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_namespace.h>
  28 #include <linux/pid.h>
  29 #include <linux/nsproxy.h>
  30 #include <linux/slab.h>
  31
  32 #include <asm/uaccess.h>
  33
  34 #include <net/protocol.h>
  35 #include <linux/skbuff.h>
  36 #include <net/sock.h>
  37 #include <net/compat.h>
  38 #include <net/scm.h>
  39 #include <net/cls_cgroup.h>
  40
  41
  42 /*
  43  *      Only allow a user to send credentials, that they could set with
  44  *      setu(g)id.
  45  */
  46
  47 static __inline__ int scm_check_creds(struct ucred *creds)
  48 {
  49         const struct cred *cred = current_cred();
  50         kuid_t uid = make_kuid(cred->user_ns, creds->uid);
  51         kgid_t gid = make_kgid(cred->user_ns, creds->gid);
  52
  53         if (!uid_valid(uid) || !gid_valid(gid))
  54                 return -EINVAL;
  55
  56         if ((creds->pid == task_tgid_vnr(current) ||
  57              ns_capable(task_active_pid_ns(current)->user_ns, CAP_SYS_ADMIN)) &&
  58             ((uid_eq(uid, cred->uid)   || uid_eq(uid, cred->euid) ||
  59               uid_eq(uid, cred->suid)) || ns_capable(cred->user_ns, CAP_SETUID)) &&
  60             ((gid_eq(gid, cred->gid)   || gid_eq(gid, cred->egid) ||
  61               gid_eq(gid, cred->sgid)) || ns_capable(cred->user_ns, CAP_SETGID))) {
  62                return 0;
  63         }
  64         return -EPERM;
  65 }
  66
  67 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
  68 {
  69         int *fdp = (int*)CMSG_DATA(cmsg);
  70         struct scm_fp_list *fpl = *fplp;
  71         struct file **fpp;
  72         int i, num;
  73
  74         num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
  75
  76         if (num <= 0)
  77                 return 0;
  78
  79         if (num > SCM_MAX_FD)
  80                 return -EINVAL;
  81
  82         if (!fpl)
  83         {
  84                 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
  85                 if (!fpl)
  86                         return -ENOMEM;
  87                 *fplp = fpl;
  88                 fpl->count = 0;
  89                 fpl->max = SCM_MAX_FD;
  90         }
  91         fpp = &fpl->fp[fpl->count];
  92
  93         if (fpl->count + num > fpl->max)
  94                 return -EINVAL;
  95
  96         /*
  97          *      Verify the descriptors and increment the usage count.
  98          */
  99
 100         for (i=0; i< num; i++)
 101         {
 102                 int fd = fdp[i];
 103                 struct file *file;
 104
 105                 if (fd < 0 || !(file = fget_raw(fd)))
 106                         return -EBADF;
 107                 *fpp++ = file;
 108                 fpl->count++;
 109         }
 110         return num;
 111 }
 112
 113 void __scm_destroy(struct scm_cookie *scm)
 114 {
 115         struct scm_fp_list *fpl = scm->fp;
 116         int i;
 117
 118         if (fpl) {
 119                 scm->fp = NULL;
 120                 for (i=fpl->count-1; i>=0; i--)
 121                         fput(fpl->fp[i]);
 122                 kfree(fpl);
 123         }
 124 }
 125 EXPORT_SYMBOL(__scm_destroy);
 126
 127 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
 128 {
 129         struct cmsghdr *cmsg;
 130         int err;
 131
 132         for_each_cmsghdr(cmsg, msg) {
 133                 err = -EINVAL;
 134
 135                 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
 136                 /* The first check was omitted in <= 2.2.5. The reasoning was
 137                    that parser checks cmsg_len in any case, so that
 138                    additional check would be work duplication.
 139                    But if cmsg_level is not SOL_SOCKET, we do not check
 140                    for too short ancillary data object at all! Oops.
