[v2,bpf-next,5/9] bpf/selftests: add selftests for exe_file acquire/release BPF kfuncs

Commit Message

Matt Bobrowski March 6, 2024, 7:40 a.m. UTC

Add a new exe_file_kfunc test suite that is responsible for verifying
the behaviour of the newly added exe_file based BPF kfuncs.

For now, this new exe_file_kfunc test suite covers the following BPF
kfuncs:

struct file *bpf_get_task_exe_file(struct task_struct *task);
struct file *bpf_get_mm_exe_file(struct mm_struct *mm);
void bpf_put_file(struct file *f);

Signed-off-by: Matt Bobrowski <[e-mail]>
---
 .../selftests/bpf/prog_tests/exe_file_kfunc.c |  49 +++++
 .../bpf/progs/exe_file_kfunc_common.h         |  23 +++
 .../bpf/progs/exe_file_kfunc_failure.c        | 181 ++++++++++++++++++
 .../bpf/progs/exe_file_kfunc_success.c        |  52 +++++
 4 files changed, 305 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/exe_file_kfunc.c
 create mode 100644 tools/testing/selftests/bpf/progs/exe_file_kfunc_common.h
 create mode 100644 tools/testing/selftests/bpf/progs/exe_file_kfunc_failure.c
 create mode 100644 tools/testing/selftests/bpf/progs/exe_file_kfunc_success.c

