net/core/scm.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* scm.c - Socket level control messages processing.
   3  *
   4  * Author:      Alexey Kuznetsov, <[email protected]>
   5  *              Alignment and value checking mods by Craig Metz
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/signal.h>
  10 #include <linux/capability.h>
  11 #include <linux/errno.h>
  12 #include <linux/sched.h>
  13 #include <linux/sched/user.h>
  14 #include <linux/mm.h>
  15 #include <linux/kernel.h>
  16 #include <linux/stat.h>
  17 #include <linux/socket.h>
  18 #include <linux/file.h>
  19 #include <linux/fcntl.h>
  20 #include <linux/net.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/netdevice.h>
  23 #include <linux/security.h>
  24 #include <linux/pid_namespace.h>
  25 #include <linux/pid.h>
  26 #include <linux/nsproxy.h>
  27 #include <linux/slab.h>
  28 #include <linux/errqueue.h>
  29 #include <linux/io_uring.h>
  30
  31 #include <linux/uaccess.h>
  32
  33 #include <net/protocol.h>
  34 #include <linux/skbuff.h>
  35 #include <net/sock.h>
  36 #include <net/compat.h>
  37 #include <net/scm.h>
  38 #include <net/cls_cgroup.h>
  39 #include <net/af_unix.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 - 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_ACCOUNT);
  85                 if (!fpl)
  86                         return -ENOMEM;
  87                 *fplp = fpl;
  88                 fpl->count = 0;
  89                 fpl->count_unix = 0;
  90                 fpl->max = SCM_MAX_FD;
  91                 fpl->user = NULL;
  92 #if IS_ENABLED(CONFIG_UNIX)
  93                 fpl->inflight = false;
  94                 fpl->dead = false;
  95                 fpl->edges = NULL;
  96                 INIT_LIST_HEAD(&fpl->vertices);
  97 #endif
  98         }
  99         fpp = &fpl->fp[fpl->count];
 100
 101         if (fpl->count + num > fpl->max)
 102                 return -EINVAL;
 103
 104         /*
 105          *      Verify the descriptors and increment the usage count.
 106          */
 107
 108         for (i=0; i< num; i++)
 109         {
 110                 int fd = fdp[i];
 111                 struct file *file;
 112
 113                 if (fd < 0 || !(file = fget_raw(fd)))
 114                         return -EBADF;
 115                 /* don't allow io_uring files */
 116                 if (io_is_uring_fops(file)) {
 117                         fput(file);
 118                         return -EINVAL;
 119                 }
 120                 if (unix_get_socket(file))
 121                         fpl->count_unix++;
 122
 123                 *fpp++ = file;
 124                 fpl->count++;
 125         }
 126
 127         if (!fpl->user)
 128                 fpl->user = get_uid(current_user());
 129
 130         return num;
 131 }
 132
 133 void __scm_destroy(struct scm_cookie *scm)
 134 {
 135         struct scm_fp_list *fpl = scm->fp;
 136         int i;
 137
 138         if (fpl) {
 139                 scm->fp = NULL;
 140                 for (i=fpl->count-1; i>=0; i--)
 141                         fput(fpl->fp[i]);
 142                 free_uid(fpl->user);
 143                 kfree(fpl);
 144         }
 145 }
 146 EXPORT_SYMBOL(__scm_destroy);
 147
 148 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
 149 {
 150         const struct proto_ops *ops = READ_ONCE(sock->ops);
 151         struct cmsghdr *cmsg;
 152         int err;
 153
 154         for_each_cmsghdr(cmsg, msg) {
 155                 err = -EINVAL;
 156
 157                 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
 158                 /* The first check was omitted in <= 2.2.5. The reasoning was
 159                    that parser checks cmsg_len in any case, so that
 160                    additional check would be work duplication.
 161                    But if cmsg_level is not SOL_SOCKET, we do not check
 162                    for too short ancillary data object at all! Oops.
