netdev - [PATCH bpf-next] bpf: prevent non-IPv4 socket to be added into sock hash

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Message-Id: <20180530212928.190650-1-tracywwnj@gmail.com>
Date:   Wed, 30 May 2018 14:29:28 -0700
From:   Wei Wang <weiwan@...gle.com>
To:     netdev@...r.kernel.org, John Fastabend <john.fastabend@...il.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Wei Wang <weiwan@...gle.com>
Subject: [PATCH bpf-next] bpf: prevent non-IPv4 socket to be added into sock hash

From: Wei Wang <weiwan@...gle.com>

Sock hash only supports IPv4 socket proto right now.
If a non-IPv4 socket gets stored in the BPF map, sk->sk_prot gets
overwritten with the v4 tcp prot.

Syskaller reported the following related issue on an IPv6 socket:
BUG: KASAN: slab-out-of-bounds in ip6_dst_idev include/net/ip6_fib.h:203 [inline]
BUG: KASAN: slab-out-of-bounds in ip6_xmit+0x2002/0x23f0 net/ipv6/ip6_output.c:264
Read of size 8 at addr ffff8801b300edb0 by task syz-executor888/4522

CPU: 0 PID: 4522 Comm: syz-executor888 Not tainted 4.17.0-rc4+ #17
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1b9/0x294 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 ip6_dst_idev include/net/ip6_fib.h:203 [inline]
 ip6_xmit+0x2002/0x23f0 net/ipv6/ip6_output.c:264
 inet6_csk_xmit+0x377/0x630 net/ipv6/inet6_connection_sock.c:139
 tcp_transmit_skb+0x1be0/0x3e40 net/ipv4/tcp_output.c:1159
 tcp_send_syn_data net/ipv4/tcp_output.c:3441 [inline]
 tcp_connect+0x2207/0x45a0 net/ipv4/tcp_output.c:3480
 tcp_v4_connect+0x1934/0x1d50 net/ipv4/tcp_ipv4.c:272
 __inet_stream_connect+0x943/0x1120 net/ipv4/af_inet.c:655
 tcp_sendmsg_fastopen net/ipv4/tcp.c:1162 [inline]
 tcp_sendmsg_locked+0x2859/0x3ee0 net/ipv4/tcp.c:1209
 tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1447
 inet_sendmsg+0x19f/0x690 net/ipv4/af_inet.c:798
 sock_sendmsg_nosec net/socket.c:629 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:639
 ___sys_sendmsg+0x805/0x940 net/socket.c:2117
 __sys_sendmsg+0x115/0x270 net/socket.c:2155
 __do_sys_sendmsg net/socket.c:2164 [inline]
 __se_sys_sendmsg net/socket.c:2162 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x43ff99
RSP: 002b:00007ffc00bd1cf8 EFLAGS: 00000217 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043ff99
RDX: 0000000020000000 RSI: 0000000020000580 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000217 R12: 00000000004018c0
R13: 0000000000401950 R14: 0000000000000000 R15: 0000000000000000

Fixes: 81110384441a ("bpf: sockmap, add hash map support")
Reported-by: syzbot+5c063698bdbfac19f363@...kaller.appspotmail.com
Signed-off-by: Wei Wang <weiwan@...gle.com>
Acked-by: Eric Dumazet <edumazet@...gle.com>
Acked-by: Willem de Bruijn <willemb@...gle.com>
---
 kernel/bpf/sockmap.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 3b28955a6383..0e7b88bc3e3f 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -2300,6 +2300,11 @@ static int sock_hash_update_elem(struct bpf_map *map,
 		return -EINVAL;
 	}
 
+	if (skops.sk->sk_family != AF_INET) {
+		fput(socket->file);
+		return -EAFNOSUPPORT;
+	}
+
 	err = sock_hash_ctx_update_elem(&skops, map, key, flags);
 	fput(socket->file);
 	return err;
-- 
2.17.1.1185.g55be947832-goog