Merge branch 'davem-next' of master.kernel.org:/pub/scm/linux/kernel/git/jgarzik...
[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                 INIT_LIST_HEAD(&fpl->list);
79                 fpl->count = 0;
80         }
81         fpp = &fpl->fp[fpl->count];
82
83         if (fpl->count + num > SCM_MAX_FD)
84                 return -EINVAL;
85
86         /*
87          *      Verify the descriptors and increment the usage count.
88          */
89
90         for (i=0; i< num; i++)
91         {
92                 int fd = fdp[i];
93                 struct file *file;
94
95                 if (fd < 0 || !(file = fget(fd)))
96                         return -EBADF;
97                 *fpp++ = file;
98                 fpl->count++;
99         }
100         return num;
101 }
102
103 void __scm_destroy(struct scm_cookie *scm)
104 {
105         struct scm_fp_list *fpl = scm->fp;
106         int i;
107
108         if (fpl) {
109                 scm->fp = NULL;
110                 if (current->scm_work_list) {
111                         list_add_tail(&fpl->list, current->scm_work_list);
112                 } else {
113                         LIST_HEAD(work_list);
114
115                         current->scm_work_list = &work_list;
116
117                         list_add(&fpl->list, &work_list);
118                         while (!list_empty(&work_list)) {
119                                 fpl = list_first_entry(&work_list, struct scm_fp_list, list);
120
121                                 list_del(&fpl->list);
122                                 for (i=fpl->count-1; i>=0; i--)
123                                         fput(fpl->fp[i]);
124                                 kfree(fpl);
125                         }
126
127                         current->scm_work_list = NULL;
128                 }
129         }
130 }
131
132 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
133 {
134         struct cmsghdr *cmsg;
135         int err;
136
137         for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
138         {
139                 err = -EINVAL;
140
141                 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
142                 /* The first check was omitted in <= 2.2.5. The reasoning was
143                    that parser checks cmsg_len in any case, so that
144                    additional check would be work duplication.
145                    But if cmsg_level is not SOL_SOCKET, we do not check
146                    for too short ancillary data object at all! Oops.
147                    OK, let's add it...
148                  */
149                 if (!CMSG_OK(msg, cmsg))
150                         goto error;
151
152                 if (cmsg->cmsg_level != SOL_SOCKET)
153                         continue;
154
155                 switch (cmsg->cmsg_type)
156                 {
157                 case SCM_RIGHTS:
158                         err=scm_fp_copy(cmsg, &p->fp);
159                         if (err<0)
160                                 goto error;
161                         break;
162                 case SCM_CREDENTIALS:
163                         if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
164                                 goto error;
165                         memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
166                         err = scm_check_creds(&p->creds);
167                         if (err)
168                                 goto error;
169                         break;
170                 default:
171                         goto error;
172                 }
173         }
174
175         if (p->fp && !p->fp->count)
176         {
177                 kfree(p->fp);
178                 p->fp = NULL;
179         }
180         return 0;
181
182 error:
183         scm_destroy(p);
184         return err;
185 }
186
187 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
188 {
189         struct cmsghdr __user *cm
190                 = (__force struct cmsghdr __user *)msg->msg_control;
191         struct cmsghdr cmhdr;
192         int cmlen = CMSG_LEN(len);
193         int err;
194
195         if (MSG_CMSG_COMPAT & msg->msg_flags)
196                 return put_cmsg_compat(msg, level, type, len, data);
197
198         if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
199                 msg->msg_flags |= MSG_CTRUNC;
200                 return 0; /* XXX: return error? check spec. */
201         }
202         if (msg->msg_controllen < cmlen) {
203                 msg->msg_flags |= MSG_CTRUNC;
204                 cmlen = msg->msg_controllen;
205         }
206         cmhdr.cmsg_level = level;
207         cmhdr.cmsg_type = type;
208         cmhdr.cmsg_len = cmlen;
209
210         err = -EFAULT;
211         if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
212                 goto out;
213         if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
214                 goto out;
215         cmlen = CMSG_SPACE(len);
216         if (msg->msg_controllen < cmlen)
217                 cmlen = msg->msg_controllen;
218         msg->msg_control += cmlen;
219         msg->msg_controllen -= cmlen;
220         err = 0;
221 out:
222         return err;
223 }
224
225 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
226 {
227         struct cmsghdr __user *cm
228                 = (__force struct cmsghdr __user*)msg->msg_control;
229
230         int fdmax = 0;
231         int fdnum = scm->fp->count;
232         struct file **fp = scm->fp->fp;
233         int __user *cmfptr;
234         int err = 0, i;
235
236         if (MSG_CMSG_COMPAT & msg->msg_flags) {
237                 scm_detach_fds_compat(msg, scm);
238                 return;
239         }
240
241         if (msg->msg_controllen > sizeof(struct cmsghdr))
242                 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
243                          / sizeof(int));
244
245         if (fdnum < fdmax)
246                 fdmax = fdnum;
247
248         for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
249              i++, cmfptr++)
250         {
251                 int new_fd;
252                 err = security_file_receive(fp[i]);
253                 if (err)
254                         break;
255                 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
256                                           ? O_CLOEXEC : 0);
257                 if (err < 0)
258                         break;
259                 new_fd = err;
260                 err = put_user(new_fd, cmfptr);
261                 if (err) {
262                         put_unused_fd(new_fd);
263                         break;
264                 }
265                 /* Bump the usage count and install the file. */
266                 get_file(fp[i]);
267                 fd_install(new_fd, fp[i]);
268         }
269
270         if (i > 0)
271         {
272                 int cmlen = CMSG_LEN(i*sizeof(int));
273                 err = put_user(SOL_SOCKET, &cm->cmsg_level);
274                 if (!err)
275                         err = put_user(SCM_RIGHTS, &cm->cmsg_type);
276                 if (!err)
277                         err = put_user(cmlen, &cm->cmsg_len);
278                 if (!err) {
279                         cmlen = CMSG_SPACE(i*sizeof(int));
280                         msg->msg_control += cmlen;
281                         msg->msg_controllen -= cmlen;
282                 }
283         }
284         if (i < fdnum || (fdnum && fdmax <= 0))
285                 msg->msg_flags |= MSG_CTRUNC;
286
287         /*
288          * All of the files that fit in the message have had their
289          * usage counts incremented, so we just free the list.
290          */
291         __scm_destroy(scm);
292 }
293
294 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
295 {
296         struct scm_fp_list *new_fpl;
297         int i;
298
299         if (!fpl)
300                 return NULL;
301
302         new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
303         if (new_fpl) {
304                 INIT_LIST_HEAD(&new_fpl->list);
305                 for (i=fpl->count-1; i>=0; i--)
306                         get_file(fpl->fp[i]);
307                 memcpy(new_fpl, fpl, sizeof(*fpl));
308         }
309         return new_fpl;
310 }
311
312 EXPORT_SYMBOL(__scm_destroy);
313 EXPORT_SYMBOL(__scm_send);
314 EXPORT_SYMBOL(put_cmsg);
315 EXPORT_SYMBOL(scm_detach_fds);
316 EXPORT_SYMBOL(scm_fp_dup);