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 30 #include <linux/uaccess.h> 31 32 #include <net/protocol.h> 33 #include <linux/skbuff.h> 34 #include <net/sock.h> 35 #include <net/compat.h> 36 #include <net/scm.h> 37 #include <net/cls_cgroup.h> 38 39 40 /* 41 * Only allow a user to send credentials, that they could set with 42 * setu(g)id. 43 */ 44 45 static __inline__ int scm_check_creds(struct ucred *creds) 46 { 47 const struct cred *cred = current_cred(); 48 kuid_t uid = make_kuid(cred->user_ns, creds->uid); 49 kgid_t gid = make_kgid(cred->user_ns, creds->gid); 50 51 if (!uid_valid(uid) || !gid_valid(gid)) 52 return -EINVAL; 53 54 if ((creds->pid == task_tgid_vnr(current) || 55 ns_capable(task_active_pid_ns(current)->user_ns, CAP_SYS_ADMIN)) && 56 ((uid_eq(uid, cred->uid) || uid_eq(uid, cred->euid) || 57 uid_eq(uid, cred->suid)) || ns_capable(cred->user_ns, CAP_SETUID)) && 58 ((gid_eq(gid, cred->gid) || gid_eq(gid, cred->egid) || 59 gid_eq(gid, cred->sgid)) || ns_capable(cred->user_ns, CAP_SETGID))) { 60 return 0; 61 } 62 return -EPERM; 63 } 64 65 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) 66 { 67 int *fdp = (int*)CMSG_DATA(cmsg); 68 struct scm_fp_list *fpl = *fplp; 69 struct file **fpp; 70 int i, num; 71 72 num = (cmsg->cmsg_len - sizeof(struct cmsghdr))/sizeof(int); 73 74 if (num <= 0) 75 return 0; 76 77 if (num > SCM_MAX_FD) 78 return -EINVAL; 79 80 if (!fpl) 81 { 82 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL_ACCOUNT); 83 if (!fpl) 84 return -ENOMEM; 85 *fplp = fpl; 86 fpl->count = 0; 87 fpl->max = SCM_MAX_FD; 88 fpl->user = NULL; 89 } 90 fpp = &fpl->fp[fpl->count]; 91 92 if (fpl->count + num > fpl->max) 93 return -EINVAL; 94 95 /* 96 * Verify the descriptors and increment the usage count. 97 */ 98 99 for (i=0; i< num; i++) 100 { 101 int fd = fdp[i]; 102 struct file *file; 103 104 if (fd < 0 || !(file = fget_raw(fd))) 105 return -EBADF; 106 *fpp++ = file; 107 fpl->count++; 108 } 109 110 if (!fpl->user) 111 fpl->user = get_uid(current_user()); 112 113 return num; 114 } 115 116 void __scm_destroy(struct scm_cookie *scm) 117 { 118 struct scm_fp_list *fpl = scm->fp; 119 int i; 120 121 if (fpl) { 122 scm->fp = NULL; 123 for (i=fpl->count-1; i>=0; i--) 124 fput(fpl->fp[i]); 125 free_uid(fpl->user); 126 kfree(fpl); 127 } 128 } 129 EXPORT_SYMBOL(__scm_destroy); 130 131 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) 132 { 133 const struct proto_ops *ops = READ_ONCE(sock->ops); 134 struct cmsghdr *cmsg; 135 int err; 136 137 for_each_cmsghdr(cmsg, msg) { 138 err = -EINVAL; 139 140 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */ 141 /* The first check was omitted in <= 2.2.5. The reasoning was 142 that parser checks cmsg_len in any case, so that 143 additional check would be work duplication. 144 But if cmsg_level is not SOL_SOCKET, we do not check 145 for too short ancillary data object at all! Oops. 146 OK, let's add it... 147 */ 148 if (!CMSG_OK(msg, cmsg)) 149 goto error; 150 151 if (cmsg->cmsg_level != SOL_SOCKET) 152 continue; 153 154 switch (cmsg->cmsg_type) 155 { 156 case SCM_RIGHTS: 157 if (!ops || ops->family != PF_UNIX) 158 goto error; 159 err=scm_fp_copy(cmsg, &p->fp); 160 if (err<0) 161 goto error; 162 break; 163 case SCM_CREDENTIALS: 164 { 165 struct ucred creds; 166 kuid_t uid; 167 kgid_t gid; 168 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) 169 goto error; 170 memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred)); 171 err = scm_check_creds(&creds); 172 if (err) 173 goto error; 174 175 p->creds.pid = creds.pid; 176 if (!p->pid || pid_vnr(p->pid) != creds.pid) { 177 struct pid *pid; 178 err = -ESRCH; 179 pid = find_get_pid(creds.pid); 180 if (!pid) 181 goto error; 182 put_pid(p->pid); 183 p->pid = pid; 184 } 185 186 err = -EINVAL; 187 uid = make_kuid(current_user_ns(), creds.uid); 188 gid = make_kgid(current_user_ns(), creds.gid); 189 if (!uid_valid(uid) || !gid_valid(gid)) 190 goto error; 191 192 p->creds.uid = uid; 193 p->creds.gid = gid; 194 break; 195 } 196 default: 197 goto error; 198 } 199 } 200 201 if (p->fp && !p->fp->count) 202 { 203 kfree(p->fp); 204 p->fp = NULL; 205 } 206 return 0; 207 208 error: 209 scm_destroy(p); 210 return err; 211 } 212 EXPORT_SYMBOL(__scm_send); 213 214 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) 215 { 216 int cmlen = CMSG_LEN(len); 217 218 if (msg->msg_flags & MSG_CMSG_COMPAT) 219 return put_cmsg_compat(msg, level, type, len, data); 