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.h> 28 #include <linux/nsproxy.h> 29 #include <linux/slab.h> 30 31 #include <asm/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 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 49 if ((creds->pid == task_tgid_vnr(current) || capable(CAP_SYS_ADMIN)) && 50 ((creds->uid == cred->uid || creds->uid == cred->euid || 51 creds->uid == cred->suid) || capable(CAP_SETUID)) && 52 ((creds->gid == cred->gid || creds->gid == cred->egid || 53 creds->gid == cred->sgid) || capable(CAP_SETGID))) { 54 return 0; 55 } 56 return -EPERM; 57 } 58 59 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) 60 { 61 int *fdp = (int*)CMSG_DATA(cmsg); 62 struct scm_fp_list *fpl = *fplp; 63 struct file **fpp; 64 int i, num; 65 66 num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int); 67 68 if (num <= 0) 69 return 0; 70 71 if (num > SCM_MAX_FD) 72 return -EINVAL; 73 74 if (!fpl) 75 { 76 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL); 77 if (!fpl) 78 return -ENOMEM; 79 *fplp = fpl; 80 fpl->count = 0; 81 fpl->max = SCM_MAX_FD; 82 } 83 fpp = &fpl->fp[fpl->count]; 84 85 if (fpl->count + num > fpl->max) 86 return -EINVAL; 87 88 /* 89 * Verify the descriptors and increment the usage count. 90 */ 91 92 for (i=0; i< num; i++) 93 { 94 int fd = fdp[i]; 95 struct file *file; 96 97 if (fd < 0 || !(file = fget_raw(fd))) 98 return -EBADF; 99 *fpp++ = file; 100 fpl->count++; 101 } 102 return num; 103 } 104 105 void __scm_destroy(struct scm_cookie *scm) 106 { 107 struct scm_fp_list *fpl = scm->fp; 108 int i; 109 110 if (fpl) { 111 scm->fp = NULL; 112 if (current->scm_work_list) { 113 list_add_tail(&fpl->list, current->scm_work_list); 114 } else { 115 LIST_HEAD(work_list); 116 117 current->scm_work_list = &work_list; 118 119 list_add(&fpl->list, &work_list); 120 while (!list_empty(&work_list)) { 121 fpl = list_first_entry(&work_list, struct scm_fp_list, list); 122 123 list_del(&fpl->list); 124 for (i=fpl->count-1; i>=0; i--) 125 fput(fpl->fp[i]); 126 kfree(fpl); 127 } 128 129 current->scm_work_list = NULL; 130 } 131 } 132 } 133 EXPORT_SYMBOL(__scm_destroy); 134 135 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) 136 { 137 struct cmsghdr *cmsg; 138 int err; 139 140 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) 141 { 142 err = -EINVAL; 143 144 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */ 145 /* The first check was omitted in <= 2.2.5. The reasoning was 146 that parser checks cmsg_len in any case, so that 147 additional check would be work duplication. 148 But if cmsg_level is not SOL_SOCKET, we do not check 149 for too short ancillary data object at all! Oops. 150 OK, let's add it... 151 */ 152 if (!CMSG_OK(msg, cmsg)) 153 goto error; 154 155 if (cmsg->cmsg_level != SOL_SOCKET) 156 continue; 157 158 switch (cmsg->cmsg_type) 159 { 160 case SCM_RIGHTS: 161 if (!sock->ops || sock->ops->family != PF_UNIX) 162 goto error; 163 err=scm_fp_copy(cmsg, &p->fp); 164 if (err<0) 165 goto error; 166 break; 167 case SCM_CREDENTIALS: 168 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) 169 goto error; 170 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred)); 171 err = scm_check_creds(&p->creds); 172 if (err) 173 goto error; 174 175 if (!p->pid || pid_vnr(p->pid) != p->creds.pid) { 176 struct pid *pid; 177 err = -ESRCH; 178 pid = find_get_pid(p->creds.pid); 179 if (!pid) 180 goto error; 181 put_pid(p->pid); 182 p->pid = pid; 183 } 184 185 if (!p->cred || 186 (p->cred->euid != p->creds.uid) || 187 (p->cred->egid != p->creds.gid)) { 188 struct cred *cred; 189 err = -ENOMEM; 190 cred = prepare_creds(); 191 if (!cred) 192 