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