Commit | Line | Data |
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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 LT |
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 | /* | |
4ec93edb | 42 | * Only allow a user to send credentials, that they could set with |
1da177e4 LT |
43 | * setu(g)id. |
44 | */ | |
45 | ||
46 | static __inline__ int scm_check_creds(struct ucred *creds) | |
47 | { | |
86a264ab | 48 | const struct cred *cred = current_cred(); |
b6dff3ec | 49 | |
b488893a | 50 | if ((creds->pid == task_tgid_vnr(current) || capable(CAP_SYS_ADMIN)) && |
b6dff3ec DH |
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))) { | |
1da177e4 LT |
55 | return 0; |
56 | } | |
57 | return -EPERM; | |
58 | } | |
59 | ||
60 | static 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 | } | |
83 | fpp = &fpl->fp[fpl->count]; | |
84 | ||
85 | if (fpl->count + num > SCM_MAX_FD) | |
86 | return -EINVAL; | |
4ec93edb | 87 | |
1da177e4 LT |
88 | /* |
89 | * Verify the descriptors and increment the usage count. | |
90 | */ | |
4ec93edb | 91 | |
1da177e4 LT |
92 | for (i=0; i< num; i++) |
93 | { | |
94 | int fd = fdp[i]; | |
95 | struct file *file; | |
96 | ||
97 | if (fd < 0 || !(file = fget(fd))) | |
98 | return -EBADF; | |
99 | *fpp++ = file; | |
100 | fpl->count++; | |
101 | } | |
102 | return num; | |
103 | } | |
104 | ||
105 | void __scm_destroy(struct scm_cookie *scm) | |
106 | { | |
107 | struct scm_fp_list *fpl = scm->fp; | |
108 | int i; | |
109 | ||
110 | if (fpl) { | |
111 | scm->fp = NULL; | |
f8d570a4 DM |
112 | if (current->scm_work_list) { |
113 | list_add_tail(&fpl->list, current->scm_work_list); | |
114 | } else { | |
115 | LIST_HEAD(work_list); | |
116 | ||
117 | current->scm_work_list = &work_list; | |
118 | ||
119 | list_add(&fpl->list, &work_list); | |
120 | while (!list_empty(&work_list)) { | |
121 | fpl = list_first_entry(&work_list, struct scm_fp_list, list); | |
122 | ||
123 | list_del(&fpl->list); | |
124 | for (i=fpl->count-1; i>=0; i--) | |
125 | fput(fpl->fp[i]); | |
126 | kfree(fpl); | |
127 | } | |
128 | ||
129 | current->scm_work_list = NULL; | |
130 | } | |
1da177e4 LT |
131 | } |
132 | } | |
133 | ||
134 | int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) | |
135 | { | |
136 | struct cmsghdr *cmsg; | |
137 | int err; | |
138 | ||
139 | for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) | |
140 | { | |
141 | err = -EINVAL; | |
142 | ||
143 | /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */ | |
144 | /* The first check was omitted in <= 2.2.5. The reasoning was | |
145 | that parser checks cmsg_len in any case, so that | |
146 | additional check would be work duplication. | |
4ec93edb | 147 | But if cmsg_level is not SOL_SOCKET, we do not check |
1da177e4 LT |
148 | for too short ancillary data object at all! Oops. |
149 | OK, let's add it... | |
150 | */ | |
151 | if (!CMSG_OK(msg, cmsg)) | |
152 | goto error; | |
153 | ||
154 | if (cmsg->cmsg_level != SOL_SOCKET) | |
155 | continue; | |
156 | ||
157 | switch (cmsg->cmsg_type) | |
158 | { | |
159 | case SCM_RIGHTS: | |
76dadd76 EB |
160 | if (!sock->ops || sock->ops->family != PF_UNIX) |
161 | goto error; | |
1da177e4 LT |
162 | err=scm_fp_copy(cmsg, &p->fp); |
163 | if (err<0) | |
164 | goto error; | |
165 | break; | |
166 | case SCM_CREDENTIALS: | |
167 | if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) | |
168 | goto error; | |
169 | memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred)); | |
170 | err = scm_check_creds(&p->creds); | |
171 | if (err) | |
172 | goto error; | |
173 | break; | |
174 | default: | |
175 | goto error; | |
176 | } | |
177 | } | |
178 | ||
179 | if (p->fp && !p->fp->count) | |
180 | { | |
181 | kfree(p->fp); | |
182 | p->fp = NULL; | |
183 | } | |
184 | return 0; | |
4ec93edb | 185 | |
1da177e4 LT |
186 | error: |
187 | scm_destroy(p); | |
188 | return err; | |
189 | } | |
190 | ||
191 | int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) | |
192 | { | |
cfcabdcc SH |
193 | struct cmsghdr __user *cm |
