skb+0x1625/0x1890
   __tcp_send_ack+0x1b8/0x340
   tcp_send_ack+0x23/0x30
   __tcp_ack_snd_check+0xa8/0x530
   ? srso_alias_return_thunk+0x5/0xfbef5
   tcp_rcv_established+0x412/0xd70
   tcp_v4_do_rcv+0x299/0x420
   tcp_v4_rcv+0x1991/0x1e10
   ip_protocol_deliver_rcu+0x50/0x220
   ip_local_deliver_finish+0x158/0x260
   ip_local_deliver+0xc8/0xe0
   ip_rcv+0xe5/0x1d0
   ? __pfx_ip_rcv+0x10/0x10
   __netif_receive_skb_one_core+0xce/0xe0
   ? process_backlog+0x28b/0x9f0
   __netif_receive_skb+0x34/0xd0
   ? process_backlog+0x28b/0x9f0
   process_backlog+0x2cb/0x9f0
   __napi_poll.constprop.0+0x61/0x280
   net_rx_action+0x332/0x670
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? find_held_lock+0x2b/0x80
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? srso_alias_return_thunk+0x5/0xfbef5
   handle_softirqs+0xda/0x480
   ? __dev_queue_xmit+0xa2c/0x1450
   do_softirq+0xa1/0xd0
   </IRQ>
   <TASK>
   __local_bh_enable_ip+0xc8/0xe0
   ? __dev_queue_xmit+0xa2c/0x1450
   __dev_queue_xmit+0xa48/0x1450
   ? ip_finish_output2+0xf4c/0x1130
   ip_finish_output2+0x6b6/0x1130
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? __ip_finish_output+0x217/0x380
   ? srso_alias_return_thunk+0x5/0xfbef5
   __ip_finish_output+0x217/0x380
   ip_output+0x99/0x120
   __ip_queue_xmit+0xae4/0xbc0
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? tcp_options_write.constprop.0+0xcb/0x3e0
   ip_queue_xmit+0x34/0x40
   __tcp_transmit_skb+0x1625/0x1890
   tcp_write_xmit+0x766/0x2fb0
   ? __entry_text_end+0x102ba9/0x102bad
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? __might_fault+0x74/0xc0
   ? srso_alias_return_thunk+0x5/0xfbef5
   __tcp_push_pending_frames+0x56/0x190
   tcp_push+0x117/0x310
   tcp_sendmsg_locked+0x14c1/0x1740
   tcp_sendmsg+0x28/0x40
   inet_sendmsg+0x5d/0x90
   sock_write_iter+0x242/0x2b0
   vfs_write+0x68d/0x800
   ? __pfx_sock_write_iter+0x10/0x10
   ksys_write+0xc8/0xf0
   __x64_sys_write+0x3d/0x50
   x64_sys_call+0xfaf/0x1f50
   do_syscall_64+0x6d/0x140
   entry_SYSCALL_64_after_hwframe+0x76/0x7e
  RIP: 0033:0x7f4d143af992
  Code: c3 8b 07 85 c0 75 24 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> e9 01 cc ff ff 41 54 b8 02 00 00 0
  RSP: 002b:00007ffd65032058 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
  RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f4d143af992
  RDX: 0000000000000025 RSI: 00007f4d143f3bcc RDI: 0000000000000005
  RBP: 00007f4d143f2b28 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4d143f3bcc
  R13: 0000000000000005 R14: 0000000000000000 R15: 00007ffd650323f0
   </TASK>

Fixes: 0b2c59720e ("l2tp: close all race conditions in l2tp_tunnel_register()")
Suggested-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot+6acef9e0a4d1f46c83d4@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=6acef9e0a4d1f46c83d4
CC: gnault@redhat.com
CC: cong.wang@bytedance.com
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Link: https://patch.msgid.link/20240806160626.1248317-1-jchapman@katalix.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-08-08 08:28:24 -07:00
James Chapman
5dfa598b24 l2tp: use pre_exit pernet hook to avoid rcu_barrier
Move the work of closing all tunnels from the pernet exit hook to
pre_exit since the core does rcu synchronisation between these steps
and we can therefore remove rcu_barrier from l2tp code.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-07-31 09:25:14 +01:00
James Chapman
0aa45570c3 l2tp: add idr consistency check in session_register
l2tp_session_register uses an idr_alloc then idr_replace pattern to
insert sessions into the session IDR. To catch invalid locking, add a
WARN_ON_ONCE if the IDR entry is modified by another thread between
alloc and replace steps.

Also add comments to make expectations clear.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-07-31 09:25:13 +01:00
James Chapman
89b768ec2d l2tp: use rcu list add/del when updating lists
l2tp_v3_session_htable and tunnel->session_list are read by lockless
getters using RCU. Use rcu list variants when adding or removing list
items.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-07-31 09:25:13 +01:00
James Chapman
24256415d1 l2tp: prevent possible tunnel refcount underflow
When a session is created, it sets a backpointer to its tunnel. When
the session refcount drops to 0, l2tp_session_free drops the tunnel
refcount if session->tunnel is non-NULL. However, session->tunnel is
set in l2tp_session_create, before the tunnel refcount is incremented
by l2tp_session_register, which leaves a small window where
session->tunnel is non-NULL when the tunnel refcount hasn't been
bumped.

