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
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
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
scm_fp_copy(struct cmsghdr * cmsg,struct scm_fp_list ** fplp)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 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
__scm_destroy(struct scm_cookie * scm)106 void __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 }
134 EXPORT_SYMBOL(__scm_destroy);
135
__scm_send(struct socket * sock,struct msghdr * msg,struct scm_cookie * p)136 int __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 (!p->pid || 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 ||
187 (p->cred->euid != p->creds.uid) ||
188 (p->cred->egid != p->creds.gid)) {
189 struct cred *cred;
190 err = -ENOMEM;
191 cred = prepare_creds();
192 if (!cred)
193 goto error;
194
195 cred->uid = cred->euid = p->creds.uid;
196 cred->gid = cred->egid = p->creds.gid;
197 if (p->cred)
198 put_cred(p->cred);
199 p->cred = cred;
200 }
201 break;
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 struct cmsghdr __user *cm
223 = (__force struct cmsghdr __user *)msg->msg_control;
224 struct cmsghdr cmhdr;
225 int cmlen = CMSG_LEN(len);
226 int err;
227
228 if (MSG_CMSG_COMPAT & msg->msg_flags)
229 return put_cmsg_compat(msg, level, type, len, data);
230
231 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
232 msg->msg_flags |= MSG_CTRUNC;
233 return 0; /* XXX: return error? check spec. */
234 }
235 if (msg->msg_controllen < cmlen) {
236 msg->msg_flags |= MSG_CTRUNC;
237 cmlen = msg->msg_controllen;
238 }
239 cmhdr.cmsg_level = level;
240 cmhdr.cmsg_type = type;
241 cmhdr.cmsg_len = cmlen;
242
243 err = -EFAULT;
244 if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
245 goto out;
246 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
247 goto out;
248 cmlen = CMSG_SPACE(len);
249 if (msg->msg_controllen < cmlen)
250 cmlen = msg->msg_controllen;
251 msg->msg_control += cmlen;
252 msg->msg_controllen -= cmlen;
253 err = 0;
254 out:
255 return err;
256 }
257 EXPORT_SYMBOL(put_cmsg);
258
scm_detach_fds(struct msghdr * msg,struct scm_cookie * scm)259 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
260 {
261 struct cmsghdr __user *cm
262 = (__force struct cmsghdr __user*)msg->msg_control;
263
264 int fdmax = 0;
265 int fdnum = scm->fp->count;
266 struct file **fp = scm->fp->fp;
267 int __user *cmfptr;
268 int err = 0, i;
269
270 if (MSG_CMSG_COMPAT & msg->msg_flags) {
271 scm_detach_fds_compat(msg, scm);
272 return;
273 }
274
275 if (msg->msg_controllen > sizeof(struct cmsghdr))
276 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
277 / sizeof(int));
278
279 if (fdnum < fdmax)
280 fdmax = fdnum;
281
282 for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
283 i++, cmfptr++)
284 {
285 int new_fd;
286 err = security_file_receive(fp[i]);
287 if (err)
288 break;
289 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
290 ? O_CLOEXEC : 0);
291 if (err < 0)
292 break;
293 new_fd = err;
294 err = put_user(new_fd, cmfptr);
295 if (err) {
296 put_unused_fd(new_fd);
297 break;
298 }
299 /* Bump the usage count and install the file. */
300 get_file(fp[i]);
301 fd_install(new_fd, fp[i]);
302 }
303
304 if (i > 0)
305 {
306 int cmlen = CMSG_LEN(i*sizeof(int));
307 err = put_user(SOL_SOCKET, &cm->cmsg_level);
308 if (!err)
309 err = put_user(SCM_RIGHTS, &cm->cmsg_type);
310 if (!err)
311 err = put_user(cmlen, &cm->cmsg_len);
312 if (!err) {
313 cmlen = CMSG_SPACE(i*sizeof(int));
314 msg->msg_control += cmlen;
315 msg->msg_controllen -= cmlen;
316 }
317 }
318 if (i < fdnum || (fdnum && fdmax <= 0))
319 msg->msg_flags |= MSG_CTRUNC;
320
321 /*
322 * All of the files that fit in the message have had their
323 * usage counts incremented, so we just free the list.
324 */
325 __scm_destroy(scm);
326 }
327 EXPORT_SYMBOL(scm_detach_fds);
328
scm_fp_dup(struct scm_fp_list * fpl)329 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
330 {
331 struct scm_fp_list *new_fpl;
332 int i;
333
334 if (!fpl)
335 return NULL;
336
337 new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
338 GFP_KERNEL);
339 if (new_fpl) {
340 for (i = 0; i < fpl->count; i++)
341 get_file(fpl->fp[i]);
342 new_fpl->max = new_fpl->count;
343 }
344 return new_fpl;
345 }
346 EXPORT_SYMBOL(scm_fp_dup);
347