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(current->nsproxy->pid_ns->user_ns, CAP_SYS_ADMIN)) &&
  58             ((uid_eq(uid, cred->uid)   || uid_eq(uid, cred->euid) ||
  59               uid_eq(uid, cred->suid)) || nsown_capable(CAP_SETUID)) &&
  60             ((gid_eq(gid, cred->gid)   || gid_eq(gid, cred->egid) ||
  61               gid_eq(gid, cred->sgid)) || nsown_capable(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 (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
 133         {
 134                 err = -EINVAL;
 135
 136                 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
 137                 /* The first check was omitted in <= 2.2.5. The reasoning was
 138                    that parser checks cmsg_len in any case, so that
 139                    additional check would be work duplication.
 140                    But if cmsg_level is not SOL_SOCKET, we do not check
 141                    for too short ancillary data object at all! Oops.
 142                    OK, let's add it...
 143                  */
 144                 if (!CMSG_OK(msg, cmsg))
 145                         goto error;
 146
 147                 if (cmsg->cmsg_level != SOL_SOCKET)
 148                         continue;
 149
 150                 switch (cmsg->cmsg_type)
 151                 {
 152                 case SCM_RIGHTS:
 153                         if (!sock->ops || sock->ops->family != PF_UNIX)
 154                                 goto error;
 155                         err=scm_fp_copy(cmsg, &p->fp);
 156                         if (err<0)
 157                                 goto error;
 158                         break;
 159                 case SCM_CREDENTIALS:
 160                 {
 161                         struct ucred creds;
 162                         kuid_t uid;
 163                         kgid_t gid;
 164                         if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
 165                                 goto error;
 166                         memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred));
 167                         err = scm_check_creds(&creds);
 168                         if (err)
 169                                 goto error;
 170
 171                         p->creds.pid = creds.pid;
 172                         if (!p->pid || pid_vnr(p->pid) != creds.pid) {
 173                                 struct pid *pid;
 174                                 err = -ESRCH;
 175                                 pid = find_get_pid(creds.pid);
 176                                 if (!pid)
 177                                         goto error;
 178                                 put_pid(p->pid);
 179                                 p->pid = pid;
 180                         }
 181
 182                         err = -EINVAL;
 183                         uid = make_kuid(current_user_ns(), creds.uid);
 184                         gid = make_kgid(current_user_ns(), creds.gid);
 185                         if (!uid_valid(uid) || !gid_valid(gid))
 186                                 goto error;
 187
 188                         p->creds.uid = uid;
 189                         p->creds.gid = gid;
 190
 191                         if (!p->cred ||
 192                             !uid_eq(p->cred->euid, uid) ||
 193                             !gid_eq(p->cred->egid, gid)) {
 194                                 struct cred *cred;
 195                                 err = -ENOMEM;
 196                                 cred = prepare_creds();
 197                                 if (!cred)
 198                                         goto error;
 199
 200                                 cred->uid = cred->euid = uid;
 201                                 cred->gid = cred->egid = gid;
 202                                 if (p->cred)
 203                                         put_cred(p->cred);
 204                                 p->cred = cred;
 205                         }
 206                         break;
 207                 }
 208                 default:
 209                         goto error;
 210                 }
 211         }
 212
 213         if (p->fp && !p->fp->count)
 214         {
 215                 kfree(p->fp);
 216                 p->fp = NULL;
 217         }
 218         return 0;
 219
 220 error:
 221         scm_destroy(p);
 222         return err;
 223 }
 224 EXPORT_SYMBOL(__scm_send);
 225
 226 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
 227 {
 228         struct cmsghdr __user *cm
 229                 = (__force struct cmsghdr __user *)msg->msg_control;
