From 4dde20b1aa85d69c4281eaac9a7cfa7d2b62ecf0 Mon Sep 17 00:00:00 2001 From: Feng Yang Date: Thu, 17 Apr 2025 09:48:46 +0800 Subject: [PATCH 1/3] libbpf: Fix event name too long error When the binary path is excessively long, the generated probe_name in libbpf exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes). This causes legacy uprobe event attachment to fail with error code -22. The fix reorders the fields to place the unique ID before the name. This ensures that even if truncation occurs via snprintf, the unique ID remains intact, preserving event name uniqueness. Additionally, explicit checks with MAX_EVENT_NAME_LEN are added to enforce length constraints. Before Fix: ./test_progs -t attach_probe/kprobe-long_name ...... libbpf: failed to add legacy kprobe event for 'bpf_testmod_looooooooooooooooooooooooooooooong_name+0x0': -EINVAL libbpf: prog 'handle_kprobe': failed to create kprobe 'bpf_testmod_looooooooooooooooooooooooooooooong_name+0x0' perf event: -EINVAL test_attach_kprobe_long_event_name:FAIL:attach_kprobe_long_event_name unexpected error: -22 test_attach_probe:PASS:uprobe_ref_ctr_cleanup 0 nsec #13/11 attach_probe/kprobe-long_name:FAIL #13 attach_probe:FAIL ./test_progs -t attach_probe/uprobe-long_name ...... libbpf: failed to add legacy uprobe event for /root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9: -EINVAL libbpf: prog 'handle_uprobe': failed to create uprobe '/root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9' perf event: -EINVAL test_attach_uprobe_long_event_name:FAIL:attach_uprobe_long_event_name unexpected error: -22 #13/10 attach_probe/uprobe-long_name:FAIL #13 attach_probe:FAIL After Fix: ./test_progs -t attach_probe/uprobe-long_name #13/10 attach_probe/uprobe-long_name:OK #13 attach_probe:OK Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED ./test_progs -t attach_probe/kprobe-long_name #13/11 attach_probe/kprobe-long_name:OK #13 attach_probe:OK Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code") Fixes: cc10623c6810 ("libbpf: Add legacy uprobe attaching support") Signed-off-by: Hengqi Chen Signed-off-by: Feng Yang Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20250417014848.59321-2-yangfeng59949@163.com --- tools/lib/bpf/libbpf.c | 43 ++++++++++++++++-------------------------- 1 file changed, 16 insertions(+), 27 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 56250b5ac5b0..fbb991c6bf19 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -60,6 +60,8 @@ #define BPF_FS_MAGIC 0xcafe4a11 #endif +#define MAX_EVENT_NAME_LEN 64 + #define BPF_FS_DEFAULT_PATH "/sys/fs/bpf" #define BPF_INSN_SZ (sizeof(struct bpf_insn)) @@ -11136,16 +11138,16 @@ static const char *tracefs_available_filter_functions_addrs(void) : TRACEFS"/available_filter_functions_addrs"; } -static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz, - const char *kfunc_name, size_t offset) +static void gen_probe_legacy_event_name(char *buf, size_t buf_sz, + const char *name, size_t offset) { static int index = 0; int i; - snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset, - __sync_fetch_and_add(&index, 1)); + snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(), + __sync_fetch_and_add(&index, 1), name, offset); - /* sanitize binary_path in the probe name */ + /* sanitize name in the probe name */ for (i = 0; buf[i]; i++) { if (!isalnum(buf[i])) buf[i] = '_'; @@ -11270,9 +11272,9 @@ int probe_kern_syscall_wrapper(int token_fd) return pfd >= 0 ? 1 : 0; } else { /* legacy mode */ - char probe_name[128]; + char probe_name[MAX_EVENT_NAME_LEN]; - gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0); + gen_probe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0); if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0) return 0; @@ -11328,10 +11330,10 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, func_name, offset, -1 /* pid */, 0 /* ref_ctr_off */); } else { - char probe_name[256]; + char probe_name[MAX_EVENT_NAME_LEN]; - gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), - func_name, offset); + gen_probe_legacy_event_name(probe_name, sizeof(probe_name), + func_name, offset); legacy_probe = strdup(probe_name); if (!legacy_probe) @@ -11875,20 +11877,6 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru return ret; } -static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz, - const char *binary_path, uint64_t offset) -{ - int i; - - snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset); - - /* sanitize binary_path in the probe name */ - for (i = 0; buf[i]; i++) { - if (!isalnum(buf[i])) - buf[i] = '_'; - } -} - static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe, const char *binary_path, size_t offset) { @@ -12312,13 +12300,14 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path, func_offset, pid, ref_ctr_off); } else { - char probe_name[PATH_MAX + 64]; + char probe_name[MAX_EVENT_NAME_LEN]; if (ref_ctr_off) return libbpf_err_ptr(-EINVAL); - gen_uprobe_legacy_event_name(probe_name, sizeof(probe_name), - binary_path, func_offset); + gen_probe_legacy_event_name(probe_name, sizeof(probe_name), + strrchr(binary_path, '/') ? : binary_path, + func_offset); legacy_probe = strdup(probe_name); if (!legacy_probe) From e1be7c45d24434bc6e04b675ae91c049e50447be Mon Sep 17 00:00:00 2001 From: Feng Yang Date: Thu, 17 Apr 2025 09:48:47 +0800 Subject: [PATCH 2/3] selftests/bpf: Add test for