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/signal.h>
13 #include <linux/errno.h>
14 #include <linux/sched.h>
16 #include <linux/kernel.h>
17 #include <linux/major.h>
18 #include <linux/stat.h>
19 #include <linux/socket.h>
20 #include <linux/file.h>
21 #include <linux/fcntl.h>
22 #include <linux/net.h>
23 #include <linux/interrupt.h>
24 #include <linux/netdevice.h>
26 #include <asm/system.h>
27 #include <asm/uaccess.h>
29 #include <net/protocol.h>
30 #include <linux/skbuff.h>
36 * Only allow a user to send credentials, that they could set with
40 static __inline__ int scm_check_creds(struct ucred *creds)
42 if ((creds->pid == current->pid || capable(CAP_SYS_ADMIN)) &&
43 ((creds->uid == current->uid || creds->uid == current->euid ||
44 creds->uid == current->suid) || capable(CAP_SETUID)) &&
45 ((creds->gid == current->gid || creds->gid == current->egid ||
46 creds->gid == current->sgid) || capable(CAP_SETGID))) {
52 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
54 int *fdp = (int*)CMSG_DATA(cmsg);
55 struct scm_fp_list *fpl = *fplp;
59 num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
69 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
75 fpp = &fpl->fp[fpl->count];
77 if (fpl->count + num > SCM_MAX_FD)
81 * Verify the descriptors and increment the usage count.
84 for (i=0; i< num; i++)
89 if (fd < 0 || !(file = fget(fd)))
97 void __scm_destroy(struct scm_cookie *scm)
99 struct scm_fp_list *fpl = scm->fp;
104 for (i=fpl->count-1; i>=0; i--)
110 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
112 struct cmsghdr *cmsg;
115 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
119 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
120 /* The first check was omitted in <= 2.2.5. The reasoning was
121 that parser checks cmsg_len in any case, so that
122 additional check would be work duplication.
123 But if cmsg_level is not SOL_SOCKET, we do not check
124 for too short ancillary data object at all! Oops.
127 if (cmsg->cmsg_len < sizeof(struct cmsghdr) ||
128 (unsigned long)(((char*)cmsg - (char*)msg->msg_control)
129 + cmsg->cmsg_len) > msg->msg_controllen)
132 if (cmsg->cmsg_level != SOL_SOCKET)
135 switch (cmsg->cmsg_type)
138 err=scm_fp_copy(cmsg, &p->fp);
142 case SCM_CREDENTIALS:
143 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
145 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
146 err = scm_check_creds(&p->creds);
155 if (p->fp && !p->fp->count)
167 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
169 struct cmsghdr *cm = (struct cmsghdr*)msg->msg_control;
170 struct cmsghdr cmhdr;
171 int cmlen = CMSG_LEN(len);
174 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
175 msg->msg_flags |= MSG_CTRUNC;
176 return 0; /* XXX: return error? check spec. */
178 if (msg->msg_controllen < cmlen) {
179 msg->msg_flags |= MSG_CTRUNC;
180 cmlen = msg->msg_controllen;
182 cmhdr.cmsg_level = level;
183 cmhdr.cmsg_type = type;
184 cmhdr.cmsg_len = cmlen;
187 if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
189 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
191 cmlen = CMSG_SPACE(len);
192 msg->msg_control += cmlen;
193 msg->msg_controllen -= cmlen;
199 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
201 struct cmsghdr *cm = (struct cmsghdr*)msg->msg_control;
204 int fdnum = scm->fp->count;
205 struct file **fp = scm->fp->fp;
209 if (msg->msg_controllen > sizeof(struct cmsghdr))
210 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
216 for (i=0, cmfptr=(int*)CMSG_DATA(cm); i<fdmax; i++, cmfptr++)
219 err = get_unused_fd();
223 err = put_user(new_fd, cmfptr);
225 put_unused_fd(new_fd);
228 /* Bump the usage count and install the file. */
230 fd_install(new_fd, fp[i]);
235 int cmlen = CMSG_LEN(i*sizeof(int));
237 err = put_user(SOL_SOCKET, &cm->cmsg_level);
239 err = put_user(SCM_RIGHTS, &cm->cmsg_type);
241 err = put_user(cmlen, &cm->cmsg_len);
243 cmlen = CMSG_SPACE(i*sizeof(int));
244 msg->msg_control += cmlen;
245 msg->msg_controllen -= cmlen;
248 if (i < fdnum || (fdnum && fdmax <= 0))
249 msg->msg_flags |= MSG_CTRUNC;
252 * All of the files that fit in the message have had their
253 * usage counts incremented, so we just free the list.
258 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
260 struct scm_fp_list *new_fpl;
266 new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
268 for (i=fpl->count-1; i>=0; i--)
269 get_file(fpl->fp[i]);
270 memcpy(new_fpl, fpl, sizeof(*fpl));