292 lines
6.4 KiB
C
292 lines
6.4 KiB
C
/* scm.c - Socket level control messages processing.
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*
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* Author: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
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* Alignment and value checking mods by Craig Metz
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <linux/signal.h>
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#include <linux/capability.h>
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#include <linux/errno.h>
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/kernel.h>
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#include <linux/stat.h>
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#include <linux/socket.h>
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#include <linux/file.h>
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#include <linux/fcntl.h>
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#include <linux/net.h>
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#include <linux/interrupt.h>
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#include <linux/netdevice.h>
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#include <linux/security.h>
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#include <asm/system.h>
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#include <asm/uaccess.h>
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#include <net/protocol.h>
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#include <linux/skbuff.h>
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#include <net/sock.h>
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#include <net/compat.h>
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#include <net/scm.h>
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/*
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* Only allow a user to send credentials, that they could set with
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* setu(g)id.
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*/
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static __inline__ int scm_check_creds(struct ucred *creds)
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{
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if ((creds->pid == current->tgid || capable(CAP_SYS_ADMIN)) &&
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((creds->uid == current->uid || creds->uid == current->euid ||
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creds->uid == current->suid) || capable(CAP_SETUID)) &&
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((creds->gid == current->gid || creds->gid == current->egid ||
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creds->gid == current->sgid) || capable(CAP_SETGID))) {
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return 0;
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}
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return -EPERM;
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}
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static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
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{
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int *fdp = (int*)CMSG_DATA(cmsg);
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struct scm_fp_list *fpl = *fplp;
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struct file **fpp;
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int i, num;
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num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
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if (num <= 0)
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return 0;
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if (num > SCM_MAX_FD)
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return -EINVAL;
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if (!fpl)
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{
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fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
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if (!fpl)
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return -ENOMEM;
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*fplp = fpl;
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fpl->count = 0;
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}
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fpp = &fpl->fp[fpl->count];
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if (fpl->count + num > SCM_MAX_FD)
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return -EINVAL;
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/*
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* Verify the descriptors and increment the usage count.
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*/
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for (i=0; i< num; i++)
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{
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int fd = fdp[i];
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struct file *file;
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if (fd < 0 || !(file = fget(fd)))
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return -EBADF;
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*fpp++ = file;
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fpl->count++;
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}
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return num;
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}
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void __scm_destroy(struct scm_cookie *scm)
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{
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struct scm_fp_list *fpl = scm->fp;
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int i;
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if (fpl) {
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scm->fp = NULL;
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for (i=fpl->count-1; i>=0; i--)
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fput(fpl->fp[i]);
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kfree(fpl);
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}
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}
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int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
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{
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struct cmsghdr *cmsg;
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int err;
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for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
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{
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err = -EINVAL;
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/* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
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/* The first check was omitted in <= 2.2.5. The reasoning was
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that parser checks cmsg_len in any case, so that
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additional check would be work duplication.
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But if cmsg_level is not SOL_SOCKET, we do not check
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for too short ancillary data object at all! Oops.
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OK, let's add it...
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*/
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if (!CMSG_OK(msg, cmsg))
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goto error;
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if (cmsg->cmsg_level != SOL_SOCKET)
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continue;
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switch (cmsg->cmsg_type)
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{
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case SCM_RIGHTS:
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err=scm_fp_copy(cmsg, &p->fp);
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if (err<0)
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goto error;
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break;
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case SCM_CREDENTIALS:
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if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
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goto error;
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memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
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err = scm_check_creds(&p->creds);
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if (err)
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goto error;
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break;
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default:
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goto error;
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}
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}
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if (p->fp && !p->fp->count)
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{
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kfree(p->fp);
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p->fp = NULL;
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}
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return 0;
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error:
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scm_destroy(p);
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return err;
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}
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int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
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{
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struct cmsghdr __user *cm = (struct cmsghdr __user *)msg->msg_control;
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struct cmsghdr cmhdr;
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int cmlen = CMSG_LEN(len);
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int err;
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if (MSG_CMSG_COMPAT & msg->msg_flags)
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return put_cmsg_compat(msg, level, type, len, data);
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if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
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msg->msg_flags |= MSG_CTRUNC;
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return 0; /* XXX: return error? check spec. */
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}
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if (msg->msg_controllen < cmlen) {
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msg->msg_flags |= MSG_CTRUNC;
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cmlen = msg->msg_controllen;
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}
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cmhdr.cmsg_level = level;
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cmhdr.cmsg_type = type;
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cmhdr.cmsg_len = cmlen;
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err = -EFAULT;
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if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
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goto out;
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if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
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goto out;
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cmlen = CMSG_SPACE(len);
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msg->msg_control += cmlen;
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msg->msg_controllen -= cmlen;
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err = 0;
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out:
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return err;
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}
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void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
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{
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struct cmsghdr __user *cm = (struct cmsghdr __user*)msg->msg_control;
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int fdmax = 0;
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int fdnum = scm->fp->count;
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struct file **fp = scm->fp->fp;
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int __user *cmfptr;
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int err = 0, i;
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if (MSG_CMSG_COMPAT & msg->msg_flags) {
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scm_detach_fds_compat(msg, scm);
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return;
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}
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if (msg->msg_controllen > sizeof(struct cmsghdr))
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fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
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/ sizeof(int));
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if (fdnum < fdmax)
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fdmax = fdnum;
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for (i=0, cmfptr=(int __user *)CMSG_DATA(cm); i<fdmax; i++, cmfptr++)
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{
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int new_fd;
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err = security_file_receive(fp[i]);
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if (err)
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break;
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err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
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? O_CLOEXEC : 0);
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if (err < 0)
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break;
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new_fd = err;
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err = put_user(new_fd, cmfptr);
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if (err) {
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put_unused_fd(new_fd);
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break;
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}
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/* Bump the usage count and install the file. */
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get_file(fp[i]);
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fd_install(new_fd, fp[i]);
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}
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if (i > 0)
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{
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int cmlen = CMSG_LEN(i*sizeof(int));
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err = put_user(SOL_SOCKET, &cm->cmsg_level);
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if (!err)
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err = put_user(SCM_RIGHTS, &cm->cmsg_type);
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if (!err)
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err = put_user(cmlen, &cm->cmsg_len);
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if (!err) {
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cmlen = CMSG_SPACE(i*sizeof(int));
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msg->msg_control += cmlen;
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msg->msg_controllen -= cmlen;
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}
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}
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if (i < fdnum || (fdnum && fdmax <= 0))
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msg->msg_flags |= MSG_CTRUNC;
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/*
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* All of the files that fit in the message have had their
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* usage counts incremented, so we just free the list.
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*/
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__scm_destroy(scm);
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}
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struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
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{
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struct scm_fp_list *new_fpl;
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int i;
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if (!fpl)
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return NULL;
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new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
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if (new_fpl) {
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for (i=fpl->count-1; i>=0; i--)
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get_file(fpl->fp[i]);
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memcpy(new_fpl, fpl, sizeof(*fpl));
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}
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return new_fpl;
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}
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EXPORT_SYMBOL(__scm_destroy);
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EXPORT_SYMBOL(__scm_send);
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EXPORT_SYMBOL(put_cmsg);
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EXPORT_SYMBOL(scm_detach_fds);
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EXPORT_SYMBOL(scm_fp_dup);
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