diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 51ade3cde8bb..e1505c9cd09e 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3733,6 +3733,23 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog, tr = prog->aux->dst_trampoline; tgt_prog = prog->aux->dst_prog; } + /* + * It is to prevent modifying struct pt_regs via kprobe_write_ctx=true + * freplace prog. Without this check, kprobe_write_ctx=true freplace + * prog is allowed to attach to kprobe_write_ctx=false kprobe prog, and + * then modify the registers of the kprobe prog's target kernel + * function. + * + * This also blocks the combination of uprobe+freplace, because it is + * unable to recognize the use of the tgt_prog as an uprobe or a kprobe + * by tgt_prog itself. At attach time, uprobe/kprobe is recognized by + * the target perf event flags in __perf_event_set_bpf_prog(). + */ + if (prog->type == BPF_PROG_TYPE_EXT && + prog->aux->kprobe_write_ctx != tgt_prog->aux->kprobe_write_ctx) { + err = -EINVAL; + goto out_unlock; + } err = bpf_link_prime(&link->link.link, &link_primer); if (err) diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c index 9e77e5da7097..38852df70c0d 100644 --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c @@ -220,11 +220,73 @@ static void test_attach_kprobe_write_ctx(void) kprobe_write_ctx__destroy(skel); } + +static void test_freplace_kprobe_write_ctx(void) +{ + struct bpf_program *prog_kprobe, *prog_ext, *prog_fentry; + struct kprobe_write_ctx *skel_kprobe, *skel_ext = NULL; + struct bpf_link *link_kprobe = NULL, *link_ext = NULL; + int err, prog_fd; + LIBBPF_OPTS(bpf_kprobe_opts, kprobe_opts); + LIBBPF_OPTS(bpf_test_run_opts, topts); + + skel_kprobe = kprobe_write_ctx__open(); + if (!ASSERT_OK_PTR(skel_kprobe, "kprobe_write_ctx__open kprobe")) + return; + + prog_kprobe = skel_kprobe->progs.kprobe_dummy; + bpf_program__set_autoload(prog_kprobe, true); + + prog_fentry = skel_kprobe->progs.fentry; + bpf_program__set_autoload(prog_fentry, true); + + err = kprobe_write_ctx__load(skel_kprobe); + if (!ASSERT_OK(err, "kprobe_write_ctx__load kprobe")) + goto out; + + skel_ext = kprobe_write_ctx__open(); + if (!ASSERT_OK_PTR(skel_ext, "kprobe_write_ctx__open ext")) + goto out; + + prog_ext = skel_ext->progs.freplace_kprobe; + bpf_program__set_autoload(prog_ext, true); + + prog_fd = bpf_program__fd(skel_kprobe->progs.kprobe_write_ctx); + bpf_program__set_attach_target(prog_ext, prog_fd, "kprobe_write_ctx"); + + err = kprobe_write_ctx__load(skel_ext); + if (!ASSERT_OK(err, "kprobe_write_ctx__load ext")) + goto out; + + prog_fd = bpf_program__fd(prog_kprobe); + link_ext = bpf_program__attach_freplace(prog_ext, prog_fd, "kprobe_dummy"); + ASSERT_ERR_PTR(link_ext, "bpf_program__attach_freplace link"); + ASSERT_EQ(libbpf_get_error(link_ext), -EINVAL, "bpf_program__attach_freplace error"); + + link_kprobe = bpf_program__attach_kprobe_opts(prog_kprobe, "bpf_fentry_test1", + &kprobe_opts); + if (!ASSERT_OK_PTR(link_kprobe, "bpf_program__attach_kprobe_opts")) + goto out; + + err = bpf_prog_test_run_opts(bpf_program__fd(prog_fentry), &topts); + ASSERT_OK(err, "bpf_prog_test_run_opts"); + +out: + bpf_link__destroy(link_ext); + bpf_link__destroy(link_kprobe); + kprobe_write_ctx__destroy(skel_ext); + kprobe_write_ctx__destroy(skel_kprobe); +} #else static void test_attach_kprobe_write_ctx(void) { test__skip(); } + +static void test_freplace_kprobe_write_ctx(void) +{ + test__skip(); +} #endif static void test_attach_probe_auto(struct test_attach_probe *skel) @@ -434,6 +496,8 @@ void test_attach_probe(void) test_attach_kprobe_long_event_name(); if (test__start_subtest("kprobe-write-ctx")) test_attach_kprobe_write_ctx(); + if (test__start_subtest("freplace-kprobe-write-ctx")) + test_freplace_kprobe_write_ctx(); cleanup: test_attach_probe__destroy(skel); diff --git a/tools/testing/selftests/bpf/progs/kprobe_write_ctx.c b/tools/testing/selftests/bpf/progs/kprobe_write_ctx.c index f77aef0474d3..adbf52afe490 100644 --- a/tools/testing/selftests/bpf/progs/kprobe_write_ctx.c +++ b/tools/testing/selftests/bpf/progs/kprobe_write_ctx.c @@ -19,4 +19,23 @@ int kprobe_multi_write_ctx(struct pt_regs *ctx) ctx->ax = 0; return 0; } + +SEC("?kprobe") +int kprobe_dummy(struct pt_regs *regs) +{ + return 0; +} + +SEC("?freplace") +int freplace_kprobe(struct pt_regs *regs) +{ + regs->di = 0; + return 0; +} + +SEC("?fentry/bpf_fentry_test1") +int BPF_PROG(fentry) +{ + return 0; +} #endif