l2tp_core.c verifies that ->session_close() is defined before calling
it. There's no need for a stub.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

pppol2tp_tunnel_ioctl() can act on an L2TPv3 tunnel, in which case
'session' may be an Ethernet pseudo-wire.

However, pppol2tp_session_ioctl() expects a PPP pseudo-wire, as it
assumes l2tp_session_priv() points to a pppol2tp_session structure. For
an Ethernet pseudo-wire l2tp_session_priv() points to an l2tp_eth_sess
structure instead, making pppol2tp_session_ioctl() access invalid
memory.

Fixes: d9e31d17 ("l2tp: Add L2TP ethernet pseudowire support")
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The /proc/net/pppol2tp handlers (pppol2tp_seq_*()) iterate over all
L2TPv2 tunnels, and rightfully expect that only PPP sessions can be
found there. However, l2tp_netlink accepts creating Ethernet sessions
regardless of the underlying tunnel version.

This confuses pppol2tp_seq_session_show(), which expects that
l2tp_session_priv() returns a pppol2tp_session structure. When the
session is an Ethernet pseudo-wire, a struct l2tp_eth_sess is returned
instead. This leads to invalid memory access when
pppol2tp_session_get_sock() later tries to dereference ps->sk.

Fixes: d9e31d17 ("l2tp: Add L2TP ethernet pseudowire support")
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

pppol2tp_connect() may create a tunnel or a session. Remove them in
case of error.

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>

If 'fd' is negative, l2tp_tunnel_create() creates a tunnel socket using
the configuration passed in 'tcfg'. Currently, pppol2tp_connect() sets
the relevant fields to zero, tricking l2tp_tunnel_create() into setting
up an unusable kernel socket.

We can't set 'tcfg' with the required fields because there's no way to
get them from the current connect() parameters. So let's restrict
kernel sockets creation to the netlink API, which is the original use
case.

Fixes: 789a4a2c ("l2tp: Add support for static unmanaged L2TPv3 tunnels")
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

l2tp_session_priv() returns a struct pppol2tp_session pointer only for
PPPoL2TP sessions. In particular, if the session is an L2TP_PWTYPE_ETH
pseudo-wire, l2tp_session_priv() returns a pointer to an l2tp_eth_sess
structure, which is much smaller than struct pppol2tp_session. This
leads to invalid memory dereference when trying to lock ps->sk_lock.

Fixes: d9e31d17 ("l2tp: Add L2TP ethernet pseudowire support")
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Define cfg.pw_type so that the new session is created with its .pwtype
field properly set (L2TP_PWTYPE_PPP).

Not setting the pseudo-wire type had several annoying effects:

  * Invalid value returned in the L2TP_ATTR_PW_TYPE attribute when
    dumping sessions with the netlink API.

  * Impossibility to delete the session using the netlink API (because
    l2tp_nl_cmd_session_delete() gets the deletion callback function
    from an array indexed by the session's pseudo-wire type).

Also, there are several cases where we should check a session's
pseudo-wire type. For example, pppol2tp_connect() should refuse to
connect a session that is not PPPoL2TP, but that requires the session's
.pwtype field to be properly set.

Fixes: f7faffa3 ("l2tp: Add L2TPv3 protocol support")
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Commit d02ba2a6 ("l2tp: fix race in pppol2tp_release with session
object destroy") tried to fix a race condition where a PPPoL2TP socket
would disappear while the L2TP session was still using it. However, it
missed the root issue which is that an L2TP session may accept to be
reconnected if its associated socket has entered the release process.

The tentative fix makes the session hold the socket it is connected to.
That saves the kernel from crashing, but introduces refcount leakage,
preventing the socket from completing the release process. Once stalled,
everything the socket depends on can't be released anymore, including
the L2TP session and the l2tp_ppp module.

