In the tx path of l2tp, l2tp_xmit_skb() calls skb_dst_set() to set
skb's dst. However, it will eventually call inet6_csk_xmit() or
ip_queue_xmit() where skb's dst will be overwritten by:

   skb_dst_set_noref(skb, dst);

without releasing the old dst in skb. Then it causes dst/dev refcnt leak:

  unregister_netdevice: waiting for eth0 to become free. Usage count = 1

This can be reproduced by simply running:

  # modprobe l2tp_eth && modprobe l2tp_ip
  # sh ./tools/testing/selftests/net/l2tp.sh

So before going to inet6_csk_xmit() or ip_queue_xmit(), skb's dst
should be dropped. This patch is to fix it by removing skb_dst_set()
from l2tp_xmit_skb() and moving skb_dst_drop() into l2tp_xmit_core().

Fixes: 3557baab ("[L2TP]: PPP over L2TP driver core")
Reported-by: NHangbin Liu <liuhangbin@gmail.com>
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Acked-by: NJames Chapman <jchapman@katalix.com>
Tested-by: NJames Chapman <jchapman@katalix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

syzbot was able to trigger a crash after using an ISDN socket
and fool l2tp.

Fix this by making sure the UDP socket is of the proper family.

BUG: KASAN: slab-out-of-bounds in setup_udp_tunnel_sock+0x465/0x540 net/ipv4/udp_tunnel.c:78
Write of size 1 at addr ffff88808ed0c590 by task syz-executor.5/3018

CPU: 0 PID: 3018 Comm: syz-executor.5 Not tainted 5.7.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x188/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd3/0x413 mm/kasan/report.c:382
 __kasan_report.cold+0x20/0x38 mm/kasan/report.c:511
 kasan_report+0x33/0x50 mm/kasan/common.c:625
 setup_udp_tunnel_sock+0x465/0x540 net/ipv4/udp_tunnel.c:78
 l2tp_tunnel_register+0xb15/0xdd0 net/l2tp/l2tp_core.c:1523
 l2tp_nl_cmd_tunnel_create+0x4b2/0xa60 net/l2tp/l2tp_netlink.c:249
 genl_family_rcv_msg_doit net/netlink/genetlink.c:673 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:718 [inline]
 genl_rcv_msg+0x627/0xdf0 net/netlink/genetlink.c:735
 netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2469
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:746
 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
 netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
 netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:672
 ____sys_sendmsg+0x6e6/0x810 net/socket.c:2352
 ___sys_sendmsg+0x100/0x170 net/socket.c:2406
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2439
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45ca29
Code: 0d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007effe76edc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004fe1c0 RCX: 000000000045ca29
RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000005
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000094e R14: 00000000004d5d00 R15: 00007effe76ee6d4

Allocated by task 3018:
 save_stack+0x1b/0x40 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 __kasan_kmalloc mm/kasan/common.c:495 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:468
 __do_kmalloc mm/slab.c:3656 [inline]
 __kmalloc+0x161/0x7a0 mm/slab.c:3665
 kmalloc include/linux/slab.h:560 [inline]
 sk_prot_alloc+0x223/0x2f0 net/core/sock.c:1612
 sk_alloc+0x36/0x1100 net/core/sock.c:1666
 data_sock_create drivers/isdn/mISDN/socket.c:600 [inline]
 mISDN_sock_create+0x272/0x400 drivers/isdn/mISDN/socket.c:796
 __sock_create+0x3cb/0x730 net/socket.c:1428
 sock_create net/socket.c:1479 [inline]
 __sys_socket+0xef/0x200 net/socket.c:1521
 __do_sys_socket net/socket.c:1530 [inline]
 __se_sys_socket net/socket.c:1528 [inline]
 __x64_sys_socket+0x6f/0xb0 net/socket.c:1528
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 2484:
 save_stack+0x1b/0x40 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 kasan_set_free_info mm/kasan/common.c:317 [inline]
 __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:456
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x109/0x2b0 mm/slab.c:3757
 kvfree+0x42/0x50 mm/util.c:603
 __free_fdtable+0x2d/0x70 fs/file.c:31
 put_files_struct fs/file.c:420 [inline]
 put_files_struct+0x248/0x2e0 fs/file.c:413
 exit_files+0x7e/0xa0 fs/file.c:445
 do_exit+0xb04/0x2dd0 kernel/exit.c:791
 do_group_exit+0x125/0x340 kernel/exit.c:894
 get_signal+0x47b/0x24e0 kernel/signal.c:2739
 do_signal+0x81/0x2240 arch/x86/kernel/signal.c:784
 exit_to_usermode_loop+0x26c/0x360 arch/x86/entry/common.c:161
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
 do_syscall_64+0x6b1/0x7d0 arch/x86/entry/common.c:305
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

The buggy address belongs to the object at ffff88808ed0c000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1424 bytes inside of
 2048-byte region [ffff88808ed0c000, ffff88808ed0c800)
The buggy address belongs to the page:
page:ffffea00023b4300 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002838208 ffffea00015ba288 ffff8880aa000e00
raw: 0000000000000000 ffff88808ed0c000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808ed0c480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88808ed0c500: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88808ed0c580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                         ^
 ffff88808ed0c600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88808ed0c680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

Fixes: 6b9f3423 ("l2tp: fix races in tunnel creation")
Fixes: fd558d18 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: James Chapman <jchapman@katalix.com>
Cc: Guillaume Nault <gnault@redhat.com>
Reported-by: Nsyzbot <syzkaller@googlegroups.com>
Acked-by: NGuillaume Nault <gnault@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In the past it was possible to create multiple L2TPv3 sessions with the
same session id as long as the sessions belonged to different tunnels.
The resulting sessions had issues when used with IP encapsulated tunnels,
but worked fine with UDP encapsulated ones. Some applications began to
rely on this behaviour to avoid having to negotiate unique session ids.

