From: Jiayuan Chen <[email protected]> Add test_tcp_custom_syncookie_protocol_check to verify that bpf_sk_assign_tcp_reqsk() rejects non-TCP skbs. The test sends a UDP packet through TC ingress where a BPF program calls bpf_sk_assign_tcp_reqsk() on it and checks that the kfunc returns an error. A UDP server recv() is used as synchronization to ensure the BPF program has finished processing before checking the result.
Without the fix in bpf_sk_assign_tcp_reqsk(), the kfunc succeeds and attaches a TCP reqsk to the UDP skb, which causes a null pointer dereference panic when the kernel processes it through the UDP receive path. Test result: ./test_progs -a tcp_custom_syncookie_protocol_check -v setup_netns:PASS:create netns 0 nsec setup_netns:PASS:ip 0 nsec write_sysctl:PASS:open sysctl 0 nsec write_sysctl:PASS:write sysctl 0 nsec setup_netns:PASS:write_sysctl 0 nsec test_tcp_custom_syncookie_protocol_check:PASS:open_and_load 0 nsec setup_tc:PASS:qdisc add dev lo clsact 0 nsec setup_tc:PASS:filter add dev lo ingress 0 nsec run_protocol_check:PASS:start tcp_server 0 nsec run_protocol_check:PASS:start udp_server 0 nsec run_protocol_check:PASS:connect udp_client 0 nsec run_protocol_check:PASS:send udp 0 nsec run_protocol_check:PASS:recv udp 0 nsec run_protocol_check:PASS:udp_intercepted 0 nsec run_protocol_check:PASS:assign_ret 0 nsec #471/1 tcp_custom_syncookie_protocol_check/IPv4 TCP:OK run_protocol_check:PASS:start tcp_server 0 nsec run_protocol_check:PASS:start udp_server 0 nsec run_protocol_check:PASS:connect udp_client 0 nsec run_protocol_check:PASS:send udp 0 nsec run_protocol_check:PASS:recv udp 0 nsec run_protocol_check:PASS:udp_intercepted 0 nsec run_protocol_check:PASS:assign_ret 0 nsec #471/2 tcp_custom_syncookie_protocol_check/IPv6 TCP:OK #471 tcp_custom_syncookie_protocol_check:OK Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED Cc: Jiayuan Chen <[email protected]> Signed-off-by: Jiayuan Chen <[email protected]> --- .../bpf/prog_tests/tcp_custom_syncookie.c | 94 ++++++++++++++- .../bpf/progs/test_tcp_custom_syncookie.c | 109 ++++++++++++++++++ 2 files changed, 199 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/tcp_custom_syncookie.c b/tools/testing/selftests/bpf/prog_tests/tcp_custom_syncookie.c index eaf441dc7e79..e46031d0786b 100644 --- a/tools/testing/selftests/bpf/prog_tests/tcp_custom_syncookie.c +++ b/tools/testing/selftests/bpf/prog_tests/tcp_custom_syncookie.c @@ -5,6 +5,7 @@ #include <sched.h> #include <stdlib.h> #include <net/if.h> +#include <netinet/in.h> #include "test_progs.h" #include "cgroup_helpers.h" @@ -47,11 +48,10 @@ static int setup_netns(void) return -1; } -static int setup_tc(struct test_tcp_custom_syncookie *skel) +static int setup_tc(int prog_fd) { LIBBPF_OPTS(bpf_tc_hook, qdisc_lo, .attach_point = BPF_TC_INGRESS); - LIBBPF_OPTS(bpf_tc_opts, tc_attach, - .prog_fd = bpf_program__fd(skel->progs.tcp_custom_syncookie)); + LIBBPF_OPTS(bpf_tc_opts, tc_attach, .prog_fd = prog_fd); qdisc_lo.ifindex = if_nametoindex("lo"); if (!ASSERT_OK(bpf_tc_hook_create(&qdisc_lo), "qdisc add dev lo clsact")) @@ -127,7 +127,7 @@ void test_tcp_custom_syncookie(void) if (!ASSERT_OK_PTR(skel, "open_and_load")) return; - if (setup_tc(skel)) + if (setup_tc(bpf_program__fd(skel->progs.tcp_custom_syncookie))) goto destroy_skel; for (i = 0; i < ARRAY_SIZE(test_cases); i++) { @@ -145,6 +145,92 @@ void test_tcp_custom_syncookie(void) destroy_skel: system("tc qdisc del dev lo clsact"); + test_tcp_custom_syncookie__destroy(skel); +} + +/* Test: bpf_sk_assign_tcp_reqsk() should reject non-TCP skb. + * + * Send a UDP packet through TC ingress where a BPF program calls + * bpf_sk_assign_tcp_reqsk() on it. The kfunc should return an error + * because the skb carries UDP, not TCP. + * + * TCP and UDP servers share the same port. The BPF program intercepts + * the UDP packet, looks up the TCP listener via the dest port, and + * attempts to assign a TCP reqsk to the UDP skb. + */ +static void run_protocol_check(struct test_tcp_custom_syncookie *skel, + int family, const char *addr) +{ + int tcp_server = -1, udp_server = -1, udp_client = -1; + char buf[32] = "test"; + int port, ret; + + tcp_server = start_server(family, SOCK_STREAM, addr, 0, 0); + if (!ASSERT_NEQ(tcp_server, -1, "start tcp_server")) + return; + + port = ntohs(get_socket_local_port(tcp_server)); + + /* UDP server on same port for synchronization and port sharing */ + udp_server = start_server(family, SOCK_DGRAM, addr, port, 0); + if (!ASSERT_NEQ(udp_server, -1, "start udp_server")) + goto