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1da177e4 LT |
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> | |
4fc268d2 | 14 | #include <linux/capability.h> |
1da177e4 LT |
15 | #include <linux/errno.h> |
16 | #include <linux/sched.h> | |
17 | #include <linux/mm.h> | |
18 | #include <linux/kernel.h> | |
1da177e4 LT |
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> | |
b488893a PE |
27 | #include <linux/pid.h> |
28 | #include <linux/nsproxy.h> | |
5a0e3ad6 | 29 | #include <linux/slab.h> |
1da177e4 | 30 | |
1da177e4 LT |
31 | #include <asm/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 | ||
39 | ||
40 | /* | |
4ec93edb | 41 | * Only allow a user to send credentials, that they could set with |
1da177e4 LT |
42 | * setu(g)id. |
43 | */ | |
44 | ||
45 | static __inline__ int scm_check_creds(struct ucred *creds) | |
46 | { | |
86a264ab | 47 | const struct cred *cred = current_cred(); |
b2e4f544 EB |
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; | |
b6dff3ec | 53 | |
b488893a | 54 | if ((creds->pid == task_tgid_vnr(current) || capable(CAP_SYS_ADMIN)) && |
b2e4f544 EB |
55 | ((uid_eq(uid, cred->uid) || uid_eq(uid, cred->euid) || |
56 | uid_eq(uid, cred->suid)) || capable(CAP_SETUID)) && | |
57 | ((gid_eq(gid, cred->gid) || gid_eq(gid, cred->egid) || | |
58 | gid_eq(gid, cred->sgid)) || capable(CAP_SETGID))) { | |
1da177e4 LT |
59 | return 0; |
60 | } | |
61 | return -EPERM; | |
62 | } | |
63 | ||
64 | static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) | |
65 | { | |
66 | int *fdp = (int*)CMSG_DATA(cmsg); | |
67 | struct scm_fp_list *fpl = *fplp; | |
68 | struct file **fpp; | |
69 | int i, num; | |
70 | ||
71 | num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int); | |
72 | ||
73 | if (num <= 0) | |
74 | return 0; | |
75 | ||
76 | if (num > SCM_MAX_FD) | |
77 | return -EINVAL; | |
78 | ||
79 | if (!fpl) | |
80 | { | |
81 | fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL); | |
82 | if (!fpl) | |
83 | return -ENOMEM; | |
84 | *fplp = fpl; | |
85 | fpl->count = 0; | |
bba14de9 | 86 | fpl->max = SCM_MAX_FD; |
1da177e4 LT |
87 | } |
88 | fpp = &fpl->fp[fpl->count]; | |
89 | ||
bba14de9 | 90 | if (fpl->count + num > fpl->max) |
1da177e4 | 91 | return -EINVAL; |
4ec93edb | 92 | |
1da177e4 LT |
93 | /* |
94 | * Verify the descriptors and increment the usage count. | |
95 | */ | |
4ec93edb | 96 | |
1da177e4 LT |
97 | for (i=0; i< num; i++) |
98 | { | |
99 | int fd = fdp[i]; | |
100 | struct file *file; | |
101 | ||
326be7b4 | 102 | if (fd < 0 || !(file = fget_raw(fd))) |
1da177e4 LT |
103 | return -EBADF; |
104 | *fpp++ = file; | |
105 | fpl->count++; | |
106 | } | |
107 | return num; | |
108 | } | |
109 | ||
110 | void __scm_destroy(struct scm_cookie *scm) | |
111 | { | |
112 | struct scm_fp_list *fpl = scm->fp; | |
113 | int i; | |
114 | ||
115 | if (fpl) { | |
116 | scm->fp = NULL; | |
6120d3db AV |
117 | for (i=fpl->count-1; i>=0; i--) |
118 | fput(fpl->fp[i]); | |
119 | kfree(fpl); | |
1da177e4 LT |
120 | } |
121 | } | |
9e34a5b5 | 122 | EXPORT_SYMBOL(__scm_destroy); |
1da177e4 LT |
123 | |
124 | int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) | |
125 | { | |
126 | struct cmsghdr *cmsg; | |
127 | int err; | |
128 | ||
129 | for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) | |
130 | { | |
131 | err = -EINVAL; | |
132 | ||
133 | /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */ | |
134 | /* The first check was omitted in <= 2.2.5. The reasoning was | |
135 | that parser checks cmsg_len in any case, so that | |
