Merge branch 'topic/jack-mechanical' into to-push
[linux-2.6] / 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/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                 if (current->scm_work_list) {
110                         list_add_tail(&fpl->list, current->scm_work_list);
111                 } else {
112                         LIST_HEAD(work_list);
113
114                         current->scm_work_list = &work_list;
115
116                         list_add(&fpl->list, &work_list);
117                         while (!list_empty(&work_list)) {
118                                 fpl = list_first_entry(&work_list, struct scm_fp_list, list);
119
120                                 list_del(&fpl->list);
121                                 for (i=fpl->count-1; i>=0; i--)
122                                         fput(fpl->fp[i]);
123                                 kfree(fpl);
124                         }
125
126                         current->scm_work_list = NULL;
127                 }
128         }
129 }
130
131 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
132 {
133         struct cmsghdr *cmsg;
134         int err;
135
136         for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
137         {
138                 err = -EINVAL;
139
140                 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
141                 /* The first check was omitted in <= 2.2.5. The reasoning was
142                    that parser checks cmsg_len in any case, so that
143                    additional check would be work duplication.
144                    But if cmsg_level is not SOL_SOCKET, we do not check
145                    for too short ancillary data object at all! Oops.
146                    OK, let's add it...
147                  */
148                 if (!CMSG_OK(msg, cmsg))
149                         goto error;
150
151                 if (cmsg->cmsg_level != SOL_SOCKET)
152                         continue;
153
154                 switch (cmsg->cmsg_type)
155                 {
156                 case SCM_RIGHTS:
157                         err=scm_fp_copy(cmsg, &p->fp);
158                         if (err<0)
159                                 goto error;
160                         break;
161                 case SCM_CREDENTIALS:
162                         if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
163                                 goto error;
164                         memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
165                         err = scm_check_creds(&p->creds);
166                         if (err)
167                                 goto error;
168                         break;
169                 default:
170                         goto error;
171                 }
172         }
173
174         if (p->fp && !p->fp->count)
175         {
176                 kfree(p->fp);
177                 p->fp = NULL;
178         }
179         return 0;
180
181 error:
182         scm_destroy(p);
183         return err;
184 }
185
186 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
187 {
188         struct cmsghdr __user *cm
189                 = (__force struct cmsghdr __user *)msg->msg_control;
190         struct cmsghdr cmhdr;
191         int cmlen = CMSG_LEN(len);
192         int err;
193
194         if (MSG_CMSG_COMPAT & msg->msg_flags)
195                 return put_cmsg_compat(msg, level, type, len, data);
196
197         if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
198                 msg->msg_flags |= MSG_CTRUNC;
199                 return 0; /* XXX: return error? check spec. */
200         }
201         if (msg->msg_controllen < cmlen) {
202                 msg->msg_flags |= MSG_CTRUNC;
203                 cmlen = msg->msg_controllen;
204         }
205         cmhdr.cmsg_level = level;
206         cmhdr.cmsg_type = type;
207         cmhdr.cmsg_len = cmlen;
208
209         err = -EFAULT;
210         if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
211                 goto out;
212         if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
213                 goto out;
214         cmlen = CMSG_SPACE(len);
215         if (msg->msg_controllen < cmlen)
216                 cmlen = msg->msg_controllen;
217         msg->msg_control += cmlen;
218         msg->msg_controllen -= cmlen;
219         err = 0;
220 out:
221         return err;
222 }
223
224 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
225 {
226         struct cmsghdr __user *cm
227                 = (__force struct cmsghdr __user*)msg->msg_control;
228
229         int fdmax = 0;
230         int fdnum = scm->fp->count;
231         struct file **fp = scm->fp->fp;
232         int __user *cmfptr;
233         int err = 0, i;
234
235         if (MSG_CMSG_COMPAT & msg->msg_flags) {
236                 scm_detach_fds_compat(msg, scm);
237                 return;
238         }
239
240         if (msg->msg_controllen > sizeof(struct cmsghdr))
241                 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
242                          / sizeof(int));
243
244         if (fdnum < fdmax)
245                 fdmax = fdnum;
246
247         for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
248              i++, cmfptr++)
249         {
250                 int new_fd;
251                 err = security_file_receive(fp[i]);
252                 if (err)
253                         break;
254                 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
255                                           ? O_CLOEXEC : 0);
256                 if (err < 0)
257                         break;
258                 new_fd = err;
259                 err = put_user(new_fd, cmfptr);
260                 if (err) {
261                         put_unused_fd(new_fd);
262                         break;
263                 }
264                 /* Bump the usage count and install the file. */
265                 get_file(fp[i]);
266                 fd_install(new_fd, fp[i]);
267         }
268
269         if (i > 0)
270         {
271                 int cmlen = CMSG_LEN(i*sizeof(int));
272                 err = put_user(SOL_SOCKET, &cm->cmsg_level);
273                 if (!err)
274                         err = put_user(SCM_RIGHTS, &cm->cmsg_type);
275                 if (!err)
276                         err = put_user(cmlen, &cm->cmsg_len);
277                 if (!err) {
278                         cmlen = CMSG_SPACE(i*sizeof(int));
279                         msg->msg_control += cmlen;
280                         msg->msg_controllen -= cmlen;
281                 }
282         }
283         if (i < fdnum || (fdnum && fdmax <= 0))
284                 msg->msg_flags |= MSG_CTRUNC;
285
286         /*
287          * All of the files that fit in the message have had their
288          * usage counts incremented, so we just free the list.
289          */
290         __scm_destroy(scm);
291 }
292
293 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
294 {
295         struct scm_fp_list *new_fpl;
296         int i;
297
298         if (!fpl)
299                 return NULL;
300
301         new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
302         if (new_fpl) {
303                 for (i=fpl->count-1; i>=0; i--)
304                         get_file(fpl->fp[i]);
305                 memcpy(new_fpl, fpl, sizeof(*fpl));
306         }
307         return new_fpl;
308 }
309
310 EXPORT_SYMBOL(__scm_destroy);
311 EXPORT_SYMBOL(__scm_send);
312 EXPORT_SYMBOL(put_cmsg);
313 EXPORT_SYMBOL(scm_detach_fds);
314 EXPORT_SYMBOL(scm_fp_dup);