Moving the assignment to l2tp_session_register is trivial but
l2tp_session_create calls l2tp_session_set_header_len which uses
session->tunnel to get the tunnel's encap. Add an encap arg to
l2tp_session_set_header_len to avoid using session->tunnel.

If l2tpv3 sessions have colliding IDs, it is possible for
l2tp_v3_session_get to race with l2tp_session_register and fetch a
session which doesn't yet have session->tunnel set. Add a check for
this case.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-07-31 09:25:13 +01:00
James Chapman
d17e899995 l2tp: free sessions using rcu
l2tp sessions may be accessed under an rcu read lock. Have them freed
via rcu and remove the now unneeded synchronize_rcu when a session is
removed.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-07-31 09:25:13 +01:00
James Chapman
fc7ec7f554 l2tp: delete sessions using work queue
When a tunnel is closed, l2tp_tunnel_closeall closes all sessions in
the tunnel. Move the work of deleting each session to the work queue
so that sessions are deleted using the same codepath whether they are
closed by user API request or their parent tunnel is closing. This
also avoids the locking dance in l2tp_tunnel_closeall where the
tunnel's session list lock was unlocked and relocked in the loop.

In l2tp_exit_net, use drain_workqueue instead of flush_workqueue
because the processing of tunnel_delete work may queue session_delete
work items which must also be processed.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-07-31 09:25:13 +01:00
James Chapman
29717a4fb7 l2tp: simplify tunnel and socket cleanup
When the l2tp tunnel socket used sk_user_data to point to its
associated l2tp tunnel, socket and tunnel cleanup had to make use of
the socket's destructor to free the tunnel only when the socket could
no longer be accessed.

Now that sk_user_data is no longer used, we can simplify socket and
tunnel cleanup:

  * If the tunnel closes first, it cleans up and drops its socket ref
    when the tunnel refcount drops to zero. If its socket was provided
    by userspace, the socket is closed and freed asynchronously, when
    userspace closes it. If its socket is a kernel socket, the tunnel
    closes the socket itself during cleanup and drops its socket ref
    when the tunnel's refcount drops to zero.

  * If the socket closes first, we initiate the closing of its
    associated tunnel. For UDP sockets, this is via the socket's
    encap_destroy hook. For L2TPIP sockets, this is via the socket's
    destroy callback. The tunnel holds a socket ref while it
    references the sock. When the tunnel is freed, it drops its socket
    ref and the socket will be cleaned up when its own refcount drops
    to zero, asynchronous to the tunnel free.

  * The tunnel socket destructor is no longer needed since the tunnel
    is no longer freed through the socket destructor.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-07-31 09:25:13 +01:00
James Chapman
0fa51a7c6f l2tp: remove unused tunnel magic field
Since l2tp no longer derives tunnel pointers directly via
sk_user_data, it is no longer useful for l2tp to check tunnel pointers
using a magic feather. Drop the tunnel's magic field.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-07-31 09:25:13 +01:00
James Chapman
4a4cd70369 l2tp: don't set sk_user_data in tunnel socket
l2tp no longer uses the tunnel socket's sk_user_data so drop the code
which sets it.

In l2tp_validate_socket use l2tp_sk_to_tunnel to check whether a given
socket is already attached to an l2tp tunnel since we can no longer
use non-null sk_user_data to indicate this.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-07-31 09:25:13 +01:00
James Chapman
2e7a280692 l2tp: lookup tunnel from socket without using sk_user_data
l2tp_sk_to_tunnel derives the tunnel from sk_user_data. Instead,
lookup the tunnel by walking the tunnel IDR for a tunnel using the
indicated sock. This is slow but l2tp_sk_to_tunnel is not used in
the datapath so performance isn't critical.

l2tp_tunnel_destruct needs a variant of l2tp_sk_to_tunnel which does
not bump the tunnel refcount since the tunnel refcount is already 0.

Change l2tp_sk_to_tunnel sk arg to const since it does not modify sk.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-07-31 09:25:12 +01:00
James Chapman
d587d82542 l2tp: make session IDR and tunnel session list coherent
Modify l2tp_session_register and l2tp_session_unhash so that the
session IDR and tunnel session lists remain coherent. To do so, hold
the session IDR lock and the tunnel's session list lock when making
any changes to either list.

Without this change, a rare race condition could hit the WARN_ON_ONCE
in l2tp_session_unhash if a thread replaced the IDR entry while
another thread was registering the same ID.

