Merge branch 'bpf: Tracing and lsm programs re-attach'

Jiri Olsa says:

====================

hi,
while adding test for pinning the module while there's
trampoline attach to it, I noticed that we don't allow
link detach and following re-attach for trampolines.
Adding that for tracing and lsm programs.

You need to have patch [1] from bpf tree for test module
attach test to pass.

v5 changes:
  - fixed missing hlist_del_init change
  - fixed several ASSERT calls
  - added extra patch for missing ';'
  - added ASSERT macros to lsm test
  - added acks

thanks,
jirka

[1] https://lore.kernel.org/bpf/20210326105900.151466-1-jolsa@kernel.org/
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/syscall.c

@@ -2650,13 +2650,24 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
 	 * - if tgt_prog == NULL when this function was called using the old
 	 *   raw_tracepoint_open API, and we need a target from prog->aux
 	 *
-         * The combination of no saved target in prog->aux, and no target
-         * specified on load is illegal, and we reject that here.
+	 * - if prog->aux->dst_trampoline and tgt_prog is NULL, the program
+	 *   was detached and is going for re-attachment.
 	 */
 	if (!prog->aux->dst_trampoline && !tgt_prog) {
-		err = -ENOENT;
+		/*
+		 * Allow re-attach for TRACING and LSM programs. If it's
+		 * currently linked, bpf_trampoline_link_prog will fail.
+		 * EXT programs need to specify tgt_prog_fd, so they
+		 * re-attach in separate code path.
+		 */
+		if (prog->type != BPF_PROG_TYPE_TRACING &&
+		    prog->type != BPF_PROG_TYPE_LSM) {
+			err = -EINVAL;
 			goto out_unlock;
 		}
+		btf_id = prog->aux->attach_btf_id;
+		key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf, btf_id);
+	}
 
 	if (!prog->aux->dst_trampoline ||
 	    (key && key != prog->aux->dst_trampoline->key)) {

kernel/bpf/trampoline.c

@@ -444,7 +444,7 @@ int bpf_trampoline_link_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
 	tr->progs_cnt[kind]++;
 	err = bpf_trampoline_update(tr);
 	if (err) {
-		hlist_del(&prog->aux->tramp_hlist);
+		hlist_del_init(&prog->aux->tramp_hlist);
 		tr->progs_cnt[kind]--;
 	}
 out:
@@ -467,7 +467,7 @@ int bpf_trampoline_unlink_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
 		tr->extension_prog = NULL;
 		goto out;
 	}
-	hlist_del(&prog->aux->tramp_hlist);
+	hlist_del_init(&prog->aux->tramp_hlist);
 	tr->progs_cnt[kind]--;
 	err = bpf_trampoline_update(tr);
 out:

tools/testing/selftests/bpf/prog_tests/fentry_test.c

@@ -3,35 +3,57 @@
 #include <test_progs.h>
 #include "fentry_test.skel.h"
 
-void test_fentry_test(void)
+static int fentry_test(struct fentry_test *fentry_skel)
 {
-	struct fentry_test *fentry_skel = NULL;
 	int err, prog_fd, i;
 	__u32 duration = 0, retval;
+	struct bpf_link *link;
 	__u64 *result;
 
-	fentry_skel = fentry_test__open_and_load();
-	if (CHECK(!fentry_skel, "fentry_skel_load", "fentry skeleton failed\n"))
-		goto cleanup;
-
 	err = fentry_test__attach(fentry_skel);
-	if (CHECK(err, "fentry_attach", "fentry attach failed: %d\n", err))
-		goto cleanup;
+	if (!ASSERT_OK(err, "fentry_attach"))
+		return err;
+
+	/* Check that already linked program can't be attached again. */
+	link = bpf_program__attach(fentry_skel->progs.test1);
+	if (!ASSERT_ERR_PTR(link, "fentry_attach_link"))
+		return -1;
 
 	prog_fd = bpf_program__fd(fentry_skel->progs.test1);
 	err = bpf_prog_test_run(prog_fd, 1, NULL, 0,
 				NULL, NULL, &retval, &duration);
-	CHECK(err || retval, "test_run",
-	      "err %d errno %d retval %d duration %d\n",
-	      err, errno, retval, duration);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(retval, 0, "test_run");
 
 	result = (__u64 *)fentry_skel->bss;
-	for (i = 0; i < 6; i++) {
-		if (CHECK(result[i] != 1, "result",
-			  "fentry_test%d failed err %lld\n", i + 1, result[i]))
-			goto cleanup;
+	for (i = 0; i < sizeof(*fentry_skel->bss) / sizeof(__u64); i++) {
+		if (!ASSERT_EQ(result[i], 1, "fentry_result"))
+			return -1;
 	}
 
