net: allow GFP_HIGHMEM in __vmalloc()
[linux-2.6.git] / 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 #include <linux/slab.h>
30
31 #include <asm/system.h>
32 #include <asm/uaccess.h>
33
34 #include <net/protocol.h>
35 #include <linux/skbuff.h>
36 #include <net/sock.h>
37 #include <net/compat.h>
38 #include <net/scm.h>
39
40
41 /*
42  *      Only allow a user to send credentials, that they could set with
43  *      setu(g)id.
44  */
45
46 static __inline__ int scm_check_creds(struct ucred *creds)
47 {
48         const struct cred *cred = current_cred();
49
50         if ((creds->pid == task_tgid_vnr(current) || capable(CAP_SYS_ADMIN)) &&
51             ((creds->uid == cred->uid   || creds->uid == cred->euid ||
52               creds->uid == cred->suid) || capable(CAP_SETUID)) &&
53             ((creds->gid == cred->gid   || creds->gid == cred->egid ||
54               creds->gid == cred->sgid) || capable(CAP_SETGID))) {
55                return 0;
56         }
57         return -EPERM;
58 }
59
60 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
61 {
62         int *fdp = (int*)CMSG_DATA(cmsg);
63         struct scm_fp_list *fpl = *fplp;
64         struct file **fpp;
65         int i, num;
66
67         num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
68
69         if (num <= 0)
70                 return 0;
71
72         if (num > SCM_MAX_FD)
73                 return -EINVAL;
74
75         if (!fpl)
76         {
77                 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
78                 if (!fpl)
79                         return -ENOMEM;
80                 *fplp = fpl;
81                 fpl->count = 0;
82         }
83         fpp = &fpl->fp[fpl->count];
84
85         if (fpl->count + num > SCM_MAX_FD)
86                 return -EINVAL;
87
88         /*
89          *      Verify the descriptors and increment the usage count.
90          */
91
92         for (i=0; i< num; i++)
93         {
94                 int fd = fdp[i];
95                 struct file *file;
96
97                 if (fd < 0 || !(file = fget(fd)))
98                         return -EBADF;
99                 *fpp++ = file;
100                 fpl->count++;
101         }
102         return num;
103 }
104
105 void __scm_destroy(struct scm_cookie *scm)
106 {
107         struct scm_fp_list *fpl = scm->fp;
108         int i;
109
110         if (fpl) {
111                 scm->fp = NULL;
112                 if (current->scm_work_list) {
113                         list_add_tail(&fpl->list, current->scm_work_list);
114                 } else {
115                         LIST_HEAD(work_list);
116
117                         current->scm_work_list = &work_list;
118
119                         list_add(&fpl->list, &work_list);
120                         while (!list_empty(&work_list)) {
121                                 fpl = list_first_entry(&work_list, struct scm_fp_list, list);
122
123                                 list_del(&fpl->list);
124                                 for (i=fpl->count-1; i>=0; i--)
125                                         fput(fpl->fp[i]);
126                                 kfree(fpl);
127                         }
128
129                         current->scm_work_list = NULL;
130                 }
131         }
132 }
133 EXPORT_SYMBOL(__scm_destroy);
134
135 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
136 {
137         struct cmsghdr *cmsg;
138         int err;
139
140         for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
141         {
142                 err = -EINVAL;
143
144                 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
145                 /* The first check was omitted in <= 2.2.5. The reasoning was
146                    that parser checks cmsg_len in any case, so that
147                    additional check would be work duplication.
148                    But if cmsg_level is not SOL_SOCKET, we do not check
149                    for too short ancillary data object at all! Oops.
