[PATCH v4 bpf-next 6/6] selftests/bpf: Add __failure tests for set/remove xattr kfuncs

[Song Liu <song@kernel.org>]

Different LSM hooks should call different versions of set/remove xattr
kfuncs (with _locked or not). Add __failure tests to make sure the
verifier can detect when the user uses the wrong kfuncs.

Signed-off-by: Song Liu <song@kernel.org>
---
 .../selftests/bpf/prog_tests/fs_kfuncs.c      |  3 +
 .../bpf/progs/test_set_remove_xattr_failure.c | 56 +++++++++++++++++++
 2 files changed, 59 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/test_set_remove_xattr_failure.c

diff --git a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c b/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
index 43a26ec69a8e..f24285ae8d43 100644
--- a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
+++ b/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
@@ -9,6 +9,7 @@
 #include <test_progs.h>
 #include "test_get_xattr.skel.h"
 #include "test_set_remove_xattr.skel.h"
+#include "test_set_remove_xattr_failure.skel.h"
 #include "test_fsverity.skel.h"
 
 static const char testfile[] = "/tmp/test_progs_fs_kfuncs";
@@ -286,6 +287,8 @@ void test_fs_kfuncs(void)
 	if (test__start_subtest("set_remove_xattr"))
 		test_set_remove_xattr();
 
+	RUN_TESTS(test_set_remove_xattr_failure);
+
 	if (test__start_subtest("fsverity"))
 		test_fsverity();
 }
diff --git a/tools/testing/selftests/bpf/progs/test_set_remove_xattr_failure.c b/tools/testing/selftests/bpf/progs/test_set_remove_xattr_failure.c
new file mode 100644
index 000000000000..ee9c7df27a93
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_set_remove_xattr_failure.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_tracing.h>
+#include "bpf_kfuncs.h"
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+static const char xattr_bar[] = "security.bpf.bar";
+char v[32];
+
+SEC("lsm.s/inode_getxattr")
+__failure __msg("calling kernel function bpf_set_dentry_xattr_locked is not allowed")
+int BPF_PROG(test_getxattr_failure_a, struct dentry *dentry, char *name)
+{
+	struct bpf_dynptr value_ptr;
+
+	bpf_dynptr_from_mem(v, sizeof(v), 0, &value_ptr);
+
+	bpf_set_dentry_xattr_locked(dentry, xattr_bar, &value_ptr, 0);
+	return 0;
+}
+
+SEC("lsm.s/inode_getxattr")
+__failure __msg("calling kernel function bpf_remove_dentry_xattr_locked is not allowed")
+int BPF_PROG(test_getxattr_failure_b, struct dentry *dentry, char *name)
+{
+	bpf_remove_dentry_xattr_locked(dentry, xattr_bar);
+	return 0;
+}
+
+SEC("lsm.s/inode_setxattr")
+__failure __msg("calling kernel function bpf_set_dentry_xattr is not allowed")
+int BPF_PROG(test_inode_setxattr_failure_a, struct mnt_idmap *idmap,
+	     struct dentry *dentry, const char *name,
+	     const void *value, size_t size, int flags)
+{
+	struct bpf_dynptr value_ptr;
+
+	bpf_dynptr_from_mem(v, sizeof(v), 0, &value_ptr);
+
+	bpf_set_dentry_xattr(dentry, xattr_bar, &value_ptr, 0);
+	return 0;
+}
+
+SEC("lsm.s/inode_setxattr")
+__failure __msg("calling kernel function bpf_remove_dentry_xattr is not allowed")
+int BPF_PROG(test_inode_setxattr_failure_b, struct mnt_idmap *idmap,
+	     struct dentry *dentry, const char *name,
+	     const void *value, size_t size, int flags)
+{
+	bpf_remove_dentry_xattr(dentry, xattr_bar);
+	return 0;
+}
-- 
2.43.5