1 #include <linux/bpf.h>
2 #include <linux/vmalloc.h>
3 #include <linux/fdtable.h>
4 #include <linux/file.h>
5 #include <linux/fs.h>
6 #include <linux/kernel.h>
7 #include <linux/idr.h>
8 #include <linux/namei.h>
9 #include <linux/user_namespace.h>
10 #include <linux/security.h>
11
bpf_ns_capable(struct user_namespace * ns,int cap)12 static bool bpf_ns_capable(struct user_namespace *ns, int cap)
13 {
14 return ns_capable(ns, cap) || (cap != CAP_SYS_ADMIN && ns_capable(ns, CAP_SYS_ADMIN));
15 }
16
bpf_token_capable(const struct bpf_token * token,int cap)17 bool bpf_token_capable(const struct bpf_token *token, int cap)
18 {
19 struct user_namespace *userns;
20
21 /* BPF token allows ns_capable() level of capabilities */
22 userns = token ? token->userns : &init_user_ns;
23 if (!bpf_ns_capable(userns, cap))
24 return false;
25 if (token && security_bpf_token_capable(token, cap) < 0)
26 return false;
27 return true;
28 }
29
bpf_token_inc(struct bpf_token * token)30 void bpf_token_inc(struct bpf_token *token)
31 {
32 atomic64_inc(&token->refcnt);
33 }
34
bpf_token_free(struct bpf_token * token)35 static void bpf_token_free(struct bpf_token *token)
36 {
37 security_bpf_token_free(token);
38 put_user_ns(token->userns);
39 kfree(token);
40 }
41
bpf_token_put_deferred(struct work_struct * work)42 static void bpf_token_put_deferred(struct work_struct *work)
43 {
44 struct bpf_token *token = container_of(work, struct bpf_token, work);
45
46 bpf_token_free(token);
47 }
48
bpf_token_put(struct bpf_token * token)49 void bpf_token_put(struct bpf_token *token)
50 {
51 if (!token)
52 return;
53
54 if (!atomic64_dec_and_test(&token->refcnt))
55 return;
56
57 INIT_WORK(&token->work, bpf_token_put_deferred);
58 schedule_work(&token->work);
59 }
60
bpf_token_release(struct inode * inode,struct file * filp)61 static int bpf_token_release(struct inode *inode, struct file *filp)
62 {
63 struct bpf_token *token = filp->private_data;
64
65 bpf_token_put(token);
66 return 0;
67 }
68
bpf_token_show_fdinfo(struct seq_file * m,struct file * filp)69 static void bpf_token_show_fdinfo(struct seq_file *m, struct file *filp)
70 {
71 struct bpf_token *token = filp->private_data;
72 u64 mask;
73
74 BUILD_BUG_ON(__MAX_BPF_CMD >= 64);
75 mask = BIT_ULL(__MAX_BPF_CMD) - 1;
76 if ((token->allowed_cmds & mask) == mask)
77 seq_printf(m, "allowed_cmds:\tany\n");
78 else
79 seq_printf(m, "allowed_cmds:\t0x%llx\n", token->allowed_cmds);
80
81 BUILD_BUG_ON(__MAX_BPF_MAP_TYPE >= 64);
82 mask = BIT_ULL(__MAX_BPF_MAP_TYPE) - 1;
83 if ((token->allowed_maps & mask) == mask)
84 seq_printf(m, "allowed_maps:\tany\n");
85 else
86 seq_printf(m, "allowed_maps:\t0x%llx\n", token->allowed_maps);
87
88 BUILD_BUG_ON(__MAX_BPF_PROG_TYPE >= 64);
89 mask = BIT_ULL(__MAX_BPF_PROG_TYPE) - 1;
90 if ((token->allowed_progs & mask) == mask)
91 seq_printf(m, "allowed_progs:\tany\n");
92 else
93 seq_printf(m, "allowed_progs:\t0x%llx\n", token->allowed_progs);
94
95 BUILD_BUG_ON(__MAX_BPF_ATTACH_TYPE >= 64);
96 mask = BIT_ULL(__MAX_BPF_ATTACH_TYPE) - 1;
97 if ((token->allowed_attachs & mask) == mask)
98 seq_printf(m, "allowed_attachs:\tany\n");
99 else
100 seq_printf(m, "allowed_attachs:\t0x%llx\n", token->allowed_attachs);
101 }
102
103 #define BPF_TOKEN_INODE_NAME "bpf-token"
104
105 static const struct inode_operations bpf_token_iops = { };
106
107 static const struct file_operations bpf_token_fops = {
108 .release = bpf_token_release,
109 .show_fdinfo = bpf_token_show_fdinfo,
110 };
111
bpf_token_create(union bpf_attr * attr)112 int bpf_token_create(union bpf_attr *attr)
113 {
114 struct bpf_mount_opts *mnt_opts;
115 struct bpf_token *token = NULL;
116 struct user_namespace *userns;
117 struct inode *inode;
118 struct file *file;
119 CLASS(fd, f)(attr->token_create.bpffs_fd);
120 struct path path;
121 struct super_block *sb;
122 umode_t mode;
123 int err, fd;
124
125 if (fd_empty(f))
126 return -EBADF;
127
128 path = fd_file(f)->f_path;
129 sb = path.dentry->d_sb;
130
131 if (path.dentry != sb->s_root)
132 return -EINVAL;
133 if (sb->s_op != &bpf_super_ops)
134 return -EINVAL;
135 err = path_permission(&path, MAY_ACCESS);
136 if (err)
137 return err;
138
139 userns = sb->s_user_ns;
140 /*
141 * Enforce that creators of BPF tokens are in the same user
142 * namespace as the BPF FS instance. This makes reasoning about
143 * permissions a lot easier and we can always relax this later.
