test_get_xattr.c

 1// SPDX-License-Identifier: GPL-2.0
 2/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
 3
 4#include "vmlinux.h"
 5#include <errno.h>
 6#include <bpf/bpf_helpers.h>
 7#include <bpf/bpf_tracing.h>
 8#include "bpf_kfuncs.h"
 9#include "bpf_misc.h"
10
11char _license[] SEC("license") = "GPL";
12
13__u32 monitored_pid;
14__u32 found_xattr_from_file;
15__u32 found_xattr_from_dentry;
16
17static const char expected_value[] = "hello";
18char value1[32];
19char value2[32];
20
21/* Matches caller of test_get_xattr() in prog_tests/fs_kfuncs.c */
22static const char xattr_names[][64] = {
23	/* The following work. */
24	"user.kfuncs",
25	"security.bpf.xxx",
26
27	/* The following do not work. */
28	"security.bpf",
29	"security.selinux"
30};
31
32SEC("lsm.s/file_open")
33int BPF_PROG(test_file_open, struct file *f)
34{
35	struct bpf_dynptr value_ptr;
36	__u32 pid;
37	int ret, i;
38
39	pid = bpf_get_current_pid_tgid() >> 32;
40	if (pid != monitored_pid)
41		return 0;
42
43	bpf_dynptr_from_mem(value1, sizeof(value1), 0, &value_ptr);
44
45	for (i = 0; i < ARRAY_SIZE(xattr_names); i++) {
46		ret = bpf_get_file_xattr(f, xattr_names[i], &value_ptr);
47		if (ret == sizeof(expected_value))
48			break;
49	}
50	if (ret != sizeof(expected_value))
51		return 0;
52	if (bpf_strncmp(value1, ret, expected_value))
53		return 0;
54	found_xattr_from_file = 1;
55	return 0;
56}
57
58SEC("lsm.s/inode_getxattr")
59int BPF_PROG(test_inode_getxattr, struct dentry *dentry, char *name)
60{
61	struct bpf_dynptr value_ptr;
62	__u32 pid;
63	int ret, i;
64
65	pid = bpf_get_current_pid_tgid() >> 32;
66	if (pid != monitored_pid)
67		return 0;
68
69	bpf_dynptr_from_mem(value2, sizeof(value2), 0, &value_ptr);
70
71	for (i = 0; i < ARRAY_SIZE(xattr_names); i++) {
72		ret = bpf_get_dentry_xattr(dentry, xattr_names[i], &value_ptr);
73		if (ret == sizeof(expected_value))
74			break;
75	}
76	if (ret != sizeof(expected_value))
77		return 0;
78	if (bpf_strncmp(value2, ret, expected_value))
79		return 0;
80	found_xattr_from_dentry = 1;
81
82	/* return non-zero to fail getxattr from user space */
83	return -EINVAL;
84}