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/system.h> 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 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 50 if ((creds->pid == task_tgid_vnr(current) || capable(CAP_SYS_ADMIN)) && 51 ((creds->uid == cred->uid || creds->uid == cred->euid || 52 creds->uid == cred->suid) || capable(CAP_SETUID)) && 53 ((creds->gid == cred->gid || creds->gid == cred->egid || 54 creds->gid == cred->sgid) || capable(CAP_SETGID))) { 55 return 0; 56 } 57 return -EPERM; 58 } 59 60 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) 61 { 62 int *fdp = (int*)CMSG_DATA(cmsg); 63 struct scm_fp_list *fpl = *fplp; 64 struct file **fpp; 65 int i, num; 66 67 num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int); 68 69 if (num <= 0) 70 return 0; 71 72 if (num > SCM_MAX_FD) 73 return -EINVAL; 74 75 if (!fpl) 76 { 77 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL); 78 if (!fpl) 79 return -ENOMEM; 80 *fplp = fpl; 81 fpl->count = 0; 82 fpl->max = SCM_MAX_FD; 83 } 84 fpp = &fpl->fp[fpl->count]; 85 86 if (fpl->count + num > fpl->max) 87 return -EINVAL; 88 89 /* 90 * Verify the descriptors and increment the usage count. 91 */ 92 93 for (i=0; i< num; i++) 94 { 95 int fd = fdp[i]; 96 struct file *file; 97 98 if (fd < 0 || !(file = fget_raw(fd))) 99 return -EBADF; 100 *fpp++ = file; 101 fpl->count++; 102 } 103 return num; 104 } 105 106 void __scm_destroy(struct scm_cookie *scm) 107 { 108 struct scm_fp_list *fpl = scm->fp; 109 int i; 110 111 if (fpl) { 112 scm->fp = NULL; 113 if (current->scm_work_list) { 114 list_add_tail(&fpl->list, current->scm_work_list); 115 } else { 116 LIST_HEAD(work_list); 117 118 current->scm_work_list = &work_list; 119 120 list_add(&fpl->list, &work_list); 121 while (!list_empty(&work_list)) { 122 fpl = list_first_entry(&work_list, struct scm_fp_list, list); 123 124 list_del(&fpl->list); 125 for (i=fpl->count-1; i>=0; i--) 126 fput(fpl->fp[i]); 127 kfree(fpl); 128 } 129 130 current->scm_work_list = NULL; 131 } 132 } 133 } 134 EXPORT_SYMBOL(__scm_destroy); 135 136 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) 137 { 138 struct cmsghdr *cmsg; 139 int err; 140 141 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) 142 { 143 err = -EINVAL; 144 145 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */ 146 /* The first check was omitted in <= 2.2.5. The reasoning was 147 that parser checks cmsg_len in any case, so that 148 additional check would be work duplication. 149 But if cmsg_level is not SOL_SOCKET, we do not check 150 for too short ancillary data object at all! Oops. 151 OK, let's add it... 152 */ 153 if (!CMSG_OK(msg, cmsg)) 154 goto error; 155 156 if (cmsg->cmsg_level != SOL_SOCKET) 157 continue; 158 159 switch (cmsg->cmsg_type) 160 { 161 case SCM_RIGHTS: 162 if (!sock->ops || sock->ops->family != PF_UNIX) 163 goto error; 164 err=scm_fp_copy(cmsg, &p->fp); 165 if (err<0) 166 goto error; 167 break; 168 case SCM_CREDENTIALS: 169 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) 170 goto error; 171 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred)); 172 err = scm_check_creds(&p->creds); 173 if (err) 174 goto error; 175 176 if (!p->pid || pid_vnr(p->pid) != p->creds.pid) { 177 struct pid *pid; 178 err = -ESRCH; 179 pid = find_get_pid(p->creds.pid); 180 if (!pid) 181 goto error; 182 put_pid(p->pid); 183 p->pid = pid; 184 } 185 186 if (!p->cred || 187 (p->cred->euid != p->creds.uid) || 188 (p->cred->egid != p->creds.gid)) { 