Test bpf atomic inode xattr labeling in inode_init_security.
Signed-off-by: David Windsor <[email protected]>
---
tools/testing/selftests/bpf/bpf_kfuncs.h | 5 +
.../selftests/bpf/prog_tests/fs_kfuncs.c | 117 ++++++++++++++++++
.../bpf/progs/test_init_inode_xattr.c | 31 +++++
3 files changed, 153 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/test_init_inode_xattr.c
diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h
b/tools/testing/selftests/bpf/bpf_kfuncs.h
index ae71e9b69051..2639f9f94195 100644
--- a/tools/testing/selftests/bpf/bpf_kfuncs.h
+++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
@@ -92,4 +92,9 @@ extern int bpf_set_dentry_xattr(struct dentry *dentry, const
char *name__str,
const struct bpf_dynptr *value_p, int flags)
__ksym __weak;
extern int bpf_remove_dentry_xattr(struct dentry *dentry, const char
*name__str) __ksym __weak;
+struct lsm_xattrs;
+extern int bpf_init_inode_xattr(struct lsm_xattrs *xattrs,
+ const char *name__str,
+ const struct bpf_dynptr *value_p) __ksym __weak;
+
#endif
diff --git a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
b/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
index 43a26ec69a8e..8b2e0d433aea 100644
--- a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
+++ b/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
@@ -10,6 +10,7 @@
#include "test_get_xattr.skel.h"
#include "test_set_remove_xattr.skel.h"
#include "test_fsverity.skel.h"
+#include "test_init_inode_xattr.skel.h"
static const char testfile[] = "/tmp/test_progs_fs_kfuncs";
@@ -268,6 +269,116 @@ static void test_fsverity(void)
remove(testfile);
}
+static void test_init_inode_xattr(void)
+{
+ struct test_init_inode_xattr *skel = NULL;
+ int fd = -1, err;
+ char value_out[64];
+ const char *testfile_new = "/tmp/test_progs_fs_kfuncs_new";
+
+ skel = test_init_inode_xattr__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "test_init_inode_xattr__open_and_load"))
+ return;
+
+ skel->bss->monitored_pid = getpid();
+ err = test_init_inode_xattr__attach(skel);
+ if (!ASSERT_OK(err, "test_init_inode_xattr__attach"))
+ goto out;
+
+ /* Trigger inode_init_security */
+ fd = open(testfile_new, O_CREAT | O_RDWR, 0644);
+ if (!ASSERT_GE(fd, 0, "create_file"))
+ goto out;
+
+ ASSERT_EQ(skel->data->init_result, 0, "init_result");
+
+ /* initxattrs prepends "security." to the name. */
+ err = getxattr(testfile_new, "security.bpf.test_label", value_out,
+ sizeof(value_out));
+ if (err < 0 && errno == ENODATA) {
+ printf("%s:SKIP:filesystem did not apply LSM xattrs\n",
+ __func__);
+ test__skip();
+ goto out;
+ }
+ if (!ASSERT_GE(err, 0, "getxattr"))
+ goto out;
+
+ ASSERT_EQ(err, (int)sizeof(skel->data->xattr_value), "xattr_size");
+ ASSERT_EQ(strncmp(value_out, "unconfined_u:object_r:user_home_t:s0",
+ sizeof("unconfined_u:object_r:user_home_t:s0")), 0,
+ "xattr_value");
+
+out:
+ close(fd);
+ test_init_inode_xattr__destroy(skel);
+ remove(testfile_new);
+}
+
+/* Keep in sync with BPF_LSM_INODE_INIT_XATTRS in include/linux/bpf_lsm.h. */
+#define INIT_INODE_XATTR_MAX 4
+
+/*
+ * Programs may attach to inode_init_security without an attach-time limit, but
+ * the kfunc only lets BPF claim INIT_INODE_XATTR_MAX xattr slots per inode.
+ * Calls beyond that budget are rejected at runtime with -ENOSPC.