 [ 7126.151795][T17511] WARNING: CPU: 3 PID: 17511 at net/l2tp/l2tp_core.c:1282 l2tp_session_delete.part.0+0x87e/0xbc0
 [ 7126.163754][T17511]  ? show_regs+0x93/0xa0
 [ 7126.164157][T17511]  ? __warn+0xe5/0x3c0
 [ 7126.164536][T17511]  ? l2tp_session_delete.part.0+0x87e/0xbc0
 [ 7126.165070][T17511]  ? report_bug+0x2e1/0x500
 [ 7126.165486][T17511]  ? l2tp_session_delete.part.0+0x87e/0xbc0
 [ 7126.166013][T17511]  ? handle_bug+0x99/0x130
 [ 7126.166428][T17511]  ? exc_invalid_op+0x35/0x80
 [ 7126.166890][T17511]  ? asm_exc_invalid_op+0x1a/0x20
 [ 7126.167372][T17511]  ? l2tp_session_delete.part.0+0x87d/0xbc0
 [ 7126.167900][T17511]  ? l2tp_session_delete.part.0+0x87e/0xbc0
 [ 7126.168429][T17511]  ? __local_bh_enable_ip+0xa4/0x120
 [ 7126.168917][T17511]  l2tp_session_delete+0x40/0x50
 [ 7126.169369][T17511]  pppol2tp_release+0x1a1/0x3f0
 [ 7126.169817][T17511]  __sock_release+0xb3/0x270
 [ 7126.170247][T17511]  ? __pfx_sock_close+0x10/0x10
 [ 7126.170697][T17511]  sock_close+0x1c/0x30
 [ 7126.171087][T17511]  __fput+0x40b/0xb90
 [ 7126.171470][T17511]  task_work_run+0x16c/0x260
 [ 7126.171897][T17511]  ? __pfx_task_work_run+0x10/0x10
 [ 7126.172362][T17511]  ? srso_alias_return_thunk+0x5/0xfbef5
 [ 7126.172863][T17511]  ? do_raw_spin_unlock+0x174/0x230
 [ 7126.173348][T17511]  do_exit+0xaae/0x2b40
 [ 7126.173730][T17511]  ? srso_alias_return_thunk+0x5/0xfbef5
 [ 7126.174235][T17511]  ? __pfx_lock_release+0x10/0x10
 [ 7126.174690][T17511]  ? srso_alias_return_thunk+0x5/0xfbef5
 [ 7126.175190][T17511]  ? do_raw_spin_lock+0x12c/0x2b0
 [ 7126.175650][T17511]  ? __pfx_do_exit+0x10/0x10
 [ 7126.176072][T17511]  ? _raw_spin_unlock_irq+0x23/0x50
 [ 7126.176543][T17511]  do_group_exit+0xd3/0x2a0
 [ 7126.176990][T17511]  __x64_sys_exit_group+0x3e/0x50
 [ 7126.177456][T17511]  x64_sys_call+0x1821/0x1830
 [ 7126.177895][T17511]  do_syscall_64+0xcb/0x250
 [ 7126.178317][T17511]  entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fixes: aa5e17e1f5 ("l2tp: store l2tpv3 sessions in per-net IDR")
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240718134348.289865-1-jchapman@katalix.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2024-07-23 11:24:46 +02:00
James Chapman
2146b7dd35 l2tp: fix l2tp_session_register with colliding l2tpv3 IDs
When handling colliding L2TPv3 session IDs, we use the existing
session IDR entry and link the new session on that using
session->coll_list. However, when using an existing IDR entry, we must
not do the idr_replace step.

Fixes: aa5e17e1f5 ("l2tp: store l2tpv3 sessions in per-net IDR")
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-07-12 04:09:18 +01:00
James Chapman
f8ad00f3fb l2tp: fix possible UAF when cleaning up tunnels
syzbot reported a UAF caused by a race when the L2TP work queue closes a
tunnel at the same time as a userspace thread closes a session in that
tunnel.

Tunnel cleanup is handled by a work queue which iterates through the
sessions contained within a tunnel, and closes them in turn.

Meanwhile, a userspace thread may arbitrarily close a session via
either netlink command or by closing the pppox socket in the case of
l2tp_ppp.

The race condition may occur when l2tp_tunnel_closeall walks the list
of sessions in the tunnel and deletes each one.  Currently this is
implemented using list_for_each_safe, but because the list spinlock is
dropped in the loop body it's possible for other threads to manipulate
the list during list_for_each_safe's list walk.  This can lead to the
list iterator being corrupted, leading to list_for_each_safe spinning.
One sequence of events which may lead to this is as follows:

 * A tunnel is created, containing two sessions A and B.
 * A thread closes the tunnel, triggering tunnel cleanup via the work
   queue.
 * l2tp_tunnel_closeall runs in the context of the work queue.  It
   removes session A from the tunnel session list, then drops the list
   lock.  At this point the list_for_each_safe temporary variable is
   pointing to the other session on the list, which is session B, and
   the list can be manipulated by other threads since the list lock has
   been released.
 * Userspace closes session B, which removes the session from its parent
   tunnel via l2tp_session_delete.  Since l2tp_tunnel_closeall has
   released the tunnel list lock, l2tp_session_delete is able to call
   list_del_init on the session B list node.
 * Back on the work queue, l2tp_tunnel_closeall resumes execution and
   will now spin forever on the same list entry until the underlying
   session structure is freed, at which point UAF occurs.

