[PATCH bpf-next v2 4/4] selftests/bpf: Add tests for struct file related CRIB kfuncs

[Juntong Deng <juntong.deng@xxxxxxxxxxx>]

This patch adds test cases for struct file related CRIB kfuncs.

The test case for bpf_fget_task() is written based on
files_test_process(), so there should only be 3 opened files,
corresponding to file descriptors 0, 1, 2.

bpf_get_file_ops_type() currently only returns FILE_OPS_UNKNOWN,
so no test cases are needed for now.

In addition, this patch adds failure test cases where bpf programs
cannot pass the verifier due to untrusted pointer arguments.

Signed-off-by: Juntong Deng <juntong.deng@xxxxxxxxxxx>
---
 tools/testing/selftests/bpf/prog_tests/crib.c |  1 +
 .../testing/selftests/bpf/progs/crib_common.h |  4 ++
 .../selftests/bpf/progs/crib_files_failure.c  | 22 +++++++++
 .../selftests/bpf/progs/crib_files_success.c  | 46 +++++++++++++++++++
 4 files changed, 73 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/crib.c b/tools/testing/selftests/bpf/prog_tests/crib.c
index 48c5156504ad..5ef887e43170 100644
--- a/tools/testing/selftests/bpf/prog_tests/crib.c
+++ b/tools/testing/selftests/bpf/prog_tests/crib.c
@@ -108,6 +108,7 @@ static void run_files_success_test(const char *prog_name)
 
 static const char * const files_success_tests[] = {
 	"test_bpf_iter_task_file",
+	"test_bpf_fget_task",
 };
 
 void test_crib(void)
diff --git a/tools/testing/selftests/bpf/progs/crib_common.h b/tools/testing/selftests/bpf/progs/crib_common.h
index 93b8f9b1bdf8..0bc77d1b02b2 100644
--- a/tools/testing/selftests/bpf/progs/crib_common.h
+++ b/tools/testing/selftests/bpf/progs/crib_common.h
@@ -18,4 +18,8 @@ extern struct file *bpf_iter_task_file_next(struct bpf_iter_task_file *it) __ksy
 extern int bpf_iter_task_file_get_fd(struct bpf_iter_task_file *it__iter) __ksym;
 extern void bpf_iter_task_file_destroy(struct bpf_iter_task_file *it) __ksym;
 
+extern struct file *bpf_fget_task(struct task_struct *task, unsigned int fd) __ksym;
+extern unsigned int bpf_get_file_ops_type(struct file *file) __ksym;
+extern void bpf_put_file(struct file *file) __ksym;
+
 #endif /* __CRIB_COMMON_H */
diff --git a/tools/testing/selftests/bpf/progs/crib_files_failure.c b/tools/testing/selftests/bpf/progs/crib_files_failure.c
index ebae01d87ff9..9360aad50c15 100644
--- a/tools/testing/selftests/bpf/progs/crib_files_failure.c
+++ b/tools/testing/selftests/bpf/progs/crib_files_failure.c
@@ -84,3 +84,25 @@ int bpf_iter_task_file_destroy_uninit_iter(void *ctx)
 
 	return 0;
 }
+
+SEC("syscall")
+__failure __msg("Possibly NULL pointer passed to trusted arg0")
+int bpf_fget_task_untrusted_file(void *ctx)
+{
+	struct task_struct *task = NULL;
+
+	bpf_fget_task(task, 1);
+
+	return 0;
+}
+
+SEC("syscall")
+__failure __msg("Possibly NULL pointer passed to trusted arg0")
+int bpf_get_file_ops_type_untrusted_file(void *ctx)
+{
+	struct file *file = NULL;
+
+	bpf_get_file_ops_type(file);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/crib_files_success.c b/tools/testing/selftests/bpf/progs/crib_files_success.c
index 92ca7d9d44c3..8dddac6a7378 100644
--- a/tools/testing/selftests/bpf/progs/crib_files_success.c
+++ b/tools/testing/selftests/bpf/progs/crib_files_success.c
@@ -71,3 +71,49 @@ int test_bpf_iter_task_file(void *ctx)
 	bpf_task_release(task);
 	return 0;
 }
+
+SEC("syscall")
+int test_bpf_fget_task(void *ctx)
+{
+	struct task_struct *task;
+	struct file *file;
+
+	task = bpf_task_from_vpid(pid);
+	if (task == NULL) {
+		err = 1;
+		return 0;
+	}
+
+	file = bpf_fget_task(task, 0);
+	if (file == NULL) {
+		err = 2;
+		goto cleanup;
+	}
+
+	bpf_put_file(file);
+
+	file = bpf_fget_task(task, 1);
+	if (file == NULL) {
+		err = 3;
+		goto cleanup;
+	}
+
+	bpf_put_file(file);
+
+	file = bpf_fget_task(task, 2);
+	if (file == NULL) {
+		err = 4;
+		goto cleanup;
+	}
+
+	bpf_put_file(file);
+
+	file = bpf_fget_task(task, 3);
+	if (file != NULL) {
+		err = 5;
+		bpf_put_file(file);
+	}
+cleanup:
+	bpf_task_release(task);
+	return 0;
+}
-- 
2.39.5