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 40 41 /* 42 * Only allow a user to send credentials, that they could set with 43 * setu(g)id. 44 */ 45 46 static __inline__ int scm_check_creds(struct ucred *creds) 47 { 48 const struct cred *cred = current_cred(); 49 kuid_t uid = make_kuid(cred->user_ns, creds->uid); 50 kgid_t gid = make_kgid(cred->user_ns, creds->gid); 51 52 if (!uid_valid(uid) || !gid_valid(gid)) 53 return -EINVAL; 54 55 if ((creds->pid == task_tgid_vnr(current) || 56 ns_capable(task_active_pid_ns(current)->user_ns, CAP_SYS_ADMIN)) && 57 ((uid_eq(uid, cred->uid) || uid_eq(uid, cred->euid) || 58 uid_eq(uid, cred->suid)) || ns_capable(cred->user_ns, CAP_SETUID)) && 59 ((gid_eq(gid, cred->gid) || gid_eq(gid, cred->egid) || 60 gid_eq(gid, cred->sgid)) || ns_capable(cred->user_ns, CAP_SETGID))) { 61 return 0; 62 } 63 return -EPERM; 64 } 65 66 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) 67 { 68 int *fdp = (int*)CMSG_DATA(cmsg); 69 struct scm_fp_list *fpl = *fplp; 70 struct file **fpp; 71 int i, num; 72 73 num = (cmsg->cmsg_len - sizeof(struct cmsghdr))/sizeof(int); 74 75 if (num <= 0) 76 return 0; 77 78 if (num > SCM_MAX_FD) 79 return -EINVAL; 80 81 if (!fpl) 82 { 83 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL_ACCOUNT); 84 if (!fpl) 85 return -ENOMEM; 86 *fplp = fpl; 87 fpl->count = 0; 88 fpl->max = SCM_MAX_FD; 89 fpl->user = NULL; 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 /* don't allow io_uring files */ 108 if (io_uring_get_socket(file)) { 109 fput(file); 110 return -EINVAL; 111 } 112 *fpp++ = file; 113 fpl->count++; 114 } 115 116 if (!fpl->user) 117 fpl->user = get_uid(current_user()); 118 119 return num; 120 } 121 122 void __scm_destroy(struct scm_cookie *scm) 123 { 124 struct scm_fp_list *fpl = scm->fp; 125 int i; 126 127 if (fpl) { 128 scm->fp = NULL; 129 for (i=fpl->count-1; i>=0; i--) 130 fput(fpl->fp[i]); 131 free_uid(fpl->user); 132 kfree(fpl); 133 } 134 } 135 EXPORT_SYMBOL(__scm_destroy); 136 137 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) 138 { 139 const struct proto_ops *ops = READ_ONCE(sock->ops); 140 struct cmsghdr *cmsg; 141 int err; 142 143 for_each_cmsghdr(cmsg, msg) { 144 err = -EINVAL; 145 146 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */ 147 /* The first check was omitted in <= 2.2.5. The reasoning was 148 that parser checks cmsg_len in any case, so that 149 additional check would be work duplication. 150 But if cmsg_level is not SOL_SOCKET, we do not check 151 for too short ancillary data object at all! Oops. 152 OK, let's add it... 153 */ 154 if (!CMSG_OK(msg, cmsg)) 155 goto error; 156 157 if (cmsg->cmsg_level != SOL_SOCKET) 158 continue; 159 160 switch (cmsg->cmsg_type) 161 { 162 case SCM_RIGHTS: 163 if (!ops || ops->family != PF_UNIX) 164 goto error; 165 err=scm_fp_copy(cmsg, &p->fp); 166 if (err<0) 167 goto error; 168 break; 169 case SCM_CREDENTIALS: 170 { 171 struct ucred creds; 172 kuid_t uid; 173 kgid_t gid; 174 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) 175 goto error; 176 memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred)); 177 err = scm_check_creds(&creds); 178 if (err) 179 goto error; 180 181 p->creds.pid = creds.pid; 182 if (!p->pid || pid_vnr(p->pid) != creds.pid) { 183 struct pid *pid; 184 err = -ESRCH; 185 pid = find_get_pid(creds.pid); 186 if (!pid) 187 goto error; 188 put_pid(p->pid); 189 p->pid = pid; 190 } 191 192 err = -EINVAL; 193 uid = make_kuid(current_user_ns(), creds.uid); 194 gid = make_kgid(current_user_ns(), creds.gid); 195 if (!uid_valid(uid) || !gid_valid(gid)) 196 goto error; 197 198 p->creds.uid = uid; 199 p->creds.gid = gid; 200 break; 201 } 202 default: 203 goto error; 204 } 205 } 206 207 if (p->fp && !p->fp->count) 208 { 209 kfree(p->fp); 210 p->fp = NULL; 211 } 212 return 0; 213 214 error: 215 scm_destroy(p); 216 return err; 217 } 218 EXPORT_SYMBOL(__scm_send); 219 220 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) 221 { 222 int cmlen = CMSG_LEN(len); 223 224 if (msg->msg_flags & MSG_CMSG_COMPAT) 225 return put_cmsg_compat(msg, level, type, len, data); 226 227 if (!msg->msg_control || msg->msg_controllen < sizeof(struct cmsghdr)) { 228 msg->msg_flags |= MSG_CTRUNC; 229 return 0; /* XXX: return error? check