1 /* scm.c - Socket level control messages processing.
3 * Author: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
4 * Alignment and value checking mods by Craig Metz
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.
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>
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>
31 #include <asm/system.h>
32 #include <asm/uaccess.h>
34 #include <net/protocol.h>
35 #include <linux/skbuff.h>
37 #include <net/compat.h>
42 * Only allow a user to send credentials, that they could set with
46 static __inline__ int scm_check_creds(struct ucred *creds)
48 const struct cred *cred = current_cred();
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))) {
60 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
62 int *fdp = (int*)CMSG_DATA(cmsg);
63 struct scm_fp_list *fpl = *fplp;
67 num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
77 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
82 fpl->max = SCM_MAX_FD;
85 fpp = &fpl->fp[fpl->count];
87 if (fpl->count + num > fpl->max)
91 * Verify the descriptors and increment the usage count.
94 for (i=0; i< num; i++)
99 if (fd < 0 || !(file = fget_raw(fd)))
106 fpl->user = get_uid(current_user());
111 void __scm_destroy(struct scm_cookie *scm)
113 struct scm_fp_list *fpl = scm->fp;
118 if (current->scm_work_list) {
119 list_add_tail(&fpl->list, current->scm_work_list);
121 LIST_HEAD(work_list);
123 current->scm_work_list = &work_list;
125 list_add(&fpl->list, &work_list);
126 while (!list_empty(&work_list)) {
127 fpl = list_first_entry(&work_list, struct scm_fp_list, list);
129 list_del(&fpl->list);
130 for (i=fpl->count-1; i>=0; i--)
136 current->scm_work_list = NULL;
140 EXPORT_SYMBOL(__scm_destroy);
142 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
144 struct cmsghdr *cmsg;
147 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
151 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
152 /* The first check was omitted in <= 2.2.5. The reasoning was
153 that parser checks cmsg_len in any case, so that
154 additional check would be work duplication.
155 But if cmsg_level is not SOL_SOCKET, we do not check
156 for too short ancillary data object at all! Oops.
159 if (!CMSG_OK(msg, cmsg))
162 if (cmsg->cmsg_level != SOL_SOCKET)
165 switch (cmsg->cmsg_type)
168 if (!sock->ops || sock->ops->family != PF_UNIX)
170 err=scm_fp_copy(cmsg, &p->fp);
174 case SCM_CREDENTIALS:
175 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
177 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
178 err = scm_check_creds(&p->creds);
182 if (!p->pid || pid_vnr(p->pid) != p->creds.pid) {
185 pid = find_get_pid(p->creds.pid);
193 (p->cred->euid != p->creds.uid) ||
194 (p->cred->egid != p->creds.gid)) {
197 cred = prepare_creds();
201 cred->uid = cred->euid = p->creds.uid;
202 cred->gid = cred->egid = p->creds.gid;
213 if (p->fp && !p->fp->count)
224 EXPORT_SYMBOL(__scm_send);
226 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
228 struct cmsghdr __user *cm
229 = (__force struct cmsghdr __user *)msg->msg_control;
230 struct cmsghdr cmhdr;
231 int cmlen = CMSG_LEN(len);
234 if (MSG_CMSG_COMPAT & msg->msg_flags)
235 return put_cmsg_compat(msg, level, type, len, data);
237 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
238 msg->msg_flags |= MSG_CTRUNC;
239 return 0; /* XXX: return error? check spec. */
241 if (msg->msg_controllen < cmlen) {
242 msg->msg_flags |= MSG_CTRUNC;
243 cmlen = msg->msg_controllen;
245 cmhdr.cmsg_level = level;
246 cmhdr.cmsg_type = type;
247 cmhdr.cmsg_len = cmlen;
250 if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
252 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
254 cmlen = CMSG_SPACE(len);
255 if (msg->msg_controllen < cmlen)
256 cmlen = msg->msg_controllen;
257 msg->msg_control += cmlen;
258 msg->msg_controllen -= cmlen;
263 EXPORT_SYMBOL(put_cmsg);
265 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
267 struct cmsghdr __user *cm
268 = (__force struct cmsghdr __user*)msg->msg_control;
271 int fdnum = scm->fp->count;
272 struct file **fp = scm->fp->fp;
276 if (MSG_CMSG_COMPAT & msg->msg_flags) {
277 scm_detach_fds_compat(msg, scm);
281 if (msg->msg_controllen > sizeof(struct cmsghdr))
282 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
288 for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
292 err = security_file_receive(fp[i]);
295 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
300 err = put_user(new_fd, cmfptr);
302 put_unused_fd(new_fd);
305 /* Bump the usage count and install the file. */
307 fd_install(new_fd, fp[i]);
312 int cmlen = CMSG_LEN(i*sizeof(int));
313 err = put_user(SOL_SOCKET, &cm->cmsg_level);
315 err = put_user(SCM_RIGHTS, &cm->cmsg_type);
317 err = put_user(cmlen, &cm->cmsg_len);
319 cmlen = CMSG_SPACE(i*sizeof(int));
320 if (msg->msg_controllen < cmlen)
321 cmlen = msg->msg_controllen;
322 msg->msg_control += cmlen;
323 msg->msg_controllen -= cmlen;
326 if (i < fdnum || (fdnum && fdmax <= 0))
327 msg->msg_flags |= MSG_CTRUNC;
330 * All of the files that fit in the message have had their
331 * usage counts incremented, so we just free the list.
335 EXPORT_SYMBOL(scm_detach_fds);
337 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
339 struct scm_fp_list *new_fpl;
345 new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
348 for (i = 0; i < fpl->count; i++)
349 get_file(fpl->fp[i]);
350 new_fpl->max = new_fpl->count;
351 new_fpl->user = get_uid(fpl->user);
355 EXPORT_SYMBOL(scm_fp_dup);