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 } 83 fpp = &fpl->fp[fpl->count]; 84 85 if (fpl->count + num > SCM_MAX_FD) 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(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 } 133 134 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) 135 { 136 struct cmsghdr *cmsg; 137 int err; 138 139 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) 140 { 141 err = -EINVAL; 142 143 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */ 144 /* The first check was omitted in <= 2.2.5. The reasoning was 145 that parser checks cmsg_len in any case, so that 146 additional check would be work duplication. 147 But if cmsg_level is not SOL_SOCKET, we do not check 148 for too short ancillary data object at all! Oops. 149 OK, let's add it... 150 */ 151 if (!CMSG_OK(msg, cmsg)) 152 goto error; 153 154 if (cmsg->cmsg_level != SOL_SOCKET) 155 continue; 156 157 switch (cmsg->cmsg_type) 158 { 159 case SCM_RIGHTS: 160 if (!sock->ops || sock->ops->family != PF_UNIX) 161 goto error; 162 err=scm_fp_copy(cmsg, &p->fp); 163 if (err<0) 164 goto error; 165 break; 166 case SCM_CREDENTIALS: 167 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) 168 goto error; 169 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred)); 170 err = scm_check_creds(&p->creds); 171 if (err) 172 goto error; 173 break; 174 default: 175 goto error; 176 } 177 } 178 179 if (p->fp && !p->fp->count) 180 { 181 kfree(p->fp); 182 p->fp = NULL; 183 } 184 return 0; 185 186 error: 187 scm_destroy(p); 188 return err; 189 } 190 191 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) 192 { 193 struct cmsghdr __user *cm 194 = (__force struct cmsghdr __user *)msg->msg_control; 195 struct cmsghdr cmhdr; 196 int cmlen = CMSG_LEN(len); 197 int err; 198 199 if (MSG_CMSG_COMPAT & msg->msg_flags) 200 return put_cmsg_compat(msg, level, type, len, data); 201 202 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) { 203 msg->msg_flags |= MSG_CTRUNC; 204 return 0; /* XXX: return error? check spec. */ 205 } 206 if (msg->msg_controllen < cmlen) { 207 msg->msg_flags |= MSG_CTRUNC; 208 cmlen = msg->msg_controllen; 209 } 210 cmhdr.cmsg_level = level; 211 cmhdr.cmsg_type = type; 212 cmhdr.cmsg_len = cmlen; 213 214 err = -EFAULT; 215 if (copy_to_user(cm, &cmhdr, sizeof cmhdr)) 216 goto out; 217 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr))) 218 goto out; 219 cmlen = CMSG_SPACE(len); 220 if (msg->msg_controllen < cmlen) 221 cmlen = msg->msg_controllen; 222 msg->msg_control += cmlen; 223 msg->msg_controllen -= cmlen; 224 err = 0; 225 out: 226 return err; 227 } 228 229 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) 230 { 231 struct cmsghdr __user *cm 232 = (__force struct cmsghdr __user*)msg->msg_control; 233 234 int fdmax = 0; 235 int fdnum = scm->fp->count; 236 struct file **fp = scm->fp->fp; 237 int __user *cmfptr; 238 int err = 0, i; 239 240 if (MSG_CMSG_COMPAT & msg->msg_flags) { 241 scm_detach_fds_compat(msg, scm); 242 return; 243 } 244 245 if (msg->msg_controllen > sizeof(struct cmsghdr)) 246 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr)) 247 / sizeof(int)); 248 249 if (fdnum < fdmax) 250 fdmax = fdnum; 251 252 for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax; 253 i++, cmfptr++) 254 { 255 int new_fd; 256 err = security_file_receive(fp[i]); 257 if (err) 258 break; 259 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags 260 ? O_CLOEXEC : 0); 261 if (err < 0) 262 break; 263 new_fd = err; 264 err = put_user(new_fd, cmfptr); 265 if (err) { 266 put_unused_fd(new_fd); 267 break; 268 } 269 /* Bump the usage count and install the file. */ 270 get_file(fp[i]); 271 fd_install(new_fd, fp[i]); 272 } 273 274 if (i > 0) 275 { 276 int cmlen = CMSG_LEN(i*sizeof(int)); 277 err = put_user(SOL_SOCKET, &cm->cmsg_level); 278 if (!err) 279 err = put_user(SCM_RIGHTS, &cm->cmsg_type); 280 if (!err) 281 err = put_user(cmlen, &cm->cmsg_len); 282 if (!err) { 283 cmlen = CMSG_SPACE(i*sizeof(int)); 284 msg->msg_control += cmlen; 285 msg->msg_controllen -= cmlen; 286 } 287 } 288 if (i < fdnum || (fdnum && fdmax <= 0)) 289 msg->msg_flags |= MSG_CTRUNC; 290 291 /* 292 * All of the files that fit in the message have had their 293 * usage counts incremented, so we just free the list. 294 */ 295 __scm_destroy(scm); 296 } 297 298 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) 299 { 300 struct scm_fp_list *new_fpl; 301 int i; 302 303 if (!fpl) 304 return NULL; 305 306 new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL); 307 if (new_fpl) { 308 for (i=fpl->count-1; i>=0; i--) 309 get_file(fpl->fp[i]); 310 memcpy(new_fpl, fpl, sizeof(*fpl)); 311 } 312 return new_fpl; 313 } 314 315 EXPORT_SYMBOL(__scm_destroy); 316 EXPORT_SYMBOL(__scm_send); 317 EXPORT_SYMBOL(put_cmsg); 318 EXPORT_SYMBOL(scm_detach_fds); 319 EXPORT_SYMBOL(scm_fp_dup); 320