1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* scm.c - Socket level control messages processing. 3 * 4 * Author: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> 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); 397