 230         struct cmsghdr cmhdr;
 231         int cmlen = CMSG_LEN(len);
 232         int err;
 233
 234         if (MSG_CMSG_COMPAT & msg->msg_flags)
 235                 return put_cmsg_compat(msg, level, type, len, data);
 236
 237         if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
 238                 msg->msg_flags |= MSG_CTRUNC;
 239                 return 0; /* XXX: return error? check spec. */
 240         }
 241         if (msg->msg_controllen < cmlen) {
 242                 msg->msg_flags |= MSG_CTRUNC;
 243                 cmlen = msg->msg_controllen;
 244         }
 245         cmhdr.cmsg_level = level;
 246         cmhdr.cmsg_type = type;
 247         cmhdr.cmsg_len = cmlen;
 248
 249         err = -EFAULT;
 250         if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
 251                 goto out;
 252         if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
 253                 goto out;
 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;
 259         err = 0;
 260 out:
 261         return err;
 262 }
 263 EXPORT_SYMBOL(put_cmsg);
 264
 265 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
 266 {
 267         struct cmsghdr __user *cm
 268                 = (__force struct cmsghdr __user*)msg->msg_control;
 269
 270         int fdmax = 0;
 271         int fdnum = scm->fp->count;
 272         struct file **fp = scm->fp->fp;
 273         int __user *cmfptr;
 274         int err = 0, i;
 275
 276         if (MSG_CMSG_COMPAT & msg->msg_flags) {
 277                 scm_detach_fds_compat(msg, scm);
 278                 return;
 279         }
 280
 281         if (msg->msg_controllen > sizeof(struct cmsghdr))
 282                 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
 283                          / sizeof(int));
 284
 285         if (fdnum < fdmax)
 286                 fdmax = fdnum;
 287
 288         for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
 289              i++, cmfptr++)
 290         {
 291                 struct socket *sock;
 292                 int new_fd;
 293                 err = security_file_receive(fp[i]);
 294                 if (err)
 295                         break;
 296                 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
 297                                           ? O_CLOEXEC : 0);
 298                 if (err < 0)
 299                         break;
 300                 new_fd = err;
 301                 err = put_user(new_fd, cmfptr);
 302                 if (err) {
 303                         put_unused_fd(new_fd);
 304                         break;
 305                 }
 306                 /* Bump the usage count and install the file. */
 307                 sock = sock_from_file(fp[i], &err);
 308                 if (sock) {
 309                         sock_update_netprioidx(sock->sk, current);
 310                         sock_update_classid(sock->sk, current);
 311                 }
 312                 fd_install(new_fd, get_file(fp[i]));
 313         }
 314
 315         if (i > 0)
 316         {
 317                 int cmlen = CMSG_LEN(i*sizeof(int));
 318                 err = put_user(SOL_SOCKET, &cm->cmsg_level);
 319                 if (!err)
 320                         err = put_user(SCM_RIGHTS, &cm->cmsg_type);
 321                 if (!err)
 322                         err = put_user(cmlen, &cm->cmsg_len);
 323                 if (!err) {
 324                         cmlen = CMSG_SPACE(i*sizeof(int));
 325                         msg->msg_control += cmlen;
 326                         msg->msg_controllen -= cmlen;
 327                 }
 328         }
 329         if (i < fdnum || (fdnum && fdmax <= 0))
 330                 msg->msg_flags |= MSG_CTRUNC;
 331
 332         /*
 333          * All of the files that fit in the message have had their
 334          * usage counts incremented, so we just free the list.
 335          */
 336         __scm_destroy(scm);
 337 }
 338 EXPORT_SYMBOL(scm_detach_fds);
 339
 340 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
 341 {
 342         struct scm_fp_list *new_fpl;
 343         int i;
 344
 345         if (!fpl)
 346                 return NULL;
 347
 348         new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
 349                           GFP_KERNEL);
 350         if (new_fpl) {
 351                 for (i = 0; i < fpl->count; i++)
 352                         get_file(fpl->fp[i]);
 353                 new_fpl->max = new_fpl->count;
 354         }
 355         return new_fpl;
 356 }
 357 EXPORT_SYMBOL(scm_fp_dup);