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authorEric Dumazet <edumazet@google.com>2018-03-06 07:54:53 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-03-31 18:12:33 +0200
commitbdb1a295ee5897b938b0decf360236e40bbe3a1c (patch)
tree047c2b4f3477eb23165f65638cffbfba9d521e7e
parent466c797f1f73f86fe1c28d81cab45d74e8f44cb6 (diff)
l2tp: do not accept arbitrary sockets
[ 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>
-rw-r--r--net/l2tp/l2tp_core.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index ec8f6a6485e3..92df832a1896 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1518,9 +1518,14 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
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);
@@ -1528,7 +1533,6 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
}
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);