[net-next-2.6.git] / net / core / scm.c

/* 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 <linux/pid.h>
#include <linux/nsproxy.h>
#include <linux/slab.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)
{
	const struct cred *cred = current_cred();

	if ((creds->pid == task_tgid_vnr(current) || capable(CAP_SYS_ADMIN)) &&
	    ((creds->uid == cred->uid   || creds->uid == cred->euid ||
	      creds->uid == cred->suid) || capable(CAP_SETUID)) &&
	    ((creds->gid == cred->gid   || creds->gid == cred->egid ||
	      creds->gid == cred->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;
		fpl->max = SCM_MAX_FD;
	}
	fpp = &fpl->fp[fpl->count];

	if (fpl->count + num > fpl->max)
		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;
		if (current->scm_work_list) {
			list_add_tail(&fpl->list, current->scm_work_list);
		} else {
			LIST_HEAD(work_list);

			current->scm_work_list = &work_list;

			list_add(&fpl->list, &work_list);
			while (!list_empty(&work_list)) {
				fpl = list_first_entry(&work_list, struct scm_fp_list, list);

				list_del(&fpl->list);
				for (i=fpl->count-1; i>=0; i--)
					fput(fpl->fp[i]);
				kfree(fpl);
			}

			current->scm_work_list = NULL;
		}
	}
}
EXPORT_SYMBOL(__scm_destroy);

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:
			if (!sock->ops || sock->ops->family != PF_UNIX)
				goto error;
			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;

			if (pid_vnr(p->pid) != p->creds.pid) {
				struct pid *pid;
				err = -ESRCH;
				pid = find_get_pid(p->creds.pid);
				if (!pid)
					goto error;
				put_pid(p->pid);
				p->pid = pid;
			}

			if ((p->cred->euid != p->creds.uid) ||
				(p->cred->egid != p->creds.gid)) {
				struct cred *cred;
				err = -ENOMEM;
				cred = prepare_creds();
				if (!cred)
					goto error;

				cred->uid = cred->euid = p->creds.uid;
				cred->gid = cred->egid = p->creds.uid;
				put_cred(p->cred);
				p->cred = cred;
			}
			break;
		default:
			goto error;
		}
	}

	if (p->fp && !p->fp->count)
	{
		kfree(p->fp);
		p->fp = NULL;
	}
	return 0;

error:
	scm_destroy(p);
	return err;
}
EXPORT_SYMBOL(__scm_send);

int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
{
	struct cmsghdr __user *cm
		= (__force 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);
	if (msg->msg_controllen < cmlen)
		cmlen = msg->msg_controllen;
	msg->msg_control += cmlen;
	msg->msg_controllen -= cmlen;
	err = 0;
out:
	return err;
}
EXPORT_SYMBOL(put_cmsg);

void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
{
	struct cmsghdr __user *cm
		= (__force 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=(__force 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_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
					  ? O_CLOEXEC : 0);
		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));
		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);
}
EXPORT_SYMBOL(scm_detach_fds);