+	fentry_test__detach(fentry_skel);
+
+	/* zero results for re-attach test */
+	memset(fentry_skel->bss, 0, sizeof(*fentry_skel->bss));
+	return 0;
+}
+
+void test_fentry_test(void)
+{
+	struct fentry_test *fentry_skel = NULL;
+	int err;
+
+	fentry_skel = fentry_test__open_and_load();
+	if (!ASSERT_OK_PTR(fentry_skel, "fentry_skel_load"))
+		goto cleanup;
+
+	err = fentry_test(fentry_skel);
+	if (!ASSERT_OK(err, "fentry_first_attach"))
+		goto cleanup;
+
+	err = fentry_test(fentry_skel);
+	ASSERT_OK(err, "fentry_second_attach");
+
 cleanup:
 	fentry_test__destroy(fentry_skel);
 }

tools/testing/selftests/bpf/prog_tests/fexit_test.c

@@ -3,35 +3,57 @@
 #include <test_progs.h>
 #include "fexit_test.skel.h"
 
-void test_fexit_test(void)
+static int fexit_test(struct fexit_test *fexit_skel)
 {
-	struct fexit_test *fexit_skel = NULL;
 	int err, prog_fd, i;
 	__u32 duration = 0, retval;
+	struct bpf_link *link;
 	__u64 *result;
 
-	fexit_skel = fexit_test__open_and_load();
-	if (CHECK(!fexit_skel, "fexit_skel_load", "fexit skeleton failed\n"))
-		goto cleanup;
-
 	err = fexit_test__attach(fexit_skel);
-	if (CHECK(err, "fexit_attach", "fexit attach failed: %d\n", err))
-		goto cleanup;
+	if (!ASSERT_OK(err, "fexit_attach"))
+		return err;
+
+	/* Check that already linked program can't be attached again. */
+	link = bpf_program__attach(fexit_skel->progs.test1);
+	if (!ASSERT_ERR_PTR(link, "fexit_attach_link"))
+		return -1;
 
 	prog_fd = bpf_program__fd(fexit_skel->progs.test1);
 	err = bpf_prog_test_run(prog_fd, 1, NULL, 0,
 				NULL, NULL, &retval, &duration);
-	CHECK(err || retval, "test_run",
-	      "err %d errno %d retval %d duration %d\n",
-	      err, errno, retval, duration);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(retval, 0, "test_run");
 
 	result = (__u64 *)fexit_skel->bss;
-	for (i = 0; i < 6; i++) {
-		if (CHECK(result[i] != 1, "result",
-			  "fexit_test%d failed err %lld\n", i + 1, result[i]))
-			goto cleanup;
+	for (i = 0; i < sizeof(*fexit_skel->bss) / sizeof(__u64); i++) {
+		if (!ASSERT_EQ(result[i], 1, "fexit_result"))
+			return -1;
 	}
 
+	fexit_test__detach(fexit_skel);
+
+	/* zero results for re-attach test */
+	memset(fexit_skel->bss, 0, sizeof(*fexit_skel->bss));
+	return 0;
+}
+
+void test_fexit_test(void)
+{
+	struct fexit_test *fexit_skel = NULL;
+	int err;
+
+	fexit_skel = fexit_test__open_and_load();
+	if (!ASSERT_OK_PTR(fexit_skel, "fexit_skel_load"))
+		goto cleanup;
+
+	err = fexit_test(fexit_skel);
+	if (!ASSERT_OK(err, "fexit_first_attach"))
+		goto cleanup;
+
+	err = fexit_test(fexit_skel);
+	ASSERT_OK(err, "fexit_second_attach");
+
 cleanup:
 	fexit_test__destroy(fexit_skel);
 }

tools/testing/selftests/bpf/prog_tests/module_attach.c

@@ -45,12 +45,18 @@ static int trigger_module_test_write(int write_sz)
 	return 0;
 }
 
