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1da177e4 LT |
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> | |
4fc268d2 | 14 | #include <linux/capability.h> |
1da177e4 LT |
15 | #include <linux/errno.h> |
16 | #include <linux/sched.h> | |
17 | #include <linux/mm.h> | |
18 | #include <linux/kernel.h> | |
1da177e4 LT |
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> | |
b488893a PE |
27 | #include <linux/pid.h> |
28 | #include <linux/nsproxy.h> | |
5a0e3ad6 | 29 | #include <linux/slab.h> |
1da177e4 | 30 | |
1da177e4 LT |
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 | /* | |
4ec93edb | 41 | * Only allow a user to send credentials, that they could set with |
1da177e4 LT |
42 | * setu(g)id. |
43 | */ | |
44 | ||
45 | static __inline__ int scm_check_creds(struct ucred *creds) | |
46 | { | |
86a264ab | 47 | const struct cred *cred = current_cred(); |
b6dff3ec | 48 | |
b488893a | 49 | if ((creds->pid == task_tgid_vnr(current) || capable(CAP_SYS_ADMIN)) && |
b6dff3ec DH |
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))) { | |
1da177e4 LT |
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; | |
bba14de9 | 81 | fpl->max = SCM_MAX_FD; |
1da177e4 LT |
82 | } |
83 | fpp = &fpl->fp[fpl->count]; | |
84 | ||
bba14de9 | 85 | if (fpl->count + num > fpl->max) |
1da177e4 | 86 | return -EINVAL; |
4ec93edb | 87 | |
1da177e4 LT |
88 | /* |
89 | * Verify the descriptors and increment the usage count. | |
90 | */ | |
4ec93edb | 91 | |
1da177e4 LT |
92 | for (i=0; i< num; i++) |
93 | { | |
94 | int fd = fdp[i]; | |
95 | struct file *file; | |
96 | ||
326be7b4 | 97 | if (fd < 0 || !(file = fget_raw(fd))) |
1da177e4 LT |
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; | |
6120d3db AV |
112 | for (i=fpl->count-1; i>=0; i--) |
113 | fput(fpl->fp[i]); | |
114 | kfree(fpl); | |
1da177e4 LT |
115 | } |
116 | } | |
9e34a5b5 | 117 | EXPORT_SYMBOL(__scm_destroy); |
1da177e4 LT |
118 | |
119 | int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) | |
120 | { | |
121 | struct cmsghdr *cmsg; | |
122 | int err; | |
123 | ||
124 | for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) | |
125 | { | |
126 | err = -EINVAL; | |
127 | ||
128 | /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */ | |
129 | /* The first check was omitted in <= 2.2.5. The reasoning was | |
130 | that parser checks cmsg_len in any case, so that | |
131 | additional check would be work duplication. | |
4ec93edb | 132 | But if cmsg_level is not SOL_SOCKET, we do not check |
1da177e4 LT |
133 | for too short ancillary data object at all! Oops. |
134 | OK, let's add it... | |
135 | */ | |
136 | if (!CMSG_OK(msg, cmsg)) | |
137 | goto error; | |
138 | ||
139 | if (cmsg->cmsg_level != SOL_SOCKET) | |
140 | continue; | |
141 | ||
142 | switch (cmsg->cmsg_type) | |
143 | { | |
144 | case SCM_RIGHTS: | |
76dadd76 EB |
145 | if (!sock->ops || sock->ops->family != PF_UNIX) |
146 | goto error; | |
1da177e4 LT |
147 | err=scm_fp_copy(cmsg, &p->fp); |
148 | if (err<0) | |
149 | goto error; | |
150 | break; | |
151 | case SCM_CREDENTIALS: | |
152 | if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) | |
153 | goto error; | |
154 | memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred)); | |
155 | err = scm_check_creds(&p->creds); | |
156 | if (err) | |
157 | goto error; | |
257b5358 | 158 | |
16e57262 | 159 | if (!p->pid || pid_vnr(p->pid) != p->creds.pid) { |
257b5358 EB |
160 | struct pid *pid; |
161 | err = -ESRCH; | |
162 | pid = find_get_pid(p->creds.pid); | |
163 | if (!pid) | |
164 | goto error; | |
165 | put_pid(p->pid); | |
166 | p->pid = pid; | |
167 | } | |
168 | ||
16e57262 ED |
169 | if (!p->cred || |
170 | (p->cred->euid != p->creds.uid) || | |
171 | (p->cred->egid != p->creds.gid)) { | |
257b5358 EB |
172 | struct cred *cred; |
173 | err = -ENOMEM; | |
174 | cred = prepare_creds(); | |
175 | if (!cred) | |
176 | goto error; | |
177 | ||
178 | cred->uid = cred->euid = p->creds.uid; | |
e33f7a9f | 179 | cred->gid = cred->egid = p->creds.gid; |
16e57262 ED |
180 | if (p->cred) |
181 | put_cred(p->cred); | |
257b5358 EB |
182 | p->cred = cred; |
183 | } | |
1da177e4 LT |
184 | break; |
185 | default: | |
186 | goto error; | |
187 | } | |
188 | } | |
189 | ||
190 | if (p->fp && !p->fp->count) | |
191 | { | |
192 | kfree(p->fp); | |
193 | p->fp = NULL; | |
194 | } | |
195 | return 0; | |
4ec93edb | 196 | |
1da177e4 LT |
