[PATCH bpf 2/2] selftests/bpf: Add test for UDP sock leak on sockmap lookup-bind-release
From: Michal Luczaj <hidden>
Date: 2026-06-23 18:38:42
Also in:
bpf, linux-kselftest, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds
Setup and join a cgroup, then attach a cgroup/connect4 program that runs sk = bpf_map_lookup_elem(sockmap, 0) bpf_bind(ctx, sa, sizeof(sa)) bpf_sk_release(sk) Unpatched kernel leaks the socket. Signed-off-by: Michal Luczaj <redacted> --- .../selftests/bpf/prog_tests/sockmap_basic.c | 50 ++++++++++++++++++++++ .../bpf/progs/test_sockmap_lookup_bind_release.c | 37 ++++++++++++++++ 2 files changed, 87 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
index cb3229711f93..11972ffdb16e 100644
--- a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
+++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c@@ -7,6 +7,7 @@ #include "test_progs.h" #include "test_skmsg_load_helpers.skel.h" +#include "test_sockmap_lookup_bind_release.skel.h" #include "test_sockmap_update.skel.h" #include "test_sockmap_invalid_update.skel.h" #include "test_sockmap_skb_verdict_attach.skel.h"
@@ -17,6 +18,7 @@ #include "test_sockmap_msg_pop_data.skel.h" #include "bpf_iter_sockmap.skel.h" +#include "cgroup_helpers.h" #include "sockmap_helpers.h" #define TCP_REPAIR 19 /* TCP sock is under repair right now */
@@ -1373,6 +1375,52 @@ static void test_sockmap_multi_channels(int sotype) test_sockmap_pass_prog__destroy(skel); } +#define LOOKUP_BIND_RELEASE_CG "/sockmap_lookup-bind-release" +#define LOOKUP_BIND_RELEASE_REP 64 + +static void test_sockmap_lookup_bind_release(void) +{ + struct test_sockmap_lookup_bind_release *skel; + struct sockaddr_in sa; + int cg, i; + + cg = cgroup_setup_and_join(LOOKUP_BIND_RELEASE_CG); + if (!ASSERT_OK_FD(cg, "cgroup_setup_and_join")) + return; + + skel = test_sockmap_lookup_bind_release__open_and_load(); + if (!ASSERT_OK_PTR(skel, "open_and_load")) + goto cleanup; + + skel->links.connect = bpf_program__attach_cgroup(skel->progs.connect, cg); + if (!ASSERT_OK_PTR(skel->links.connect, "attach_cgroup")) + goto destroy; + + sa.sin_family = AF_INET; + sa.sin_port = bpf_htons(1234); + sa.sin_addr.s_addr = bpf_htonl(INADDR_LOOPBACK); + + for (i = 0; i < LOOKUP_BIND_RELEASE_REP; ++i) { + __close_fd int sk; + + sk = xsocket(AF_INET, SOCK_DGRAM, 0); + if (sk < 0) + break; + + if (xbpf_map_update_elem(bpf_map__fd(skel->maps.sockmap), &u32(0), + &sk, BPF_ANY)) + break; + + if (xconnect(sk, (struct sockaddr *)&sa, sizeof(sa))) + break; + } + +destroy: + test_sockmap_lookup_bind_release__destroy(skel); +cleanup: + cleanup_cgroup_environment(); +} + void test_sockmap_basic(void) { if (test__start_subtest("sockmap create_update_free"))
@@ -1451,4 +1499,6 @@ void test_sockmap_basic(void) test_sockmap_multi_channels(SOCK_STREAM); if (test__start_subtest("sockmap udp multi channels")) test_sockmap_multi_channels(SOCK_DGRAM); + if (test__start_subtest("sockmap lookup-bind-release")) + test_sockmap_lookup_bind_release(); }
diff --git a/tools/testing/selftests/bpf/progs/test_sockmap_lookup_bind_release.c b/tools/testing/selftests/bpf/progs/test_sockmap_lookup_bind_release.c
new file mode 100644
index 000000000000..cc77b193893b
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_sockmap_lookup_bind_release.c@@ -0,0 +1,37 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/bpf.h> +#include <linux/in.h> +#include <bpf/bpf_helpers.h> + +struct { + __uint(type, BPF_MAP_TYPE_SOCKMAP); + __uint(max_entries, 1); + __type(key, int); + __type(value, int); +} sockmap SEC(".maps"); + +SEC("cgroup/connect4") +int connect(struct bpf_sock_addr *ctx) +{ + struct bpf_sock *sk; + int ret = SK_DROP; + + sk = bpf_map_lookup_elem(&sockmap, &(int){0}); + if (sk) { + if (sk == ctx->sk) { + struct sockaddr_in sa = { + .sin_family = ctx->user_family, + .sin_port = ctx->user_port, + .sin_addr.s_addr = ctx->user_ip4 + }; + + ret = !bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)); + } + + bpf_sk_release(sk); + } + + return ret; +} + +char _license[] SEC("license") = "GPL";
--
2.54.0