close_tcp; + + skel->bss->udp_intercepted = false; + skel->data->assign_ret = -1; + + udp_client = connect_to_fd(udp_server, 0); + if (!ASSERT_NEQ(udp_client, -1, "connect udp_client")) + goto close_udp_server; + ret = send(udp_client, buf, sizeof(buf), 0); + if (!ASSERT_EQ(ret, sizeof(buf), "send udp")) + goto close_udp_client; + + /* recv() ensures TC ingress BPF has processed the skb */ + ret = recv(udp_server, buf, sizeof(buf), 0); + if (!ASSERT_EQ(ret, sizeof(buf), "recv udp")) + goto close_udp_client; + + ASSERT_EQ(skel->bss->udp_intercepted, true, "udp_intercepted"); + + /* assign_ret == 0 means kfunc accepted UDP skb (bug). + * assign_ret < 0 means kfunc correctly rejected it (fixed). + */ + ASSERT_NEQ(skel->data->assign_ret, 0, "assign_ret"); + +close_udp_client: + close(udp_client); +close_udp_server: + close(udp_server); +close_tcp: + close(tcp_server); +} + +void test_tcp_custom_syncookie_protocol_check(void) +{ + struct test_tcp_custom_syncookie *skel; + int i; + + if (setup_netns()) + return; + + skel = test_tcp_custom_syncookie__open_and_load(); + if (!ASSERT_OK_PTR(skel, "open_and_load")) + return; + + if (setup_tc(bpf_program__fd(skel->progs.tcp_custom_syncookie_badproto))) + goto destroy_skel; + + for (i = 0; i < ARRAY_SIZE(test_cases); i++) { + if (!test__start_subtest(test_cases[i].name)) + continue; + + run_protocol_check(skel, test_cases[i].family, + test_cases[i].addr); + } + +destroy_skel: + system("tc qdisc del dev lo clsact"); test_tcp_custom_syncookie__destroy(skel); } diff --git a/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c b/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c index 7d5293de1952..c4834abea9c5 100644 --- a/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c +++ b/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c @@ -588,4 +588,113 @@ int tcp_custom_syncookie(struct __sk_buff *skb) return tcp_handle_ack(&ctx); } +/* Test: call bpf_sk_assign_tcp_reqsk() on a UDP skb. + * The kfunc should reject it because the skb is not TCP. + * + * TCP and UDP servers share the same port. The BPF program intercepts + * UDP packets, looks up the TCP listener on the same port, and tries + * to assign a TCP reqsk to the UDP skb. + */ +int assign_ret = -1; +bool udp_intercepted = false; + +static int badproto_lookup_assign(struct __sk_buff *skb, struct udphdr *udp, + struct bpf_sock_tuple *tuple, u32 tuple_size) +{ + struct bpf_tcp_req_attrs attrs = {}; + struct bpf_sock *skc; + struct sock *sk; + + skc = bpf_skc_lookup_tcp(skb, tuple, tuple_size, -1, 0); + if (!skc) + return TC_ACT_OK; + + if (skc->state != TCP_LISTEN) { + bpf_sk_release(skc); + return TC_ACT_OK; + } + + sk = (struct sock *)bpf_skc_to_tcp_sock(skc); + if (!sk) { + bpf_sk_release(skc); + return TC_ACT_OK; + } + + attrs.mss = 1460; + attrs.wscale_ok = 1; + attrs.snd_wscale = 7; + attrs.rcv_wscale = 7; + attrs.sack_ok = 1; + + assign_ret = bpf_sk_assign_tcp_reqsk(skb, sk, &attrs, sizeof(attrs)); + + bpf_sk_release(skc); + return TC_ACT_OK; +} + +SEC("tc") +int tcp_custom_syncookie_badproto(struct __sk_buff *skb) +{ + void *data = (void *)(long)skb->data; + void *data_end = (void *)(long)skb->data_end; + struct bpf_sock_tuple tuple = {}; + struct ethhdr *eth; + struct iphdr *iph; + struct ipv6hdr *ip6h; + struct udphdr *udp; + + eth = (struct ethhdr *)data; + if (eth + 1 > data_end) + return TC_ACT_OK; + + switch (bpf_ntohs(eth->h_proto)) { + case ETH_P_IP: + iph = (struct iphdr *)(eth + 1); + if (iph + 1 > data_end) + return TC_ACT_OK; + + if (iph->protocol != IPPROTO_UDP) + return TC_ACT_OK; + + udp = (struct udphdr *)(iph + 1); + if (udp + 1 > data_end) + return TC_ACT_OK; + + udp_intercepted = true; + + tuple.ipv4.saddr = iph->saddr; + tuple.ipv4.daddr = iph->daddr; + tuple.ipv4.sport = udp->source; + tuple.ipv4.dport = udp->dest; + + return badproto_lookup_assign(skb, udp, &tuple, + sizeof(tuple.ipv4)); + case ETH_P_IPV6: + ip6h = (struct ipv6hdr *)(eth + 1); + if (ip6h + 1 > data_end) + return TC_ACT_OK; + + if (ip6h->nexthdr != IPPROTO_UDP) + return TC_ACT_OK; + + udp = (struct udphdr *)(ip6h + 1); + if (udp + 1 > data_end) + return TC_ACT_OK; + + udp_intercepted = true; + + __builtin_memcpy(tuple.ipv6.saddr, &ip6h->saddr, + sizeof(tuple.ipv6.saddr)); + __builtin_memcpy(tuple.ipv6.daddr, &ip6h->daddr, + sizeof(tuple.ipv6.daddr)); + tuple.ipv6.sport = udp->source; + tuple.ipv6.dport = udp->dest; + + return badproto_lookup_assign(skb, udp, &tuple, + sizeof(tuple.ipv6)); + default: + return TC_ACT_OK; + } +} + char _license[] SEC("license") = "GPL"; -- 2.43.0
