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 if ((creds->pid == task_tgid_vnr(current) || capable(CAP_SYS_ADMIN)) && 48 ((creds->uid == current->uid || creds->uid == current->euid || 49 creds->uid == current->suid) || capable(CAP_SETUID)) && 50 ((creds->gid == current->gid || creds->gid == current->egid || 51 creds->gid == current->sgid) || capable(CAP_SETGID))) { 52 return 0; 53 } 54 return -EPERM; 55 } 56 57 static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) 58 { 59 int *fdp = (int*)CMSG_DATA(cmsg); 60 struct scm_fp_list *fpl = *fplp; 61 struct file **fpp; 62 int i, num; 63 64 num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int); 65 66 if (num <= 0) 67 return 0; 68 69 if (num > SCM_MAX_FD) 70 return -EINVAL; 71 72 if (!fpl) 73 { 74 fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL); 75 if (!fpl) 76 return -ENOMEM; 77 *fplp = fpl; 78 fpl->count = 0; 79 } 80 fpp = &fpl->fp[fpl->count]; 81 82 if (fpl->count + num > SCM_MAX_FD) 83 return -EINVAL; 84 85 /* 86 * Verify the descriptors and increment the usage count. 87 */ 88 89 for (i=0; i< num; i++) 90 { 91 int fd = fdp[i]; 92 struct file *file; 93 94 if (fd < 0 || !(file = fget(fd))) 95 return -EBADF; 96 *fpp++ = file; 97 fpl->count++; 98 } 99 return num; 100 } 101 102 void __scm_destroy(struct scm_cookie *scm) 103 { 104 struct scm_fp_list *fpl = scm->fp; 105 int i; 106 107 if (fpl) { 108 scm->fp = NULL; 109 if (current->scm_work_list) { 110 list_add_tail(&fpl->list, current->scm_work_list); 111 } else { 112 LIST_HEAD(work_list); 113 114 current->scm_work_list = &work_list; 115 116 list_add(&fpl->list, &work_list); 117 while (!list_empty(&work_list)) { 118 fpl = list_first_entry(&work_list, struct scm_fp_list, list); 119 120 list_del(&fpl->list); 121 for (i=fpl->count-1; i>=0; i--) 122 fput(fpl->fp[i]); 123 kfree(fpl); 124 } 125 126 current->scm_work_list = NULL; 127 } 128 } 129 } 130 131 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) 132 { 133 struct cmsghdr *cmsg; 134 int err; 135 136 for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) 137 { 138 err = -EINVAL; 139 140 /* Verify that cmsg_len is at least sizeof(struct cmsghdr) */ 141 /* The first check was omitted in <= 2.2.5. The reasoning was 142 that parser checks cmsg_len in any case, so that 143 additional check would be work duplication. 144 But if cmsg_level is not SOL_SOCKET, we do not check 145 for too short ancillary data object at all! Oops. 146 OK, let's add it... 147 */ 148 if (!CMSG_OK(msg, cmsg)) 149 goto error; 150 151 if (cmsg->cmsg_level != SOL_SOCKET) 152 continue; 153 154 switch (cmsg->cmsg_type) 155 { 156 case SCM_RIGHTS: 157 err=scm_fp_copy(cmsg, &p->fp); 158 if (err<0) 159 goto error; 160 break; 161 case SCM_CREDENTIALS: 162 if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) 163 goto error; 164 memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred)); 165 err = scm_check_creds(&p->creds); 166 if (err) 167 goto error; 168 break; 169 default: 170 goto error; 171 } 172 } 173 174 if (p->fp && !p->fp->count) 175 { 176 kfree(p->fp); 177 p->fp = NULL; 178 } 179 return 0; 180 181 error: 182 scm_destroy(p); 183 return err; 184 } 185 186 int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) 187 { 