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(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 - 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 break; 191 } 192 default: 193 goto error; 194 } 195 } 196 197 if (p->fp && !p->fp->count) 198 { 199 kfree(p->fp); 200 p->fp = NULL; 201 } 202 return 0; 203 204 error: 205 scm_destroy(p); 206 return err; 207 } 208 EXPORT_SYMBOL(__scm_send); 209 210 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) 211 { 212 struct cmsghdr __user *cm 213 = (__force struct cmsghdr __user *)msg->msg_control; 214 struct cmsghdr cmhdr; 215 int cmlen = CMSG_LEN(len); 216 int err; 217 218 if (MSG_CMSG_COMPAT & msg->msg_flags) 219 return put_cmsg_compat(msg, level, type, len, data); 220 221 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) { 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 cmhdr.cmsg_level = level; 230 cmhdr.cmsg_type = type; 231 cmhdr.cmsg_len = cmlen; 232 233 err = -EFAULT; 234 if (copy_to_user(cm, &cmhdr, sizeof cmhdr)) 235 goto out; 236 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr))) 237 goto out; 238 cmlen = CMSG_SPACE(len); 239 if (msg->msg_controllen < cmlen) 240 cmlen = msg->msg_controllen; 241 msg->msg_control += cmlen; 242 msg->msg_controllen -= cmlen; 243 err = 0; 244 out: 245 return err; 246 } 247 EXPORT_SYMBOL(put_cmsg); 248 249 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) 250 { 251 struct cmsghdr __user *cm 252 = (__force struct cmsghdr __user*)msg->msg_control; 253 254 int fdmax = 0; 255 int fdnum = scm->fp->count; 256 struct file **fp = scm->fp->fp; 257 int __user *cmfptr; 258 int err = 0, i; 259 260 if (MSG_CMSG_COMPAT & msg->msg_flags) { 261 scm_detach_fds_compat(msg, scm); 262 return; 263 } 264 265 if (msg->msg_controllen > sizeof(struct cmsghdr)) 266 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr)) 267 / sizeof(int)); 268 269 if (fdnum < fdmax) 270 fdmax = fdnum; 271 272 for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax; 273 i++, cmfptr++) 274 { 275 struct socket *sock; 276 int new_fd; 277 err = security_file_receive(fp[i]); 278 if (err) 279 break; 280 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags 281 ? O_CLOEXEC : 0); 282 if (err < 0) 283 break; 284 new_fd = err; 285 err = put_user(new_fd, cmfptr); 286 if (err) { 287 put_unused_fd(new_fd); 288 break; 289 } 290 /* Bump the usage count and install the file. */ 291 sock = sock_from_file(fp[i], &err); 292 if (sock) { 293 sock_update_netprioidx(sock->sk); 294 sock_update_classid(sock->sk); 295 } 296 fd_install(new_fd, get_file(fp[i])); 297 } 298 299 if (i > 0) 300 { 301 int cmlen = CMSG_LEN(i*sizeof(int)); 302 err = put_user(SOL_SOCKET, &cm->cmsg_level); 303 if (!err) 304 err = put_user(SCM_RIGHTS, &cm->cmsg_type); 305 if (!err) 306 err = put_user(cmlen, &cm->cmsg_len); 307 if (!err) { 308 cmlen = CMSG_SPACE(i*sizeof(int)); 309 msg->msg_control += cmlen; 310 msg->msg_controllen -= cmlen; 311 } 312 } 313 if (i < fdnum || (fdnum && fdmax <= 0)) 314 msg->msg_flags |= MSG_CTRUNC; 315 316 /* 317 * All of the files that fit in the message have had their 318 * usage counts incremented, so we just free the list. 319 */ 320 __scm_destroy(scm); 321 } 322 EXPORT_SYMBOL(scm_detach_fds); 323 324 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) 325 { 326 struct scm_fp_list *new_fpl; 327 int i; 328 329 if (!fpl) 330 return NULL; 331 332 new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]), 333 GFP_KERNEL); 334 if (new_fpl) { 335 for (i = 0; i < fpl->count; i++) 336 get_file(fpl->fp[i]); 337 new_fpl->max = new_fpl->count; 338 } 339 return new_fpl; 340 } 341 EXPORT_SYMBOL(scm_fp_dup); 342