goto error; 193 194 cred->uid = cred->euid = p->creds.uid; 195 cred->gid = cred->egid = p->creds.gid; 196 if (p->cred) 197 put_cred(p->cred); 198 p->cred = cred; 199 } 200 break; 201 default: 202 goto error; 203 } 204 } 205 206 if (p->fp && !p->fp->count) 207 { 208 kfree(p->fp); 209 p->fp = NULL; 210 } 211 return 0; 212 213 error: 214 scm_destroy(p); 215 return err; 216 } 217 EXPORT_SYMBOL(__scm_send); 218 219 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) 220 { 221 struct cmsghdr __user *cm 222 = (__force struct cmsghdr __user *)msg->msg_control; 223 struct cmsghdr cmhdr; 224 int cmlen = CMSG_LEN(len); 225 int err; 226 227 if (MSG_CMSG_COMPAT & msg->msg_flags) 228 return put_cmsg_compat(msg, level, type, len, data); 229 230 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) { 231 msg->msg_flags |= MSG_CTRUNC; 232 return 0; /* XXX: return error? check spec. */ 233 } 234 if (msg->msg_controllen < cmlen) { 235 msg->msg_flags |= MSG_CTRUNC; 236 cmlen = msg->msg_controllen; 237 } 238 cmhdr.cmsg_level = level; 239 cmhdr.cmsg_type = type; 240 cmhdr.cmsg_len = cmlen; 241 242 err = -EFAULT; 243 if (copy_to_user(cm, &cmhdr, sizeof cmhdr)) 244 goto out; 245 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr))) 246 goto out; 247 cmlen = CMSG_SPACE(len); 248 if (msg->msg_controllen < cmlen) 249 cmlen = msg->msg_controllen; 250 msg->msg_control += cmlen; 251 msg->msg_controllen -= cmlen; 252 err = 0; 253 out: 254 return err; 255 } 256 EXPORT_SYMBOL(put_cmsg); 257 258 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) 259 { 260 struct cmsghdr __user *cm 261 = (__force struct cmsghdr __user*)msg->msg_control; 262 263 int fdmax = 0; 264 int fdnum = scm->fp->count; 265 struct file **fp = scm->fp->fp; 266 int __user *cmfptr; 267 int err = 0, i; 268 269 if (MSG_CMSG_COMPAT & msg->msg_flags) { 270 scm_detach_fds_compat(msg, scm); 271 return; 272 } 273 274 if (msg->msg_controllen > sizeof(struct cmsghdr)) 275 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr)) 276 / sizeof(int)); 277 278 if (fdnum < fdmax) 279 fdmax = fdnum; 280 281 for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax; 282 i++, cmfptr++) 283 { 284 int new_fd; 285 err = security_file_receive(fp[i]); 286 if (err) 287 break; 288 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags 289 ? O_CLOEXEC : 0); 290 if (err < 0) 291 break; 292 new_fd = err; 293 err = put_user(new_fd, cmfptr); 294 if (err) { 295 put_unused_fd(new_fd); 296 break; 297 } 298 /* Bump the usage count and install the file. */ 299 get_file(fp[i]); 300 fd_install(new_fd, fp[i]); 301 } 302 303 if (i > 0) 304 { 305 int cmlen = CMSG_LEN(i*sizeof(int)); 306 err = put_user(SOL_SOCKET, &cm->cmsg_level); 307 if (!err) 308 err = put_user(SCM_RIGHTS, &cm->cmsg_type); 309 if (!err) 310 err = put_user(cmlen, &cm->cmsg_len); 311 if (!err) { 312 cmlen = CMSG_SPACE(i*sizeof(int)); 313 msg->msg_control += cmlen; 314 msg->msg_controllen -= cmlen; 315 } 316 } 317 if (i < fdnum || (fdnum && fdmax <= 0)) 318 msg->msg_flags |= MSG_CTRUNC; 319 320 /* 321 * All of the files that fit in the message have had their 322 * usage counts incremented, so we just free the list. 323 */ 324 __scm_destroy(scm); 325 } 326 EXPORT_SYMBOL(scm_detach_fds); 327 328 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) 329 { 330 struct scm_fp_list *new_fpl; 331 int i; 332 333 if (!fpl) 334 return NULL; 335 336 new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]), 337 GFP_KERNEL); 338 if (new_fpl) { 339 for (i = 0; i < fpl->count; i++) 340 get_file(fpl->fp[i]); 341 new_fpl->max = new_fpl->count; 342 } 343 return new_fpl; 344 } 345 EXPORT_SYMBOL(scm_fp_dup); 346