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
30 #include <asm/system.h>
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 /*
41 * Only allow a user to send credentials, that they could set with
42 * setu(g)id.
43 */
44
45 static __inline__ int scm_check_creds(struct ucred *creds)
46 {
47 if ((creds->pid == task_tgid_vnr(current) || capable(CAP_SYS_ADMIN)) &&
48 ((creds->uid == current->uid || creds->uid == current->euid ||
49 creds->uid == current->suid) || capable(CAP_SETUID)) &&
50 ((creds->gid == current->gid || creds->gid == current->egid ||
51 creds->gid == current->sgid) || capable(CAP_SETGID))) {
52 return 0;
53 }
54 return -EPERM;
55 }
56
57 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
58 {
59 int *fdp = (int*)CMSG_DATA(cmsg);
60 struct scm_fp_list *fpl = *fplp;
61 struct file **fpp;
62 int i, num;
63
64 num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
65
66 if (num <= 0)
67 return 0;
68
69 if (num > SCM_MAX_FD)
70 return -EINVAL;
71
72 if (!fpl)
73 {
74 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
75 if (!fpl)
76 return -ENOMEM;
77 *fplp = fpl;
78 fpl->count = 0;
79 }
80 fpp = &fpl->fp[fpl->count];
81
82 if (fpl->count + num > SCM_MAX_FD)
83 return -EINVAL;
84
85 /*
86 * Verify the descriptors and increment the usage count.
87 */
88
89 for (i=0; i< num; i++)
90 {
91 int fd = fdp[i];
92 struct file *file;
93
94 if (fd < 0 || !(file = fget(fd)))
95 return -EBADF;
96 *fpp++ = file;
97 fpl->count++;
98 }
99 return num;
100 }
101
102 void __scm_destroy(struct scm_cookie *scm)
103 {
104 struct scm_fp_list *fpl = scm->fp;
105 int i;
106
107 if (fpl) {
108 scm->fp = NULL;
109 for (i=fpl->count-1; i>=0; i--)
110 fput(fpl->fp[i]);
111 kfree(fpl);
112 }
113 }
114
115 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
116 {
117 struct cmsghdr *cmsg;
118 int err;
119
120 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
121 {
122 err = -EINVAL;
123
124 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
125 /* The first check was omitted in <= 2.2.5. The reasoning was
126 that parser checks cmsg_len in any case, so that
127 additional check would be work duplication.
128 But if cmsg_level is not SOL_SOCKET, we do not check
129 for too short ancillary data object at all! Oops.
130 OK, let's add it...
131 */
132 if (!CMSG_OK(msg, cmsg))
133 goto error;
134
135 if (cmsg->cmsg_level != SOL_SOCKET)
136 continue;
137
138 switch (cmsg->cmsg_type)
139 {
140 case SCM_RIGHTS:
141 err=scm_fp_copy(cmsg, &p->fp);
142 if (err<0)
143 goto error;
144 break;
145 case SCM_CREDENTIALS:
146 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
147 goto error;
148 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
149 err = scm_check_creds(&p->creds);
150 if (err)
151 goto error;
152 break;
153 default:
154 goto error;
155 }
156 }
157
158 if (p->fp && !p->fp->count)
159 {
160 kfree(p->fp);
161 p->fp = NULL;
162 }
163 return 0;
164
165 error:
166 scm_destroy(p);
167 return err;
168 }
169
170 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
171 {
172 struct cmsghdr __user *cm
173 = (__force struct cmsghdr __user *)msg->msg_control;
174 struct cmsghdr cmhdr;
175 int cmlen = CMSG_LEN(len);
176 int err;
177
178 if (MSG_CMSG_COMPAT & msg->msg_flags)
179 return put_cmsg_compat(msg, level, type, len, data);
180
181 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
182 msg->msg_flags |= MSG_CTRUNC;
183 return 0; /* XXX: return error? check spec. */
184 }
185 if (msg->msg_controllen < cmlen) {
186 msg->msg_flags |= MSG_CTRUNC;
187 cmlen = msg->msg_controllen;
188 }
189 cmhdr.cmsg_level = level;
190 cmhdr.cmsg_type = type;
191 cmhdr.cmsg_len = cmlen;
192
193 err = -EFAULT;
194 if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
195 goto out;
196 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
197 goto out;
198 cmlen = CMSG_SPACE(len);
199 if (msg->msg_controllen < cmlen)
200 cmlen = msg->msg_controllen;
201 msg->msg_control += cmlen;
202 msg->msg_controllen -= cmlen;
203 err = 0;
204 out:
205 return err;
206 }
207
208 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
209 {
210 struct cmsghdr __user *cm
211 = (__force struct cmsghdr __user*)msg->msg_control;
212
213 int fdmax = 0;
214 int fdnum = scm->fp->count;
215 struct file **fp = scm->fp->fp;
216 int __user *cmfptr;
217 int err = 0, i;
218
219 if (MSG_CMSG_COMPAT & msg->msg_flags) {
220 scm_detach_fds_compat(msg, scm);
221 return;
222 }
223
224 if (msg->msg_controllen > sizeof(struct cmsghdr))
225 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
226 / sizeof(int));
227
228 if (fdnum < fdmax)
229 fdmax = fdnum;
230
231 for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
232 i++, cmfptr++)
233 {
234 int new_fd;
235 err = security_file_receive(fp[i]);
236 if (err)
237 break;
238 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
239 ? O_CLOEXEC : 0);
240 if (err < 0)
241 break;
242 new_fd = err;
243 err = put_user(new_fd, cmfptr);
244 if (err) {
245 put_unused_fd(new_fd);
246 break;
247 }
248 /* Bump the usage count and install the file. */
249 get_file(fp[i]);
250 fd_install(new_fd, fp[i]);
251 }
252
253 if (i > 0)
254 {
255 int cmlen = CMSG_LEN(i*sizeof(int));
256 err = put_user(SOL_SOCKET, &cm->cmsg_level);
257 if (!err)
258 err = put_user(SCM_RIGHTS, &cm->cmsg_type);
259 if (!err)
260 err = put_user(cmlen, &cm->cmsg_len);
261 if (!err) {
262 cmlen = CMSG_SPACE(i*sizeof(int));
263 msg->msg_control += cmlen;
264 msg->msg_controllen -= cmlen;
265 }
266 }
267 if (i < fdnum || (fdnum && fdmax <= 0))
268 msg->msg_flags |= MSG_CTRUNC;
269
270 /*
271 * All of the files that fit in the message have had their
272 * usage counts incremented, so we just free the list.
273 */
274 __scm_destroy(scm);
275 }
276
277 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
278 {
279 struct scm_fp_list *new_fpl;
280 int i;
281
282 if (!fpl)
283 return NULL;
284
285 new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
286 if (new_fpl) {
287 for (i=fpl->count-1; i>=0; i--)
288 get_file(fpl->fp[i]);
289 memcpy(new_fpl, fpl, sizeof(*fpl));
290 }
291 return new_fpl;
292 }
293
294 EXPORT_SYMBOL(__scm_destroy);
295 EXPORT_SYMBOL(__scm_send);
296 EXPORT_SYMBOL(put_cmsg);
297 EXPORT_SYMBOL(scm_detach_fds);
298 EXPORT_SYMBOL(scm_fp_dup);
299
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