 163                    OK, let's add it...
 164                  */
 165                 if (!CMSG_OK(msg, cmsg))
 166                         goto error;
 167
 168                 if (cmsg->cmsg_level != SOL_SOCKET)
 169                         continue;
 170
 171                 switch (cmsg->cmsg_type)
 172                 {
 173                 case SCM_RIGHTS:
 174                         if (!ops || ops->family != PF_UNIX)
 175                                 goto error;
 176                         err=scm_fp_copy(cmsg, &p->fp);
 177                         if (err<0)
 178                                 goto error;
 179                         break;
 180                 case SCM_CREDENTIALS:
 181                 {
 182                         struct ucred creds;
 183                         kuid_t uid;
 184                         kgid_t gid;
 185                         if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
 186                                 goto error;
 187                         memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred));
 188                         err = scm_check_creds(&creds);
 189                         if (err)
 190                                 goto error;
 191
 192                         p->creds.pid = creds.pid;
 193                         if (!p->pid || pid_vnr(p->pid) != creds.pid) {
 194                                 struct pid *pid;
 195                                 err = -ESRCH;
 196                                 pid = find_get_pid(creds.pid);
 197                                 if (!pid)
 198                                         goto error;
 199                                 put_pid(p->pid);
 200                                 p->pid = pid;
 201                         }
 202
 203                         err = -EINVAL;
 204                         uid = make_kuid(current_user_ns(), creds.uid);
 205                         gid = make_kgid(current_user_ns(), creds.gid);
 206                         if (!uid_valid(uid) || !gid_valid(gid))
 207                                 goto error;
 208
 209                         p->creds.uid = uid;
 210                         p->creds.gid = gid;
 211                         break;
 212                 }
 213                 default:
 214                         goto error;
 215                 }
 216         }
 217
 218         if (p->fp && !p->fp->count)
 219         {
 220                 kfree(p->fp);
 221                 p->fp = NULL;
 222         }
 223         return 0;
 224
 225 error:
 226         scm_destroy(p);
 227         return err;
 228 }
 229 EXPORT_SYMBOL(__scm_send);
 230
 231 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
 232 {
 233         int cmlen = CMSG_LEN(len);
 234
 235         if (msg->msg_flags & MSG_CMSG_COMPAT)
 236                 return put_cmsg_compat(msg, level, type, len, data);
 237
 238         if (!msg->msg_control || msg->msg_controllen < sizeof(struct cmsghdr)) {
 239                 msg->msg_flags |= MSG_CTRUNC;
 240                 return 0; /* XXX: return error? check spec. */
 241         }
 242         if (msg->msg_controllen < cmlen) {
 243                 msg->msg_flags |= MSG_CTRUNC;
 244                 cmlen = msg->msg_controllen;
 245         }
 246
 247         if (msg->msg_control_is_user) {
 248                 struct cmsghdr __user *cm = msg->msg_control_user;
 249
 250                 check_object_size(data, cmlen - sizeof(*cm), true);
 251
 252                 if (!user_write_access_begin(cm, cmlen))
 253                         goto efault;
 254
 255                 unsafe_put_user(cmlen, &cm->cmsg_len, efault_end);
 256                 unsafe_put_user(level, &cm->cmsg_level, efault_end);
 257                 unsafe_put_user(type, &cm->cmsg_type, efault_end);
 258                 unsafe_copy_to_user(CMSG_USER_DATA(cm), data,
 259                                     cmlen - sizeof(*cm), efault_end);
 260                 user_write_access_end();
 261         } else {
 262                 struct cmsghdr *cm = msg->msg_control;
 263
 264                 cm->cmsg_level = level;
 265                 cm->cmsg_type = type;
 266                 cm->cmsg_len = cmlen;
 267                 memcpy(CMSG_DATA(cm), data, cmlen - sizeof(*cm));
 268         }
 269
 270         cmlen = min(CMSG_SPACE(len), msg->msg_controllen);
 271         if (msg->msg_control_is_user)
 272                 msg->msg_control_user += cmlen;
 273         else
