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); 358