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