220 221 if (!msg->msg_control || msg->msg_controllen < sizeof(struct cmsghdr)) { 222 msg->msg_flags |= MSG_CTRUNC; 223 return 0; /* XXX: return error? check spec. */ 224 } 225 if (msg->msg_controllen < cmlen) { 226 msg->msg_flags |= MSG_CTRUNC; 227 cmlen = msg->msg_controllen; 228 } 229 230 if (msg->msg_control_is_user) { 231 struct cmsghdr __user *cm = msg->msg_control_user; 232 233 check_object_size(data, cmlen - sizeof(*cm), true); 234 235 if (!user_write_access_begin(cm, cmlen)) 236 goto efault; 237 238 unsafe_put_user(cmlen, &cm->cmsg_len, efault_end); 239 unsafe_put_user(level, &cm->cmsg_level, efault_end); 240 unsafe_put_user(type, &cm->cmsg_type, efault_end); 241 unsafe_copy_to_user(CMSG_USER_DATA(cm), data, 242 cmlen - sizeof(*cm), efault_end); 243 user_write_access_end(); 244 } else { 245 struct cmsghdr *cm = msg->msg_control; 246 247 cm->cmsg_level = level; 248 cm->cmsg_type = type; 249 cm->cmsg_len = cmlen; 250 memcpy(CMSG_DATA(cm), data, cmlen - sizeof(*cm)); 251 } 252 253 cmlen = min(CMSG_SPACE(len), msg->msg_controllen); 254 if (msg->msg_control_is_user) 255 msg->msg_control_user += cmlen; 256 else 257 msg->msg_control += cmlen; 258 msg->msg_controllen -= cmlen; 259 return 0; 260 261 efault_end: 262 user_write_access_end(); 263 efault: 264 return -EFAULT; 265 } 266 EXPORT_SYMBOL(put_cmsg); 267 268 void put_cmsg_scm_timestamping64(struct msghdr *msg, struct scm_timestamping_internal *tss_internal) 269 { 270 struct scm_timestamping64 tss; 271 int i; 272 273 for (i = 0; i < ARRAY_SIZE(tss.ts); i++) { 274 tss.ts[i].tv_sec = tss_internal->ts[i].tv_sec; 275 tss.ts[i].tv_nsec = tss_internal->ts[i].tv_nsec; 276 } 277 278 put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_NEW, sizeof(tss), &tss); 279 } 280 EXPORT_SYMBOL(put_cmsg_scm_timestamping64); 281 282 void put_cmsg_scm_timestamping(struct msghdr *msg, struct scm_timestamping_internal *tss_internal) 283 { 284 struct scm_timestamping tss; 285 int i; 286 287 for (i = 0; i < ARRAY_SIZE(tss.ts); i++) { 288 tss.ts[i].tv_sec = tss_internal->ts[i].tv_sec; 289 tss.ts[i].tv_nsec = tss_internal->ts[i].tv_nsec; 290 } 291 292 put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPING_OLD, sizeof(tss), &tss); 293 } 294 EXPORT_SYMBOL(put_cmsg_scm_timestamping); 295 296 static int scm_max_fds(struct msghdr *msg) 297 { 298 if (msg->msg_controllen <= sizeof(struct cmsghdr)) 299 return 0; 300 return (msg->msg_controllen - sizeof(struct cmsghdr)) / sizeof(int); 301 } 302 303 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) 304 { 305 struct cmsghdr __user *cm = 306 (__force struct cmsghdr __user *)msg->msg_control_user; 307 unsigned int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0; 308 int fdmax = min_t(int, scm_max_fds(msg), scm->fp->count); 309 int __user *cmsg_data = CMSG_USER_DATA(cm); 310 int err = 0, i; 311 312 /* no use for FD passing from kernel space callers */ 313 if (WARN_ON_ONCE(!msg->msg_control_is_user)) 314 return; 315 316 if (msg->msg_flags & MSG_CMSG_COMPAT) { 317 scm_detach_fds_compat(msg, scm); 318 return; 319 } 320 321 for (i = 0; i < fdmax; i++) { 322 err = receive_fd_user(scm->fp->fp[i], cmsg_data + i, o_flags); 323 if (err < 0) 324 break; 325 } 326 327 if (i > 0) { 328 int cmlen = CMSG_LEN(i * sizeof(int)); 329 330 err = put_user(SOL_SOCKET, &cm->cmsg_level); 331 if (!err) 332 err = put_user(SCM_RIGHTS, &cm->cmsg_type); 333 if (!err) 334 err = put_user(cmlen, &cm->cmsg_len); 335 if (!err) { 336 cmlen = CMSG_SPACE(i * sizeof(int)); 337 if (msg->msg_controllen < cmlen) 338 cmlen = msg->msg_controllen; 339 msg->msg_control_user += cmlen; 340 msg->msg_controllen -= cmlen; 341 } 342 } 343 344 if (i < scm->fp->count || (scm->fp->count && fdmax <= 0)) 345 msg->msg_flags |= MSG_CTRUNC; 346 347 /* 348 * All of the files that fit in the message have had their usage counts 349 * incremented, so we just free the list. 350 */ 351 __scm_destroy(scm); 352 } 353 EXPORT_SYMBOL(scm_detach_fds); 354 355 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) 356 { 357 struct scm_fp_list *new_fpl; 358 int i; 359 360 if (!fpl) 361 return NULL; 362 363 new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]), 364 GFP_KERNEL_ACCOUNT); 365 if (new_fpl) { 366 for (i = 0; i < fpl->count; i++) 367 get_file(fpl->fp[i]); 368 new_fpl->max = new_fpl->count; 369 new_fpl->user = get_uid(fpl->user); 370 } 371 return new_fpl; 372 } 373 EXPORT_SYMBOL(scm_fp_dup); 374