Some time ago a change was made to require session ids to be unique across
all tunnels, breaking the applications making use of this "feature".

This change relaxes the duplicate session id check to allow duplicates
if both of the colliding sessions belong to UDP encapsulated tunnels.

Fixes: dbdbc73b ("l2tp: fix duplicate session creation")
Signed-off-by: NRidge Kennedy <ridge.kennedy@alliedtelesis.co.nz>
Acked-by: NJames Chapman <jchapman@katalix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Passing NULL to l2tp_pernet causes a crash via BUG_ON.
Dereferencing net in net_generic() also has the same effect.
This patch removes the redundant BUG_ON check on the same parameter.
Signed-off-by: NXu Wang <vulab@iscas.ac.cn>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

commit 174e2381
("sk_buff: drop all skb extensions on free and skb scrubbing") made napi
recycle always drop skb extensions.  The additional skb_ext_del() that is
performed via nf_reset on napi skb recycle is not needed anymore.

Most nf_reset() calls in the stack are there so queued skb won't block
'rmmod nf_conntrack' indefinitely.

This removes the skb_ext_del from nf_reset, and renames it to a more
fitting nf_reset_ct().

In a few selected places, add a call to skb_ext_reset to make sure that
no active extensions remain.

I am submitting this for "net", because we're still early in the release
cycle.  The patch applies to net-next too, but I think the rename causes
needless divergence between those trees.
Suggested-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NFlorian Westphal <fw@strlen.de>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

Based on 2 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NEnrico Weigelt <info@metux.net>
Reviewed-by: NKate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: NAllison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.deSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

BUG: unable to handle kernel NULL pointer dereference at 0000000000000128
PGD 0 P4D 0
Oops: 0000 [#1
CPU: 0 PID: 5697 Comm: modprobe Tainted: G        W         5.1.0-rc7+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
RIP: 0010:__lock_acquire+0x53/0x10b0
Code: 8b 1c 25 40 5e 01 00 4c 8b 6d 10 45 85 e4 0f 84 bd 06 00 00 44 8b 1d 7c d2 09 02 49 89 fe 41 89 d2 45 85 db 0f 84 47 02 00 00 <48> 81 3f a0 05 70 83 b8 00 00 00 00 44 0f 44 c0 83 fe 01 0f 86 3a
RSP: 0018:ffffc90001c07a28 EFLAGS: 00010002
RAX: 0000000000000000 RBX: ffff88822f038440 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000128
RBP: ffffc90001c07a88 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000001
R13: 0000000000000000 R14: 0000000000000128 R15: 0000000000000000
FS:  00007fead0811540(0000) GS:ffff888237a00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000128 CR3: 00000002310da000 CR4: 00000000000006f0
Call Trace:
 ? __lock_acquire+0x24e/0x10b0
 lock_acquire+0xdf/0x230
 ? flush_workqueue+0x71/0x530
 flush_workqueue+0x97/0x530
 ? flush_workqueue+0x71/0x530
 l2tp_exit_net+0x170/0x2b0 [l2tp_core
 ? l2tp_exit_net+0x93/0x2b0 [l2tp_core
 ops_exit_list.isra.6+0x36/0x60
 unregister_pernet_operations+0xb8/0x110
 unregister_pernet_device+0x25/0x40
 l2tp_init+0x55/0x1000 [l2tp_core
 ? 0xffffffffa018d000
 do_one_initcall+0x6c/0x3cc
 ? do_init_module+0x22/0x1f1
 ? rcu_read_lock_sched_held+0x97/0xb0
 ? kmem_cache_alloc_trace+0x325/0x3b0
 do_init_module+0x5b/0x1f1
 load_module+0x1db1/0x2690
 ? m_show+0x1d0/0x1d0
 __do_sys_finit_module+0xc5/0xd0
 __x64_sys_finit_module+0x15/0x20
 do_syscall_64+0x6b/0x1d0
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7fead031a839
Code: 00 f3 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 8b 0d 1f f6 2c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe8d9acca8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
RAX: ffffffffffffffda RBX: 0000560078398b80 RCX: 00007fead031a839
RDX: 0000000000000000 RSI: 000056007659dc2e RDI: 0000000000000003
RBP: 000056007659dc2e R08: 0000000000000000 R09: 0000560078398b80
R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000
R13: 00005600783a04a0 R14: 0000000000040000 R15: 0000560078398b80
Modules linked in: l2tp_core(+) e1000 ip_tables ipv6 [last unloaded: l2tp_core
CR2: 0000000000000128
---[ end trace 8322b2b8bf83f8e1

If alloc_workqueue fails in l2tp_init, l2tp_net_ops
is unregistered on failure path. Then l2tp_exit_net
is called which will flush NULL workqueue, this patch
add a NULL check to fix it.