The root issue is that, when releasing a connected PPPoL2TP socket, the
session's ->sk pointer (RCU-protected) is reset to NULL and we have to
wait for a grace period before destroying the socket. The socket drops
the session in its ->sk_destruct callback function, so the session
will exist until the last reference on the socket is dropped.
Therefore, there is a time frame where pppol2tp_connect() may accept
reconnecting a session, as it only checks ->sk to figure out if the
session is connected. This time frame is shortened by the fact that
pppol2tp_release() calls l2tp_session_delete(), making the session
unreachable before resetting ->sk. However, pppol2tp_connect() may
grab the session before it gets unhashed by l2tp_session_delete(), but
it may test ->sk after the later got reset. The race is not so hard to
trigger and syzbot found a pretty reliable reproducer:
https://syzkaller.appspot.com/bug?id=418578d2a4389074524e04d641eacb091961b2cf

Before d02ba2a6, another race could let pppol2tp_release()
overwrite the ->__sk pointer of an L2TP session, thus tricking
pppol2tp_put_sk() into calling sock_put() on a socket that is different
than the one for which pppol2tp_release() was originally called. To get
there, we had to trigger the race described above, therefore having one
PPPoL2TP socket being released, while the session it is connected to is
reconnecting to a different PPPoL2TP socket. When releasing this new
socket fast enough, pppol2tp_release() overwrites the session's
->__sk pointer with the address of the new socket, before the first
pppol2tp_put_sk() call gets scheduled. Then the pppol2tp_put_sk() call
invoked by the original socket will sock_put() the new socket,
potentially dropping its last reference. When the second
pppol2tp_put_sk() finally runs, its socket has already been freed.

With d02ba2a6, the session takes a reference on both sockets.
Furthermore, the session's ->sk pointer is reset in the
pppol2tp_session_close() callback function rather than in
pppol2tp_release(). Therefore, ->__sk can't be overwritten and
pppol2tp_put_sk() is called only once (l2tp_session_delete() will only
run pppol2tp_session_close() once, to protect the session against
concurrent deletion requests). Now pppol2tp_put_sk() will properly
sock_put() the original socket, but the new socket will remain, as
l2tp_session_delete() prevented the release process from completing.
Here, we don't depend on the ->__sk race to trigger the bug. Getting
into the pppol2tp_connect() race is enough to leak the reference, no
matter when new socket is released.

So it all boils down to pppol2tp_connect() failing to realise that the
session has already been connected. This patch drops the unneeded extra
reference counting (mostly reverting d02ba2a6) and checks that
neither ->sk nor ->__sk is set before allowing a session to be
connected.

Fixes: d02ba2a6 ("l2tp: fix race in pppol2tp_release with session object destroy")
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Variants of proc_create{,_data} that directly take a struct seq_operations
and deal with network namespaces in ->open and ->release.  All callers of
proc_create + seq_open_net converted over, and seq_{open,release}_net are
removed entirely.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

The 'pppol2tp' procfs and 'l2tp/tunnels' debugfs files handle reference
counting of sessions differently than for tunnels.

For consistency, use the same mechanism for handling both sessions and
tunnels. That is, drop the reference on the previous session just
before looking up the next one (rather than in .show()). If necessary
(if dump stops before *_next_session() returns NULL), drop the last
reference in .stop().
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Check sockaddr_len before dereferencing sp->sa_protocol, to ensure that
it actually points to valid data.

Fixes: fd558d18 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Reported-by: syzbot+a70ac890b23b1bf29f5c@syzkaller.appspotmail.com
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Commit 0e0c3fee ("l2tp: hold reference on tunnels printed in pppol2tp proc file")
assumed that if pppol2tp_seq_stop() was called with non-NULL private
data (the 'v' pointer), then pppol2tp_seq_start() would not be called
again. It turns out that this isn't guaranteed, and overflowing the
seq_file's buffer in pppol2tp_seq_show() is a way to get into this
situation.

Therefore, pppol2tp_seq_stop() needs to reset pd->tunnel, so that
pppol2tp_seq_start() won't drop a reference again if it gets called.
We also have to clear pd->session, because the rest of the code expects
a non-NULL tunnel when pd->session is set.

The l2tp_debugfs module has the same issue. Fix it in the same way.

