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/signal.h>
13 #include <linux/errno.h>
14 #include <linux/sched.h>
15 #include <linux/mm.h>
16 #include <linux/kernel.h>
17 #include <linux/major.h>
18 #include <linux/stat.h>
19 #include <linux/socket.h>
20 #include <linux/file.h>
21 #include <linux/fcntl.h>
22 #include <linux/net.h>
23 #include <linux/interrupt.h>
24 #include <linux/netdevice.h>
25
26 #include <asm/system.h>
27 #include <asm/uaccess.h>
28
29 #include <net/protocol.h>
30 #include <linux/skbuff.h>
31 #include <net/sock.h>
32 #include <net/scm.h>
33
34
35 /*
36 * Only allow a user to send credentials, that they could set with
37 * setu(g)id.
38 */
39
scm_check_creds(struct ucred * creds)40 static __inline__ int scm_check_creds(struct ucred *creds)
41 {
42 if ((creds->pid == current->pid || capable(CAP_SYS_ADMIN)) &&
43 ((creds->uid == current->uid || creds->uid == current->euid ||
44 creds->uid == current->suid) || capable(CAP_SETUID)) &&
45 ((creds->gid == current->gid || creds->gid == current->egid ||
46 creds->gid == current->sgid) || capable(CAP_SETGID))) {
47 return 0;
48 }
49 return -EPERM;
50 }
51
scm_fp_copy(struct cmsghdr * cmsg,struct scm_fp_list ** fplp)52 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
53 {
54 int *fdp = (int*)CMSG_DATA(cmsg);
55 struct scm_fp_list *fpl = *fplp;
56 struct file **fpp;
57 int i, num;
58
59 num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
60
61 if (num <= 0)
62 return 0;
63
64 if (num > SCM_MAX_FD)
65 return -EINVAL;
66
67 if (!fpl)
68 {
69 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
70 if (!fpl)
71 return -ENOMEM;
72 *fplp = fpl;
73 INIT_LIST_HEAD(&fpl->list);
74 fpl->count = 0;
75 }
76 fpp = &fpl->fp[fpl->count];
77
78 if (fpl->count + num > SCM_MAX_FD)
79 return -EINVAL;
80
81 /*
82 * Verify the descriptors and increment the usage count.
83 */
84
85 for (i=0; i< num; i++)
86 {
87 int fd = fdp[i];
88 struct file *file;
89
90 if (fd < 0 || !(file = fget(fd)))
91 return -EBADF;
92 *fpp++ = file;
93 fpl->count++;
94 }
95 return num;
96 }
97
__scm_destroy(struct scm_cookie * scm)98 void __scm_destroy(struct scm_cookie *scm)
99 {
100 struct scm_fp_list *fpl = scm->fp;
101 int i;
102
103 if (fpl) {
104 scm->fp = NULL;
105 if (current->scm_work_list) {
106 list_add_tail(&fpl->list, current->scm_work_list);
107 } else {
108 LIST_HEAD(work_list);
109
110 current->scm_work_list = &work_list;
111
112 list_add(&fpl->list, &work_list);
113 while (!list_empty(&work_list)) {
114 fpl = list_entry(work_list.next, struct scm_fp_list, list);
115
116 list_del(&fpl->list);
117 for (i=fpl->count-1; i>=0; i--)
118 fput(fpl->fp[i]);
119 kfree(fpl);
120 }
121
122 current->scm_work_list = NULL;
123 }
124 }
125 }
126
__scm_send(struct socket * sock,struct msghdr * msg,struct scm_cookie * p)127 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
128 {
129 struct cmsghdr *cmsg;
130 int err;
131
132 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
133 {
134 err = -EINVAL;
135
136 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
137 /* The first check was omitted in <= 2.2.5. The reasoning was
138 that parser checks cmsg_len in any case, so that
139 additional check would be work duplication.
140 But if cmsg_level is not SOL_SOCKET, we do not check
141 for too short ancillary data object at all! Oops.