Fixes: 67e04c29 ("l2tp: unregister l2tp_net_ops on failure path")
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Acked-by: NGuillaume Nault <gnault@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Before taking a refcount on a rcu protected structure,
we need to make sure the refcount is not zero.

syzbot reported :

refcount_t: increment on 0; use-after-free.
WARNING: CPU: 1 PID: 23533 at lib/refcount.c:156 refcount_inc_checked lib/refcount.c:156 [inline]
WARNING: CPU: 1 PID: 23533 at lib/refcount.c:156 refcount_inc_checked+0x61/0x70 lib/refcount.c:154
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 23533 Comm: syz-executor.2 Not tainted 5.1.0-rc7+ #93
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 panic+0x2cb/0x65c kernel/panic.c:214
 __warn.cold+0x20/0x45 kernel/panic.c:571
 report_bug+0x263/0x2b0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:179 [inline]
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:refcount_inc_checked lib/refcount.c:156 [inline]
RIP: 0010:refcount_inc_checked+0x61/0x70 lib/refcount.c:154
Code: 1d 98 2b 2a 06 31 ff 89 de e8 db 2c 40 fe 84 db 75 dd e8 92 2b 40 fe 48 c7 c7 20 7a a1 87 c6 05 78 2b 2a 06 01 e8 7d d9 12 fe <0f> 0b eb c1 90 90 90 90 90 90 90 90 90 90 90 55 48 89 e5 41 57 41
RSP: 0018:ffff888069f0fba8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 000000000000f353 RSI: ffffffff815afcb6 RDI: ffffed100d3e1f67
RBP: ffff888069f0fbb8 R08: ffff88809b1845c0 R09: ffffed1015d23ef1
R10: ffffed1015d23ef0 R11: ffff8880ae91f787 R12: ffff8880a8f26968
R13: 0000000000000004 R14: dffffc0000000000 R15: ffff8880a49a6440
 l2tp_tunnel_inc_refcount net/l2tp/l2tp_core.h:240 [inline]
 l2tp_tunnel_get+0x250/0x580 net/l2tp/l2tp_core.c:173
 pppol2tp_connect+0xc00/0x1c70 net/l2tp/l2tp_ppp.c:702
 __sys_connect+0x266/0x330 net/socket.c:1808
 __do_sys_connect net/socket.c:1819 [inline]
 __se_sys_connect net/socket.c:1816 [inline]
 __x64_sys_connect+0x73/0xb0 net/socket.c:1816

Fixes: 54652eb1 ("l2tp: hold tunnel while looking up sessions in l2tp_netlink")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Reported-by: Nsyzbot <syzkaller@googlegroups.com>
Cc: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Canonical way to fetch sk_user_data from an encap_rcv() handler called
from UDP stack in rcu protected section is to use rcu_dereference_sk_user_data(),
otherwise compiler might read it multiple times.

Fixes: d00fa9ad ("il2tp: fix races with tunnel socket close")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: James Chapman <jchapman@katalix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The size of L2TPv2 header with all optional fields is 14 bytes.
l2tp_udp_recv_core only moves 10 bytes to the linear part of a
skb. This may lead to l2tp_recv_common read data outside of a skb.

This patch make sure that there is at least 14 bytes in the linear
part of a skb to meet the maximum need of l2tp_udp_recv_core and
l2tp_recv_common. The minimum size of both PPP HDLC-like frame and
Ethernet frame is larger than 14 bytes, so we are safe to do so.

Also remove L2TP_HDR_SIZE_NOSEQ, it is unused now.

Fixes: fd558d18 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Suggested-by: NGuillaume Nault <gnault@redhat.com>
Signed-off-by: NJacob Wen <jian.w.wen@oracle.com>
Acked-by: NGuillaume Nault <gnault@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Use pskb_may_pull() to make sure the optional fields are in skb linear
parts, so we can safely read them later.

It's easy to reproduce the issue with a net driver that supports paged
skb data. Just create a L2TPv3 over IP tunnel and then generates some
network traffic.
Once reproduced, rx err in /sys/kernel/debug/l2tp/tunnels will increase.

Changes in v4:
1. s/l2tp_v3_pull_opt/l2tp_v3_ensure_opt_in_linear/
2. s/tunnel->version != L2TP_HDR_VER_2/tunnel->version == L2TP_HDR_VER_3/
3. Add 'Fixes' in commit messages.

Changes in v3:
1. To keep consistency, move the code out of l2tp_recv_common.
2. Use "net" instead of "net-next", since this is a bug fix.

Changes in v2:
1. Only fix L2TPv3 to make code simple.
   To fix both L2TPv3 and L2TPv2, we'd better refactor l2tp_recv_common.
   It's complicated to do so.
2. Reloading pointers after pskb_may_pull

Fixes: f7faffa3 ("l2tp: Add L2TPv3 protocol support")
Fixes: 0d76751f ("l2tp: Add L2TPv3 IP encapsulation (no UDP) support")
Fixes: a32e0eec ("l2tp: introduce L2TPv3 IP encapsulation support for IPv6")
Signed-off-by: NJacob Wen <jian.w.wen@oracle.com>
Acked-by: NGuillaume Nault <gnault@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This issue happens when trying to add an existent tunnel. It
doesn't call sock_put() before returning -EEXIST to release
the sock refcnt that was held by calling sock_hold() before
the existence check.

This patch is to fix it by holding the sock after doing the
existence check.

Fixes: f6cd651b ("l2tp: fix race in duplicate tunnel detection")
Reported-by: NJianlin Shi <jishi@redhat.com>
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Reviewed-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In l2tp code, if it is a L2TP_UDP_ENCAP tunnel, tunnel->sk points to a
UDP socket. User could call sendmsg() on both this tunnel and the UDP
socket itself concurrently. As l2tp_xmit_skb() holds socket lock and call
__sk_dst_check() to refresh sk->sk_dst_cache, while udpv6_sendmsg() is
lockless and call sk_dst_check() to refresh sk->sk_dst_cache, there
could be a race and cause the dst cache to be freed multiple times.
So we fix l2tp side code to always call sk_dst_check() to garantee
xchg() is called when refreshing sk->sk_dst_cache to avoid race
conditions.