Fixes: 0e0c3fee ("l2tp: hold reference on tunnels printed in pppol2tp proc file")
Fixes: f726214d ("l2tp: hold reference on tunnels printed in l2tp/tunnels debugfs file")
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>

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

Unlike sessions, we can't drop the reference held on tunnels in
pppol2tp_seq_show(). Tunnels are reused across several calls to
pppol2tp_seq_start() when iterating over sessions. These iterations
need the tunnel for accessing the next session. Therefore the only safe
moment for dropping the reference is just before searching for the next
tunnel.

Normally, the last invocation of pppol2tp_next_tunnel() doesn't find
any new tunnel, so it drops the last tunnel without taking any new
reference. However, in case of error, pppol2tp_seq_stop() is called
directly, so we have to drop the reference there.

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>

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>

Prefer the direct use of octal for permissions.

Done with checkpatch -f --types=SYMBOLIC_PERMS --fix-inplace
and some typing.

Miscellanea:

o Whitespace neatening around these conversions.
Signed-off-by: NJoe Perches <joe@perches.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>

These pernet_operations just create and destroy /proc entries,
and they can safely marked as async:

pppoe_net_ops
vlan_net_ops
canbcm_pernet_ops
kcm_net_ops
pfkey_net_ops
pppol2tp_net_ops
phonet_net_ops
Signed-off-by: NKirill Tkhai <ktkhai@virtuozzo.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>

pppol2tp_release uses call_rcu to put the final ref on its socket. But
the session object doesn't hold a ref on the session socket so may be
freed while the pppol2tp_put_sk RCU callback is scheduled. Fix this by
having the session hold a ref on its socket until the session is
destroyed. It is this ref that is dropped via call_rcu.

Sessions are also deleted via l2tp_tunnel_closeall. This must now also put
the final ref via call_rcu. So move the call_rcu call site into
pppol2tp_session_close so that this happens in both destroy paths. A
common destroy path should really be implemented, perhaps with
l2tp_tunnel_closeall calling l2tp_session_delete like pppol2tp_release
does, but this will be looked at later.

ODEBUG: activate active (active state 1) object type: rcu_head hint:           (null)
WARNING: CPU: 3 PID: 13407 at lib/debugobjects.c:291 debug_print_object+0x166/0x220
Modules linked in:
CPU: 3 PID: 13407 Comm: syzbot_19c09769 Not tainted 4.16.0-rc2+ #38
Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
RIP: 0010:debug_print_object+0x166/0x220
RSP: 0018:ffff880013647a00 EFLAGS: 00010082
RAX: dffffc0000000008 RBX: 0000000000000003 RCX: ffffffff814d3333
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff88001a59f6d0
RBP: ffff880013647a40 R08: 0000000000000000 R09: 0000000000000001
R10: ffff8800136479a8 R11: 0000000000000000 R12: 0000000000000001
R13: ffffffff86161420 R14: ffffffff85648b60 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88001a580000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020e77000 CR3: 0000000006022000 CR4: 00000000000006e0
Call Trace:
 debug_object_activate+0x38b/0x530
 ? debug_object_assert_init+0x3b0/0x3b0
 ? __mutex_unlock_slowpath+0x85/0x8b0
 ? pppol2tp_session_destruct+0x110/0x110
 __call_rcu.constprop.66+0x39/0x890
 ? __call_rcu.constprop.66+0x39/0x890
 call_rcu_sched+0x17/0x20
 pppol2tp_release+0x2c7/0x440
 ? fcntl_setlk+0xca0/0xca0
 ? sock_alloc_file+0x340/0x340
 sock_release+0x92/0x1e0
 sock_close+0x1b/0x20
 __fput+0x296/0x6e0
 ____fput+0x1a/0x20
 task_work_run+0x127/0x1a0
 do_exit+0x7f9/0x2ce0
 ? SYSC_connect+0x212/0x310
 ? mm_update_next_owner+0x690/0x690
 ? up_read+0x1f/0x40
 ? __do_page_fault+0x3c8/0xca0
 do_group_exit+0x10d/0x330
 ? do_group_exit+0x330/0x330
 SyS_exit_group+0x22/0x30
 do_syscall_64+0x1e0/0x730
 ? trace_hardirqs_off_thunk+0x1a/0x1c
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f362e471259
RSP: 002b:00007ffe389abe08 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f362e471259
RDX: 00007f362e471259 RSI: 000000000000002e RDI: 0000000000000000
RBP: 00007ffe389abe30 R08: 0000000000000000 R09: 00007f362e944270
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000400b60
R13: 00007ffe389abf50 R14: 0000000000000000 R15: 0000000000000000
Code: 8d 3c dd a0 8f 64 85 48 89 fa 48 c1 ea 03 80 3c 02 00 75 7b 48 8b 14 dd a0 8f 64 85 4c 89 f6 48 c7 c7 20 85 64 85 e
8 2a 55 14 ff <0f> 0b 83 05 ad 2a 68 04 01 48 83 c4 18 5b 41 5c 41 5d 41 5e 41

