1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* scm.c - Socket level control messages processing. |
3 | * |
4 | * Author: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> |
5 | * Alignment and value checking mods by Craig Metz |
6 | */ |
7 | |
8 | #include <linux/module.h> |
9 | #include <linux/signal.h> |
10 | #include <linux/capability.h> |
11 | #include <linux/errno.h> |
12 | #include <linux/sched.h> |
13 | #include <linux/sched/user.h> |
14 | #include <linux/mm.h> |
15 | #include <linux/kernel.h> |
16 | #include <linux/stat.h> |
17 | #include <linux/socket.h> |
18 | #include <linux/file.h> |
19 | #include <linux/fcntl.h> |
20 | #include <linux/net.h> |
21 | #include <linux/interrupt.h> |
22 | #include <linux/netdevice.h> |
23 | #include <linux/security.h> |
24 | #include <linux/pid_namespace.h> |
25 | #include <linux/pid.h> |
26 | #include <linux/nsproxy.h> |
27 | #include <linux/slab.h> |
28 | #include <linux/errqueue.h> |
29 | #include <linux/io_uring.h> |
30 | |
31 | #include <linux/uaccess.h> |
32 | |
33 | #include <net/protocol.h> |
34 | #include <linux/skbuff.h> |
35 | #include <net/sock.h> |
36 | #include <net/compat.h> |
37 | #include <net/scm.h> |
38 | #include <net/cls_cgroup.h> |
39 | #include <net/af_unix.h> |
40 | |
41 | |
42 | /* |
43 | * Only allow a user to send credentials, that they could set with |
44 | * setu(g)id. |
45 | */ |
46 | |
47 | static __inline__ int scm_check_creds(struct ucred *creds) |
48 | { |
49 | const struct cred *cred = current_cred(); |
50 | kuid_t uid = make_kuid(from: cred->user_ns, uid: creds->uid); |
51 | kgid_t gid = make_kgid(from: cred->user_ns, gid: creds->gid); |
52 | |
53 | if (!uid_valid(uid) || !gid_valid(gid)) |
54 | return -EINVAL; |
55 | |
56 | if ((creds->pid == task_tgid_vnr(current) || |
57 | ns_capable(ns: task_active_pid_ns(current)->user_ns, CAP_SYS_ADMIN)) && |
58 | ((uid_eq(left: uid, right: cred->uid) || uid_eq(left: uid, right: cred->euid) || |
59 | uid_eq(left: uid, right: cred->suid)) || ns_capable(ns: cred->user_ns, CAP_SETUID)) && |
60 | ((gid_eq(left: gid, right: cred->gid) || gid_eq(left: gid, right: cred->egid) || |
61 | gid_eq(left: gid, right: cred->sgid)) || ns_capable(ns: cred->user_ns, CAP_SETGID))) { |
62 | return 0; |
63 | } |
64 | return -EPERM; |
65 | } |
66 | |
67 | static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) |
68 | { |
69 | int *fdp = (int*)CMSG_DATA(cmsg); |
70 | struct scm_fp_list *fpl = *fplp; |
71 | struct file **fpp; |
72 | int i, num; |
73 | |
74 | num = (cmsg->cmsg_len - sizeof(struct cmsghdr))/sizeof(int); |
75 | |
76 | if (num <= 0) |
77 | return 0; |
78 | |
79 | if (num > SCM_MAX_FD) |
80 | return -EINVAL; |
81 | |
82 | if (!fpl) |
83 | { |
84 | fpl = kmalloc(size: sizeof(struct scm_fp_list), GFP_KERNEL_ACCOUNT); |
85 | if (!fpl) |
86 | return -ENOMEM; |
87 | *fplp = fpl; |
88 | fpl->count = 0; |
89 | fpl->count_unix = 0; |
90 | fpl->max = SCM_MAX_FD; |
91 | fpl->user = NULL; |
92 | } |
93 | fpp = &fpl->fp[fpl->count]; |
94 | |
95 | if (fpl->count + num > fpl->max) |
96 | return -EINVAL; |
97 | |
98 | /* |
99 | * Verify the descriptors and increment the usage count. |
100 | */ |
101 | |
102 | for (i=0; i< num; i++) |
103 | { |
104 | int fd = fdp[i]; |
105 | struct file *file; |
106 | |
107 | if (fd < 0 || !(file = fget_raw(fd))) |
108 | return -EBADF; |
109 | /* don't allow io_uring files */ |
110 | if (io_is_uring_fops(file)) { |
111 | fput(file); |
112 | return -EINVAL; |
113 | } |
114 | if (unix_get_socket(filp: file)) |
115 | fpl->count_unix++; |
116 | |
117 | *fpp++ = file; |
118 | fpl->count++; |
119 | } |
120 | |
121 | if (!fpl->user) |
122 | fpl->user = get_uid(current_user()); |
123 | |
124 | return num; |
125 | } |
126 | |
127 | void __scm_destroy(struct scm_cookie *scm) |
128 | { |
129 | struct scm_fp_list *fpl = scm->fp; |
130 | int i; |
131 | |
132 | if (fpl) { |
133 | scm->fp = NULL; |
