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