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/exe_file_kfunc.c b/tools/testing/selftests/bpf/prog_tests/exe_file_kfunc.c
new file mode 100644
index 000000000000..5900c1d4e820
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/exe_file_kfunc.c
@@ -0,0 +1,49 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Google LLC. */
+
+#define _GNU_SOURCE
+#include <test_progs.h>
+
+#include "exe_file_kfunc_failure.skel.h"
+#include "exe_file_kfunc_success.skel.h"
+
+static void run_test(const char *prog_name)
+{
+	struct bpf_link *link;
+	struct bpf_program *prog;
+	struct exe_file_kfunc_success *skel;
+
+	skel = exe_file_kfunc_success__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "file_kfunc_success__open_and_load"))
+		return;
+
+	link = NULL;
+	prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+		goto cleanup;
+
+	link = bpf_program__attach(prog);
+	ASSERT_OK_PTR(link, "bpf_program__attach");
+cleanup:
+	bpf_link__destroy(link);
+	exe_file_kfunc_success__destroy(skel);
+}
+
+static const char * const success_tests[] = {
+	"get_task_exe_file_and_put_kfunc_from_current",
+	"get_task_exe_file_and_put_kfunc_from_argument",
+	"get_mm_exe_file_and_put_kfunc_from_current",
+};
+
+void test_exe_file_kfunc(void)
+{
+	int i = 0;
+
+	for (; i < ARRAY_SIZE(success_tests); i++) {
+		if (!test__start_subtest(success_tests[i]))
+			continue;
+		run_test(success_tests[i]);
+	}
+
+	RUN_TESTS(exe_file_kfunc_failure);
+}
diff --git a/tools/testing/selftests/bpf/progs/exe_file_kfunc_common.h b/tools/testing/selftests/bpf/progs/exe_file_kfunc_common.h
new file mode 100644
index 000000000000..6623bcc130c3
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/exe_file_kfunc_common.h
@@ -0,0 +1,23 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Google LLC. */
+
+#ifndef _FILE_KFUNC_COMMON_H
+#define _FILE_KFUNC_COMMON_H
+
+#include <vmlinux.h>
+#include <errno.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#include "bpf_misc.h"
+
+struct mm_struct *bpf_task_mm_grab(struct task_struct *task) __ksym;
+void bpf_mm_drop(struct mm_struct *mm) __ksym;
+
+struct file *bpf_get_task_exe_file(struct task_struct *task) __ksym;
+struct file *bpf_get_mm_exe_file(struct mm_struct *mm) __ksym;
+void bpf_put_file(struct file *f) __ksym;
+
+char _license[] SEC("license") = "GPL";
+
+#endif /* _FILE_KFUNC_COMMON_H */
diff --git a/tools/testing/selftests/bpf/progs/exe_file_kfunc_failure.c b/tools/testing/selftests/bpf/progs/exe_file_kfunc_failure.c
new file mode 100644
index 000000000000..8a4464481531
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/exe_file_kfunc_failure.c
@@ -0,0 +1,181 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Google LLC. */
+
+#include "exe_file_kfunc_common.h"
+
+SEC("lsm.s/file_open")
+__failure __msg("Possibly NULL pointer passed to trusted arg0")
+int BPF_PROG(get_task_exe_file_kfunc_null)
+{
+	struct file *acquired;
+
+	/* Can't pass a NULL pointer to bpf_get_task_exe_file(). */
+	acquired = bpf_get_task_exe_file(NULL);
+	bpf_put_file(acquired);
+
+	return 0;
+}
+
+SEC("lsm.s/file_open")
+__failure __msg("Possibly NULL pointer passed to trusted arg0")
+int BPF_PROG(get_mm_exe_file_kfunc_null)
+{
+	struct file *acquired;
+
+	/* Can't pass a NULL pointer to bpf_get_mm_exe_file(). */
+	acquired = bpf_get_mm_exe_file(NULL);
+	bpf_put_file(acquired);
+
+	return 0;
+}
+
+SEC("lsm.s/inode_getxattr")
+__failure __msg("arg#0 pointer type STRUCT task_struct must point to scalar, or struct with scalar")
+int BPF_PROG(get_task_exe_file_kfunc_fp)
+{
+	u64 x;
+	struct file *acquired;
+	struct task_struct *fp;
+
+	fp = (struct task_struct *)&x;
+	/* Can't pass random frame pointer to bpf_get_task_exe_file(). */
+	acquired = bpf_get_task_exe_file(fp);
+	bpf_put_file(acquired);
+
+	return 0;
+}
+
+SEC("lsm.s/inode_getxattr")
+__failure __msg("arg#0 pointer type STRUCT mm_struct must point to scalar, or struct with scalar")
+int BPF_PROG(get_mm_exe_file_kfunc_fp)
+{
+	int x;
+	struct file *acquired;
+	struct mm_struct *fp;
+
+	fp = (struct mm_struct *)&x;
+	/* Can't pass random frame pointer to bpf_get_mm_exe_file(). */
+	acquired = bpf_get_mm_exe_file(fp);
+	if (!acquired)
+		return 0;
