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 (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->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.uid; 196 put_cred(p->cred); 197 p->cred = cred; 198 } 199 break; 200 default: 201 goto error; 202 } 203 } 204 205 if (p->fp && !p->fp->count) 206 { 207 kfree(p->fp); 208 p->fp = NULL; 209 } 210 return 0; 211 212 error: 213 scm_destroy(p); 214 return err; 215 } 216 EXPORT_SYMBOL(__scm_send); 217 218 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) 219 { 220 struct cmsghdr __user *cm 221 = (__force struct cmsghdr __user *)msg->msg_control; 222 struct cmsghdr cmhdr; 223 int cmlen = CMSG_LEN(len); 224 int err; 225 226 if (MSG_CMSG_COMPAT & msg->msg_flags) 227 return put_cmsg_compat(msg, level, type, len, data); 228 229 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) { 230 msg->msg_flags |= MSG_CTRUNC; 231 return 0; /* XXX: return error? check spec. */ 232 } 233 if (msg->msg_controllen < cmlen) { 234 msg->msg_flags |= MSG_CTRUNC; 235 cmlen = msg->msg_controllen; 236 } 237 cmhdr.cmsg_level = level; 238 cmhdr.cmsg_type = type; 239 cmhdr.cmsg_len = cmlen; 240 241 err = -EFAULT; 242 if (copy_to_user(cm, &cmhdr, sizeof cmhdr)) 243 goto out; 244 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr))) 245 goto out; 246 cmlen = CMSG_SPACE(len); 247 if (msg->msg_controllen < cmlen) 248 cmlen = msg->msg_controllen; 249 msg->msg_control += cmlen; 250 msg->msg_controllen -= cmlen; 251 err = 0; 252 out: 253 return err; 254 } 255 EXPORT_SYMBOL(put_cmsg); 256 257 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) 258 { 259 struct cmsghdr __user *cm 260 = (__force struct cmsghdr __user*)msg->msg_control; 261 262 int fdmax = 0; 263 int fdnum = scm->fp->count; 264 struct file **fp = scm->fp->fp; 265 int __user *cmfptr; 266 int err = 0, i; 267 268 if (MSG_CMSG_COMPAT & msg->msg_flags) { 269 scm_detach_fds_compat(msg, scm); 270 return; 271 } 272 273 if (msg->msg_controllen > sizeof(struct cmsghdr)) 274 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr)) 275 / sizeof(int)); 276 277 if (fdnum < fdmax) 278 fdmax = fdnum; 279 280 for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax; 281 i++, cmfptr++) 282 { 283 int new_fd; 284 err = security_file_receive(fp[i]); 285 if (err) 286 break; 287 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags 288 ? O_CLOEXEC : 0); 289 if (err < 0) 290 break; 291 new_fd = err; 292 err = put_user(new_fd, cmfptr); 293 if (err) { 294 put_unused_fd(new_fd); 295 break; 296 } 297 /* Bump the usage count and install the file. */ 298 get_file(fp[i]); 299 fd_install(new_fd, fp[i]); 300 } 301 302 if (i > 0) 303 { 304 int cmlen = CMSG_LEN(i*sizeof(int)); 305 err = put_user(SOL_SOCKET, &cm->cmsg_level); 306 if (!err) 307 err = put_user(SCM_RIGHTS, &cm->cmsg_type); 308 if (!err) 309 err = put_user(cmlen, &cm->cmsg_len); 310 if (!err) { 311 cmlen = CMSG_SPACE(i*sizeof(int)); 312 msg->msg_control += cmlen; 313 msg->msg_controllen -= cmlen; 314 } 315 } 316 if (i < fdnum || (fdnum && fdmax <= 0)) 317 msg->msg_flags |= MSG_CTRUNC; 318 319 /* 320 * All of the files that fit in the message have had their 321 * usage counts incremented, so we just free the list. 322 */ 323 __scm_destroy(scm); 324 } 325 EXPORT_SYMBOL(scm_detach_fds); 326 327 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) 328 { 329 struct scm_fp_list *new_fpl; 330 int i; 331 332 if (!fpl) 333 return NULL; 334 335 new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]), 336 GFP_KERNEL); 337 if (new_fpl) { 338 for (i = 0; i < fpl->count; i++) 339 get_file(fpl->fp[i]); 340 new_fpl->max = new_fpl->count; 341 } 342 return new_fpl; 343 } 344 EXPORT_SYMBOL(scm_fp_dup); 345