150                    OK, let's add it...
151                  */
152                 if (!CMSG_OK(msg, cmsg))
153                         goto error;
154
155                 if (cmsg->cmsg_level != SOL_SOCKET)
156                         continue;
157
158                 switch (cmsg->cmsg_type)
159                 {
160                 case SCM_RIGHTS:
161                         if (!sock->ops || sock->ops->family != PF_UNIX)
162                                 goto error;
163                         err=scm_fp_copy(cmsg, &p->fp);
164                         if (err<0)
165                                 goto error;
166                         break;
167                 case SCM_CREDENTIALS:
168                         if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
169                                 goto error;
170                         memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
171                         err = scm_check_creds(&p->creds);
172                         if (err)
173                                 goto error;
174
175                         if (pid_vnr(p->pid) != p->creds.pid) {
176                                 struct pid *pid;
177                                 err = -ESRCH;
178                                 pid = find_get_pid(p->creds.pid);
179                                 if (!pid)
180                                         goto error;
181                                 put_pid(p->pid);
182                                 p->pid = pid;
183                         }
184
185                         if ((p->cred->euid != p->creds.uid) ||
186                                 (p->cred->egid != p->creds.gid)) {
187                                 struct cred *cred;
188                                 err = -ENOMEM;
189                                 cred = prepare_creds();
190                                 if (!cred)
191                                         goto error;
192
193                                 cred->uid = cred->euid = p->creds.uid;
194                                 cred->gid = cred->egid = p->creds.uid;
195                                 put_cred(p->cred);
196                                 p->cred = cred;
197                         }
198                         break;
199                 default:
200                         goto error;
201                 }
202         }
203
204         if (p->fp && !p->fp->count)
205         {
206                 kfree(p->fp);
207                 p->fp = NULL;
208         }
209         return 0;
210
211 error:
212         scm_destroy(p);
213         return err;
214 }
215 EXPORT_SYMBOL(__scm_send);
216
217 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
218 {
219         struct cmsghdr __user *cm
220                 = (__force struct cmsghdr __user *)msg->msg_control;
221         struct cmsghdr cmhdr;
222         int cmlen = CMSG_LEN(len);
223         int err;
224
225         if (MSG_CMSG_COMPAT & msg->msg_flags)
226                 return put_cmsg_compat(msg, level, type, len, data);
227
228         if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
229                 msg->msg_flags |= MSG_CTRUNC;
230                 return 0; /* XXX: return error? check spec. */
231         }
232         if (msg->msg_controllen < cmlen) {
233                 msg->msg_flags |= MSG_CTRUNC;
234                 cmlen = msg->msg_controllen;
235         }
236         cmhdr.cmsg_level = level;
237         cmhdr.cmsg_type = type;
238         cmhdr.cmsg_len = cmlen;
239
240         err = -EFAULT;
241         if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
242                 goto out;
243         if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
244                 goto out;
245         cmlen = CMSG_SPACE(len);
246         if (msg->msg_controllen < cmlen)
247                 cmlen = msg->msg_controllen;
248         msg->msg_control += cmlen;
249         msg->msg_controllen -= cmlen;
250         err = 0;
251 out:
252         return err;
253 }
254 EXPORT_SYMBOL(put_cmsg);
255
256 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
257 {
258         struct cmsghdr __user *cm
259                 = (__force struct cmsghdr __user*)msg->msg_control;
260
261         int fdmax = 0;
262         int fdnum = scm->fp->count;
263         struct file **fp = scm->fp->fp;
264         int __user *cmfptr;
265         int err = 0, i;
266
267         if (MSG_CMSG_COMPAT & msg->msg_flags) {
268                 scm_detach_fds_compat(msg, scm);
269                 return;
270         }
271
272         if (msg->msg_controllen > sizeof(struct cmsghdr))
273                 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
274                          / sizeof(int));
275
276         if (fdnum < fdmax)
277                 fdmax = fdnum;
278
279         for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
280              i++, cmfptr++)
281         {
282                 int new_fd;
283                 err = security_file_receive(fp[i]);
284                 if (err)
285                         break;
286                 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
287                                           ? O_CLOEXEC : 0);
288                 if (err < 0)
289                         break;
290                 new_fd = err;
291                 err = put_user(new_fd, cmfptr);
292                 if (err) {
293                         put_unused_fd(new_fd);
294                         break;
295                 }
296                 /* Bump the usage count and install the file. */
297                 get_file(fp[i]);
298                 fd_install(new_fd, fp[i]);
299         }
300
301         if (i > 0)
302         {
303                 int cmlen = CMSG_LEN(i*sizeof(int));
304                 err = put_user(SOL_SOCKET, &cm->cmsg_level);
305                 if (!err)
306                         err = put_user(SCM_RIGHTS, &cm->cmsg_type);
307                 if (!err)
308                         err = put_user(cmlen, &cm->cmsg_len);
309                 if (!err) {
310                         cmlen = CMSG_SPACE(i*sizeof(int));
311                         msg->msg_control += cmlen;
312                         msg->msg_controllen -= cmlen;
313                 }
314         }
315         if (i < fdnum || (fdnum && fdmax <= 0))
316                 msg->msg_flags |= MSG_CTRUNC;
317
318         /*
319          * All of the files that fit in the message have had their
320          * usage counts incremented, so we just free the list.
321          */
322         __scm_destroy(scm);
323 }
324 EXPORT_SYMBOL(scm_detach_fds);
325
326 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
327 {
328         struct scm_fp_list *new_fpl;
329         int i;
330
331         if (!fpl)
332                 return NULL;
333
334         new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
335         if (new_fpl) {
336                 for (i=fpl->count-1; i>=0; i--)
337                         get_file(fpl->fp[i]);
338                 memcpy(new_fpl, fpl, sizeof(*fpl));
339         }
340         return new_fpl;
341 }
342 EXPORT_SYMBOL(scm_fp_dup);