136 | additional check would be work duplication. | |
4ec93edb | 137 | But if cmsg_level is not SOL_SOCKET, we do not check |
1da177e4 LT |
138 | for too short ancillary data object at all! Oops. |
139 | OK, let's add it... | |
140 | */ | |
141 | if (!CMSG_OK(msg, cmsg)) | |
142 | goto error; | |
143 | ||
144 | if (cmsg->cmsg_level != SOL_SOCKET) | |
145 | continue; | |
146 | ||
147 | switch (cmsg->cmsg_type) | |
148 | { | |
149 | case SCM_RIGHTS: | |
76dadd76 EB |
150 | if (!sock->ops || sock->ops->family != PF_UNIX) |
151 | goto error; | |
1da177e4 LT |
152 | err=scm_fp_copy(cmsg, &p->fp); |
153 | if (err<0) | |
154 | goto error; | |
155 | break; | |
156 | case SCM_CREDENTIALS: | |
b2e4f544 | 157 | { |
dbe9a417 | 158 | struct ucred creds; |
b2e4f544 EB |
159 | kuid_t uid; |
160 | kgid_t gid; | |
1da177e4 LT |
161 | if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) |
162 | goto error; | |
dbe9a417 EB |
163 | memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred)); |
164 | err = scm_check_creds(&creds); | |
1da177e4 LT |
165 | if (err) |
166 | goto error; | |
257b5358 | 167 | |
dbe9a417 EB |
168 | p->creds.pid = creds.pid; |
169 | if (!p->pid || pid_vnr(p->pid) != creds.pid) { | |
257b5358 EB |
170 | struct pid *pid; |
171 | err = -ESRCH; | |
dbe9a417 | 172 | pid = find_get_pid(creds.pid); |
257b5358 EB |
173 | if (!pid) |
174 | goto error; | |
175 | put_pid(p->pid); | |
176 | p->pid = pid; | |
177 | } | |
178 | ||
b2e4f544 | 179 | err = -EINVAL; |
dbe9a417 EB |
180 | uid = make_kuid(current_user_ns(), creds.uid); |
181 | gid = make_kgid(current_user_ns(), creds.gid); | |
b2e4f544 EB |
182 | if (!uid_valid(uid) || !gid_valid(gid)) |
183 | goto error; | |
184 | ||
dbe9a417 EB |
185 | p->creds.uid = uid; |
186 | p->creds.gid = gid; | |
187 | ||
16e57262 | 188 | if (!p->cred || |
b2e4f544 EB |
189 | !uid_eq(p->cred->euid, uid) || |
190 | !gid_eq(p->cred->egid, gid)) { | |
257b5358 EB |
191 | struct cred *cred; |
192 | err = -ENOMEM; | |
193 | cred = prepare_creds(); | |
194 | if (!cred) | |
195 | goto error; | |
196 | ||
b2e4f544 EB |
197 | cred->uid = cred->euid = uid; |
198 | cred->gid = cred->egid = gid; | |
16e57262 ED |
199 | if (p->cred) |
200 | put_cred(p->cred); | |
257b5358 EB |
201 | p->cred = cred; |
202 | } | |
1da177e4 | 203 | break; |
b2e4f544 | 204 | } |
1da177e4 LT |
205 | default: |
206 | goto error; | |
207 | } | |
208 | } | |
209 | ||
210 | if (p->fp && !p->fp->count) | |
211 | { | |
212 | kfree(p->fp); | |
213 | p->fp = NULL; | |
214 | } | |
215 | return 0; | |
4ec93edb | 216 | |
1da177e4 LT |
217 | error: |
218 | scm_destroy(p); | |
219 | return err; | |
220 | } | |
9e34a5b5 | 221 | EXPORT_SYMBOL(__scm_send); |
1da177e4 LT |
222 | |
223 | int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) | |
224 | { | |
cfcabdcc SH |
225 | struct cmsghdr __user *cm |
226 | = (__force struct cmsghdr __user *)msg->msg_control; | |
1da177e4 LT |
227 | struct cmsghdr cmhdr; |
228 | int cmlen = CMSG_LEN(len); | |
229 | int err; | |
230 | ||
231 | if (MSG_CMSG_COMPAT & msg->msg_flags) | |
232 | return put_cmsg_compat(msg, level, type, len, data); | |
233 | ||
234 | if (cm==NULL || msg->msg_controllen < sizeof(*cm)) { | |
235 | msg->msg_flags |= MSG_CTRUNC; | |
236 | return 0; /* XXX: return error? check spec. */ | |
237 | } | |
238 | if (msg->msg_controllen < cmlen) { | |
239 | msg->msg_flags |= MSG_CTRUNC; | |
240 | cmlen = msg->msg_controllen; | |
241 | } | |
242 | cmhdr.cmsg_level = level; | |
243 | cmhdr.cmsg_type = type; | |
244 | cmhdr.cmsg_len = cmlen; | |
245 | ||
246 | err = -EFAULT; | |