+ */
+static void test_init_inode_xattr_slot_limit(void)
+{
+ struct test_init_inode_xattr *skel[INIT_INODE_XATTR_MAX + 1] = {};
+ struct bpf_link *link[INIT_INODE_XATTR_MAX + 1] = {};
+ const char *testfile_slot = "/tmp/test_progs_fs_kfuncs_slot";
+ int ok = 0, nospc = 0, other = 0;
+ int i, fd = -1;
+
+ /* All programs attach successfully; there is no attach-time cap. */
+ for (i = 0; i <= INIT_INODE_XATTR_MAX; i++) {
+ skel[i] = test_init_inode_xattr__open_and_load();
+ if (!ASSERT_OK_PTR(skel[i], "open_and_load"))
+ goto out;
+
+ skel[i]->bss->monitored_pid = getpid();
+
+ link[i] =
bpf_program__attach_lsm(skel[i]->progs.test_init_inode_xattr);
+ if (!ASSERT_OK_PTR(link[i], "attach"))
+ goto out;
+ }
+
+ /* Trigger inode_init_security once with all programs attached. */
+ fd = open(testfile_slot, O_CREAT | O_RDWR, 0644);
+ if (!ASSERT_GE(fd, 0, "create_file"))
+ goto out;
+
+ /*
+ * Exactly INIT_INODE_XATTR_MAX programs claim a slot; the program past
+ * the budget gets -ENOSPC. The order in which programs run is not
+ * guaranteed, so count results instead of indexing.
+ */
+ for (i = 0; i <= INIT_INODE_XATTR_MAX; i++) {
+ int res = skel[i]->data->init_result;
+
+ if (res == 0)
+ ok++;
+ else if (res == -ENOSPC)
+ nospc++;
+ else
+ other++;
+ }
+
+ ASSERT_EQ(ok, INIT_INODE_XATTR_MAX, "slots_within_budget");
+ ASSERT_EQ(nospc, 1, "slot_over_budget");
+ ASSERT_EQ(other, 0, "unexpected_result");
+
+out:
+ if (fd >= 0)
+ close(fd);
+ for (i = 0; i <= INIT_INODE_XATTR_MAX; i++) {
+ bpf_link__destroy(link[i]);
+ test_init_inode_xattr__destroy(skel[i]);
+ }
+ remove(testfile_slot);
+}
+
void test_fs_kfuncs(void)
{
/* Matches xattr_names in progs/test_get_xattr.c */
@@ -288,4 +399,10 @@ void test_fs_kfuncs(void)
if (test__start_subtest("fsverity"))
test_fsverity();
+
+ if (test__start_subtest("init_inode_xattr"))
+ test_init_inode_xattr();
+
+ if (test__start_subtest("init_inode_xattr_slot_limit"))
+ test_init_inode_xattr_slot_limit();
}
diff --git a/tools/testing/selftests/bpf/progs/test_init_inode_xattr.c
b/tools/testing/selftests/bpf/progs/test_init_inode_xattr.c
new file mode 100644
index 000000000000..cb378db957aa
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_init_inode_xattr.c
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Cisco Systems, Inc. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_tracing.h>
+#include "bpf_kfuncs.h"
+
+char _license[] SEC("license") = "GPL";
+
+__u32 monitored_pid;
+int init_result = -1;
+
+static const char xattr_name[] = "bpf.test_label";
+char xattr_value[] = "unconfined_u:object_r:user_home_t:s0";
+
+SEC("lsm.s/inode_init_security")
+int BPF_PROG(test_init_inode_xattr, struct inode *inode, struct inode *dir,
+ const struct qstr *qstr, struct lsm_xattrs *xattrs)
+{
+ struct bpf_dynptr value_ptr;
+ __u32 pid;
+
+ pid = bpf_get_current_pid_tgid() >> 32;
+ if (pid != monitored_pid)
+ return 0;
+
+ bpf_dynptr_from_mem(xattr_value, sizeof(xattr_value), 0, &value_ptr);
+ init_result = bpf_init_inode_xattr(xattrs, xattr_name, &value_ptr);
+
+ return 0;
+}
--
2.53.0