Syzkaller reported stack trace:
BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_unless include/linux/atomic.h:575 [inline]
BUG: KASAN: use-after-free in atomic_add_unless include/linux/atomic.h:597 [inline]
BUG: KASAN: use-after-free in dst_hold_safe include/net/dst.h:308 [inline]
BUG: KASAN: use-after-free in ip6_hold_safe+0xe6/0x670 net/ipv6/route.c:1029
Read of size 4 at addr ffff8801aea9a880 by task syz-executor129/4829

CPU: 0 PID: 4829 Comm: syz-executor129 Not tainted 4.18.0-rc7-next-20180802+ #30
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
 kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272
 atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
 atomic_fetch_add_unless include/linux/atomic.h:575 [inline]
 atomic_add_unless include/linux/atomic.h:597 [inline]
 dst_hold_safe include/net/dst.h:308 [inline]
 ip6_hold_safe+0xe6/0x670 net/ipv6/route.c:1029
 rt6_get_pcpu_route net/ipv6/route.c:1249 [inline]
 ip6_pol_route+0x354/0xd20 net/ipv6/route.c:1922
 ip6_pol_route_output+0x54/0x70 net/ipv6/route.c:2098
 fib6_rule_lookup+0x283/0x890 net/ipv6/fib6_rules.c:122
 ip6_route_output_flags+0x2c5/0x350 net/ipv6/route.c:2126
 ip6_dst_lookup_tail+0x1278/0x1da0 net/ipv6/ip6_output.c:978
 ip6_dst_lookup_flow+0xc8/0x270 net/ipv6/ip6_output.c:1079
 ip6_sk_dst_lookup_flow+0x5ed/0xc50 net/ipv6/ip6_output.c:1117
 udpv6_sendmsg+0x2163/0x36b0 net/ipv6/udp.c:1354
 inet_sendmsg+0x1a1/0x690 net/ipv4/af_inet.c:798
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:632
 ___sys_sendmsg+0x51d/0x930 net/socket.c:2115
 __sys_sendmmsg+0x240/0x6f0 net/socket.c:2210
 __do_sys_sendmmsg net/socket.c:2239 [inline]
 __se_sys_sendmmsg net/socket.c:2236 [inline]
 __x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2236
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x446a29
Code: e8 ac b8 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 0f 83 eb 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f4de5532db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00000000006dcc38 RCX: 0000000000446a29
RDX: 00000000000000b8 RSI: 0000000020001b00 RDI: 0000000000000003
RBP: 00000000006dcc30 R08: 00007f4de5533700 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dcc3c
R13: 00007ffe2b830fdf R14: 00007f4de55339c0 R15: 0000000000000001

Fixes: 71b1391a ("l2tp: ensure sk->dst is still valid")
Reported-by: syzbot+05f840f3b04f211bad55@syzkaller.appspotmail.com
Signed-off-by: NWei Wang <weiwan@google.com>
Signed-off-by: NMartin KaFai Lau <kafai@fb.com>
Cc: Guillaume Nault <g.nault@alphalink.fr>
Cc: David Ahern <dsahern@gmail.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

l2tp_session_get() is used for two different purposes. If 'tunnel' is
NULL, the session is searched globally in the supplied network
namespace. Otherwise it is searched exclusively in the tunnel context.

Callers always know the context in which they need to search the
session. But some of them do provide both a namespace and a tunnel,
making the semantic of the call unclear.

This patch defines l2tp_tunnel_get_session() for lookups done in a
tunnel and restricts l2tp_session_get() to namespace searches.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This attribute's handling is broken. It can only be used when creating
Ethernet pseudo-wires, in which case its value can be used as the
initial MTU for the l2tpeth device.
However, when handling update requests, L2TP_ATTR_MTU only modifies
session->mtu. This value is never propagated to the l2tpeth device.
Dump requests also return the value of session->mtu, which is not
synchronised anymore with the device MTU.

The same problem occurs if the device MTU is properly updated using the
generic IFLA_MTU attribute. In this case, session->mtu is not updated,
and L2TP_ATTR_MTU will report an invalid value again when dumping the
session.

It does not seem worthwhile to complexify l2tp_eth.c to synchronise
session->mtu with the device MTU. Even the ip-l2tp manpage advises to
use 'ip link' to initialise the MTU of l2tpeth devices (iproute2 does
not handle L2TP_ATTR_MTU at all anyway). So let's just ignore it
entirely.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This field is not used.

Treat PPPIOC*MRU the same way as PPPIOC*FLAGS: "get" requests return 0,
while "set" requests vadidate the user supplied pointer but discard its
value.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The tunnel reception hook is only used by l2tp_ppp for skipping PPP
framing bytes. This is a session specific operation, but once a PPP
session sets ->recv_payload_hook on its tunnel, all frames received by
the tunnel will enter pppol2tp_recv_payload_hook(), including those
targeted at Ethernet sessions (an L2TPv3 tunnel can multiplex PPP and
Ethernet sessions).