The solution is to iterate over the tunnel's session list using
list_first_entry_not_null to avoid the possibility of the list
iterator pointing at a list item which may be removed during the walk.

Also, have l2tp_tunnel_closeall ref each session while it processes it
to prevent another thread from freeing it.

	cpu1				cpu2
	---				---
					pppol2tp_release()

	spin_lock_bh(&tunnel->list_lock);
	for (;;) {
		session = list_first_entry_or_null(&tunnel->session_list,
						   struct l2tp_session, list);
		if (!session)
			break;
		list_del_init(&session->list);
		spin_unlock_bh(&tunnel->list_lock);

 					l2tp_session_delete(session);

		l2tp_session_delete(session);
		spin_lock_bh(&tunnel->list_lock);
	}
	spin_unlock_bh(&tunnel->list_lock);

Calling l2tp_session_delete on the same session twice isn't a problem
per-se, but if cpu2 manages to destruct the socket and unref the
session to zero before cpu1 progresses then it would lead to UAF.

Reported-by: syzbot+b471b7c936301a59745b@syzkaller.appspotmail.com
Reported-by: syzbot+c041b4ce3a6dfd1e63e2@syzkaller.appspotmail.com
Fixes: d18d3f0a24 ("l2tp: replace hlist with simple list for per-tunnel session list")
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Link: https://patch.msgid.link/20240704152508.1923908-1-jchapman@katalix.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2024-07-09 11:06:21 +02:00
Thorsten Blum
47c130130d l2tp: Remove duplicate included header file trace.h
Remove duplicate included header file trace.h and the following warning
reported by make includecheck:

  trace.h is included more than once

Compile-tested only.

Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>
Link: https://patch.msgid.link/20240703061147.691973-2-thorsten.blum@toblux.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2024-07-04 12:37:58 +02:00
James Chapman
a8a8d89dbd l2tp: remove incorrect __rcu attribute
This fixes a sparse warning.

Fixes: d18d3f0a24 ("l2tp: replace hlist with simple list for per-tunnel session list")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202406220754.evK8Hrjw-lkp@intel.com/
Signed-off-by: James Chapman <jchapman@katalix.com>
Link: https://patch.msgid.link/20240624082945.1925009-1-jchapman@katalix.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-06-25 08:29:42 -07:00
James Chapman
d18d3f0a24 l2tp: replace hlist with simple list for per-tunnel session list
The per-tunnel session list is no longer used by the
datapath. However, we still need a list of sessions in the tunnel for
l2tp_session_get_nth, which is used by management code. (An
alternative might be to walk each session IDR list, matching only
sessions of a given tunnel.)

Replace the per-tunnel hlist with a per-tunnel list. In functions
which walk a list of sessions of a tunnel, walk this list instead.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-06-21 11:33:34 +01:00
James Chapman
8c6245af4f l2tp: drop the now unused l2tp_tunnel_get_session
All users of l2tp_tunnel_get_session are now gone so it can be
removed.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-06-21 11:33:34 +01:00
James Chapman
5f77c18ea5 l2tp: use IDR for all session lookups
Add generic session getter which uses IDR. Replace all users of
l2tp_tunnel_get_session which uses the per-tunnel session list to use
the generic getter.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-06-21 11:33:34 +01:00
James Chapman
c37e0138ca l2tp: don't use sk_user_data in l2tp_udp_encap_err_recv
If UDP sockets are aliased, sk might be the wrong socket. There's no
benefit to using sk_user_data to do some checks on the associated
tunnel context. Just report the error anyway, like udp core does.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-06-21 11:33:33 +01:00
James Chapman
ff6a2ac23c l2tp: refactor udp recv to lookup to not use sk_user_data
Modify UDP decap to not use the tunnel pointer which comes from the
sock's sk_user_data when parsing the L2TP header. By looking up the
destination session using only the packet contents we avoid potential
UDP 5-tuple aliasing issues which arise from depending on the socket
that received the packet.

Drop the useless error messages on short packet or on failing to find
a session since the tunnel pointer might point to a different tunnel
if multiple sockets use the same 5-tuple.

Short packets (those not big enough to contain an L2TP header) are no
longer counted in the tunnel's invalid counter because we can't derive
the tunnel until we parse the l2tp header to lookup the session.

l2tp_udp_encap_recv was a small wrapper around l2tp_udp_recv_core which
used sk_user_data to derive a tunnel pointer in an RCU-safe way. But
we no longer need the tunnel pointer, so remove that code and combine
the two functions.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-06-21 11:33:33 +01:00
James Chapman
2a3339f6c9 l2tp: store l2tpv2 sessions in per-net IDR
L2TPv2 sessions are currently kept in a per-tunnel hashlist, keyed by
16-bit session_id. When handling received L2TPv2 packets, we need to
first derive the tunnel using the 16-bit tunnel_id or sock, then
lookup the session in a per-tunnel hlist using the 16-bit session_id.