134 | for (i=fpl->count-1; i>=0; i--) |
135 | fput(fpl->fp[i]); |
136 | free_uid(fpl->user); |
137 | kfree(objp: fpl); |
138 | } |
139 | } |
140 | EXPORT_SYMBOL(__scm_destroy); |
141 | |
142 | int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) |
143 | { |
144 | const struct proto_ops *ops = READ_ONCE(sock->ops); |
145 | struct cmsghdr *cmsg; |
146 | int err; |
147 | |
148 | for_each_cmsghdr(cmsg, msg) { |
149 | err = -EINVAL; |
150 | |
151 | /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */ |
152 | /* The first check was omitted in <= 2.2.5. The reasoning was |
153 | that parser checks cmsg_len in any case, so that |
154 | additional check would be work duplication. |
155 | But if cmsg_level is not SOL_SOCKET, we do not check |
156 | for too short ancillary data object at all! Oops. |
157 | OK, let's add it... |
158 | */ |
159 | if (!CMSG_OK(msg, cmsg)) |
160 | goto error; |
161 | |
162 | if (cmsg->cmsg_level != SOL_SOCKET) |
163 | continue; |
164 | |
165 | switch (cmsg->cmsg_type) |
166 | { |
167 | case SCM_RIGHTS: |
168 | if (!ops || ops->family != PF_UNIX) |
169 | goto error; |
170 | err=scm_fp_copy(cmsg, fplp: &p->fp); |
171 | if (err<0) |
172 | goto error; |
173 | break; |
174 | case SCM_CREDENTIALS: |
175 | { |
176 | struct ucred creds; |
177 | kuid_t uid; |
178 | kgid_t gid; |
179 | if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) |
180 | goto error; |
181 | memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred)); |
182 | err = scm_check_creds(creds: &creds); |
183 | if (err) |
184 | goto error; |
185 | |
186 | p->creds.pid = creds.pid; |
187 | if (!p->pid || pid_vnr(pid: p->pid) != creds.pid) { |
188 | struct pid *pid; |
189 | err = -ESRCH; |
190 | pid = find_get_pid(nr: creds.pid); |
191 | if (!pid) |
192 | goto error; |
193 | put_pid(pid: p->pid); |
194 | p->pid = pid; |
195 | } |
196 | |
197 | err = -EINVAL; |
198 | uid = make_kuid(current_user_ns(), uid: creds.uid); |
199 | gid = make_kgid(current_user_ns(), gid: creds.gid); |
200 | if (!uid_valid(uid) || !gid_valid(gid)) |
201 | goto error; |
202 | |
203 | p->creds.uid = uid; |
204 | p->creds.gid = gid; |
205 | break; |
206 | } |
207 | default: |
208 | goto error; |
209 | } |
210 | } |
211 | |
212 | if (p->fp && !p->fp->count) |
213 | { |
214 | kfree(objp: p->fp); |
215 | p->fp = NULL; |
216 | } |
217 | return 0; |
218 | |
219 | error: |
220 | scm_destroy(scm: p); |
221 | return err; |
222 | } |
223 | EXPORT_SYMBOL(__scm_send); |
224 | |
225 | int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) |
226 | { |
227 | int cmlen = CMSG_LEN(len); |
228 | |
229 | if (msg->msg_flags & MSG_CMSG_COMPAT) |
230 | return put_cmsg_compat(msg, level, type, len, data); |
231 | |
232 | if (!msg->msg_control || msg->msg_controllen < sizeof(struct cmsghdr)) { |
233 | msg->msg_flags |= MSG_CTRUNC; |
234 | return 0; /* XXX: return error? check spec. */ |
235 | } |
236 | if (msg->msg_controllen < cmlen) { |
237 | msg->msg_flags |= MSG_CTRUNC; |
238 | cmlen = msg->msg_controllen; |
239 | } |
240 | |
241 | if (msg->msg_control_is_user) { |
242 | struct cmsghdr __user *cm = msg->msg_control_user; |
243 | |
244 | check_object_size(ptr: data, n: cmlen - sizeof(*cm), to_user: true); |
245 | |
246 | if (!user_write_access_begin(cm, cmlen)) |
247 | goto efault; |
248 | |
249 | unsafe_put_user(cmlen, &cm->cmsg_len, efault_end); |
250 | unsafe_put_user(level, &cm->cmsg_level, efault_end); |
251 | unsafe_put_user(type, &cm->cmsg_type, efault_end); |
252 | unsafe_copy_to_user(CMSG_USER_DATA(cm), data, |
253 | cmlen - sizeof(*cm), efault_end); |
254 | user_write_access_end(); |
255 | } else { |
256 | struct cmsghdr *cm = msg->msg_control; |
257 | |
258 | cm->cmsg_level = level; |
259 | cm->cmsg_type = type; |
260 | cm->cmsg_len = cmlen; |
261 | memcpy(CMSG_DATA(cm), data, cmlen - sizeof(*cm)); |
262 | } |
263 | |
264 | cmlen = min(CMSG_SPACE(len), msg->msg_controllen); |
