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