142 OK, let's add it...
143 */
144 if (!CMSG_OK(msg, cmsg))
145 goto error;
146
147 if (cmsg->cmsg_level != SOL_SOCKET)
148 continue;
149
150 switch (cmsg->cmsg_type)
151 {
152 case SCM_RIGHTS:
153 err=scm_fp_copy(cmsg, &p->fp);
154 if (err<0)
155 goto error;
156 break;
157 case SCM_CREDENTIALS:
158 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
159 goto error;
160 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
161 err = scm_check_creds(&p->creds);
162 if (err)
163 goto error;
164 break;
165 default:
166 goto error;
167 }
168 }
169
170 if (p->fp && !p->fp->count)
171 {
172 kfree(p->fp);
173 p->fp = NULL;
174 }
175 return 0;
176
177 error:
178 scm_destroy(p);
179 return err;
180 }
181
put_cmsg(struct msghdr * msg,int level,int type,int len,void * data)182 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
183 {
184 struct cmsghdr *cm = (struct cmsghdr*)msg->msg_control;
185 struct cmsghdr cmhdr;
186 int cmlen = CMSG_LEN(len);
187 int err;
188
189 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
190 msg->msg_flags |= MSG_CTRUNC;
191 return 0; /* XXX: return error? check spec. */
192 }
193 if (msg->msg_controllen < cmlen) {
194 msg->msg_flags |= MSG_CTRUNC;
195 cmlen = msg->msg_controllen;
196 }
197 cmhdr.cmsg_level = level;
198 cmhdr.cmsg_type = type;
199 cmhdr.cmsg_len = cmlen;
200
201 err = -EFAULT;
202 if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
203 goto out;
204 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
205 goto out;
206 cmlen = CMSG_SPACE(len);
207 msg->msg_control += cmlen;
208 msg->msg_controllen -= cmlen;
209 err = 0;
210 out:
211 return err;
212 }
213
scm_detach_fds(struct msghdr * msg,struct scm_cookie * scm)214 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
215 {
216 struct cmsghdr *cm = (struct cmsghdr*)msg->msg_control;
217
218 int fdmax = 0;
219 int fdnum = scm->fp->count;
220 struct file **fp = scm->fp->fp;
221 int *cmfptr;
222 int err = 0, i;
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=(int*)CMSG_DATA(cm); i<fdmax; i++, cmfptr++)
232 {
233 int new_fd;
234 err = get_unused_fd();
235 if (err < 0)
236 break;
237 new_fd = err;
238 err = put_user(new_fd, cmfptr);
239 if (err) {
240 put_unused_fd(new_fd);
241 break;
242 }
243 /* Bump the usage count and install the file. */
244 get_file(fp[i]);
245 fd_install(new_fd, fp[i]);
246 }
247
248 if (i > 0)
249 {
250 int cmlen = CMSG_LEN(i*sizeof(int));
251 if (!err)
252 err = put_user(SOL_SOCKET, &cm->cmsg_level);
253 if (!err)
254 err = put_user(SCM_RIGHTS, &cm->cmsg_type);
255 if (!err)
256 err = put_user(cmlen, &cm->cmsg_len);
257 if (!err) {
258 cmlen = CMSG_SPACE(i*sizeof(int));
259 msg->msg_control += cmlen;
260 msg->msg_controllen -= cmlen;
261 }
262 }
263 if (i < fdnum || (fdnum && fdmax <= 0))
264 msg->msg_flags |= MSG_CTRUNC;
265
266 /*
267 * All of the files that fit in the message have had their
268 * usage counts incremented, so we just free the list.
269 */
270 __scm_destroy(scm);
271 }
272
scm_fp_dup(struct scm_fp_list * fpl)273 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
274 {
275 struct scm_fp_list *new_fpl;
276 int i;
277
278 if (!fpl)
279 return NULL;
280
281 new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
282 if (new_fpl) {
283 INIT_LIST_HEAD(&new_fpl->list);
284 for (i=fpl->count-1; i>=0; i--)
285 get_file(fpl->fp[i]);
286 memcpy(new_fpl, fpl, sizeof(*fpl));
287 }
288 return new_fpl;
289 }
290