188 struct cmsghdr __user *cm 189 = (__force struct cmsghdr __user *)msg->msg_control; 190 struct cmsghdr cmhdr; 191 int cmlen = CMSG_LEN(len); 192 int err; 193 194 if (MSG_CMSG_COMPAT & msg->msg_flags) 195 return put_cmsg_compat(msg, level, type, len, data); 196 197 if (cm==NULL || msg->msg_controllen < sizeof(*cm)) { 198 msg->msg_flags |= MSG_CTRUNC; 199 return 0; /* XXX: return error? check spec. */ 200 } 201 if (msg->msg_controllen < cmlen) { 202 msg->msg_flags |= MSG_CTRUNC; 203 cmlen = msg->msg_controllen; 204 } 205 cmhdr.cmsg_level = level; 206 cmhdr.cmsg_type = type; 207 cmhdr.cmsg_len = cmlen; 208 209 err = -EFAULT; 210 if (copy_to_user(cm, &cmhdr, sizeof cmhdr)) 211 goto out; 212 if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr))) 213 goto out; 214 cmlen = CMSG_SPACE(len); 215 if (msg->msg_controllen < cmlen) 216 cmlen = msg->msg_controllen; 217 msg->msg_control += cmlen; 218 msg->msg_controllen -= cmlen; 219 err = 0; 220 out: 221 return err; 222 } 223 224 void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) 225 { 226 struct cmsghdr __user *cm 227 = (__force struct cmsghdr __user*)msg->msg_control; 228 229 int fdmax = 0; 230 int fdnum = scm->fp->count; 231 struct file **fp = scm->fp->fp; 232 int __user *cmfptr; 233 int err = 0, i; 234 235 if (MSG_CMSG_COMPAT & msg->msg_flags) { 236 scm_detach_fds_compat(msg, scm); 237 return; 238 } 239 240 if (msg->msg_controllen > sizeof(struct cmsghdr)) 241 fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr)) 242 / sizeof(int)); 243 244 if (fdnum < fdmax) 245 fdmax = fdnum; 246 247 for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax; 248 i++, cmfptr++) 249 { 250 int new_fd; 251 err = security_file_receive(fp[i]); 252 if (err) 253 break; 254 err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags 255 ? O_CLOEXEC : 0); 256 if (err < 0) 257 break; 258 new_fd = err; 259 err = put_user(new_fd, cmfptr); 260 if (err) { 261 put_unused_fd(new_fd); 262 break; 263 } 264 /* Bump the usage count and install the file. */ 265 get_file(fp[i]); 266 fd_install(new_fd, fp[i]); 267 } 268 269 if (i > 0) 270 { 271 int cmlen = CMSG_LEN(i*sizeof(int)); 272 err = put_user(SOL_SOCKET, &cm->cmsg_level); 273 if (!err) 274 err = put_user(SCM_RIGHTS, &cm->cmsg_type); 275 if (!err) 276 err = put_user(cmlen, &cm->cmsg_len); 277 if (!err) { 278 cmlen = CMSG_SPACE(i*sizeof(int)); 279 msg->msg_control += cmlen; 280 msg->msg_controllen -= cmlen; 281 } 282 } 283 if (i < fdnum || (fdnum && fdmax <= 0)) 284 msg->msg_flags |= MSG_CTRUNC; 285 286 /* 287 * All of the files that fit in the message have had their 288 * usage counts incremented, so we just free the list. 289 */ 290 __scm_destroy(scm); 291 } 292 293 struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) 294 { 295 struct scm_fp_list *new_fpl; 296 int i; 297 298 if (!fpl) 299 return NULL; 300 301 new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL); 302 if (new_fpl) { 303 for (i=fpl->count-1; i>=0; i--) 304 get_file(fpl->fp[i]); 305 memcpy(new_fpl, fpl, sizeof(*fpl)); 306 } 307 return new_fpl; 308 } 309 310 EXPORT_SYMBOL(__scm_destroy); 311 EXPORT_SYMBOL(__scm_send); 312 EXPORT_SYMBOL(put_cmsg); 313 EXPORT_SYMBOL(scm_detach_fds); 314 EXPORT_SYMBOL(scm_fp_dup); 315