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