We want to avoid using sk_user_data in the datapath and double lookups
on every packet. So instead, use a per-net IDR to hold L2TPv2
sessions, keyed by a 32-bit value derived from the 16-bit tunnel_id
and session_id. This will allow the L2TPv2 UDP receive datapath to
lookup a session with a single lookup without deriving the tunnel
first.

L2TPv2 sessions are held in their own IDR to avoid potential
key collisions with L2TPv3 sessions.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-06-21 11:33:33 +01:00
James Chapman
aa5e17e1f5 l2tp: store l2tpv3 sessions in per-net IDR
L2TPv3 sessions are currently held in one of two fixed-size hash
lists: either a per-net hashlist (IP-encap), or a per-tunnel hashlist
(UDP-encap), keyed by the L2TPv3 32-bit session_id.

In order to lookup L2TPv3 sessions in UDP-encap tunnels efficiently
without finding the tunnel first via sk_user_data, UDP sessions are
now kept in a per-net session list, keyed by session ID. Convert the
existing per-net hashlist to use an IDR for better performance when
there are many sessions and have L2TPv3 UDP sessions use the same IDR.

Although the L2TPv3 RFC states that the session ID alone identifies
the session, our implementation has allowed the same session ID to be
used in different L2TP UDP tunnels. To retain support for this, a new
per-net session hashtable is used, keyed by the sock and session
ID. If on creating a new session, a session already exists with that
ID in the IDR, the colliding sessions are added to the new hashtable
and the existing IDR entry is flagged. When looking up sessions, the
approach is to first check the IDR and if no unflagged match is found,
check the new hashtable. The sock is made available to session getters
where session ID collisions are to be considered. In this way, the new
hashtable is used only for session ID collisions so can be kept small.

For managing session removal, we need a list of colliding sessions
matching a given ID in order to update or remove the IDR entry of the
ID. This is necessary to detect session ID collisions when future
sessions are created. The list head is allocated on first collision
of a given ID and refcounted.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-06-21 11:33:33 +01:00
James Chapman
a744e2d03a l2tp: remove unused list_head member in l2tp_tunnel
Remove an unused variable in struct l2tp_tunnel which was left behind
by commit c4d48a58f3 ("l2tp: convert l2tp_tunnel_list to idr").

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-06-21 11:33:33 +01:00
Tom Parkin
6e828dc60e l2tp: fix ICMP error handling for UDP-encap sockets
Since commit a36e185e8c
("udp: Handle ICMP errors for tunnels with same destination port on both endpoints")
UDP's handling of ICMP errors has allowed for UDP-encap tunnels to
determine socket associations in scenarios where the UDP hash lookup
could not.

Subsequently, commit d26796ae58
("udp: check udp sock encap_type in __udp_lib_err")
subtly tweaked the approach such that UDP ICMP error handling would be
skipped for any UDP socket which has encapsulation enabled.

In the case of L2TP tunnel sockets using UDP-encap, this latter
modification effectively broke ICMP error reporting for the L2TP
control plane.

To a degree this isn't catastrophic inasmuch as the L2TP control
protocol defines a reliable transport on top of the underlying packet
switching network which will eventually detect errors and time out.

However, paying attention to the ICMP error reporting allows for more
timely detection of errors in L2TP userspace, and aids in debugging
connectivity issues.

Reinstate ICMP error handling for UDP encap L2TP tunnels:

 * implement struct udp_tunnel_sock_cfg .encap_err_rcv in order to allow
   the L2TP code to handle ICMP errors;

 * only implement error-handling for tunnels which have a managed
   socket: unmanaged tunnels using a kernel socket have no userspace to
   report errors back to;

 * flag the error on the socket, which allows for userspace to get an
   error such as -ECONNREFUSED back from sendmsg/recvmsg;

 * pass the error into ip[v6]_icmp_error() which allows for userspace to
   get extended error information via. MSG_ERRQUEUE.

Fixes: d26796ae58 ("udp: check udp sock encap_type in __udp_lib_err")
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Link: https://lore.kernel.org/r/20240513172248.623261-1-tparkin@katalix.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-05-17 12:15:22 -07:00
Samuel Thibault
364798056f l2tp: Support different protocol versions with same IP/port quadruple
628bc3e5a1 ("l2tp: Support several sockets with same IP/port quadruple")
added support for several L2TPv2 tunnels using the same IP/port quadruple,
but if an L2TPv3 socket exists it could eat all the trafic. We thus have to
first use the version from the packet to get the proper tunnel, and only
then check that the version matches.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: James Chapman <jchapman@katalix.com>
Link: https://lore.kernel.org/r/20240509205812.4063198-1-samuel.thibault@ens-lyon.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-05-13 15:49:42 -07:00
Samuel Thibault
628bc3e5a1 l2tp: Support several sockets with same IP/port quadruple
Some l2tp providers will use 1701 as origin port and open several
tunnels for the same origin and target. On the Linux side, this
may mean opening several sockets, but then trafic will go to only
one of them, losing the trafic for the tunnel of the other socket
(or leaving it up to userland, consuming a lot of cpu%).