247 | if (copy_to_user(cm, &cmhdr, sizeof cmhdr)) | |
4ec93edb | 248 | goto out; |
1da177e4 LT |
249 | if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr))) |
250 | goto out; | |
251 | cmlen = CMSG_SPACE(len); | |
1ac70e7a WY |
252 | if (msg->msg_controllen < cmlen) |
253 | cmlen = msg->msg_controllen; | |
1da177e4 LT |
254 | msg->msg_control += cmlen; |
255 | msg->msg_controllen -= cmlen; | |
256 | err = 0; | |
257 | out: | |
258 | return err; | |
259 | } | |
9e34a5b5 | 260 | EXPORT_SYMBOL(put_cmsg); |
1da177e4 LT |
261 | |
262 | void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) | |
263 | { | |
cfcabdcc SH |
264 | struct cmsghdr __user *cm |
265 | = (__force struct cmsghdr __user*)msg->msg_control; | |
1da177e4 LT |
266 | |
267 | int fdmax = 0; | |
268 | int fdnum = scm->fp->count; | |
269 | struct file **fp = scm->fp->fp; | |
270 | int __user *cmfptr; | |
271 | int err = 0, i; | |
272 | ||
273 | if (MSG_CMSG_COMPAT & msg->msg_flags) { | |
274 | scm_detach_fds_compat(msg, scm); | |
275 | return; | |
276 | } | |
277 | ||
278 | if (msg->msg_controllen > sizeof(struct cmsghdr)) | |
279 | fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr)) | |
280 | / sizeof(int)); | |
281 | ||
282 | if (fdnum < fdmax) | |
283 | fdmax = fdnum; | |
284 | ||
cfcabdcc SH |
285 | for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax; |
286 | i++, cmfptr++) | |
1da177e4 | 287 | { |
48a87cc2 | 288 | struct socket *sock; |
1da177e4 LT |
289 | int new_fd; |
290 | err = security_file_receive(fp[i]); | |
291 | if (err) | |
292 | break; | |
4a19542e UD |
293 | err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags |
294 | ? O_CLOEXEC : 0); | |
1da177e4 LT |
295 | if (err < 0) |
296 | break; | |
297 | new_fd = err; | |
298 | err = put_user(new_fd, cmfptr); | |
299 | if (err) { | |
300 | put_unused_fd(new_fd); | |
301 | break; | |
302 | } | |
303 | /* Bump the usage count and install the file. */ | |
304 | get_file(fp[i]); | |
48a87cc2 JF |
305 | sock = sock_from_file(fp[i], &err); |
306 | if (sock) | |
307 | sock_update_netprioidx(sock->sk, current); | |
1da177e4 LT |
308 | fd_install(new_fd, fp[i]); |
309 | } | |
310 | ||
311 | if (i > 0) | |
312 | { | |
313 | int cmlen = CMSG_LEN(i*sizeof(int)); | |
effee6a0 | 314 | err = put_user(SOL_SOCKET, &cm->cmsg_level); |
1da177e4 LT |
315 | if (!err) |
316 | err = put_user(SCM_RIGHTS, &cm->cmsg_type); | |
317 | if (!err) | |
318 | err = put_user(cmlen, &cm->cmsg_len); | |
319 | if (!err) { | |
320 | cmlen = CMSG_SPACE(i*sizeof(int)); | |
321 | msg->msg_control += cmlen; | |
322 | msg->msg_controllen -= cmlen; | |
323 | } | |
324 | } | |
325 | if (i < fdnum || (fdnum && fdmax <= 0)) | |
326 | msg->msg_flags |= MSG_CTRUNC; | |
327 | ||
328 | /* | |
329 | * All of the files that fit in the message have had their | |
330 | * usage counts incremented, so we just free the list. | |
331 | */ | |
332 | __scm_destroy(scm); | |
333 | } | |
9e34a5b5 | 334 | EXPORT_SYMBOL(scm_detach_fds); |
1da177e4 LT |
335 | |
336 | struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) | |
337 | { | |
338 | struct scm_fp_list *new_fpl; | |
339 | int i; | |
340 | ||
341 | if (!fpl) | |
342 | return NULL; | |
343 | ||
bba14de9 ED |
344 | new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]), |
345 | GFP_KERNEL); | |
1da177e4 | 346 | if (new_fpl) { |
bba14de9 | 347 | for (i = 0; i < fpl->count; i++) |
1da177e4 | 348 | get_file(fpl->fp[i]); |
bba14de9 | 349 | new_fpl->max = new_fpl->count; |
1da177e4 LT |
350 | } |
351 | return new_fpl; | |
352 | } | |
1da177e4 | 353 | EXPORT_SYMBOL(scm_fp_dup); |