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