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