194 | = (__force struct cmsghdr __user *)msg->msg_control; | |
1da177e4 LT |
195 | struct cmsghdr cmhdr; |
196 | int cmlen = CMSG_LEN(len); | |
197 | int err; | |
198 | ||
199 | if (MSG_CMSG_COMPAT & msg->msg_flags) | |
200 | return put_cmsg_compat(msg, level, type, len, data); | |
201 | ||
202 | if (cm==NULL || msg->msg_controllen < sizeof(*cm)) { | |
203 | msg->msg_flags |= MSG_CTRUNC; | |
204 | return 0; /* XXX: return error? check spec. */ | |
205 | } | |
206 | if (msg->msg_controllen < cmlen) { | |
207 | msg->msg_flags |= MSG_CTRUNC; | |
208 | cmlen = msg->msg_controllen; | |
209 | } | |
210 | cmhdr.cmsg_level = level; | |
211 | cmhdr.cmsg_type = type; | |
212 | cmhdr.cmsg_len = cmlen; | |
213 | ||
214 | err = -EFAULT; | |
215 | if (copy_to_user(cm, &cmhdr, sizeof cmhdr)) | |
4ec93edb | 216 | goto out; |
1da177e4 LT |
217 | if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr))) |
218 | goto out; | |
219 | cmlen = CMSG_SPACE(len); | |
1ac70e7a WY |
220 | if (msg->msg_controllen < cmlen) |
221 | cmlen = msg->msg_controllen; | |
1da177e4 LT |
222 | msg->msg_control += cmlen; |
223 | msg->msg_controllen -= cmlen; | |
224 | err = 0; | |
225 | out: | |
226 | return err; | |
227 | } | |
228 | ||
229 | void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) | |
230 | { | |
cfcabdcc SH |
231 | struct cmsghdr __user *cm |
232 | = (__force struct cmsghdr __user*)msg->msg_control; | |
1da177e4 LT |
233 | |
234 | int fdmax = 0; | |
235 | int fdnum = scm->fp->count; | |
236 | struct file **fp = scm->fp->fp; | |
237 | int __user *cmfptr; | |
238 | int err = 0, i; | |
239 | ||
240 | if (MSG_CMSG_COMPAT & msg->msg_flags) { | |
241 | scm_detach_fds_compat(msg, scm); | |
242 | return; | |
243 | } | |
244 | ||
245 | if (msg->msg_controllen > sizeof(struct cmsghdr)) | |
246 | fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr)) | |
247 | / sizeof(int)); | |
248 | ||
249 | if (fdnum < fdmax) | |
250 | fdmax = fdnum; | |
251 | ||
cfcabdcc SH |
252 | for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax; |
253 | i++, cmfptr++) | |
1da177e4 LT |
254 | { |
255 | int new_fd; | |
256 | err = security_file_receive(fp[i]); | |
257 | if (err) | |
258 | break; | |
4a19542e UD |
259 | err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags |
260 | ? O_CLOEXEC : 0); | |
1da177e4 LT |
261 | if (err < 0) |
262 | break; | |
263 | new_fd = err; | |
264 | err = put_user(new_fd, cmfptr); | |
265 | if (err) { | |
266 | put_unused_fd(new_fd); | |
267 | break; | |
268 | } | |
269 | /* Bump the usage count and install the file. */ | |
270 | get_file(fp[i]); | |
271 | fd_install(new_fd, fp[i]); | |
272 | } | |
273 | ||
274 | if (i > 0) | |
275 | { | |
276 | int cmlen = CMSG_LEN(i*sizeof(int)); | |
effee6a0 | 277 | err = put_user(SOL_SOCKET, &cm->cmsg_level); |
1da177e4 LT |
278 | if (!err) |
279 | err = put_user(SCM_RIGHTS, &cm->cmsg_type); | |
280 | if (!err) | |
281 | err = put_user(cmlen, &cm->cmsg_len); | |
282 | if (!err) { | |
283 | cmlen = CMSG_SPACE(i*sizeof(int)); | |
284 | msg->msg_control += cmlen; | |
285 | msg->msg_controllen -= cmlen; | |
286 | } | |
287 | } | |
288 | if (i < fdnum || (fdnum && fdmax <= 0)) | |
289 | msg->msg_flags |= MSG_CTRUNC; | |
290 | ||
291 | /* | |
292 | * All of the files that fit in the message have had their | |
293 | * usage counts incremented, so we just free the list. | |
294 | */ | |
295 | __scm_destroy(scm); | |
296 | } | |
297 | ||
298 | struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) | |
299 | { | |
300 | struct scm_fp_list *new_fpl; | |
301 | int i; | |
302 | ||
303 | if (!fpl) | |
304 | return NULL; | |
305 | ||
306 | new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL); | |
307 | if (new_fpl) { | |
308 | for (i=fpl->count-1; i>=0; i--) | |
309 | get_file(fpl->fp[i]); | |
310 | memcpy(new_fpl, fpl, sizeof(*fpl)); | |
311 | } | |
312 | return new_fpl; | |
313 | } | |
314 | ||
315 | EXPORT_SYMBOL(__scm_destroy); | |
316 | EXPORT_SYMBOL(__scm_send); | |
317 | EXPORT_SYMBOL(put_cmsg); | |
318 | EXPORT_SYMBOL(scm_detach_fds); | |
319 | EXPORT_SYMBOL(scm_fp_dup); |