+	bpf_put_file(acquired);
+
+	return 0;
+}
+
+SEC("lsm.s/file_open")
+__failure __msg("R1 must be referenced or trusted")
+int BPF_PROG(get_task_exe_file_kfunc_untrusted)
+{
+	struct file *acquired;
+	struct task_struct *parent;
+
+	/* Walking a trusted struct task_struct returned from
+	 * bpf_get_current_task_btf() yields an untrusted pointer. */
+	parent = bpf_get_current_task_btf()->parent;
+	/* Can't pass untrusted pointer to bpf_get_task_exe_file(). */
+	acquired = bpf_get_task_exe_file(parent);
+	if (!acquired)
+		return 0;
+	bpf_put_file(acquired);
+
+	return 0;
+}
+
+SEC("lsm.s/file_open")
+__failure __msg("R1 must be referenced or trusted")
+int BPF_PROG(get_mm_exe_file_kfunc_untrusted)
+{
+	struct file *acquired;
+	struct mm_struct *mm;
+
+	/* Walking a struct task_struct obtained from bpf_get_current_task_btf()
+	 * yields an untrusted pointer. */
+	mm = bpf_get_current_task_btf()->mm;
+	/* Can't pass untrusted pointer to bpf_get_mm_exe_file(). */
+	acquired = bpf_get_mm_exe_file(mm);
+	if (!acquired)
+		return 0;
+	bpf_put_file(acquired);
+
+	return 0;
+}
+
+SEC("lsm.s/file_open")
+__failure __msg("Unreleased reference")
+int BPF_PROG(get_task_exe_file_kfunc_unreleased)
+{
+	struct file *acquired;
+
+	acquired = bpf_get_task_exe_file(bpf_get_current_task_btf());
+	if (!acquired)
+		return 0;
+	__sink(acquired);
+
+	/* Acquired but never released. */
+	return 0;
+}
+
+SEC("lsm.s/file_open")
+__failure __msg("Unreleased reference")
+int BPF_PROG(get_mm_exe_file_kfunc_unreleased)
+{
+	struct file *acquired;
+	struct mm_struct *mm;
+
+	mm = bpf_task_mm_grab(bpf_get_current_task_btf());
+	if (!mm)
+		return 0;
+
+	acquired = bpf_get_mm_exe_file(mm);
+	if (!acquired) {
+		bpf_mm_drop(mm);
+		return 0;
+	}
+	__sink(acquired);
+	bpf_mm_drop(mm);
+
+	/* Acquired but never released. */
+	return 0;
+}
+
+SEC("lsm/file_open")
+__failure __msg("program must be sleepable to call sleepable kfunc bpf_put_file")
+int BPF_PROG(put_file_kfunc_not_sleepable, struct file *f)
+{
+	struct file *acquired;
+
+	acquired = bpf_get_task_exe_file(bpf_get_current_task_btf());
+	if (!acquired)
+		return 0;
+
+	/* Can't call bpf_put_file() from non-sleepable BPF program. */
+	bpf_put_file(acquired);
+
+	return 0;
+}
+
+SEC("lsm.s/file_open")
+__failure __msg("release kernel function bpf_put_file expects")
+int BPF_PROG(put_file_kfunc_unacquired, struct file *f)
+{
+	/* Can't release an unacquired pointer. */
+	bpf_put_file(f);
+
+	return 0;
+}
+
+SEC("tp_btf/task_newtask")
+__failure __msg("calling kernel function bpf_get_task_exe_file is not allowed")
+int BPF_PROG(get_task_exe_file_kfunc_not_lsm_prog, struct task_struct *task)
+{
+	struct file *acquired;
+
+	/* bpf_get_task_exe_file() can only be called from BPF LSM program. */
+	acquired = bpf_get_task_exe_file(bpf_get_current_task_btf());
+	if (!acquired)
+		return 0;
+	bpf_put_file(acquired);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/exe_file_kfunc_success.c b/tools/testing/selftests/bpf/progs/exe_file_kfunc_success.c
new file mode 100644
index 000000000000..ae789cb0a9ae
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/exe_file_kfunc_success.c
@@ -0,0 +1,52 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Google LLC. */
+
+#include "exe_file_kfunc_common.h"
+
+SEC("lsm.s/file_open")
+int BPF_PROG(get_task_exe_file_and_put_kfunc_from_current)
+{
+	struct file *acquired;
+
+	acquired = bpf_get_task_exe_file(bpf_get_current_task_btf());
+	if (!acquired)
+		return 0;
+	bpf_put_file(acquired);
+
+	return 0;
+}
+
+SEC("lsm.s/task_alloc")
+int BPF_PROG(get_task_exe_file_and_put_kfunc_from_argument,
+	     struct task_struct *task)
+{
+	struct file *acquired;
+
+	acquired = bpf_get_task_exe_file(task);
+	if (!acquired)
+		return 0;
+	bpf_put_file(acquired);
+
+	return 0;
+}
+
+SEC("lsm.s/file_open")
+int BPF_PROG(get_mm_exe_file_and_put_kfunc_from_current)
+{
+	struct file *acquired;
+	struct mm_struct *mm;
+
+	mm = bpf_task_mm_grab(bpf_get_current_task_btf());
+	if (!mm)
+		return 0;
+
+	acquired = bpf_get_mm_exe_file(mm);
+	if (!acquired) {
+		bpf_mm_drop(mm);
+		return 0;
+	}
+	bpf_put_file(acquired);
+	bpf_mm_drop(mm);
+
+	return 0;
+}