spec. */ 230 } 231 if (msg->msg_controllen < cmlen) { 232 msg->msg_flags |= MSG_CTRUNC; 233 cmlen = msg->msg_controllen; 234 } 235 236 if (msg->msg_control_is_user) { 237 struct cmsghdr __user *cm = msg->msg_control_user; 238 239 check_object_size(data, cmlen - sizeof(*cm), true); 240 241 if (!user_write_access_begin(cm, cmlen)) 242 goto efault; 243 244 unsafe_put_user(cmlen, &cm->cmsg_len, efault_end); 245 unsafe_put_user(level, &cm->cmsg_level, efault_end); 246 unsafe_put_user(type, &cm->cmsg_type, efault_end); 247 unsafe_copy_to_user(CMSG_USER_DATA(cm), data, 248 cmlen - sizeof(*cm), efault_end); 249 user_write_access_end(); 250 } else { 251 struct cmsghdr *cm = msg->msg_control; 252 253 cm->cmsg_level = level; 254 cm->cmsg_type = type; 255 cm->cmsg_len = cmlen; 256 memcpy(CMSG_DATA(cm), data, cmlen - sizeof(*cm)); 257 } 258 259 cmlen = min(CMSG_SPACE(len), msg->msg_controllen); 260 if (msg->msg_control_is_user) 261 msg->msg_control_user += cmlen; 262 else 263 msg->msg_control += cmlen; 264 msg->msg_controllen -= cmlen; 265 return 0; 266 267 efault_end: 268 user_write_access_end(); 269 efault: 270 return -EFAULT; 271 } 272 EXPORT_SYMBOL(put_cmsg); 273 274 void put_cmsg_scm_timestamping64(struct msghdr *msg, struct scm_timestamping_internal *tss_internal) 275 { 276 struct scm_timestamping64 tss; 277 int i; 278 279 for (i = 0; i < ARRAY_SIZE(tss.ts); i++) { 280 tss.ts[i].tv_sec = tss_internal->ts[i].tv_sec; 281 tss.ts[i].tv_nsec = tss_internal->ts[i].tv_nsec; 282 } 283 284 put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_NEW, sizeof(tss), &tss); 285 } 286 EXPORT_SYMBOL(put_cmsg_scm_timestamping64); 287 288 void put_cmsg_scm_timestamping(struct msghdr *msg, struct scm_timestamping_internal *tss_internal) 289 { 290 struct scm_timestamping tss; 291 int i; 292 293 for (i = 0; i < ARRAY_SIZE(tss.ts); i++) { 294 tss.ts[i].tv_sec = tss_internal->ts[i].tv_sec; 295 tss.ts[i].tv_nsec = tss_internal->ts[i].tv_nsec; 296 } 297 298 put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_OLD, sizeof(tss), &tss); 299 } 300 EXPORT_SYMBOL(put_cmsg_scm_timestamping); 301 302 static int scm_max_fds(struct msghdr *msg) 303 { 304 if (msg->msg_controllen <= sizeof(struct cmsghdr)) 305 return 0; 306 return (msg->msg_controllen - sizeof(struct cmsghdr)) / sizeof(int); 307 } 308 309 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) 310 { 311 struct cmsghdr __user *cm = 312 (__force struct cmsghdr __user *)msg->msg_control_user; 313 unsigned int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0; 314 int fdmax = min_t(int, scm_max_fds(msg), scm->fp->count); 315 int __user *cmsg_data = CMSG_USER_DATA(cm); 316 int err = 0, i; 317 318 /* no use for FD passing from kernel space callers */ 319 if (WARN_ON_ONCE(!msg->msg_control_is_user)) 320 return; 321 322 if (msg->msg_flags & MSG_CMSG_COMPAT) { 323 scm_detach_fds_compat(msg, scm); 324 return; 325 } 326 327 for (i = 0; i < fdmax; i++) { 328 err = receive_fd_user(scm->fp->fp[i], cmsg_data + i, o_flags); 329 if (err < 0) 330 break; 331 } 332 333 if (i > 0) { 334 int cmlen = CMSG_LEN(i * sizeof(int)); 335 336 err = put_user(SOL_SOCKET, &cm->cmsg_level); 337 if (!err) 338 err = put_user(SCM_RIGHTS, &cm->cmsg_type); 339 if (!err) 340 err = put_user(cmlen, &cm->cmsg_len); 341 if (!err) { 342 cmlen = CMSG_SPACE(i * sizeof(int)); 343 if (msg->msg_controllen < cmlen) 344 cmlen = msg->msg_controllen; 345 msg->msg_control_user += cmlen; 346 msg->msg_controllen -= cmlen; 347 } 348 } 349 350 if (i < scm->fp->count || (scm->fp->count && fdmax <= 0)) 351 msg->msg_flags |= MSG_CTRUNC; 352 353 /* 354 * All of the files that fit in the message have had their usage counts 355 * incremented, so we just free the list. 356 */ 357 __scm_destroy(scm); 358 } 359 EXPORT_SYMBOL(scm_detach_fds); 360 361 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) 362 { 363 struct scm_fp_list *new_fpl; 364 int i; 365 366 if (!fpl) 367 return NULL; 368 369 new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]), 370 GFP_KERNEL_ACCOUNT); 371 if (new_fpl) { 372 for (i = 0; i < fpl->count; i++) 373 get_file(fpl->fp[i]); 374 new_fpl->max = new_fpl->count; 375 new_fpl->user = get_uid(fpl->user); 376 } 377 return new_fpl; 378 } 379 EXPORT_SYMBOL(scm_fp_dup); 380