This can also happen when the l2tp provider uses a cluster, and
load-balancing happens to migrate from one origin IP to another one,
for which a socket was already established. Managing reassigning
tunnels from one socket to another would be very hairy for userland.

Lastly, as documented in l2tpconfig(1), as client it may be necessary
to use 1701 as origin port for odd firewalls reasons, which could
prevent from establishing several tunnels to a l2tp server, for the
same reason: trafic would get only on one of the two sockets.

With the V2 protocol it is however easy to route trafic to the proper
tunnel, by looking up the tunnel number in the network namespace. This
fixes the three cases altogether.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20240506215336.1470009-1-samuel.thibault@ens-lyon.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2024-05-09 15:50:36 +02:00
Eric Dumazet
70a36f5713 udp: annotate data-races around udp->encap_type
syzbot/KCSAN complained about UDP_ENCAP_L2TPINUDP setsockopt() racing.

Add READ_ONCE()/WRITE_ONCE() to document races on this lockless field.

syzbot report was:
BUG: KCSAN: data-race in udp_lib_setsockopt / udp_lib_setsockopt

read-write to 0xffff8881083603fa of 1 bytes by task 16557 on cpu 0:
udp_lib_setsockopt+0x682/0x6c0
udp_setsockopt+0x73/0xa0 net/ipv4/udp.c:2779
sock_common_setsockopt+0x61/0x70 net/core/sock.c:3697
__sys_setsockopt+0x1c9/0x230 net/socket.c:2263
__do_sys_setsockopt net/socket.c:2274 [inline]
__se_sys_setsockopt net/socket.c:2271 [inline]
__x64_sys_setsockopt+0x66/0x80 net/socket.c:2271
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

read-write to 0xffff8881083603fa of 1 bytes by task 16554 on cpu 1:
udp_lib_setsockopt+0x682/0x6c0
udp_setsockopt+0x73/0xa0 net/ipv4/udp.c:2779
sock_common_setsockopt+0x61/0x70 net/core/sock.c:3697
__sys_setsockopt+0x1c9/0x230 net/socket.c:2263
__do_sys_setsockopt net/socket.c:2274 [inline]
__se_sys_setsockopt net/socket.c:2271 [inline]
__x64_sys_setsockopt+0x66/0x80 net/socket.c:2271
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x01 -> 0x05

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16554 Comm: syz-executor.5 Not tainted 6.5.0-rc7-syzkaller-00004-gf7757129e3de #0

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2023-09-14 16:16:36 +02:00
Eric Dumazet
b9fb10d131 l2tp: prevent lockdep issue in l2tp_tunnel_register()
lockdep complains with the following lock/unlock sequence:

     lock_sock(sk);
     write_lock_bh(&sk->sk_callback_lock);
[1]  release_sock(sk);
[2]  write_unlock_bh(&sk->sk_callback_lock);

We need to swap [1] and [2] to fix this issue.

Fixes: 0b2c59720e ("l2tp: close all race conditions in l2tp_tunnel_register()")
Reported-by: syzbot+bbd35b345c7cab0d9a08@syzkaller.appspotmail.com
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/netdev/20230114030137.672706-1-xiyou.wangcong@gmail.com/T/#m1164ff20628671b0f326a24cb106ab3239c70ce3
Cc: Cong Wang <cong.wang@bytedance.com>
Cc: Guillaume Nault <gnault@redhat.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2023-01-18 14:44:54 +00:00
Cong Wang
0b2c59720e l2tp: close all race conditions in l2tp_tunnel_register()
The code in l2tp_tunnel_register() is racy in several ways:

1. It modifies the tunnel socket _after_ publishing it.

2. It calls setup_udp_tunnel_sock() on an existing socket without
   locking.

3. It changes sock lock class on fly, which triggers many syzbot
   reports.

This patch amends all of them by moving socket initialization code
before publishing and under sock lock. As suggested by Jakub, the
l2tp lockdep class is not necessary as we can just switch to
bh_lock_sock_nested().

Fixes: 37159ef2c1 ("l2tp: fix a lockdep splat")
Fixes: 6b9f34239b ("l2tp: fix races in tunnel creation")
Reported-by: syzbot+52866e24647f9a23403f@syzkaller.appspotmail.com
Reported-by: syzbot+94cc2a66fc228b23f360@syzkaller.appspotmail.com
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Guillaume Nault <gnault@redhat.com>
Cc: Jakub Sitnicki <jakub@cloudflare.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Parkin <tparkin@katalix.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2023-01-16 13:40:55 +00:00
Cong Wang
c4d48a58f3 l2tp: convert l2tp_tunnel_list to idr
l2tp uses l2tp_tunnel_list to track all registered tunnels and
to allocate tunnel ID's. IDR can do the same job.

