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 a BPF program that calls bpf_sk_assign_tcp_reqsk() on it and checks that the kfunc returns an error.
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 test_tcp_custom_syncookie_protocol_check:PASS:start tcp_server 0 nsec test_tcp_custom_syncookie_protocol_check:PASS:getsockname 0 nsec setup_tc:PASS:qdisc add dev lo clsact 0 nsec setup_tc:PASS:filter add dev lo ingress 0 nsec test_tcp_custom_syncookie_protocol_check:PASS:udp socket 0 nsec test_tcp_custom_syncookie_protocol_check:PASS:sendto udp 0 nsec test_tcp_custom_syncookie_protocol_check:PASS:udp_intercepted 0 nsec test_tcp_custom_syncookie_protocol_check:PASS:assign_ret 0 nsec #471 tcp_custom_syncookie_protocol_check:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Jiayuan Chen <[email protected]> Signed-off-by: Jiayuan Chen <[email protected]> --- .../bpf/prog_tests/tcp_custom_syncookie.c | 81 ++++++++++++++++++- .../bpf/progs/test_tcp_custom_syncookie.c | 79 ++++++++++++++++++ 2 files changed, 156 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..e622c5befa70 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 +145,79 @@ 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 a BPF program that calls + * bpf_sk_assign_tcp_reqsk() on it. The kfunc should return -EINVAL + * because the skb carries UDP, not TCP. + * + * Currently the kfunc lacks L4 protocol check, so assign_ret == 0 + * indicates the bug is present. + */ +void test_tcp_custom_syncookie_protocol_check(void) +{ + struct test_tcp_custom_syncookie *skel; + struct sockaddr_in tcp_addr, udp_addr; + socklen_t addr_len = sizeof(tcp_addr); + int tcp_server = -1, udp_client = -1; + char buf[32] = "test"; + int ret; + + if (setup_netns()) + return; + + skel = test_tcp_custom_syncookie__open_and_load(); + if (!ASSERT_OK_PTR(skel, "open_and_load")) + return; + /* Create a TCP listener so the BPF can find a LISTEN socket */ + tcp_server = start_server(AF_INET, SOCK_STREAM, "127.0.0.1", 0, 0); + if (!ASSERT_NEQ(tcp_server, -1, "start tcp_server")) + goto destroy_skel; + + ret = getsockname(tcp_server, (struct sockaddr *)&tcp_addr, &addr_len); + if (!ASSERT_OK(ret, "getsockname")) + goto close_tcp; + + skel->bss->tcp_listener_port = ntohs(tcp_addr.sin_port); + skel->bss->udp_test_port = 9999; + + ret = bpf_program__fd(skel->progs.tcp_custom_syncookie_badproto); + if (setup_tc(ret)) + goto close_tcp; + + udp_client = socket(AF_INET, SOCK_DGRAM, 0); + if (!ASSERT_NEQ(udp_client, -1, "udp socket")) + goto cleanup_tc; + + memset(&udp_addr, 0, sizeof(udp_addr)); + udp_addr.sin_family = AF_INET; + udp_addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK); + udp_addr.sin_port = htons(9999); + + ret = sendto(udp_client, buf, sizeof(buf), 0, + (struct sockaddr *)&udp_addr, sizeof(udp_addr)); + ASSERT_EQ(ret, sizeof(buf), "sendto udp"); + + /* Wait for TC ingress BPF to process the skb. */ + kern_sync_rcu(); + + 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"); + +cleanup_tc: + system("tc qdisc del dev lo clsact"); + if (udp_client >= 0) + close(udp_client); +close_tcp: + close(tcp_server); +destroy_skel: 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..386705b6c9f2 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 +588,83 @@ 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, but currently it doesn't check L4 protocol. + */ +__u16 tcp_listener_port = 0; +__u16 udp_test_port = 0; +int assign_ret = -1; +bool udp_intercepted = false; + +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 bpf_tcp_req_attrs attrs = {}; + struct ethhdr *eth; + struct iphdr *iph; + struct udphdr *udp; + struct bpf_sock *skc; + struct sock *sk; + + eth = (struct ethhdr *)data; + if (eth + 1 > data_end) + return TC_ACT_OK; + + if (bpf_ntohs(eth->h_proto) != ETH_P_IP) + return TC_ACT_OK; + + 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; + + if (bpf_ntohs(udp->dest) != udp_test_port) + 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 = bpf_htons(tcp_listener_port); + + skc = bpf_skc_lookup_tcp(skb, &tuple, sizeof(tuple.ipv4), -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; + + /* Call bpf_sk_assign_tcp_reqsk on a UDP skb. */ + assign_ret = bpf_sk_assign_tcp_reqsk(skb, sk, &attrs, sizeof(attrs)); + + bpf_sk_release(skc); + + /* Let the packet continue into the kernel */ + return TC_ACT_OK; +} + char _license[] SEC("license") = "GPL"; -- 2.43.0
