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