189 struct cred *cred; 190 err = -ENOMEM; 191 cred = prepare_creds(); 192 if (!cred) 193 goto error; 194 195 cred->uid = cred->euid = p->creds.uid; 196 cred->gid = cred->egid = p->creds.gid; 197 if (p->cred) 198 put_cred(p->cred); 199 p->cred = cred; 200 } 201 break; 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 struct cmsghdr __user *cm 223 = (__force struct cmsghdr __user *)msg->msg_control; 224 struct cmsghdr cmhdr; 225 int cmlen = CMSG_LEN(len); 226 int err; 227 228 if (MSG_CMSG_COMPAT & msg->msg_flags) 229 return put_cmsg_compat(msg, level, type, len, data); 230 231 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) { 232 msg->msg_flags |= MSG_CTRUNC; 233 return 0; /* XXX: return error? check spec. */ 234 } 235 if (msg->msg_controllen < cmlen) { 236 msg->msg_flags |= MSG_CTRUNC; 237 cmlen = msg->msg_controllen; 238 } 239 cmhdr.cmsg_level = level; 240 cmhdr.cmsg_type = type; 241 cmhdr.cmsg_len = cmlen; 242 243 err = -EFAULT; 244 if (copy_to_user(cm, &cmhdr, sizeof cmhdr)) 245 goto out; 246 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr))) 247 goto out; 248 cmlen = CMSG_SPACE(len); 249 if (msg->msg_controllen < cmlen) 250 cmlen = msg->msg_controllen; 251 msg->msg_control += cmlen; 252 msg->msg_controllen -= cmlen; 253 err = 0; 254 out: 255 return err; 256 } 257 EXPORT_SYMBOL(put_cmsg); 258 259 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) 260 { 261 struct cmsghdr __user *cm 262 = (__force struct cmsghdr __user*)msg->msg_control; 263 264 int fdmax = 0; 265 int fdnum = scm->fp->count; 266 struct file **fp = scm->fp->fp; 267 int __user *cmfptr; 268 int err = 0, i; 269 270 if (MSG_CMSG_COMPAT & msg->msg_flags) { 271 scm_detach_fds_compat(msg, scm); 272 return; 273 } 274 275 if (msg->msg_controllen > sizeof(struct cmsghdr)) 276 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr)) 277 / sizeof(int)); 278 279 if (fdnum < fdmax) 280 fdmax = fdnum; 281 282 for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax; 283 i++, cmfptr++) 284 { 285 int new_fd; 286 err = security_file_receive(fp[i]); 287 if (err) 288 break; 289 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags 290 ? O_CLOEXEC : 0); 291 if (err < 0) 292 break; 293 new_fd = err; 294 err = put_user(new_fd, cmfptr); 295 if (err) { 296 put_unused_fd(new_fd); 297 break; 298 } 299 /* Bump the usage count and install the file. */ 300 get_file(fp[i]); 301 fd_install(new_fd, fp[i]); 302 } 303 304 if (i > 0) 305 { 306 int cmlen = CMSG_LEN(i*sizeof(int)); 307 err = put_user(SOL_SOCKET, &cm->cmsg_level); 308 if (!err) 309 err = put_user(SCM_RIGHTS, &cm->cmsg_type); 310 if (!err) 311 err = put_user(cmlen, &cm->cmsg_len); 312 if (!err) { 313 cmlen = CMSG_SPACE(i*sizeof(int)); 314 msg->msg_control += cmlen; 315 msg->msg_controllen -= cmlen; 316 } 317 } 318 if (i < fdnum || (fdnum && fdmax <= 0)) 319 msg->msg_flags |= MSG_CTRUNC; 320 321 /* 322 * All of the files that fit in the message have had their 323 * usage counts incremented, so we just free the list. 324 */ 325 __scm_destroy(scm); 326 } 327 EXPORT_SYMBOL(scm_detach_fds); 328 329 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) 330 { 331 struct scm_fp_list *new_fpl; 332 int i; 333 334 if (!fpl) 335 return NULL; 336 337 new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]), 338 GFP_KERNEL); 339 if (new_fpl) { 340 for (i = 0; i < fpl->count; i++) 341 get_file(fpl->fp[i]); 342 new_fpl->max = new_fpl->count; 343 } 344 return new_fpl; 345 } 346 EXPORT_SYMBOL(scm_fp_dup); 347