File: /usr/src/linux/net/core/scm.c
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 <linux/inet.h>
30 #include <net/ip.h>
31 #include <net/protocol.h>
32 #include <net/tcp.h>
33 #include <net/udp.h>
34 #include <linux/skbuff.h>
35 #include <net/sock.h>
36 #include <net/scm.h>
37
38
39 /*
40 * Only allow a user to send credentials, that they could set with
41 * setu(g)id.
42 */
43
44 static __inline__ int scm_check_creds(struct ucred *creds)
45 {
46 if ((creds->pid == current->pid || capable(CAP_SYS_ADMIN)) &&
47 ((creds->uid == current->uid || creds->uid == current->euid ||
48 creds->uid == current->suid) || capable(CAP_SETUID)) &&
49 ((creds->gid == current->gid || creds->gid == current->egid ||
50 creds->gid == current->sgid) || capable(CAP_SETGID))) {
51 return 0;
52 }
53 return -EPERM;
54 }
55
56 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
57 {
58 int *fdp = (int*)CMSG_DATA(cmsg);
59 struct scm_fp_list *fpl = *fplp;
60 struct file **fpp;
61 int i, num;
62
63 num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
64
65 if (num <= 0)
66 return 0;
67
68 if (num > SCM_MAX_FD)
69 return -EINVAL;
70
71 if (!fpl)
72 {
73 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
74 if (!fpl)
75 return -ENOMEM;
76 *fplp = fpl;
77 fpl->count = 0;
78 }
79 fpp = &fpl->fp[fpl->count];
80
81 if (fpl->count + num > SCM_MAX_FD)
82 return -EINVAL;
83
84 /*
85 * Verify the descriptors and increment the usage count.
86 */
87
88 for (i=0; i< num; i++)
89 {
90 int fd = fdp[i];
91 struct file *file;
92
93 if (fd < 0 || !(file = fget(fd)))
94 return -EBADF;
95 *fpp++ = file;
96 fpl->count++;
97 }
98 return num;
99 }
100
101 void __scm_destroy(struct scm_cookie *scm)
102 {
103 struct scm_fp_list *fpl = scm->fp;
104 int i;
105
106 if (fpl) {
107 scm->fp = NULL;
108 for (i=fpl->count-1; i>=0; i--)
109 fput(fpl->fp[i]);
110 kfree(fpl);
111 }
112 }
113
114 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
115 {
116 struct cmsghdr *cmsg;
117 int err;
118
119 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
120 {
121 err = -EINVAL;
122
123 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
124 /* The first check was omitted in <= 2.2.5. The reasoning was
125 that parser checks cmsg_len in any case, so that
126 additional check would be work duplication.
127 But if cmsg_level is not SOL_SOCKET, we do not check
128 for too short ancillary data object at all! Oops.
129 OK, let's add it...
130 */
131 if (cmsg->cmsg_len < sizeof(struct cmsghdr) ||
132 (unsigned long)(((char*)cmsg - (char*)msg->msg_control)
133 + cmsg->cmsg_len) > msg->msg_controllen)
134 goto error;
135
136 if (cmsg->cmsg_level != SOL_SOCKET)
137 continue;
138
139 switch (cmsg->cmsg_type)
140 {
141 case SCM_RIGHTS:
142 err=scm_fp_copy(cmsg, &p->fp);
143 if (err<0)
144 goto error;
145 break;
146 case SCM_CREDENTIALS:
147 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
148 goto error;
149 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
150 err = scm_check_creds(&p->creds);
151 if (err)
152 goto error;
153 break;
154 default:
155 goto error;
156 }
157 }
158
159 if (p->fp && !p->fp->count)
160 {
161 kfree(p->fp);
162 p->fp = NULL;
163 }
164 return 0;
165
166 error:
167 scm_destroy(p);
168 return err;
169 }
170
171 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
172 {
173 struct cmsghdr *cm = (struct cmsghdr*)msg->msg_control;
174 struct cmsghdr cmhdr;
175 int cmlen = CMSG_LEN(len);
176 int err;
177
178 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
179 msg->msg_flags |= MSG_CTRUNC;
180 return 0; /* XXX: return error? check spec. */
181 }
182 if (msg->msg_controllen < cmlen) {
183 msg->msg_flags |= MSG_CTRUNC;
184 cmlen = msg->msg_controllen;
185 }
186 cmhdr.cmsg_level = level;
187 cmhdr.cmsg_type = type;
188 cmhdr.cmsg_len = cmlen;
189
190 err = -EFAULT;
191 if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
192 goto out;
193 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
194 goto out;
195 cmlen = CMSG_SPACE(len);
196 msg->msg_control += cmlen;
197 msg->msg_controllen -= cmlen;
198 err = 0;
199 out:
200 return err;
201 }
202
203 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
204 {
205 struct cmsghdr *cm = (struct cmsghdr*)msg->msg_control;
206
207 int fdmax = 0;
208 int fdnum = scm->fp->count;
209 struct file **fp = scm->fp->fp;
210 int *cmfptr;
211 int err = 0, i;
212
213 if (msg->msg_controllen > sizeof(struct cmsghdr))
214 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
215 / sizeof(int));
216
217 if (fdnum < fdmax)
218 fdmax = fdnum;
219
220 for (i=0, cmfptr=(int*)CMSG_DATA(cm); i<fdmax; i++, cmfptr++)
221 {
222 int new_fd;
223 err = get_unused_fd();
224 if (err < 0)
225 break;
226 new_fd = err;
227 err = put_user(new_fd, cmfptr);
228 if (err) {
229 put_unused_fd(new_fd);
230 break;
231 }
232 /* Bump the usage count and install the file. */
233 get_file(fp[i]);
234 fd_install(new_fd, fp[i]);
235 }
236
237 if (i > 0)
238 {
239 int cmlen = CMSG_LEN(i*sizeof(int));
240 if (!err)
241 err = put_user(SOL_SOCKET, &cm->cmsg_level);
242 if (!err)
243 err = put_user(SCM_RIGHTS, &cm->cmsg_type);
244 if (!err)
245 err = put_user(cmlen, &cm->cmsg_len);
246 if (!err) {
247 cmlen = CMSG_SPACE(i*sizeof(int));
248 msg->msg_control += cmlen;
249 msg->msg_controllen -= cmlen;
250 }
251 }
252 if (i < fdnum || (fdnum && fdmax <= 0))
253 msg->msg_flags |= MSG_CTRUNC;
254
255 /*
256 * All of the files that fit in the message have had their
257 * usage counts incremented, so we just free the list.
258 */
259 __scm_destroy(scm);
260 }
261
262 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
263 {
264 struct scm_fp_list *new_fpl;
265 int i;
266
267 if (!fpl)
268 return NULL;
269
270 new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
271 if (new_fpl) {
272 for (i=fpl->count-1; i>=0; i--)
273 get_file(fpl->fp[i]);
274 memcpy(new_fpl, fpl, sizeof(*fpl));
275 }
276 return new_fpl;
277 }
278