More importantly, with IDR we can hold the ID before a successful
registration so that we don't need to worry about late error
handling, it is not easy to rollback socket changes.

This is a preparation for the following fix.

Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Guillaume Nault <gnault@redhat.com>
Cc: Jakub Sitnicki <jakub@cloudflare.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Parkin <tparkin@katalix.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2023-01-16 13:40:54 +00:00
Jakub Sitnicki
af295e854a l2tp: Don't sleep and disable BH under writer-side sk_callback_lock
When holding a reader-writer spin lock we cannot sleep. Calling
setup_udp_tunnel_sock() with write lock held violates this rule, because we
end up calling percpu_down_read(), which might sleep, as syzbot reports
[1]:

 __might_resched.cold+0x222/0x26b kernel/sched/core.c:9890
 percpu_down_read include/linux/percpu-rwsem.h:49 [inline]
 cpus_read_lock+0x1b/0x140 kernel/cpu.c:310
 static_key_slow_inc+0x12/0x20 kernel/jump_label.c:158
 udp_tunnel_encap_enable include/net/udp_tunnel.h:187 [inline]
 setup_udp_tunnel_sock+0x43d/0x550 net/ipv4/udp_tunnel_core.c:81
 l2tp_tunnel_register+0xc51/0x1210 net/l2tp/l2tp_core.c:1509
 pppol2tp_connect+0xcdc/0x1a10 net/l2tp/l2tp_ppp.c:723

Trim the writer-side critical section for sk_callback_lock down to the
minimum, so that it covers only operations on sk_user_data.

Also, when grabbing the sk_callback_lock, we always need to disable BH, as
Eric points out. Failing to do so leads to deadlocks because we acquire
sk_callback_lock in softirq context, which can get stuck waiting on us if:

1) it runs on the same CPU, or

       CPU0
       ----
  lock(clock-AF_INET6);
  <Interrupt>
    lock(clock-AF_INET6);

2) lock ordering leads to priority inversion

       CPU0                    CPU1
       ----                    ----
  lock(clock-AF_INET6);
                               local_irq_disable();
                               lock(&tcp_hashinfo.bhash[i].lock);
                               lock(clock-AF_INET6);
  <Interrupt>
    lock(&tcp_hashinfo.bhash[i].lock);

... as syzbot reports [2,3]. Use the _bh variants for write_(un)lock.

[1] https://lore.kernel.org/netdev/0000000000004e78ec05eda79749@google.com/
[2] https://lore.kernel.org/netdev/000000000000e38b6605eda76f98@google.com/
[3] https://lore.kernel.org/netdev/000000000000dfa31e05eda76f75@google.com/

v2:
- Check and set sk_user_data while holding sk_callback_lock for both
  L2TP encapsulation types (IP and UDP) (Tetsuo)

Cc: Tom Parkin <tparkin@katalix.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Fixes: b68777d54f ("l2tp: Serialize access to sk_user_data with sk_callback_lock")
Reported-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot+703d9e154b3b58277261@syzkaller.appspotmail.com
Reported-by: syzbot+50680ced9e98a61f7698@syzkaller.appspotmail.com
Reported-by: syzbot+de987172bb74a381879b@syzkaller.appspotmail.com
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2022-11-23 12:45:19 +00:00
Jakub Sitnicki
b68777d54f l2tp: Serialize access to sk_user_data with sk_callback_lock
sk->sk_user_data has multiple users, which are not compatible with each
other. Writers must synchronize by grabbing the sk->sk_callback_lock.

l2tp currently fails to grab the lock when modifying the underlying tunnel
socket fields. Fix it by adding appropriate locking.

We err on the side of safety and grab the sk_callback_lock also inside the
sk_destruct callback overridden by l2tp, even though there should be no
refs allowing access to the sock at the time when sk_destruct gets called.

v4:
- serialize write to sk_user_data in l2tp sk_destruct

v3:
- switch from sock lock to sk_callback_lock
- document write-protection for sk_user_data

v2:
- update Fixes to point to origin of the bug
- use real names in Reported/Tested-by tags

Cc: Tom Parkin <tparkin@katalix.com>
Fixes: 3557baabf2 ("[L2TP]: PPP over L2TP driver core")
Reported-by: Haowei Yan <g1042620637@gmail.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2022-11-16 12:52:19 +00:00
Tom Parkin
07b8ca3792 net/l2tp: convert tunnel rwlock_t to rcu
Previously commit e02d494d2c ("l2tp: Convert rwlock to RCU") converted
most, but not all, rwlock instances in the l2tp subsystem to RCU.

The remaining rwlock protects the per-tunnel hashlist of sessions which
is used for session lookups in the UDP-encap data path.

Convert the remaining rwlock to rcu to improve performance of UDP-encap
tunnels.

Note that the tunnel and session, which both live on RCU-protected
lists, use slightly different approaches to incrementing their refcounts
in the various getter functions.

The tunnel has to use refcount_inc_not_zero because the tunnel shutdown
process involves dropping the refcount to zero prior to synchronizing
RCU readers (via. kfree_rcu).

