Test bpf atomic inode xattr labeling in inode_init_security. Signed-off-by: David Windsor --- 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 +#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