This is a note to let you know that I've just added the patch titled
l2tp: do not accept arbitrary sockets
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
l2tp-do-not-accept-arbitrary-sockets.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Mar 29 08:53:48 CEST 2018
From: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Tue, 6 Mar 2018 07:54:53 -0800
Subject: l2tp: do not accept arbitrary sockets
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ 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@xxxxxxxxxxxx>
Acked-by: James Chapman <jchapman@xxxxxxxxxxx>
==================================================================
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@xxxxxxxxxx>
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -1517,9 +1517,14 @@ 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);
@@ -1527,7 +1532,6 @@ 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@xxxxxxxxxx are
queue-3.18/ipv6-fix-access-to-non-linear-packet-in-ndisc_fill_redirect_hdr_option.patch
queue-3.18/skbuff-fix-not-waking-applications-when-errors-are-enqueued.patch
queue-3.18/l2tp-do-not-accept-arbitrary-sockets.patch