From 969fb456ffb43d87894a295dbe6a0a722691552a Mon Sep 17 00:00:00 2001 From: Eduard Zingerman Date: Wed, 15 Apr 2026 13:03:56 -0700 Subject: [PATCH] selftests/bpf: verify kallsyms entries for token-loaded subprograms Add a test that loads an XDP program with a global subprogram using a BPF token from a user namespace, then verifies that both the main program and the subprogram appear in /proc/kallsyms. This exercises the bpf_prog_kallsyms_add() path for subprograms and would have caught the missing aux->token copy in bpf_jit_subprogs(). load_kallsyms_local() filters out kallsyms with zero addresses. For a process with limited capabilities to read kallsym addresses the following sysctl variables have to be set to zero: - /proc/sys/kernel/perf_event_paranoid - /proc/sys/kernel/kptr_restrict Set these variables using sysctl_set() utility function extracted from unpriv_bpf_disabled.c to a separate c/header. Since the test modifies global system state, mark it as serial. Signed-off-by: Eduard Zingerman Link: https://lore.kernel.org/r/20260415-subprog-token-fix-v4-2-9bd000e8b068@gmail.com Signed-off-by: Alexei Starovoitov --- tools/testing/selftests/bpf/Makefile | 1 + .../testing/selftests/bpf/prog_tests/token.c | 86 ++++++++++++++++++- .../bpf/prog_tests/unpriv_bpf_disabled.c | 21 +---- .../selftests/bpf/progs/token_kallsyms.c | 19 ++++ tools/testing/selftests/bpf/sysctl_helpers.c | 37 ++++++++ tools/testing/selftests/bpf/sysctl_helpers.h | 8 ++ 6 files changed, 149 insertions(+), 23 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/token_kallsyms.c create mode 100644 tools/testing/selftests/bpf/sysctl_helpers.c create mode 100644 tools/testing/selftests/bpf/sysctl_helpers.h diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index 78e60040811e..6ef6872adbc3 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -751,6 +751,7 @@ TRUNNER_EXTRA_SOURCES := test_progs.c \ btf_helpers.c \ cap_helpers.c \ unpriv_helpers.c \ + sysctl_helpers.c \ netlink_helpers.c \ jit_disasm_helpers.c \ io_helpers.c \ diff --git a/tools/testing/selftests/bpf/prog_tests/token.c b/tools/testing/selftests/bpf/prog_tests/token.c index b81dde283052..f2f5d36ae00a 100644 --- a/tools/testing/selftests/bpf/prog_tests/token.c +++ b/tools/testing/selftests/bpf/prog_tests/token.c @@ -1,9 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 /* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */ #define _GNU_SOURCE -#include #include -#include "cap_helpers.h" #include #include #include @@ -15,9 +13,17 @@ #include #include #include + +#include "bpf_util.h" +#include "cap_helpers.h" +#include "sysctl_helpers.h" +#include "test_progs.h" +#include "trace_helpers.h" + #include "priv_map.skel.h" #include "priv_prog.skel.h" #include "dummy_st_ops_success.skel.h" +#include "token_kallsyms.skel.h" #include "token_lsm.skel.h" #include "priv_freplace_prog.skel.h" @@ -1045,6 +1051,58 @@ err_out: return -EINVAL; } +static bool kallsyms_has_bpf_func(struct ksyms *ksyms, const char *func_name) +{ + char name[256]; + int i; + + for (i = 0; i < ksyms->sym_cnt; i++) { + if (sscanf(ksyms->syms[i].name, "bpf_prog_%*[^_]_%255s", name) == 1 && + strcmp(name, func_name) == 0) + return true; + } + return false; +} + +static int userns_obj_priv_prog_kallsyms(int mnt_fd, struct token_lsm *lsm_skel) +{ + const char *func_names[] = { "xdp_main", "token_ksym_subprog" }; + LIBBPF_OPTS(bpf_object_open_opts, opts); + struct token_kallsyms *skel; + struct ksyms *ksyms = NULL; + char buf[256]; + int i, err; + + snprintf(buf, sizeof(buf), "/proc/self/fd/%d", mnt_fd); + opts.bpf_token_path = buf; + skel = token_kallsyms__open_opts(&opts); + if (!ASSERT_OK_PTR(skel, "token_kallsyms__open_opts")) + return -EINVAL; + + err = token_kallsyms__load(skel); + if (!ASSERT_OK(err, "token_kallsyms__load")) + goto cleanup; + + ksyms = load_kallsyms_local(); + if (!ASSERT_OK_PTR(ksyms, "load_kallsyms_local")) { + err = -EINVAL; + goto cleanup; + } + + for (i = 0; i < ARRAY_SIZE(func_names); i++) { + if (!ASSERT_TRUE(kallsyms_has_bpf_func(ksyms, func_names[i]), + func_names[i])) { + err = -EINVAL; + break; + } + } + +cleanup: + free_kallsyms_local(ksyms); + token_kallsyms__destroy(skel); + return err; +} + #define bit(n) (1ULL << (n)) static int userns_bpf_token_info(int mnt_fd, struct token_lsm *lsm_skel) @@ -1082,7 +1140,7 @@ cleanup: return err; } -void test_token(void) +void serial_test_token(void) { if (test__start_subtest("map_token")) { struct bpffs_opts opts = { @@ -1194,4 +1252,26 @@ void test_token(void) subtest_userns(&opts, userns_bpf_token_info); } + if (test__start_subtest("obj_priv_prog_kallsyms")) { + char perf_paranoid_orig[32] = {}; + char kptr_restrict_orig[32] = {}; + struct bpffs_opts opts = { + .cmds = bit(BPF_BTF_LOAD) | bit(BPF_PROG_LOAD), + .progs = bit(BPF_PROG_TYPE_XDP), + .attachs = ~0ULL, + }; + + if (sysctl_set_or_fail("/proc/sys/kernel/perf_event_paranoid", perf_paranoid_orig, "0")) + goto cleanup; + if (sysctl_set_or_fail("/proc/sys/kernel/kptr_restrict", kptr_restrict_orig, "0")) + goto cleanup; + + subtest_userns(&opts, userns_obj_priv_prog_kallsyms); + +cleanup: + if (perf_paranoid_orig[0]) + sysctl_set_or_fail("/proc/sys/kernel/perf_event_paranoid", NULL, perf_paranoid_orig); + if (kptr_restrict_orig[0]) + sysctl_set_or_fail("/proc/sys/kernel/kptr_restrict", NULL, kptr_restrict_orig); + } } diff --git a/tools/testing/selftests/bpf/prog_tests/unpriv_bpf_disabled.c b/tools/testing/selftests/bpf/prog_tests/unpriv_bpf_disabled.c index 472f4f9fa95f..64404602b9ab 100644 --- a/tools/testing/selftests/bpf/prog_tests/unpriv_bpf_disabled.c +++ b/tools/testing/selftests/bpf/prog_tests/unpriv_bpf_disabled.c @@ -8,6 +8,7 @@ #include "cap_helpers.h" #include "bpf_util.h" +#include "sysctl_helpers.h" /* Using CAP_LAST_CAP is risky here, since it can get pulled in from * an old /usr/include/linux/capability.h and be < CAP_BPF; as a result @@ -36,26 +37,6 @@ static void process_perfbuf(void *ctx, int cpu, void *data, __u32 len) got_perfbuf_val = *(__u32 *)data; } -static int sysctl_set(const char *sysctl_path, char *old_val, const char *new_val) -{ - int ret = 0; - FILE *fp; - - fp = fopen(sysctl_path, "r+"); - if (!fp) - return -errno; - if (old_val && fscanf(fp, "%s", old_val) <= 0) { - ret = -ENOENT; - } else if (!old_val || strcmp(old_val, new_val) != 0) { - fseek(fp, 0, SEEK_SET); - if (fprintf(fp, "%s", new_val) < 0) - ret = -errno; - } - fclose(fp); - - return ret; -} - static void test_unpriv_bpf_disabled_positive(struct test_unpriv_bpf_disabled *skel, __u32 prog_id, int prog_fd, int perf_fd, char **map_paths, int *map_fds) diff --git a/tools/testing/selftests/bpf/progs/token_kallsyms.c b/tools/testing/selftests/bpf/progs/token_kallsyms.c new file mode 100644 index 000000000000..c9f9344f3eb2 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/token_kallsyms.c @@ -0,0 +1,19 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */ + +#include "vmlinux.h" +#include + +char _license[] SEC("license") = "GPL"; + +__weak +int token_ksym_subprog(void) +{ + return 0; +} + +SEC("xdp") +int xdp_main(struct xdp_md *xdp) +{ + return token_ksym_subprog(); +} diff --git a/tools/testing/selftests/bpf/sysctl_helpers.c b/tools/testing/selftests/bpf/sysctl_helpers.c new file mode 100644 index 000000000000..e2bd824f12d5 --- /dev/null +++ b/tools/testing/selftests/bpf/sysctl_helpers.c @@ -0,0 +1,37 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include + +#include "sysctl_helpers.h" +#include "test_progs.h" + +int sysctl_set(const char *sysctl_path, char *old_val, const char *new_val) +{ + int ret = 0; + FILE *fp; + + fp = fopen(sysctl_path, "r+"); + if (!fp) + return -errno; + if (old_val && fscanf(fp, "%s", old_val) <= 0) { + ret = -ENOENT; + } else if (!old_val || strcmp(old_val, new_val) != 0) { + fseek(fp, 0, SEEK_SET); + if (fprintf(fp, "%s", new_val) < 0) + ret = -errno; + } + fclose(fp); + + return ret; +} + +int sysctl_set_or_fail(const char *sysctl_path, char *old_val, const char *new_val) +{ + int err; + + err = sysctl_set(sysctl_path, old_val, new_val); + if (err) + PRINT_FAIL("failed to set %s to %s: %s\n", sysctl_path, new_val, strerror(-err)); + return err; +} diff --git a/tools/testing/selftests/bpf/sysctl_helpers.h b/tools/testing/selftests/bpf/sysctl_helpers.h new file mode 100644 index 000000000000..35e37bfe1b3b --- /dev/null +++ b/tools/testing/selftests/bpf/sysctl_helpers.h @@ -0,0 +1,8 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __SYSCTL_HELPERS_H +#define __SYSCTL_HELPERS_H + +int sysctl_set(const char *sysctl_path, char *old_val, const char *new_val); +int sysctl_set_or_fail(const char *sysctl_path, char *old_val, const char *new_val); + +#endif