attaching uprobe with long event names This test verifies that attaching uprobe/uretprobe with long event names does not trigger EINVAL errors. Signed-off-by: Feng Yang Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20250417014848.59321-3-yangfeng59949@163.com --- .../selftests/bpf/prog_tests/attach_probe.c | 49 +++++++++++++++++++ 1 file changed, 49 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c index 329c7862b52d..9b7f36f39c32 100644 --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c @@ -122,6 +122,52 @@ static void test_attach_probe_manual(enum probe_attach_mode attach_mode) test_attach_probe_manual__destroy(skel); } +/* attach uprobe/uretprobe long event name testings */ +static void test_attach_uprobe_long_event_name(void) +{ + DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, uprobe_opts); + struct bpf_link *uprobe_link, *uretprobe_link; + struct test_attach_probe_manual *skel; + ssize_t uprobe_offset; + char path[PATH_MAX] = {0}; + + skel = test_attach_probe_manual__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel_kprobe_manual_open_and_load")) + return; + + uprobe_offset = get_uprobe_offset(&trigger_func); + if (!ASSERT_GE(uprobe_offset, 0, "uprobe_offset")) + goto cleanup; + + if (!ASSERT_GT(readlink("/proc/self/exe", path, PATH_MAX - 1), 0, "readlink")) + goto cleanup; + + /* manual-attach uprobe/uretprobe */ + uprobe_opts.attach_mode = PROBE_ATTACH_MODE_LEGACY; + uprobe_opts.ref_ctr_offset = 0; + uprobe_opts.retprobe = false; + uprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uprobe, + 0 /* self pid */, + path, + uprobe_offset, + &uprobe_opts); + if (!ASSERT_OK_PTR(uprobe_link, "attach_uprobe_long_event_name")) + goto cleanup; + skel->links.handle_uprobe = uprobe_link; + + uprobe_opts.retprobe = true; + uretprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uretprobe, + -1 /* any pid */, + path, + uprobe_offset, &uprobe_opts); + if (!ASSERT_OK_PTR(uretprobe_link, "attach_uretprobe_long_event_name")) + goto cleanup; + skel->links.handle_uretprobe = uretprobe_link; + +cleanup: + test_attach_probe_manual__destroy(skel); +} + static void test_attach_probe_auto(struct test_attach_probe *skel) { struct bpf_link *uprobe_err_link; @@ -323,6 +369,9 @@ void test_attach_probe(void) if (test__start_subtest("uprobe-ref_ctr")) test_uprobe_ref_ctr(skel); + if (test__start_subtest("uprobe-long_name")) + test_attach_uprobe_long_event_name(); + cleanup: test_attach_probe__destroy(skel); ASSERT_EQ(uprobe_ref_ctr, 0, "uprobe_ref_ctr_cleanup"); From 9b72f3e5b76007d8ef9c7743561d4c9298a086ab Mon Sep 17 00:00:00 2001 From: Feng Yang Date: Thu, 17 Apr 2025 09:48:48 +0800 Subject: [PATCH 3/3] selftests/bpf: Add test for attaching kprobe with long event names This test verifies that attaching kprobe/kretprobe with long event names does not trigger EINVAL errors. Signed-off-by: Feng Yang Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20250417014848.59321-4-yangfeng59949@163.com --- .../selftests/bpf/prog_tests/attach_probe.c | 35 +++++++++++++++++++ .../selftests/bpf/test_kmods/bpf_testmod.c | 4 +++ 2 files changed, 39 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c index 9b7f36f39c32..cabc51c2ca6b 100644 --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c @@ -168,6 +168,39 @@ static void test_attach_uprobe_long_event_name(void) test_attach_probe_manual__destroy(skel); } +/* attach kprobe/kretprobe long event name testings */ +static void test_attach_kprobe_long_event_name(void) +{ + DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, kprobe_opts); + struct bpf_link *kprobe_link, *kretprobe_link; + struct test_attach_probe_manual *skel; + + skel = test_attach_probe_manual__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel_kprobe_manual_open_and_load")) + return; + + /* manual-attach kprobe/kretprobe */ + kprobe_opts.attach_mode = PROBE_ATTACH_MODE_LEGACY; + kprobe_opts.retprobe = false; + kprobe_link = bpf_program__attach_kprobe_opts(skel->progs.handle_kprobe, + "bpf_testmod_looooooooooooooooooooooooooooooong_name", + &kprobe_opts); + if (!ASSERT_OK_PTR(kprobe_link, "attach_kprobe_long_event_name")) + goto cleanup; + skel->links.handle_kprobe = kprobe_link; + + kprobe_opts.retprobe = true; + kretprobe_link = bpf_program__attach_kprobe_opts(skel->progs.handle_kretprobe, + "bpf_testmod_looooooooooooooooooooooooooooooong_name", + &kprobe_opts); + if (!ASSERT_OK_PTR(kretprobe_link, "attach_kretprobe_long_event_name")) + goto cleanup; + skel->links.handle_kretprobe = kretprobe_link; + +cleanup: + test_attach_probe_manual__destroy(skel); +} + static void test_attach_probe_auto(struct test_attach_probe *skel) { struct bpf_link *uprobe_err_link; @@ -371,6 +404,8 @@ void test_attach_probe(void) if (test__start_subtest("uprobe-long_name")) test_attach_uprobe_long_event_name(); + if (test__start_subtest("kprobe-long_name")) + test_attach_kprobe_long_event_name(); cleanup: test_attach_probe__destroy(skel); diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c index f38eaf0d35ef..2e54b95ad898 100644 --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c @@ -134,6 +134,10 @@ bpf_testmod_test_arg_ptr_to_struct(struct bpf_testmod_struct_arg_1 *a) { return bpf_testmod_test_struct_arg_result; } +__weak noinline void bpf_testmod_looooooooooooooooooooooooooooooong_name(void) +{ +} + __bpf_kfunc void bpf_testmod_test_mod_kfunc(int i) {