Fixes: ee40fb2e ("l2tp: protect sock pointer of struct pppol2tp_session with RCU")
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 ppp session 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 session will be detached anyway).

BUG: KASAN: use-after-free in inet_shutdown+0x5d/0x1c0
Read of size 4 at addr ffff880010ea3ac0 by task syzbot_347bd5ac/8296

CPU: 3 PID: 8296 Comm: syzbot_347bd5ac Not tainted 4.16.0-rc1+ #91
Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
Call Trace:
 dump_stack+0x101/0x157
 ? inet_shutdown+0x5d/0x1c0
 print_address_description+0x78/0x260
 ? inet_shutdown+0x5d/0x1c0
 kasan_report+0x240/0x360
 __asan_load4+0x78/0x80
 inet_shutdown+0x5d/0x1c0
 ? pppol2tp_show+0x80/0x80
 pppol2tp_session_close+0x68/0xb0
 l2tp_tunnel_closeall+0x199/0x210
 ? udp_v6_flush_pending_frames+0x90/0x90
 l2tp_udp_encap_destroy+0x6b/0xc0
 ? l2tp_tunnel_del_work+0x2e0/0x2e0
 udpv6_destroy_sock+0x8c/0x90
 sk_common_release+0x47/0x190
 udp_lib_close+0x15/0x20
 inet_release+0x85/0xd0
 inet6_release+0x43/0x60
 sock_release+0x53/0x100
 ? sock_alloc_file+0x260/0x260
 sock_close+0x1b/0x20
 __fput+0x19f/0x380
 ____fput+0x1a/0x20
 task_work_run+0xd2/0x110
 exit_to_usermode_loop+0x18d/0x190
 do_syscall_64+0x389/0x3b0
 entry_SYSCALL_64_after_hwframe+0x26/0x9b
RIP: 0033:0x7fe240a45259
RSP: 002b:00007fe241132df8 EFLAGS: 00000297 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007fe240a45259
RDX: 00007fe240a45259 RSI: 0000000000000000 RDI: 00000000000000a5
RBP: 00007fe241132e20 R08: 00007fe241133700 R09: 0000000000000000
R10: 00007fe241133700 R11: 0000000000000297 R12: 0000000000000000
R13: 00007ffc49aff84f R14: 0000000000000000 R15: 00007fe241141040

Allocated by task 8331:
 save_stack+0x43/0xd0
 kasan_kmalloc+0xad/0xe0
 kasan_slab_alloc+0x12/0x20
 kmem_cache_alloc+0x144/0x3e0
 sock_alloc_inode+0x22/0x130
 alloc_inode+0x3d/0xf0
 new_inode_pseudo+0x1c/0x90
 sock_alloc+0x30/0x110
 __sock_create+0xaa/0x4c0
 SyS_socket+0xbe/0x130
 do_syscall_64+0x128/0x3b0
 entry_SYSCALL_64_after_hwframe+0x26/0x9b