 141                    OK, let's add it...
 142                  */
 143                 if (!CMSG_OK(msg, cmsg))
 144                         goto error;
 145
 146                 if (cmsg->cmsg_level != SOL_SOCKET)
 147                         continue;
 148
 149                 switch (cmsg->cmsg_type)
 150                 {
 151                 case SCM_RIGHTS:
 152                         if (!sock->ops || sock->ops->family != PF_UNIX)
 153                                 goto error;
 154                         err=scm_fp_copy(cmsg, &p->fp);
 155                         if (err<0)
 156                                 goto error;
 157                         break;
 158                 case SCM_CREDENTIALS:
 159                 {
 160                         struct ucred creds;
 161                         kuid_t uid;
 162                         kgid_t gid;
 163                         if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
 164                                 goto error;
 165                         memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred));
 166                         err = scm_check_creds(&creds);
 167                         if (err)
 168                                 goto error;
 169
 170                         p->creds.pid = creds.pid;
 171                         if (!p->pid || pid_vnr(p->pid) != creds.pid) {
 172                                 struct pid *pid;
 173                                 err = -ESRCH;
 174                                 pid = find_get_pid(creds.pid);
 175                                 if (!pid)
 176                                         goto error;
 177                                 put_pid(p->pid);
 178                                 p->pid = pid;
 179                         }
 180
 181                         err = -EINVAL;
 182                         uid = make_kuid(current_user_ns(), creds.uid);
 183                         gid = make_kgid(current_user_ns(), creds.gid);
 184                         if (!uid_valid(uid) || !gid_valid(gid))
 185                                 goto error;
 186
 187                         p->creds.uid = uid;
 188                         p->creds.gid = gid;
 189                         break;
 190                 }
 191                 default:
 192                         goto error;
 193                 }
 194         }
 195
 196         if (p->fp && !p->fp->count)
 197         {
 198                 kfree(p->fp);
 199                 p->fp = NULL;
 200         }
 201         return 0;
 202
 203 error:
 204         scm_destroy(p);
 205         return err;
 206 }
 207 EXPORT_SYMBOL(__scm_send);
 208
 209 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
 210 {
 211         struct cmsghdr __user *cm
 212                 = (__force struct cmsghdr __user *)msg->msg_control;
 213         struct cmsghdr cmhdr;
 214         int cmlen = CMSG_LEN(len);
 215         int err;
 216
 217         if (MSG_CMSG_COMPAT & msg->msg_flags)
 218                 return put_cmsg_compat(msg, level, type, len, data);
 219
 220         if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
 221                 msg->msg_flags |= MSG_CTRUNC;
 222                 return 0; /* XXX: return error? check spec. */
 223         }
 224         if (msg->msg_controllen < cmlen) {
 225                 msg->msg_flags |= MSG_CTRUNC;
 226                 cmlen = msg->msg_controllen;
 227         }
 228         cmhdr.cmsg_level = level;
 229         cmhdr.cmsg_type = type;
 230         cmhdr.cmsg_len = cmlen;
 231
 232         err = -EFAULT;
 233         if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
 234                 goto out;
 235         if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
 236                 goto out;
 237         cmlen = CMSG_SPACE(len);
 238         if (msg->msg_controllen < cmlen)
 239                 cmlen = msg->msg_controllen;
 240         msg->msg_control += cmlen;
 241         msg->msg_controllen -= cmlen;
 242         err = 0;
 243 out:
 244         return err;
 245 }
 246 EXPORT_SYMBOL(put_cmsg);
 247
 248 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
 249 {
 250         struct cmsghdr __user *cm
 251                 = (__force struct cmsghdr __user*)msg->msg_control;
 252
 253         int fdmax = 0;
 254         int fdnum = scm->fp->count;
 255         struct file **fp = scm->fp->fp;
 256         int __user *cmfptr;
 257         int err = 0, i;
 258
 259         if (MSG_CMSG_COMPAT & msg->msg_flags) {
 260                 scm_detach_fds_compat(msg, scm);
 261                 return;
 262         }
 263
 264         if (msg->msg_controllen > sizeof(struct cmsghdr))
 265                 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
 266                          / sizeof(int));
 267
 268         if (fdnum < fdmax)
 269                 fdmax = fdnum;
 270
 271         for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
 272              i++, cmfptr++)
 273         {
 274                 struct socket *sock;
 275                 int new_fd;
 276                 err = security_file_receive(fp[i]);
 277                 if (err)
 278                         break;
 279                 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
 280                                           ? O_CLOEXEC : 0);
 281                 if (err < 0)
 282                         break;
 283                 new_fd = err;
 284                 err = put_user(new_fd, cmfptr);
 285                 if (err) {
 286                         put_unused_fd(new_fd);
 287                         break;
 288                 }
 289                 /* Bump the usage count and install the file. */
 290                 sock = sock_from_file(fp[i], &err);
 291                 if (sock) {
 292                         sock_update_netprioidx(sock->sk);
 293                         sock_update_classid(sock->sk);
 294                 }
 295                 fd_install(new_fd, get_file(fp[i]));
 296         }
 297
 298         if (i > 0)
 299         {
 300                 int cmlen = CMSG_LEN(i*sizeof(int));
 301                 err = put_user(SOL_SOCKET, &cm->cmsg_level);
 302                 if (!err)
 303                         err = put_user(SCM_RIGHTS, &cm->cmsg_type);
 304                 if (!err)
 305                         err = put_user(cmlen, &cm->cmsg_len);
 306                 if (!err) {
 307                         cmlen = CMSG_SPACE(i*sizeof(int));
 308                         msg->msg_control += cmlen;
 309                         msg->msg_controllen -= cmlen;
 310                 }
 311         }
 312         if (i < fdnum || (fdnum && fdmax <= 0))
 313                 msg->msg_flags |= MSG_CTRUNC;
 314
 315         /*
 316          * All of the files that fit in the message have had their
 317          * usage counts incremented, so we just free the list.
 318          */
 319         __scm_destroy(scm);
 320 }
 321 EXPORT_SYMBOL(scm_detach_fds);
 322
 323 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
 324 {
 325         struct scm_fp_list *new_fpl;
 326         int i;
 327
 328         if (!fpl)
 329                 return NULL;
 330
 331         new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
 332                           GFP_KERNEL);
 333         if (new_fpl) {
 334                 for (i = 0; i < fpl->count; i++)
 335                         get_file(fpl->fp[i]);
 336                 new_fpl->max = new_fpl->count;
 337         }
 338         return new_fpl;
 339 }
 340 EXPORT_SYMBOL(scm_fp_dup);