 274                 msg->msg_control += cmlen;
 275         msg->msg_controllen -= cmlen;
 276         return 0;
 277
 278 efault_end:
 279         user_write_access_end();
 280 efault:
 281         return -EFAULT;
 282 }
 283 EXPORT_SYMBOL(put_cmsg);
 284
 285 void put_cmsg_scm_timestamping64(struct msghdr *msg, struct scm_timestamping_internal *tss_internal)
 286 {
 287         struct scm_timestamping64 tss;
 288         int i;
 289
 290         for (i = 0; i < ARRAY_SIZE(tss.ts); i++) {
 291                 tss.ts[i].tv_sec = tss_internal->ts[i].tv_sec;
 292                 tss.ts[i].tv_nsec = tss_internal->ts[i].tv_nsec;
 293         }
 294
 295         put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_NEW, sizeof(tss), &tss);
 296 }
 297 EXPORT_SYMBOL(put_cmsg_scm_timestamping64);
 298
 299 void put_cmsg_scm_timestamping(struct msghdr *msg, struct scm_timestamping_internal *tss_internal)
 300 {
 301         struct scm_timestamping tss;
 302         int i;
 303
 304         for (i = 0; i < ARRAY_SIZE(tss.ts); i++) {
 305                 tss.ts[i].tv_sec = tss_internal->ts[i].tv_sec;
 306                 tss.ts[i].tv_nsec = tss_internal->ts[i].tv_nsec;
 307         }
 308
 309         put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_OLD, sizeof(tss), &tss);
 310 }
 311 EXPORT_SYMBOL(put_cmsg_scm_timestamping);
 312
 313 static int scm_max_fds(struct msghdr *msg)
 314 {
 315         if (msg->msg_controllen <= sizeof(struct cmsghdr))
 316                 return 0;
 317         return (msg->msg_controllen - sizeof(struct cmsghdr)) / sizeof(int);
 318 }
 319
 320 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
 321 {
 322         struct cmsghdr __user *cm =
 323                 (__force struct cmsghdr __user *)msg->msg_control_user;
 324         unsigned int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0;
 325         int fdmax = min_t(int, scm_max_fds(msg), scm->fp->count);
 326         int __user *cmsg_data = CMSG_USER_DATA(cm);
 327         int err = 0, i;
 328
 329         /* no use for FD passing from kernel space callers */
 330         if (WARN_ON_ONCE(!msg->msg_control_is_user))
 331                 return;
 332
 333         if (msg->msg_flags & MSG_CMSG_COMPAT) {
 334                 scm_detach_fds_compat(msg, scm);
 335                 return;
 336         }
 337
 338         for (i = 0; i < fdmax; i++) {
 339                 err = scm_recv_one_fd(scm->fp->fp[i], cmsg_data + i, o_flags);
 340                 if (err < 0)
 341                         break;
 342         }
 343
 344         if (i > 0) {
 345                 int cmlen = CMSG_LEN(i * sizeof(int));
 346
 347                 err = put_user(SOL_SOCKET, &cm->cmsg_level);
 348                 if (!err)
 349                         err = put_user(SCM_RIGHTS, &cm->cmsg_type);
 350                 if (!err)
 351                         err = put_user(cmlen, &cm->cmsg_len);
 352                 if (!err) {
 353                         cmlen = CMSG_SPACE(i * sizeof(int));
 354                         if (msg->msg_controllen < cmlen)
 355                                 cmlen = msg->msg_controllen;
 356                         msg->msg_control_user += cmlen;
 357                         msg->msg_controllen -= cmlen;
 358                 }
 359         }
 360
 361         if (i < scm->fp->count || (scm->fp->count && fdmax <= 0))
 362                 msg->msg_flags |= MSG_CTRUNC;
 363
 364         /*
 365          * All of the files that fit in the message have had their usage counts
 366          * incremented, so we just free the list.
 367          */
 368         __scm_destroy(scm);
 369 }
 370 EXPORT_SYMBOL(scm_detach_fds);
 371
 372 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
 373 {
 374         struct scm_fp_list *new_fpl;
 375         int i;
 376
 377         if (!fpl)
 378                 return NULL;
 379
 380         new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
 381                           GFP_KERNEL_ACCOUNT);
 382         if (new_fpl) {
 383                 for (i = 0; i < fpl->count; i++)
 384                         get_file(fpl->fp[i]);
 385
 386                 new_fpl->max = new_fpl->count;
 387                 new_fpl->user = get_uid(fpl->user);
 388 #if IS_ENABLED(CONFIG_UNIX)
 389                 new_fpl->inflight = false;
 390                 new_fpl->edges = NULL;
 391                 INIT_LIST_HEAD(&new_fpl->vertices);
 392 #endif
 393         }
 394         return new_fpl;
 395 }
 396 EXPORT_SYMBOL(scm_fp_dup);