From: Eric Dumazet Date: Tue, 6 Mar 2018 15:54:53 +0000 (-0800) Subject: l2tp: do not accept arbitrary sockets X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=2d5b0ed04c5ab5e0bd7626b27161ea055e578963;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git 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 Acked-by: James Chapman ================================================================== 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 Reported-by: syzbot Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c index af22aa8ae35b..490d7360222e 100644 --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -1562,9 +1562,14 @@ 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); @@ -1572,7 +1577,6 @@ 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);