So this mechanism is wrong, and uselessly complex. Let's just move this
functionality to the pppol2tp rx handler and drop ->recv_payload_hook.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NStephen Hemminger <stephen@networkplumber.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

It always returns 0, and nobody reads the return value anyway.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Replace 'l2tp_pernet(tunnel->l2tp_net)' with 'pn', which has been set
on the preceding line.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This function is only used in l2tp_core.c.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This function is only used in l2tp_core.c.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Use l2tp_tunnel_get_nth() instead of l2tp_tunnel_find_nth(), to be safe
against concurrent tunnel deletion.

Use the same mechanism as in l2tp_ppp.c for dropping the reference
taken by l2tp_tunnel_get_nth(). That is, drop the reference just
before looking up the next tunnel. In case of error, drop the last
accessed tunnel in l2tp_dfs_seq_stop().

That was the last use of l2tp_tunnel_find_nth().

Fixes: 0ad66140 ("l2tp: Add debugfs files for dumping l2tp debug info")
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

l2tp_tunnel_find_nth() is unsafe: no reference is held on the returned
tunnel, therefore it can be freed whenever the caller uses it.
This patch defines l2tp_tunnel_get_nth() which works similarly, but
also takes a reference on the returned tunnel. The caller then has to
drop it after it stops using the tunnel.

Convert netlink dumps to make them safe against concurrent tunnel
deletion.

Fixes: 309795f4 ("l2tp: Add netlink control API for L2TP")
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

We can't use l2tp_tunnel_find() to prevent l2tp_nl_cmd_tunnel_create()
from creating a duplicate tunnel. A tunnel can be concurrently
registered after l2tp_tunnel_find() returns. Therefore, searching for
duplicates must be done at registration time.

Finally, remove l2tp_tunnel_find() entirely as it isn't use anywhere
anymore.

Fixes: 309795f4 ("l2tp: Add netlink control API for L2TP")
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

l2tp_tunnel_create() inserts the new tunnel into the namespace's tunnel
list and sets the socket's ->sk_user_data field, before returning it to
the caller. Therefore, there are two ways the tunnel can be accessed
and freed, before the caller even had the opportunity to take a
reference. In practice, syzbot could crash the module by closing the
socket right after a new tunnel was returned to pppol2tp_create().

This patch moves tunnel registration out of l2tp_tunnel_create(), so
that the caller can safely hold a reference before publishing the
tunnel. This second step is done with the new l2tp_tunnel_register()
function, which is now responsible for associating the tunnel to its
socket and for inserting it into the namespace's list.

While moving the code to l2tp_tunnel_register(), a few modifications
have been done. First, the socket validation tests are done in a helper
function, for clarity. Also, modifying the socket is now done after
having inserted the tunnel to the namespace's tunnels list. This will
allow insertion to fail, without having to revert theses modifications
in the error path (a followup patch will check for duplicate tunnels
before insertion). Either the socket is a kernel socket which we
control, or it is a user-space socket for which we have a reference on
the file descriptor. In any case, the socket isn't going to be closed
from under us.

Reported-by: syzbot+fbeeb5c3b538e8545644@syzkaller.appspotmail.com
Fixes: fd558d18 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Synchronous pernet_operations are not allowed anymore.
All are asynchronous. So, drop the structure member.
Signed-off-by: NKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Init method is rather simple. Exit method queues del_work
for every tunnel from per-net list. This seems to be safe
to be marked async.
Signed-off-by: NKirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The l2tp_tunnel_create() function checks for v4mapped ipv6
sockets and cache that flag, so that l2tp core code can
reusing it at xmit time.

If the socket is provided by the userspace, the connection
status of the tunnel sockets can change between the tunnel
creation and the xmit call, so that syzbot is able to
trigger the following splat:

BUG: KASAN: use-after-free in ip6_dst_idev include/net/ip6_fib.h:192
[inline]
BUG: KASAN: use-after-free in ip6_xmit+0x1f76/0x2260
net/ipv6/ip6_output.c:264
Read of size 8 at addr ffff8801bd949318 by task syz-executor4/23448

CPU: 0 PID: 23448 Comm: syz-executor4 Not tainted 4.16.0-rc4+ #65
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x24d lib/dump_stack.c:53
  print_address_description+0x73/0x250 mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report+0x23c/0x360 mm/kasan/report.c:412
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
  ip6_dst_idev include/net/ip6_fib.h:192 [inline]
  ip6_xmit+0x1f76/0x2260 net/ipv6/ip6_output.c:264
  inet6_csk_xmit+0x2fc/0x580 net/ipv6/inet6_connection_sock.c:139
  l2tp_xmit_core net/l2tp/l2tp_core.c:1053 [inline]
  l2tp_xmit_skb+0x105f/0x1410 net/l2tp/l2tp_core.c:1148
  pppol2tp_sendmsg+0x470/0x670 net/l2tp/l2tp_ppp.c:341
  sock_sendmsg_nosec net/socket.c:630 [inline]
  sock_sendmsg+0xca/0x110 net/socket.c:640
  ___sys_sendmsg+0x767/0x8b0 net/socket.c:2046
  __sys_sendmsg+0xe5/0x210 net/socket.c:2080
  SYSC_sendmsg net/socket.c:2091 [inline]
  SyS_sendmsg+0x2d/0x50 net/socket.c:2087
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x453e69
RSP: 002b:00007f819593cc68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f819593d6d4 RCX: 0000000000453e69
RDX: 0000000000000081 RSI: 000000002037ffc8 RDI: 0000000000000004
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000004c3 R14: 00000000006f72e8 R15: 0000000000000000