144 */
145 if (current_user_ns() != userns)
146 return -EPERM;
147 if (!ns_capable(userns, CAP_BPF))
148 return -EPERM;
149
150 /* Creating BPF token in init_user_ns doesn't make much sense. */
151 if (current_user_ns() == &init_user_ns)
152 return -EOPNOTSUPP;
153
154 mnt_opts = sb->s_fs_info;
155 if (mnt_opts->delegate_cmds == 0 &&
156 mnt_opts->delegate_maps == 0 &&
157 mnt_opts->delegate_progs == 0 &&
158 mnt_opts->delegate_attachs == 0)
159 return -ENOENT; /* no BPF token delegation is set up */
160
161 mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());
162 inode = bpf_get_inode(sb, NULL, mode);
163 if (IS_ERR(inode))
164 return PTR_ERR(inode);
165
166 inode->i_op = &bpf_token_iops;
167 inode->i_fop = &bpf_token_fops;
168 clear_nlink(inode); /* make sure it is unlinked */
169
170 file = alloc_file_pseudo(inode, path.mnt, BPF_TOKEN_INODE_NAME, O_RDWR, &bpf_token_fops);
171 if (IS_ERR(file)) {
172 iput(inode);
173 return PTR_ERR(file);
174 }
175
176 token = kzalloc(sizeof(*token), GFP_USER);
177 if (!token) {
178 err = -ENOMEM;
179 goto out_file;
180 }
181
182 atomic64_set(&token->refcnt, 1);
183
184 /* remember bpffs owning userns for future ns_capable() checks */
185 token->userns = get_user_ns(userns);
186
187 token->allowed_cmds = mnt_opts->delegate_cmds;
188 token->allowed_maps = mnt_opts->delegate_maps;
189 token->allowed_progs = mnt_opts->delegate_progs;
190 token->allowed_attachs = mnt_opts->delegate_attachs;
191
192 err = security_bpf_token_create(token, attr, &path);
193 if (err)
194 goto out_token;
195
196 fd = get_unused_fd_flags(O_CLOEXEC);
197 if (fd < 0) {
198 err = fd;
199 goto out_token;
200 }
201
202 file->private_data = token;
203 fd_install(fd, file);
204
205 return fd;
206
207 out_token:
208 bpf_token_free(token);
209 out_file:
210 fput(file);
211 return err;
212 }
213
bpf_token_get_from_fd(u32 ufd)214 struct bpf_token *bpf_token_get_from_fd(u32 ufd)
215 {
216 CLASS(fd, f)(ufd);
217 struct bpf_token *token;
218
219 if (fd_empty(f))
220 return ERR_PTR(-EBADF);
221 if (fd_file(f)->f_op != &bpf_token_fops)
222 return ERR_PTR(-EINVAL);
223
224 token = fd_file(f)->private_data;
225 bpf_token_inc(token);
226
227 return token;
228 }
229
bpf_token_allow_cmd(const struct bpf_token * token,enum bpf_cmd cmd)230 bool bpf_token_allow_cmd(const struct bpf_token *token, enum bpf_cmd cmd)
231 {
232 if (!token)
233 return false;
234 if (!(token->allowed_cmds & BIT_ULL(cmd)))
235 return false;
236 return security_bpf_token_cmd(token, cmd) == 0;
237 }
238
bpf_token_allow_map_type(const struct bpf_token * token,enum bpf_map_type type)239 bool bpf_token_allow_map_type(const struct bpf_token *token, enum bpf_map_type type)
240 {
241 if (!token || type >= __MAX_BPF_MAP_TYPE)
242 return false;
243
244 return token->allowed_maps & BIT_ULL(type);
245 }
246
bpf_token_allow_prog_type(const struct bpf_token * token,enum bpf_prog_type prog_type,enum bpf_attach_type attach_type)247 bool bpf_token_allow_prog_type(const struct bpf_token *token,
248 enum bpf_prog_type prog_type,
249 enum bpf_attach_type attach_type)
250 {
251 if (!token || prog_type >= __MAX_BPF_PROG_TYPE || attach_type >= __MAX_BPF_ATTACH_TYPE)
252 return false;
253
254 return (token->allowed_progs & BIT_ULL(prog_type)) &&
255 (token->allowed_attachs & BIT_ULL(attach_type));
256 }
257