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