197 | error: |
198 | scm_destroy(p); | |
199 | return err; | |
200 | } | |
9e34a5b5 | 201 | EXPORT_SYMBOL(__scm_send); |
1da177e4 LT |
202 | |
203 | int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) | |
204 | { | |
cfcabdcc SH |
205 | struct cmsghdr __user *cm |
206 | = (__force struct cmsghdr __user *)msg->msg_control; | |
1da177e4 LT |
207 | struct cmsghdr cmhdr; |
208 | int cmlen = CMSG_LEN(len); | |
209 | int err; | |
210 | ||
211 | if (MSG_CMSG_COMPAT & msg->msg_flags) | |
212 | return put_cmsg_compat(msg, level, type, len, data); | |
213 | ||
214 | if (cm==NULL || msg->msg_controllen < sizeof(*cm)) { | |
215 | msg->msg_flags |= MSG_CTRUNC; | |
216 | return 0; /* XXX: return error? check spec. */ | |
217 | } | |
218 | if (msg->msg_controllen < cmlen) { | |
219 | msg->msg_flags |= MSG_CTRUNC; | |
220 | cmlen = msg->msg_controllen; | |
221 | } | |
222 | cmhdr.cmsg_level = level; | |
223 | cmhdr.cmsg_type = type; | |
224 | cmhdr.cmsg_len = cmlen; | |
225 | ||
226 | err = -EFAULT; | |
227 | if (copy_to_user(cm, &cmhdr, sizeof cmhdr)) | |
4ec93edb | 228 | goto out; |
1da177e4 LT |
229 | if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr))) |
230 | goto out; | |
231 | cmlen = CMSG_SPACE(len); | |
1ac70e7a WY |
232 | if (msg->msg_controllen < cmlen) |
233 | cmlen = msg->msg_controllen; | |
1da177e4 LT |
234 | msg->msg_control += cmlen; |
235 | msg->msg_controllen -= cmlen; | |
236 | err = 0; | |
237 | out: | |
238 | return err; | |
239 | } | |
9e34a5b5 | 240 | EXPORT_SYMBOL(put_cmsg); |
1da177e4 LT |
241 | |
242 | void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) | |
243 | { | |
cfcabdcc SH |
244 | struct cmsghdr __user *cm |
245 | = (__force struct cmsghdr __user*)msg->msg_control; | |
1da177e4 LT |
246 | |
247 | int fdmax = 0; | |
248 | int fdnum = scm->fp->count; | |
249 | struct file **fp = scm->fp->fp; | |
250 | int __user *cmfptr; | |
251 | int err = 0, i; | |
252 | ||
253 | if (MSG_CMSG_COMPAT & msg->msg_flags) { | |
254 | scm_detach_fds_compat(msg, scm); | |
255 | return; | |
256 | } | |
257 | ||
258 | if (msg->msg_controllen > sizeof(struct cmsghdr)) | |
259 | fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr)) | |
260 | / sizeof(int)); | |
261 | ||
262 | if (fdnum < fdmax) | |
263 | fdmax = fdnum; | |
264 | ||
cfcabdcc SH |
265 | for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax; |
266 | i++, cmfptr++) | |
1da177e4 LT |
267 | { |
268 | int new_fd; | |
269 | err = security_file_receive(fp[i]); | |
270 | if (err) | |
271 | break; | |
4a19542e UD |
272 | err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags |
273 | ? O_CLOEXEC : 0); | |
1da177e4 LT |
274 | if (err < 0) |
275 | break; | |
276 | new_fd = err; | |
277 | err = put_user(new_fd, cmfptr); | |
278 | if (err) { | |
279 | put_unused_fd(new_fd); | |
280 | break; | |
281 | } | |
282 | /* Bump the usage count and install the file. */ | |
283 | get_file(fp[i]); | |
284 | fd_install(new_fd, fp[i]); | |
285 | } | |
286 | ||
287 | if (i > 0) | |
288 | { | |
289 | int cmlen = CMSG_LEN(i*sizeof(int)); | |
effee6a0 | 290 | err = put_user(SOL_SOCKET, &cm->cmsg_level); |
1da177e4 LT |
291 | if (!err) |
292 | err = put_user(SCM_RIGHTS, &cm->cmsg_type); | |
293 | if (!err) | |
294 | err = put_user(cmlen, &cm->cmsg_len); | |
295 | if (!err) { | |
296 | cmlen = CMSG_SPACE(i*sizeof(int)); | |
297 | msg->msg_control += cmlen; | |
298 | msg->msg_controllen -= cmlen; | |
299 | } | |
300 | } | |
301 | if (i < fdnum || (fdnum && fdmax <= 0)) | |
302 | msg->msg_flags |= MSG_CTRUNC; | |
303 | ||
304 | /* | |
305 | * All of the files that fit in the message have had their | |
306 | * usage counts incremented, so we just free the list. | |
307 | */ | |
308 | __scm_destroy(scm); | |
309 | } | |
9e34a5b5 | 310 | EXPORT_SYMBOL(scm_detach_fds); |
1da177e4 LT |
311 | |
312 | struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) | |
313 | { | |
314 | struct scm_fp_list *new_fpl; | |
315 | int i; | |
316 | ||
317 | if (!fpl) | |
318 | return NULL; | |
319 | ||
bba14de9 ED |
320 | new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]), |
321 | GFP_KERNEL); | |
1da177e4 | 322 | if (new_fpl) { |
bba14de9 | 323 | for (i = 0; i < fpl->count; i++) |
1da177e4 | 324 | get_file(fpl->fp[i]); |
bba14de9 | 325 | new_fpl->max = new_fpl->count; |
1da177e4 LT |
326 | } |
327 | return new_fpl; | |
328 | } | |
1da177e4 | 329 | EXPORT_SYMBOL(scm_fp_dup); |