This change addresses the issues:
* explicitly checking for TCP_ESTABLISHED for user space provided sockets
* dropping the v4mapped flag usage - it can become outdated - and
  explicitly invoking ipv6_addr_v4mapped() instead

The issue is apparently there since ancient times.

v1 -> v2: (many thanks to Guillaume)
 - with csum issue introduced in v1
 - replace pr_err with pr_debug
 - fix build issue with IPV6 disabled
 - move l2tp_sk_is_v4mapped in l2tp_core.c

v2 -> v3:
 - don't update inet_daddr for v4mapped address, unneeded
 - drop rendundant check at creation time

Reported-and-tested-by: syzbot+92fa328176eb07e4ac1a@syzkaller.appspotmail.com
Fixes: 3557baab ("[L2TP]: PPP over L2TP driver core")
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

syzkaller found an issue caused by lack of sufficient checks
in l2tp_tunnel_create()

RAW sockets can not be considered as UDP ones for instance.

In another patch, we shall replace all pr_err() by less intrusive
pr_debug() so that syzkaller can find other bugs faster.
Acked-by: NGuillaume Nault <g.nault@alphalink.fr>
Acked-by: NJames Chapman <jchapman@katalix.com>

==================================================================
BUG: KASAN: slab-out-of-bounds in setup_udp_tunnel_sock+0x3ee/0x5f0 net/ipv4/udp_tunnel.c:69
dst_release: dst:00000000d53d0d0f refcnt:-1
Write of size 1 at addr ffff8801d013b798 by task syz-executor3/6242

CPU: 1 PID: 6242 Comm: syz-executor3 Not tainted 4.16.0-rc2+ #253
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23b/0x360 mm/kasan/report.c:412
 __asan_report_store1_noabort+0x17/0x20 mm/kasan/report.c:435
 setup_udp_tunnel_sock+0x3ee/0x5f0 net/ipv4/udp_tunnel.c:69
 l2tp_tunnel_create+0x1354/0x17f0 net/l2tp/l2tp_core.c:1596
 pppol2tp_connect+0x14b1/0x1dd0 net/l2tp/l2tp_ppp.c:707
 SYSC_connect+0x213/0x4a0 net/socket.c:1640
 SyS_connect+0x24/0x30 net/socket.c:1621
 do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Fixes: fd558d18 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Reported-by: Nsyzbot <syzkaller@googlegroups.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

l2tp_tunnel_get walks the tunnel list to find a matching tunnel
instance and if a match is found, its refcount is increased before
returning the tunnel pointer. But when tunnel objects are destroyed,
they are on the tunnel list after their refcount hits zero. Fix this
by moving the code that removes the tunnel from the tunnel list from
the tunnel socket destructor into in the l2tp_tunnel_delete path,
before the tunnel refcount is decremented.

refcount_t: increment on 0; use-after-free.
WARNING: CPU: 3 PID: 13507 at lib/refcount.c:153 refcount_inc+0x47/0x50
Modules linked in:
CPU: 3 PID: 13507 Comm: syzbot_6e6a5ec8 Not tainted 4.16.0-rc2+ #36
Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
RIP: 0010:refcount_inc+0x47/0x50
RSP: 0018:ffff8800136ffb20 EFLAGS: 00010286
RAX: dffffc0000000008 RBX: ffff880017068e68 RCX: ffffffff814d3333
RDX: 0000000000000000 RSI: ffff88001a59f6d8 RDI: ffff88001a59f6d8
RBP: ffff8800136ffb28 R08: 0000000000000000 R09: 0000000000000000
R10: ffff8800136ffab0 R11: 0000000000000000 R12: ffff880017068e50
R13: 0000000000000000 R14: ffff8800174da800 R15: 0000000000000004
FS:  00007f403ab1e700(0000) GS:ffff88001a580000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000205fafd2 CR3: 0000000016770000 CR4: 00000000000006e0
Call Trace:
 l2tp_tunnel_get+0x2dd/0x4e0
 pppol2tp_connect+0x428/0x13c0
 ? pppol2tp_session_create+0x170/0x170
 ? __might_fault+0x115/0x1d0
 ? lock_downgrade+0x860/0x860
 ? __might_fault+0xe5/0x1d0
 ? security_socket_connect+0x8e/0xc0
 SYSC_connect+0x1b6/0x310
 ? SYSC_bind+0x280/0x280
 ? __do_page_fault+0x5d1/0xca0
 ? up_read+0x1f/0x40
 ? __do_page_fault+0x3c8/0xca0
 SyS_connect+0x29/0x30
 ? SyS_accept+0x40/0x40
 do_syscall_64+0x1e0/0x730
 ? trace_hardirqs_off_thunk+0x1a/0x1c
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f403a42f259
RSP: 002b:00007f403ab1dee8 EFLAGS: 00000296 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00000000205fafe4 RCX: 00007f403a42f259
RDX: 000000000000002e RSI: 00000000205fafd2 RDI: 0000000000000004
RBP: 00007f403ab1df20 R08: 00007f403ab1e700 R09: 0000000000000000
R10: 00007f403ab1e700 R11: 0000000000000296 R12: 0000000000000000
R13: 00007ffc81906cbf R14: 0000000000000000 R15: 00007f403ab2b040
Code: 3b ff 5b 5d c3 e8 ca 5f 3b ff 80 3d 49 8e 66 04 00 75 ea e8 bc 5f 3b ff 48 c7 c7 60 69 64 85 c6 05 34 8e 66 04 01 e8 59 49 15 ff <0f> 0b eb ce 0f 1f 44 00 00 55 48 89 e5 41 56 41 55 41 54 53 49