Freed by task 8314:
 save_stack+0x43/0xd0
 __kasan_slab_free+0x11a/0x170
 kasan_slab_free+0xe/0x10
 kmem_cache_free+0x88/0x2b0
 sock_destroy_inode+0x49/0x50
 destroy_inode+0x77/0xb0
 evict+0x285/0x340
 iput+0x429/0x530
 dentry_unlink_inode+0x28c/0x2c0
 __dentry_kill+0x1e3/0x2f0
 dput.part.21+0x500/0x560
 dput+0x24/0x30
 __fput+0x2aa/0x380
 ____fput+0x1a/0x20
 task_work_run+0xd2/0x110
 exit_to_usermode_loop+0x18d/0x190
 do_syscall_64+0x389/0x3b0
 entry_SYSCALL_64_after_hwframe+0x26/0x9b

Fixes: fd558d18 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
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>

Changes since v1:
Added changes in these files:
    drivers/infiniband/hw/usnic/usnic_transport.c
    drivers/staging/lustre/lnet/lnet/lib-socket.c
    drivers/target/iscsi/iscsi_target_login.c
    drivers/vhost/net.c
    fs/dlm/lowcomms.c
    fs/ocfs2/cluster/tcp.c
    security/tomoyo/network.c

Before:
All these functions either return a negative error indicator,
or store length of sockaddr into "int *socklen" parameter
and return zero on success.

"int *socklen" parameter is awkward. For example, if caller does not
care, it still needs to provide on-stack storage for the value
it does not need.

None of the many FOO_getname() functions of various protocols
ever used old value of *socklen. They always just overwrite it.

This change drops this parameter, and makes all these functions, on success,
return length of sockaddr. It's always >= 0 and can be differentiated
from an error.

Tests in callers are changed from "if (err)" to "if (err < 0)", where needed.

rpc_sockname() lost "int buflen" parameter, since its only use was
to be passed to kernel_getsockname() as &buflen and subsequently
not used in any way.

Userspace API is not changed.

    text    data     bss      dec     hex filename
30108430 2633624  873672 33615726 200ef6e vmlinux.before.o
30108109 2633612  873672 33615393 200ee21 vmlinux.o
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
CC: David S. Miller <davem@davemloft.net>
CC: linux-kernel@vger.kernel.org
CC: netdev@vger.kernel.org
CC: linux-bluetooth@vger.kernel.org
CC: linux-decnet-user@lists.sourceforge.net
CC: linux-wireless@vger.kernel.org
CC: linux-rdma@vger.kernel.org
CC: linux-sctp@vger.kernel.org
CC: linux-nfs@vger.kernel.org
CC: linux-x25@vger.kernel.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Remove the switch block in l2tp_nl_cmd_session_create() that
checks pseudowire-specific parameters since just L2TP_PWTYPE_ETH and
L2TP_PWTYPE_PPP are currently supported and no actual checks are
performed. Moreover the L2TP_PWTYPE_IP/default case presents a harmless
issue in error handling (break instead of goto out_tunnel)
Signed-off-by: NLorenzo Bianconi <lorenzo.bianconi@redhat.com>
Acked-by: NGuillaume Nault <g.nault@alphalink.fr>
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>

Add sanity check on l2specific_type provided by userspace in
l2tp_nl_cmd_session_create() since just L2TP_L2SPECTYPE_DEFAULT and
L2TP_L2SPECTYPE_NONE are currently supported.
Moreover explicitly set l2specific_type to L2TP_L2SPECTYPE_DEFAULT
only if the userspace does not provide a value for it
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>

/proc has been ignoring struct file_operations::owner field for 10 years.
Specifically, it started with commit 786d7e16
("Fix rmmod/read/write races in /proc entries"). Notice the chunk where
inode->i_fop is initialized with proxy struct file_operations for
regular files:

	-               if (de->proc_fops)
	-                       inode->i_fop = de->proc_fops;
	+               if (de->proc_fops) {
	+                       if (S_ISREG(inode->i_mode))
	+                               inode->i_fop = &proc_reg_file_ops;
	+                       else
	+                               inode->i_fop = de->proc_fops;
	+               }

VFS stopped pinning module at this point.
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.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 820da535 ("l2tp: fix missing print session offset
info").  The peer_offset parameter is removed.
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>