+static int delete_module(const char *name, int flags)
+{
+	return syscall(__NR_delete_module, name, flags);
+}
+
 void test_module_attach(void)
 {
 	const int READ_SZ = 456;
 	const int WRITE_SZ = 457;
 	struct test_module_attach* skel;
 	struct test_module_attach__bss *bss;
+	struct bpf_link *link;
 	int err;
 
 	skel = test_module_attach__open();
@@ -84,6 +90,23 @@ void test_module_attach(void)
 	ASSERT_EQ(bss->fexit_ret, -EIO, "fexit_tet");
 	ASSERT_EQ(bss->fmod_ret_read_sz, READ_SZ, "fmod_ret");
 
+	test_module_attach__detach(skel);
+
+	/* attach fentry/fexit and make sure it get's module reference */
+	link = bpf_program__attach(skel->progs.handle_fentry);
+	if (!ASSERT_OK_PTR(link, "attach_fentry"))
+		goto cleanup;
+
+	ASSERT_ERR(delete_module("bpf_testmod", 0), "delete_module");
+	bpf_link__destroy(link);
+
+	link = bpf_program__attach(skel->progs.handle_fexit);
+	if (!ASSERT_OK_PTR(link, "attach_fexit"))
+		goto cleanup;
+
+	ASSERT_ERR(delete_module("bpf_testmod", 0), "delete_module");
+	bpf_link__destroy(link);
+
 cleanup:
 	test_module_attach__destroy(skel);
 }

tools/testing/selftests/bpf/prog_tests/test_lsm.c

@@ -51,43 +51,64 @@ int exec_cmd(int *monitored_pid)
 	return -EINVAL;
 }
 
-void test_test_lsm(void)
+static int test_lsm(struct lsm *skel)
 {
-	struct lsm *skel = NULL;
-	int err, duration = 0;
+	struct bpf_link *link;
 	int buf = 1234;
-
-	skel = lsm__open_and_load();
-	if (CHECK(!skel, "skel_load", "lsm skeleton failed\n"))
-		goto close_prog;
+	int err;
 
 	err = lsm__attach(skel);
-	if (CHECK(err, "attach", "lsm attach failed: %d\n", err))
-		goto close_prog;
+	if (!ASSERT_OK(err, "attach"))
+		return err;
+
+	/* Check that already linked program can't be attached again. */
+	link = bpf_program__attach(skel->progs.test_int_hook);
+	if (!ASSERT_ERR_PTR(link, "attach_link"))
+		return -1;
 
 	err = exec_cmd(&skel->bss->monitored_pid);
-	if (CHECK(err < 0, "exec_cmd", "err %d errno %d\n", err, errno))
-		goto close_prog;
+	if (!ASSERT_OK(err, "exec_cmd"))
+		return err;
 
-	CHECK(skel->bss->bprm_count != 1, "bprm_count", "bprm_count = %d\n",
-	      skel->bss->bprm_count);
+	ASSERT_EQ(skel->bss->bprm_count, 1, "bprm_count");
 
 	skel->bss->monitored_pid = getpid();
 
 	err = stack_mprotect();
-	if (CHECK(errno != EPERM, "stack_mprotect", "want err=EPERM, got %d\n",
-		  errno))
-		goto close_prog;
+	if (!ASSERT_EQ(errno, EPERM, "stack_mprotect"))
+		return err;
 
-	CHECK(skel->bss->mprotect_count != 1, "mprotect_count",
-	      "mprotect_count = %d\n", skel->bss->mprotect_count);
+	ASSERT_EQ(skel->bss->mprotect_count, 1, "mprotect_count");
 
 	syscall(__NR_setdomainname, &buf, -2L);
 	syscall(__NR_setdomainname, 0, -3L);
 	syscall(__NR_setdomainname, ~0L, -4L);
 
-	CHECK(skel->bss->copy_test != 3, "copy_test",
-	      "copy_test = %d\n", skel->bss->copy_test);
+	ASSERT_EQ(skel->bss->copy_test, 3, "copy_test");
+
+	lsm__detach(skel);
+
+	skel->bss->copy_test = 0;
+	skel->bss->bprm_count = 0;
+	skel->bss->mprotect_count = 0;
+	return 0;
+}
+
+void test_test_lsm(void)
+{
+	struct lsm *skel = NULL;
+	int err;
+
+	skel = lsm__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "lsm_skel_load"))
+		goto close_prog;
+
+	err = test_lsm(skel);
+	if (!ASSERT_OK(err, "test_lsm_first_attach"))
+		goto close_prog;
+
+	err = test_lsm(skel);
+	ASSERT_OK(err, "test_lsm_second_attach");
 
 close_prog:
 	lsm__destroy(skel);