Fixes: f8ccac0e ("l2tp: put tunnel socket release on a workqueue")
Reported-and-tested-by: syzbot+19c09769f14b48810113@syzkaller.appspotmail.com
Reported-and-tested-by: syzbot+347bd5acde002e353a36@syzkaller.appspotmail.com
Reported-and-tested-by: syzbot+6e6a5ec8de31a94cd015@syzkaller.appspotmail.com
Reported-and-tested-by: syzbot+9df43faf09bd400f2993@syzkaller.appspotmail.com
Signed-off-by: NJames Chapman <jchapman@katalix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The tunnel socket tunnel->sock (struct sock) is accessed when
preparing a new ppp session on a tunnel at pppol2tp_session_init. If
the socket is closed by a thread while another is creating a new
session, the threads race. In pppol2tp_connect, the tunnel object may
be created if the pppol2tp socket is associated with the special
session_id 0 and the tunnel socket is looked up using the provided
fd. When handling this, pppol2tp_connect cannot sock_hold the tunnel
socket to prevent it being destroyed during pppol2tp_connect since
this may itself may race with the socket being destroyed. Doing
sockfd_lookup in pppol2tp_connect isn't sufficient to prevent
tunnel->sock going away either because a given tunnel socket fd may be
reused between calls to pppol2tp_connect. Instead, have
l2tp_tunnel_create sock_hold the tunnel socket before it does
sockfd_put. This ensures that the tunnel's socket is always extant
while the tunnel object exists. Hold a ref on the socket until the
tunnel is destroyed and ensure that all tunnel destroy paths go
through a common function (l2tp_tunnel_delete) since this will do the
final sock_put to release the tunnel socket.

Since the tunnel's socket is now guaranteed to exist if the tunnel
exists, we no longer need to use sockfd_lookup via l2tp_sock_to_tunnel
to derive the tunnel from the socket since this is always
sk_user_data.

Also, sessions no longer sock_hold the tunnel socket since sessions
already hold a tunnel ref and the tunnel sock will not be freed until
the tunnel is freed. Removing these sock_holds in
l2tp_session_register avoids a possible sock leak in the
pppol2tp_connect error path if l2tp_session_register succeeds but
attaching a ppp channel fails. The pppol2tp_connect error path could
have been fixed instead and have the sock ref dropped when the session
is freed, but doing a sock_put of the tunnel socket when the session
is freed would require a new session_free callback. It is simpler to
just remove the sock_hold of the tunnel socket in
l2tp_session_register, now that the tunnel socket lifetime is
guaranteed.

Finally, some init code in l2tp_tunnel_create is reordered to ensure
that the new tunnel object's refcount is set and the tunnel socket ref
is taken before the tunnel socket destructor callbacks are set.

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Modules linked in:
CPU: 0 PID: 4360 Comm: syzbot_19c09769 Not tainted 4.16.0-rc2+ #34
Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
RIP: 0010:pppol2tp_session_init+0x1d6/0x500
RSP: 0018:ffff88001377fb40 EFLAGS: 00010212
RAX: dffffc0000000000 RBX: ffff88001636a940 RCX: ffffffff84836c1d
RDX: 0000000000000045 RSI: 0000000055976744 RDI: 0000000000000228
RBP: ffff88001377fb60 R08: ffffffff84836bc8 R09: 0000000000000002
R10: ffff88001377fab8 R11: 0000000000000001 R12: 0000000000000000
R13: ffff88001636aac8 R14: ffff8800160f81c0 R15: 1ffff100026eff76
FS:  00007ffb3ea66700(0000) GS:ffff88001a400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020e77000 CR3: 0000000016261000 CR4: 00000000000006f0
Call Trace:
 pppol2tp_connect+0xd18/0x13c0
 ? pppol2tp_session_create+0x170/0x170
 ? __might_fault+0x115/0x1d0
 ? lock_downgrade+0x860/0x860
 ? __might_fault+0xe5/0x1d0
 ? security_socket_connect+0x8e/0xc0
 SYSC_connect+0x1b6/0x310
 ? SYSC_bind+0x280/0x280
 ? __do_page_fault+0x5d1/0xca0
 ? up_read+0x1f/0x40
 ? __do_page_fault+0x3c8/0xca0
 SyS_connect+0x29/0x30
 ? SyS_accept+0x40/0x40
 do_syscall_64+0x1e0/0x730
 ? trace_hardirqs_off_thunk+0x1a/0x1c
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7ffb3e376259
RSP: 002b:00007ffeda4f6508 EFLAGS: 00000202 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000020e77012 RCX: 00007ffb3e376259
RDX: 000000000000002e RSI: 0000000020e77000 RDI: 0000000000000004
RBP: 00007ffeda4f6540 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000400b60
R13: 00007ffeda4f6660 R14: 0000000000000000 R15: 0000000000000000
Code: 80 3d b0 ff 06 02 00 0f 84 07 02 00 00 e8 13 d6 db fc 49 8d bc 24 28 02 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 f
a 48 c1 ea 03 <80> 3c 02 00 0f 85 ed 02 00 00 4d 8b a4 24 28 02 00 00 e8 13 16

Fixes: 80d84ef3 ("l2tp: prevent l2tp_tunnel_delete racing with userspace close")
Signed-off-by: NJames Chapman <jchapman@katalix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Previously, if a tunnel was closed, we called inet_shutdown to mark
the socket as unconnected such that userspace would get errors and
then close the socket. This could race with userspace closing the
socket. Instead, leave userspace to close the socket in its own time
(our tunnel will be detached anyway).

BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0
IP: __lock_acquire+0x263/0x1630
PGD 0 P4D 0
Oops: 0000 [#1] SMP KASAN
Modules linked in:
CPU: 2 PID: 42 Comm: kworker/u8:2 Not tainted 4.15.0-rc7+ #129
Workqueue: l2tp l2tp_tunnel_del_work
RIP: 0010:__lock_acquire+0x263/0x1630
RSP: 0018:ffff88001a37fc70 EFLAGS: 00010002
RAX: 0000000000000001 RBX: 0000000000000088 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88001a37fd18 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 00000000000076fd R12: 00000000000000a0
R13: ffff88001a3722c0 R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88001ad00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000000a0 CR3: 000000001730b000 CR4: 00000000000006e0
Call Trace:
 ? __lock_acquire+0xc77/0x1630
 ? console_trylock+0x11/0xa0
 lock_acquire+0x117/0x230
 ? lock_sock_nested+0x3a/0xa0
 _raw_spin_lock_bh+0x3a/0x50
 ? lock_sock_nested+0x3a/0xa0
 lock_sock_nested+0x3a/0xa0
 inet_shutdown+0x33/0xf0
 l2tp_tunnel_del_work+0x60/0xef
 process_one_work+0x1ea/0x5f0
 ? process_one_work+0x162/0x5f0
 worker_thread+0x48/0x3e0
 ? trace_hardirqs_on+0xd/0x10
 kthread+0x108/0x140
 ? process_one_work+0x5f0/0x5f0
 ? kthread_stop+0x2a0/0x2a0
 ret_from_fork+0x24/0x30
Code: 00 41 81 ff ff 1f 00 00 0f 87 7a 13 00 00 45 85 f6 49 8b 85
68 08 00 00 0f 84 ae 03 00 00 c7 44 24 18 00 00 00 00 e9 f0 00 00 00 <49> 81 3c
24 80 93 3f 83 b8 00 00 00 00 44 0f 44 c0 83 fe 01 0f
RIP: __lock_acquire+0x263/0x1630 RSP: ffff88001a37fc70
CR2: 00000000000000a0

Fixes: 309795f4 ("l2tp: Add netlink control API for L2TP")
Signed-off-by: NJames Chapman <jchapman@katalix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Remove l2specific_len configuration parameter since now L2-Specific
Sublayer length is computed according to l2specific_type provided by
userspace.
Reviewed-by: NGuillaume Nault <g.nault@alphalink.fr>
Tested-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NLorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Remove l2specific_len dependency while building l2tpv3 header or
parsing the received frame since default L2-Specific Sublayer is
always four bytes long and we don't need to rely on a user supplied
value.
Moreover in l2tp netlink code there are no sanity checks to
enforce the relation between l2specific_len and l2specific_type,
so sending a malformed netlink message is possible to set
l2specific_type to L2TP_L2SPECTYPE_DEFAULT (or even
L2TP_L2SPECTYPE_NONE) and set l2specific_len to a value greater than
4 leaking memory on the wire and sending corrupted frames.
Reviewed-by: NGuillaume Nault <g.nault@alphalink.fr>
Tested-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NLorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The "offset" option has been removed by
commit 900631ee ("l2tp: remove configurable payload offset").
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Acked-by: NJames Chapman <jchapman@katalix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

If L2TP_ATTR_OFFSET is set to a non-zero value in L2TPv3 tunnels, it
results in L2TPv3 packets being transmitted which might not be
compliant with the L2TPv3 RFC. This patch has l2tp ignore the offset
setting and send all packets with no offset.

In more detail:

L2TPv2 supports a variable offset from the L2TPv2 header to the
payload. The offset value is indicated by an optional field in the
L2TP header.  Our L2TP implementation already detects the presence of
the optional offset and skips that many bytes when handling data
received packets. All transmitted packets are always transmitted with
no offset.

L2TPv3 has no optional offset field in the L2TPv3 packet
header. Instead, L2TPv3 defines optional fields in a "Layer-2 Specific
Sublayer". At the time when the original L2TP code was written, there
was talk at IETF of offset being implemented in a new Layer-2 Specific
Sublayer. A L2TP_ATTR_OFFSET netlink attribute was added so that this
offset could be configured and the intention was to allow it to be
also used to set the tx offset for L2TPv2. However, no L2TPv3 offset
was ever specified and the L2TP_ATTR_OFFSET parameter was forgotten
about.

Setting L2TP_ATTR_OFFSET results in L2TPv3 packets being transmitted
with the specified number of bytes padding between L2TPv3 header and
payload. This is not compliant with L2TPv3 RFC3931. This change
removes the configurable offset altogether while retaining
L2TP_ATTR_OFFSET for backwards compatibility. Any L2TP_ATTR_OFFSET
value is ignored.
Signed-off-by: NJames Chapman <jchapman@katalix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Revert commit f15bc54e ("l2tp: add peer_offset parameter"). This
is removed because it is adding another configurable offset and
configurable offsets are being removed.
Signed-off-by: NJames Chapman <jchapman@katalix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Introduce peer_offset parameter in order to add the capability
to specify two different values for payload offset on tx/rx side.
If just offset is provided by userspace use it for rx side as well
in order to maintain compatibility with older l2tp versions
Signed-off-by: NLorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Be sure that l2tp_session_hlist array initialized in net_init hook
was return to initial state.
Signed-off-by: NVasily Averin <vvs@virtuozzo.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>