From 8d6650646ce49e9a5b8c5c23eb94f74b1749f70f Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Fri, 1 Dec 2023 10:01:38 -0800 Subject: [PATCH 1/2] bpf: syzkaller found null ptr deref in unix_bpf proto add I added logic to track the sock pair for stream_unix sockets so that we ensure lifetime of the sock matches the time a sockmap could reference the sock (see fixes tag). I forgot though that we allow af_unix unconnected sockets into a sock{map|hash} map. This is problematic because previous fixed expected sk_pair() to exist and did not NULL check it. Because unconnected sockets have a NULL sk_pair this resulted in the NULL ptr dereference found by syzkaller. BUG: KASAN: null-ptr-deref in unix_stream_bpf_update_proto+0x72/0x430 net/unix/unix_bpf.c:171 Write of size 4 at addr 0000000000000080 by task syz-executor360/5073 Call Trace: ... sock_hold include/net/sock.h:777 [inline] unix_stream_bpf_update_proto+0x72/0x430 net/unix/unix_bpf.c:171 sock_map_init_proto net/core/sock_map.c:190 [inline] sock_map_link+0xb87/0x1100 net/core/sock_map.c:294 sock_map_update_common+0xf6/0x870 net/core/sock_map.c:483 sock_map_update_elem_sys+0x5b6/0x640 net/core/sock_map.c:577 bpf_map_update_value+0x3af/0x820 kernel/bpf/syscall.c:167 We considered just checking for the null ptr and skipping taking a ref on the NULL peer sock. But, if the socket is then connected() after being added to the sockmap we can cause the original issue again. So instead this patch blocks adding af_unix sockets that are not in the ESTABLISHED state. Reported-by: Eric Dumazet Reported-by: syzbot+e8030702aefd3444fb9e@syzkaller.appspotmail.com Fixes: 8866730aed51 ("bpf, sockmap: af_unix stream sockets need to hold ref for pair sock") Acked-by: Jakub Sitnicki Signed-off-by: John Fastabend Link: https://lore.kernel.org/r/20231201180139.328529-2-john.fastabend@gmail.com Signed-off-by: Martin KaFai Lau --- include/net/sock.h | 5 +++++ net/core/sock_map.c | 2 ++ 2 files changed, 7 insertions(+) diff --git a/include/net/sock.h b/include/net/sock.h index 1d6931caf0c3..0201136b0b9c 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -2799,6 +2799,11 @@ static inline bool sk_is_tcp(const struct sock *sk) return sk->sk_type == SOCK_STREAM && sk->sk_protocol == IPPROTO_TCP; } +static inline bool sk_is_stream_unix(const struct sock *sk) +{ + return sk->sk_family == AF_UNIX && sk->sk_type == SOCK_STREAM; +} + /** * sk_eat_skb - Release a skb if it is no longer needed * @sk: socket to eat this skb from diff --git a/net/core/sock_map.c b/net/core/sock_map.c index 4292c2ed1828..27d733c0f65e 100644 --- a/net/core/sock_map.c +++ b/net/core/sock_map.c @@ -536,6 +536,8 @@ static bool sock_map_sk_state_allowed(const struct sock *sk) { if (sk_is_tcp(sk)) return (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_LISTEN); + if (sk_is_stream_unix(sk)) + return (1 << sk->sk_state) & TCPF_ESTABLISHED; return true; } From 50d96f05af6787a34b4eca2ee3fc1993289c4c24 Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Fri, 1 Dec 2023 10:01:39 -0800 Subject: [PATCH 2/2] bpf: sockmap, test for unconnected af_unix sock Add test to sockmap_basic to ensure af_unix sockets that are not connected can not be added to the map. Ensure we keep DGRAM sockets working however as these will not be connected typically. Signed-off-by: John Fastabend Acked-by: Jakub Sitnicki Link: https://lore.kernel.org/r/20231201180139.328529-3-john.fastabend@gmail.com Signed-off-by: Martin KaFai Lau --- .../selftests/bpf/prog_tests/sockmap_basic.c | 34 +++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c index f75f84d0b3d7..7c2241fae19a 100644 --- a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c @@ -524,6 +524,37 @@ static void test_sockmap_skb_verdict_peek(void) test_sockmap_pass_prog__destroy(pass); } +static void test_sockmap_unconnected_unix(void) +{ + int err, map, stream = 0, dgram = 0, zero = 0; + struct test_sockmap_pass_prog *skel; + + skel = test_sockmap_pass_prog__open_and_load(); + if (!ASSERT_OK_PTR(skel, "open_and_load")) + return; + + map = bpf_map__fd(skel->maps.sock_map_rx); + + stream = xsocket(AF_UNIX, SOCK_STREAM, 0); + if (stream < 0) + return; + + dgram = xsocket(AF_UNIX, SOCK_DGRAM, 0); + if (dgram < 0) { + close(stream); + return; + } + + err = bpf_map_update_elem(map, &zero, &stream, BPF_ANY); + ASSERT_ERR(err, "bpf_map_update_elem(stream)"); + + err = bpf_map_update_elem(map, &zero, &dgram, BPF_ANY); + ASSERT_OK(err, "bpf_map_update_elem(dgram)"); + + close(stream); + close(dgram); +} + void test_sockmap_basic(void) { if (test__start_subtest("sockmap create_update_free")) @@ -566,4 +597,7 @@ void test_sockmap_basic(void) test_sockmap_skb_verdict_fionread(false); if (test__start_subtest("sockmap skb_verdict msg_f_peek")) test_sockmap_skb_verdict_peek(); + + if (test__start_subtest("sockmap unconnected af_unix")) + test_sockmap_unconnected_unix(); }