This is a note to let you know that I've just added the patch titled

l2tp: do not accept arbitrary sockets

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: l2tp-do-not-accept-arbitrary-sockets.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Wed Mar 28 20:16:33 CEST 2018

From: Eric Dumazet edumazet@google.com Date: Tue, 6 Mar 2018 07:54:53 -0800 Subject: l2tp: do not accept arbitrary sockets

From: Eric Dumazet edumazet@google.com

[ Upstream commit 17cfe79a65f98abe535261856c5aef14f306dff7 ]

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: Guillaume Nault g.nault@alphalink.fr Acked-by: James 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: fd558d186df2 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/l2tp/l2tp_core.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -1612,9 +1612,14 @@ int l2tp_tunnel_create(struct net *net, encap = cfg->encap;

/* Quick sanity checks */ + err = -EPROTONOSUPPORT; + if (sk->sk_type != SOCK_DGRAM) { + pr_debug("tunl %hu: fd %d wrong socket type\n", + tunnel_id, fd); + goto err; + } switch (encap) { case L2TP_ENCAPTYPE_UDP: - err = -EPROTONOSUPPORT; if (sk->sk_protocol != IPPROTO_UDP) { pr_err("tunl %hu: fd %d wrong protocol, got %d, expected %d\n", tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP); @@ -1622,7 +1627,6 @@ int l2tp_tunnel_create(struct net *net, } break; case L2TP_ENCAPTYPE_IP: - err = -EPROTONOSUPPORT; if (sk->sk_protocol != IPPROTO_L2TP) { pr_err("tunl %hu: fd %d wrong protocol, got %d, expected %d\n", tunnel_id, fd, sk->sk_protocol, IPPROTO_L2TP);

Patches currently in stable-queue which might be from edumazet@google.com are

queue-4.9/ipv6-fix-access-to-non-linear-packet-in-ndisc_fill_redirect_hdr_option.patch queue-4.9/skbuff-fix-not-waking-applications-when-errors-are-enqueued.patch queue-4.9/l2tp-do-not-accept-arbitrary-sockets.patch queue-4.9/net-use-skb_to_full_sk-in-skb_update_prio.patch queue-4.9/ieee802154-6lowpan-fix-possible-null-deref-in-lowpan_device_event.patch