/* scm.c - Socket level control messages processing.
*
* Author: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
* Alignment and value checking mods by Craig Metz
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/stat.h>
#include <linux/socket.h>
#include <linux/file.h>
#include <linux/fcntl.h>
#include <linux/net.h>
#include <linux/interrupt.h>
#include <linux/netdevice.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <linux/inet.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/scm.h>
/*
* Only allow a user to send credentials, that they could set with
* setu(g)id.
*/
44 static __inline__ int scm_check_creds(struct ucred *creds)
{
if ((creds->pid == current->pid || capable(CAP_SYS_ADMIN)) &&
((creds->uid == current->uid || creds->uid == current->euid ||
creds->uid == current->suid) || capable(CAP_SETUID)) &&
((creds->gid == current->gid || creds->gid == current->egid ||
50 creds->gid == current->sgid) || capable(CAP_SETGID))) {
51 return 0;
}
53 return -EPERM;
}
56 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
{
int *fdp = (int*)CMSG_DATA(cmsg);
struct scm_fp_list *fpl = *fplp;
struct file **fpp;
int i, num;
num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
65 if (num <= 0)
66 return 0;
68 if (num > SCM_MAX_FD)
69 return -EINVAL;
71 if (!fpl)
{
fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
74 if (!fpl)
75 return -ENOMEM;
*fplp = fpl;
fpl->count = 0;
}
fpp = &fpl->fp[fpl->count];
81 if (fpl->count + num > SCM_MAX_FD)
82 return -EINVAL;
/*
* Verify the descriptors and increment the usage count.
*/
88 for (i=0; i< num; i++)
{
int fd = fdp[i];
struct file *file;
93 if (fd < 0 || !(file = fget(fd)))
94 return -EBADF;
*fpp++ = file;
fpl->count++;
}
98 return num;
}
101 void __scm_destroy(struct scm_cookie *scm)
{
struct scm_fp_list *fpl = scm->fp;
int i;
106 if (fpl) {
scm->fp = NULL;
108 for (i=fpl->count-1; i>=0; i--)
fput(fpl->fp[i]);
kfree(fpl);
}
}
114 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
{
struct cmsghdr *cmsg;
int err;
119 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
{
err = -EINVAL;
/* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
/* The first check was omitted in <= 2.2.5. The reasoning was
that parser checks cmsg_len in any case, so that
additional check would be work duplication.
But if cmsg_level is not SOL_SOCKET, we do not check
for too short ancillary data object at all! Oops.
OK, let's add it...
*/
if (cmsg->cmsg_len < sizeof(struct cmsghdr) ||
(unsigned long)(((char*)cmsg - (char*)msg->msg_control)
133 + cmsg->cmsg_len) > msg->msg_controllen)
134 goto error;
136 if (cmsg->cmsg_level != SOL_SOCKET)
137 continue;
139 switch (cmsg->cmsg_type)
{
141 case SCM_RIGHTS:
err=scm_fp_copy(cmsg, &p->fp);
143 if (err<0)
144 goto error;
145 break;
146 case SCM_CREDENTIALS:
147 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
148 goto error;
memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
err = scm_check_creds(&p->creds);
151 if (err)
152 goto error;
153 break;
154 default:
155 goto error;
}
}
159 if (p->fp && !p->fp->count)
{
kfree(p->fp);
p->fp = NULL;
}
164 return 0;
error:
scm_destroy(p);
168 return err;
}
171 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
{
struct cmsghdr *cm = (struct cmsghdr*)msg->msg_control;
struct cmsghdr cmhdr;
int cmlen = CMSG_LEN(len);
int err;
178 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
msg->msg_flags |= MSG_CTRUNC;
180 return 0; /* XXX: return error? check spec. */
}
182 if (msg->msg_controllen < cmlen) {
msg->msg_flags |= MSG_CTRUNC;
cmlen = msg->msg_controllen;
}
cmhdr.cmsg_level = level;
cmhdr.cmsg_type = type;
cmhdr.cmsg_len = cmlen;
err = -EFAULT;
191 if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
192 goto out;
193 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
194 goto out;
cmlen = CMSG_SPACE(len);
msg->msg_control += cmlen;
msg->msg_controllen -= cmlen;
err = 0;
out:
200 return err;
}
203 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
{
struct cmsghdr *cm = (struct cmsghdr*)msg->msg_control;
int fdmax = 0;
int fdnum = scm->fp->count;
struct file **fp = scm->fp->fp;
int *cmfptr;
int err = 0, i;
213 if (msg->msg_controllen > sizeof(struct cmsghdr))
fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
/ sizeof(int));
217 if (fdnum < fdmax)
fdmax = fdnum;
220 for (i=0, cmfptr=(int*)CMSG_DATA(cm); i<fdmax; i++, cmfptr++)
{
int new_fd;
err = get_unused_fd();
224 if (err < 0)
225 break;
new_fd = err;
err = put_user(new_fd, cmfptr);
228 if (err) {
put_unused_fd(new_fd);
230 break;
}
/* Bump the usage count and install the file. */
get_file(fp[i]);
fd_install(new_fd, fp[i]);
}
237 if (i > 0)
{
int cmlen = CMSG_LEN(i*sizeof(int));
240 if (!err)
err = put_user(SOL_SOCKET, &cm->cmsg_level);
242 if (!err)
err = put_user(SCM_RIGHTS, &cm->cmsg_type);
244 if (!err)
err = put_user(cmlen, &cm->cmsg_len);
246 if (!err) {
cmlen = CMSG_SPACE(i*sizeof(int));
msg->msg_control += cmlen;
msg->msg_controllen -= cmlen;
}
}
252 if (i < fdnum || (fdnum && fdmax <= 0))
msg->msg_flags |= MSG_CTRUNC;
/*
* All of the files that fit in the message have had their
* usage counts incremented, so we just free the list.
*/
__scm_destroy(scm);
}
262 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
{
struct scm_fp_list *new_fpl;
int i;
267 if (!fpl)
268 return NULL;
new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
271 if (new_fpl) {
272 for (i=fpl->count-1; i>=0; i--)
get_file(fpl->fp[i]);
memcpy(new_fpl, fpl, sizeof(*fpl));
}
276 return new_fpl;
}