By contrast, the session shutdown removes the session from the list(s)
it is on, synchronizes with readers, and then decrements the session
refcount.  Since the getter functions increment the session refcount
with the RCU read lock held we prevent getters seeing a zero session
refcount, and therefore don't need to use refcount_inc_not_zero.

Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-11-29 12:11:25 +00:00
Xiyu Yang
9b6ff7eb66 net/l2tp: Fix reference count leak in l2tp_udp_recv_core
The reference count leak issue may take place in an error handling
path. If both conditions of tunnel->version == L2TP_HDR_VER_3 and the
return value of l2tp_v3_ensure_opt_in_linear is nonzero, the function
would directly jump to label invalid, without decrementing the reference
count of the l2tp_session object session increased earlier by
l2tp_tunnel_get_session(). This may result in refcount leaks.

Fix this issue by decrease the reference count before jumping to the
label invalid.

Fixes: 4522a70db7 ("l2tp: fix reading optional fields of L2TPv3")
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-09-09 11:00:20 +01:00
Gong, Sishuai
69e16d01d1 net: fix a concurrency bug in l2tp_tunnel_register()
l2tp_tunnel_register() registers a tunnel without fully
initializing its attribute. This can allow another kernel thread
running l2tp_xmit_core() to access the uninitialized data and
then cause a kernel NULL pointer dereference error, as shown below.

Thread 1    Thread 2
//l2tp_tunnel_register()
list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
           //pppol2tp_connect()
           tunnel = l2tp_tunnel_get(sock_net(sk), info.tunnel_id);
           // Fetch the new tunnel
           ...
           //l2tp_xmit_core()
           struct sock *sk = tunnel->sock;
           ...
           bh_lock_sock(sk);
           //Null pointer error happens
tunnel->sock = sk;

Fix this bug by initializing tunnel->sock before adding the
tunnel into l2tp_tunnel_list.

Reviewed-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Sishuai Gong <sishuai@purdue.edu>
Reported-by: Sishuai Gong <sishuai@purdue.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-04-27 14:23:13 -07:00
Bhaskar Chowdhury
aa785f93fc net: l2tp: Fix a typo
s/verifed/verified/

Signed-off-by: Bhaskar Chowdhury <unixbhaskar@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-03-22 13:17:49 -07:00
Matthias Schiffer
3e59e88567 net: l2tp: reduce log level of messages in receive path, add counter instead
Commit 5ee759cda5 ("l2tp: use standard API for warning log messages")
changed a number of warnings about invalid packets in the receive path
so that they are always shown, instead of only when a special L2TP debug
flag is set. Even with rate limiting these warnings can easily cause
significant log spam - potentially triggered by a malicious party
sending invalid packets on purpose.

In addition these warnings were noticed by projects like Tunneldigger [1],
which uses L2TP for its data path, but implements its own control
protocol (which is sufficiently different from L2TP data packets that it
would always be passed up to userspace even with future extensions of
L2TP).

Some of the warnings were already redundant, as l2tp_stats has a counter
for these packets. This commit adds one additional counter for invalid
packets that are passed up to userspace. Packets with unknown session are
not counted as invalid, as there is nothing wrong with the format of
these packets.

With the additional counter, all of these messages are either redundant
or benign, so we reduce them to pr_debug_ratelimited().

[1] https://github.com/wlanslovenija/tunneldigger/issues/160

Fixes: 5ee759cda5 ("l2tp: use standard API for warning log messages")
Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-03-03 16:55:02 -08:00
Tom Parkin
f52e4b27d1 l2tp: fix up inconsistent rx/tx statistics
Historically L2TP core statistics count the L2TP header in the
per-session and per-tunnel byte counts tracked for transmission and
receipt.

Now that l2tp_xmit_skb updates tx stats, it is necessary for
l2tp_xmit_core to pass out the length of the transmitted packet so that
the statistics can be updated correctly.

Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-09-18 14:36:54 -07:00
Tom Parkin
9d319a8e93 l2tp: avoid duplicated code in l2tp_tunnel_closeall
l2tp_tunnel_closeall is called as a part of tunnel shutdown in order to
close all the sessions held by the tunnel.  The code it uses to close a
session duplicates what l2tp_session_delete does.

Rather than duplicating the code, have l2tp_tunnel_closeall call
l2tp_session_delete instead.

This involves a very minor change to locking in l2tp_tunnel_closeall.
Previously, l2tp_tunnel_closeall checked the session "dead" flag while
holding tunnel->hlist_lock.  This allowed for the code to step to the
next session in the list without releasing the lock if the current
session happened to be in the process of closing already.

By calling l2tp_session_delete instead, l2tp_tunnel_closeall must now
drop and regain the hlist lock for each session in the tunnel list.
Given that the likelihood of a session being in the process of closing
when the tunnel is closed, it seems worth this very minor potential
loss of efficiency to avoid duplication of the session delete code.

Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-09-03 12:19:03 -07:00