265 | if (msg->msg_control_is_user) |
266 | msg->msg_control_user += cmlen; |
267 | else |
268 | msg->msg_control += cmlen; |
269 | msg->msg_controllen -= cmlen; |
270 | return 0; |
271 | |
272 | efault_end: |
273 | user_write_access_end(); |
274 | efault: |
275 | return -EFAULT; |
276 | } |
277 | EXPORT_SYMBOL(put_cmsg); |
278 | |
279 | void put_cmsg_scm_timestamping64(struct msghdr *msg, struct scm_timestamping_internal *tss_internal) |
280 | { |
281 | struct scm_timestamping64 tss; |
282 | int i; |
283 | |
284 | for (i = 0; i < ARRAY_SIZE(tss.ts); i++) { |
285 | tss.ts[i].tv_sec = tss_internal->ts[i].tv_sec; |
286 | tss.ts[i].tv_nsec = tss_internal->ts[i].tv_nsec; |
287 | } |
288 | |
289 | put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_NEW, sizeof(tss), &tss); |
290 | } |
291 | EXPORT_SYMBOL(put_cmsg_scm_timestamping64); |
292 | |
293 | void put_cmsg_scm_timestamping(struct msghdr *msg, struct scm_timestamping_internal *tss_internal) |
294 | { |
295 | struct scm_timestamping tss; |
296 | int i; |
297 | |
298 | for (i = 0; i < ARRAY_SIZE(tss.ts); i++) { |
299 | tss.ts[i].tv_sec = tss_internal->ts[i].tv_sec; |
300 | tss.ts[i].tv_nsec = tss_internal->ts[i].tv_nsec; |
301 | } |
302 | |
303 | put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_OLD, sizeof(tss), &tss); |
304 | } |
305 | EXPORT_SYMBOL(put_cmsg_scm_timestamping); |
306 | |
307 | static int scm_max_fds(struct msghdr *msg) |
308 | { |
309 | if (msg->msg_controllen <= sizeof(struct cmsghdr)) |
310 | return 0; |
311 | return (msg->msg_controllen - sizeof(struct cmsghdr)) / sizeof(int); |
312 | } |
313 | |
314 | void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) |
315 | { |
316 | struct cmsghdr __user *cm = |
317 | (__force struct cmsghdr __user *)msg->msg_control_user; |
318 | unsigned int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0; |
319 | int fdmax = min_t(int, scm_max_fds(msg), scm->fp->count); |
320 | int __user *cmsg_data = CMSG_USER_DATA(cm); |
321 | int err = 0, i; |
322 | |
323 | /* no use for FD passing from kernel space callers */ |
324 | if (WARN_ON_ONCE(!msg->msg_control_is_user)) |
325 | return; |
326 | |
327 | if (msg->msg_flags & MSG_CMSG_COMPAT) { |
328 | scm_detach_fds_compat(msg, scm); |
329 | return; |
330 | } |
331 | |
332 | for (i = 0; i < fdmax; i++) { |
333 | err = scm_recv_one_fd(f: scm->fp->fp[i], ufd: cmsg_data + i, flags: o_flags); |
334 | if (err < 0) |
335 | break; |
336 | } |
337 | |
338 | if (i > 0) { |
339 | int cmlen = CMSG_LEN(i * sizeof(int)); |
340 | |
341 | err = put_user(SOL_SOCKET, &cm->cmsg_level); |
342 | if (!err) |
343 | err = put_user(SCM_RIGHTS, &cm->cmsg_type); |
344 | if (!err) |
345 | err = put_user(cmlen, &cm->cmsg_len); |
346 | if (!err) { |
347 | cmlen = CMSG_SPACE(i * sizeof(int)); |
348 | if (msg->msg_controllen < cmlen) |
349 | cmlen = msg->msg_controllen; |
350 | msg->msg_control_user += cmlen; |
351 | msg->msg_controllen -= cmlen; |
352 | } |
353 | } |
354 | |
355 | if (i < scm->fp->count || (scm->fp->count && fdmax <= 0)) |
356 | msg->msg_flags |= MSG_CTRUNC; |
357 | |
358 | /* |
359 | * All of the files that fit in the message have had their usage counts |
360 | * incremented, so we just free the list. |
361 | */ |
362 | __scm_destroy(scm); |
363 | } |
364 | EXPORT_SYMBOL(scm_detach_fds); |
365 | |
366 | struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) |
367 | { |
368 | struct scm_fp_list *new_fpl; |
369 | int i; |
370 | |
371 | if (!fpl) |
372 | return NULL; |
373 | |
374 | new_fpl = kmemdup(p: fpl, offsetof(struct scm_fp_list, fp[fpl->count]), |
375 | GFP_KERNEL_ACCOUNT); |
376 | if (new_fpl) { |
377 | for (i = 0; i < fpl->count; i++) |
378 | get_file(f: fpl->fp[i]); |
379 | new_fpl->max = new_fpl->count; |
380 | new_fpl->user = get_uid(u: fpl->user); |
381 | } |
382 | return new_fpl; |
383 | } |
384 | EXPORT_SYMBOL(scm_fp_dup); |
385 | |