1 // SPDX-License-Identifier: GPL-2.0 1
2 /* Copyright (c) 2024 Google LLC. */
3
4 #include <linux/bpf.h>
5 #include <linux/btf.h>
6 #include <linux/btf_ids.h>
7 #include <linux/dcache.h>
8 #include <linux/fs.h>
9 #include <linux/file.h>
10 #include <linux/mm.h>
11 #include <linux/xattr.h>
12
13 __bpf_kfunc_start_defs();
14
15 /**
16 * bpf_get_task_exe_file - get a reference on
17 * the mm_struct that
18 * task_struct
19 * @task: task_struct of which the nested mm_s
20 * reference on
21 *
22 * Get a reference on the exe_file struct file
23 * nested within the supplied *task*. The refe
24 * this BPF kfunc must be released using bpf_p
25 * bpf_put_file() on the returned referenced s
26 * acquired by this BPF kfunc will result in t
27 * the BPF verifier.
28 *
29 * This BPF kfunc may only be called from BPF
30 *
31 * Internally, this BPF kfunc leans on get_tas
32 * bpf_get_task_exe_file() would be analogous
33 * directly in kernel context.
34 *
35 * Return: A referenced struct file pointer to
36 * mm_struct that is nested within the supplie
37 * returned.
38 */
39 __bpf_kfunc struct file *bpf_get_task_exe_file
40 {
41 return get_task_exe_file(task);
42 }
43
44 /**
45 * bpf_put_file - put a reference on the suppl
46 * @file: file to put a reference on
47 *
48 * Put a reference on the supplied *file*. Onl
49 * passed to this BPF kfunc. Attempting to pas
50 * any other arbitrary pointer for that matter
51 * being rejected by the BPF verifier.
52 *
53 * This BPF kfunc may only be called from BPF
54 */
55 __bpf_kfunc void bpf_put_file(struct file *fil
56 {
57 fput(file);
58 }
59
60 /**
61 * bpf_path_d_path - resolve the pathname for
62 * @path: path to resolve the pathname for
63 * @buf: buffer to return the resolved pathnam
64 * @buf__sz: length of the supplied buffer
65 *
66 * Resolve the pathname for the supplied *path
67 * kfunc is the safer variant of the legacy bp
68 * used in place of bpf_d_path() whenever poss
69 * semantics, meaning that the supplied *path*
70 * reference, or else the BPF program will be
71 * verifier.
72 *
73 * This BPF kfunc may only be called from BPF
74 *
75 * Return: A positive integer corresponding to
76 * pathname in *buf*, including the NUL termin
77 * negative integer is returned.
78 */
79 __bpf_kfunc int bpf_path_d_path(struct path *p
80 {
81 int len;
82 char *ret;
83
84 if (!buf__sz)
85 return -EINVAL;
86
87 ret = d_path(path, buf, buf__sz);
88 if (IS_ERR(ret))
89 return PTR_ERR(ret);
90
91 len = buf + buf__sz - ret;
92 memmove(buf, ret, len);
93 return len;
94 }
95
96 /**
97 * bpf_get_dentry_xattr - get xattr of a dentr
98 * @dentry: dentry to get xattr from
99 * @name__str: name of the xattr
100 * @value_p: output buffer of the xattr value
101 *
102 * Get xattr *name__str* of *dentry* and store
103 *
104 * For security reasons, only *name__str* with
105 *
106 * Return: 0 on success, a negative value on e
107 */
108 __bpf_kfunc int bpf_get_dentry_xattr(struct de
109 struct bp
110 {
111 struct bpf_dynptr_kern *value_ptr = (s
112 struct inode *inode = d_inode(dentry);
113 u32 value_len;
114 void *value;
115 int ret;
116
117 if (WARN_ON(!inode))
118 return -EINVAL;
119
120 if (strncmp(name__str, XATTR_USER_PREF
121 return -EPERM;
122
123 value_len = __bpf_dynptr_size(value_pt
124 value = __bpf_dynptr_data_rw(value_ptr
125 if (!value)
126 return -EINVAL;
127
128 ret = inode_permission(&nop_mnt_idmap,
129 if (ret)
130 return ret;
131 return __vfs_getxattr(dentry, inode, n
132 }
133
134 /**
135 * bpf_get_file_xattr - get xattr of a file
136 * @file: file to get xattr from
137 * @name__str: name of the xattr
138 * @value_p: output buffer of the xattr value
139 *
140 * Get xattr *name__str* of *file* and store t
141 *
142 * For security reasons, only *name__str* with
143 *
144 * Return: 0 on success, a negative value on e
145 */
146 __bpf_kfunc int bpf_get_file_xattr(struct file
147 struct bpf_
148 {
149 struct dentry *dentry;
150
151 dentry = file_dentry(file);
152 return bpf_get_dentry_xattr(dentry, na
153 }
154
155 __bpf_kfunc_end_defs();
156
157 BTF_KFUNCS_START(bpf_fs_kfunc_set_ids)
158 BTF_ID_FLAGS(func, bpf_get_task_exe_file,
159 KF_ACQUIRE | KF_TRUSTED_ARGS | KF
160 BTF_ID_FLAGS(func, bpf_put_file, KF_RELEASE)
161 BTF_ID_FLAGS(func, bpf_path_d_path, KF_TRUSTED
162 BTF_ID_FLAGS(func, bpf_get_dentry_xattr, KF_SL
163 BTF_ID_FLAGS(func, bpf_get_file_xattr, KF_SLEE
164 BTF_KFUNCS_END(bpf_fs_kfunc_set_ids)
165
166 static int bpf_fs_kfuncs_filter(const struct b
167 {
168 if (!btf_id_set8_contains(&bpf_fs_kfun
169 prog->type == BPF_PROG_TYPE_LSM)
170 return 0;
171 return -EACCES;
172 }
173
174 static const struct btf_kfunc_id_set bpf_fs_kf
175 .owner = THIS_MODULE,
176 .set = &bpf_fs_kfunc_set_ids,
177 .filter = bpf_fs_kfuncs_filter,
178 };
179
180 static int __init bpf_fs_kfuncs_init(void)
181 {
182 return register_btf_kfunc_id_set(BPF_P
183 }
184
185 late_initcall(bpf_fs_kfuncs_init);
186
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