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 err=scm_fp_copy(cmsg, &p->fp); 160 if (err<0) 161 goto error; 162 break; 163 case SCM_CREDENTIALS: 164 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) 165 goto error; 166 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred)); 167 err = scm_check_creds(&p->creds); 168 if (err) 169 goto error; 170 break; 171 default: 172 goto error; 173 } 174 } 175 176 if (p->fp && !p->fp->count) 177 { 178 kfree(p->fp); 179 p->fp = NULL; 180 } 181 return 0; 182 183 error: 184 scm_destroy(p); 185 return err; 186 } 187 188 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) 189 { 190 struct cmsghdr __user *cm 191 = (__force struct cmsghdr __user *)msg->msg_control; 192 struct cmsghdr cmhdr; 193 int cmlen = CMSG_LEN(len); 194 int err; 195 196 if (MSG_CMSG_COMPAT & msg->msg_flags) 197 return put_cmsg_compat(msg, level, type, len, data); 198 199 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) { 200 msg->msg_flags |= MSG_CTRUNC; 201 return 0; /* XXX: return error? check spec. */ 202 } 203 if (msg->msg_controllen < cmlen) { 204 msg->msg_flags |= MSG_CTRUNC; 205 cmlen = msg->msg_controllen; 206 } 207 cmhdr.cmsg_level = level; 208 cmhdr.cmsg_type = type; 209 cmhdr.cmsg_len = cmlen; 210 211 err = -EFAULT; 212 if (copy_to_user(cm, &cmhdr, sizeof cmhdr)) 213 goto out; 214 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr))) 215 goto out; 216 cmlen = CMSG_SPACE(len); 217 if (msg->msg_controllen < cmlen) 218 cmlen = msg->msg_controllen; 219 msg->msg_control += cmlen; 220 msg->msg_controllen -= cmlen; 221 err = 0; 222 out: 223 return err; 224 } 225 226 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) 227 { 228 struct cmsghdr __user *cm 229 = (__force struct cmsghdr __user*)msg->msg_control; 230 231 int fdmax = 0; 232 int fdnum = scm->fp->count; 233 struct file **fp = scm->fp->fp; 234 int __user *cmfptr; 235 int err = 0, i; 236 237 if (MSG_CMSG_COMPAT & msg->msg_flags) { 238 scm_detach_fds_compat(msg, scm); 239 return; 240 } 241 242 if (msg->msg_controllen > sizeof(struct cmsghdr)) 243 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr)) 244 / sizeof(int)); 245 246 if (fdnum < fdmax) 247 fdmax = fdnum; 248 249 for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax; 250 i++, cmfptr++) 251 { 252 int new_fd; 253 err = security_file_receive(fp[i]); 254 if (err) 255 break; 256 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags 257 ? O_CLOEXEC : 0); 258 if (err < 0) 259 break; 260 new_fd = err; 261 err = put_user(new_fd, cmfptr); 262 if (err) { 263 put_unused_fd(new_fd); 264 break; 265 } 266 /* Bump the usage count and install the file. */ 267 get_file(fp[i]); 268 fd_install(new_fd, fp[i]); 269 } 270 271 if (i > 0) 272 { 273 int cmlen = CMSG_LEN(i*sizeof(int)); 274 err = put_user(SOL_SOCKET, &cm->cmsg_level); 275 if (!err) 276 err = put_user(SCM_RIGHTS, &cm->cmsg_type); 277 if (!err) 278 err = put_user(cmlen, &cm->cmsg_len); 279 if (!err) { 280 cmlen = CMSG_SPACE(i*sizeof(int)); 281 msg->msg_control += cmlen; 282 msg->msg_controllen -= cmlen; 283 } 284 } 285 if (i < fdnum || (fdnum && fdmax <= 0)) 286 msg->msg_flags |= MSG_CTRUNC; 287 288 /* 289 * All of the files that fit in the message have had their 290 * usage counts incremented, so we just free the list. 291 */ 292 __scm_destroy(scm); 293 } 294 295 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) 296 { 297 struct scm_fp_list *new_fpl; 298 int i; 299 300 if (!fpl) 301 return NULL; 302 303 new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL); 304 if (new_fpl) { 305 for (i=fpl->count-1; i>=0; i--) 306 get_file(fpl->fp[i]); 307 memcpy(new_fpl, fpl, sizeof(*fpl)); 308 } 309 return new_fpl; 310 } 311 312 EXPORT_SYMBOL(__scm_destroy); 313 EXPORT_SYMBOL(__scm_send); 314 EXPORT_SYMBOL(put_cmsg); 315 EXPORT_SYMBOL(scm_detach_fds); 316 EXPORT_SYMBOL(scm_fp_dup); 317