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 = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
			  GFP_KERNEL);
	if (new_fpl) {
		for (i = 0; i < fpl->count; i++)
			get_file(fpl->fp[i]);
		new_fpl->max = new_fpl->count;
	}
	return new_fpl;
}
EXPORT_SYMBOL(scm_fp_dup);
Commit	Line	Data
1da177e4 LT	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>
4fc268d2	14	#include <linux/capability.h>
1da177e4 LT	15	#include <linux/errno.h>
	16	#include <linux/sched.h>
	17	#include <linux/mm.h>
	18	#include <linux/kernel.h>
1da177e4 LT	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>
b488893a PE	27	#include <linux/pid.h>
b488893a PE	28	#include <linux/nsproxy.h>
5a0e3ad6	29	#include <linux/slab.h>
1da177e4 LT	30
	31	#include <asm/system.h>
	32	#include <asm/uaccess.h>
	33
	34	#include <net/protocol.h>
	35	#include <linux/skbuff.h>
	36	#include <net/sock.h>
	37	#include <net/compat.h>
	38	#include <net/scm.h>
	39
	40
	41	/*
4ec93edb	42	* Only allow a user to send credentials, that they could set with
1da177e4 LT	43	* setu(g)id.
	44	*/
	45
	46	static __inline__ int scm_check_creds(struct ucred *creds)
	47	{
86a264ab	48	const struct cred *cred = current_cred();
b6dff3ec	49
b488893a	50	if ((creds->pid == task_tgid_vnr(current) \|\| capable(CAP_SYS_ADMIN)) &&
b6dff3ec DH	51	((creds->uid == cred->uid \|\| creds->uid == cred->euid \|\|
	52	creds->uid == cred->suid) \|\| capable(CAP_SETUID)) &&
	53	((creds->gid == cred->gid \|\| creds->gid == cred->egid \|\|
	54	creds->gid == cred->sgid) \|\| capable(CAP_SETGID))) {
1da177e4 LT	55	return 0;
	56	}
	57	return -EPERM;
	58	}
	59
	60	static int scm_fp_copy(struct cmsghdr cmsg, struct scm_fp_list *fplp)
	61	{
	62	int fdp = (int)CMSG_DATA(cmsg);
	63	struct scm_fp_list fpl = fplp;
	64	struct file **fpp;
	65	int i, num;
	66
	67	num = (cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr)))/sizeof(int);
	68
	69	if (num <= 0)
	70	return 0;
	71
	72	if (num > SCM_MAX_FD)
	73	return -EINVAL;
	74
	75	if (!fpl)
	76	{
	77	fpl = kmalloc(sizeof(struct scm_fp_list), GFP_KERNEL);
	78	if (!fpl)
	79	return -ENOMEM;
	80	*fplp = fpl;
	81	fpl->count = 0;
bba14de9	82	fpl->max = SCM_MAX_FD;
1da177e4 LT	83	}
	84	fpp = &fpl->fp[fpl->count];
	85
bba14de9	86	if (fpl->count + num > fpl->max)
1da177e4	87	return -EINVAL;
4ec93edb	88
1da177e4 LT	89	/*
	90	* Verify the descriptors and increment the usage count.
	91	*/
4ec93edb	92
1da177e4 LT	93	for (i=0; i< num; i++)
	94	{
	95	int fd = fdp[i];
	96	struct file *file;
	97
	98	if (fd < 0 \|\| !(file = fget(fd)))
	99	return -EBADF;
	100	*fpp++ = file;
	101	fpl->count++;
	102	}
	103	return num;
	104	}
	105
	106	void __scm_destroy(struct scm_cookie *scm)
	107	{
	108	struct scm_fp_list *fpl = scm->fp;
	109	int i;
	110
	111	if (fpl) {
	112	scm->fp = NULL;
f8d570a4 DM	113	if (current->scm_work_list) {
	114	list_add_tail(&fpl->list, current->scm_work_list);
	115	} else {
	116	LIST_HEAD(work_list);
	117
	118	current->scm_work_list = &work_list;
	119
	120	list_add(&fpl->list, &work_list);
	121	while (!list_empty(&work_list)) {
	122	fpl = list_first_entry(&work_list, struct scm_fp_list, list);
	123
	124	list_del(&fpl->list);
	125	for (i=fpl->count-1; i>=0; i--)
	126	fput(fpl->fp[i]);
	127	kfree(fpl);
	128	}
	129
	130	current->scm_work_list = NULL;
	131	}
1da177e4 LT	132	}
1da177e4 LT	133	}
9e34a5b5	134	EXPORT_SYMBOL(__scm_destroy);
1da177e4 LT	135
	136	int __scm_send(struct socket sock, struct msghdr msg, struct scm_cookie *p)
	137	{
	138	struct cmsghdr *cmsg;
	139	int err;
	140
	141	for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
	142	{
	143	err = -EINVAL;
	144
	145	/* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
	146	/* The first check was omitted in <= 2.2.5. The reasoning was
	147	that parser checks cmsg_len in any case, so that
	148	additional check would be work duplication.
4ec93edb	149	But if cmsg_level is not SOL_SOCKET, we do not check
1da177e4 LT	150	for too short ancillary data object at all! Oops.
	151	OK, let's add it...
	152	*/
	153	if (!CMSG_OK(msg, cmsg))
	154	goto error;
	155
	156	if (cmsg->cmsg_level != SOL_SOCKET)
	157	continue;
	158
	159	switch (cmsg->cmsg_type)
	160	{
	161	case SCM_RIGHTS:
76dadd76 EB	162	if (!sock->ops \|\| sock->ops->family != PF_UNIX)
76dadd76 EB	163	goto error;
1da177e4 LT	164	err=scm_fp_copy(cmsg, &p->fp);
	165	if (err<0)
	166	goto error;
	167	break;
	168	case SCM_CREDENTIALS:
	169	if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
	170	goto error;
	171	memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
	172	err = scm_check_creds(&p->creds);
	173	if (err)
	174	goto error;
257b5358 EB	175
	176	if (pid_vnr(p->pid) != p->creds.pid) {
	177	struct pid *pid;
	178	err = -ESRCH;
	179	pid = find_get_pid(p->creds.pid);
	180	if (!pid)
	181	goto error;
	182	put_pid(p->pid);
	183	p->pid = pid;
	184	}
	185
	186	if ((p->cred->euid != p->creds.uid) \|\|
	187	(p->cred->egid != p->creds.gid)) {
	188	struct cred *cred;
	189	err = -ENOMEM;
	190	cred = prepare_creds();
	191	if (!cred)
	192	goto error;
	193
	194	cred->uid = cred->euid = p->creds.uid;
	195	cred->gid = cred->egid = p->creds.uid;
	196	put_cred(p->cred);
	197	p->cred = cred;
	198	}
1da177e4 LT	199	break;
	200	default:
	201	goto error;
	202	}
	203	}
	204
	205	if (p->fp && !p->fp->count)
	206	{
	207	kfree(p->fp);
	208	p->fp = NULL;
	209	}
	210	return 0;
4ec93edb	211
1da177e4 LT	212	error:
	213	scm_destroy(p);
	214	return err;
	215	}
9e34a5b5	216	EXPORT_SYMBOL(__scm_send);
1da177e4 LT	217
	218	int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
	219	{
cfcabdcc SH	220	struct cmsghdr __user *cm
cfcabdcc SH	221	= (__force struct cmsghdr __user *)msg->msg_control;
1da177e4 LT	222	struct cmsghdr cmhdr;
	223	int cmlen = CMSG_LEN(len);
	224	int err;
	225
	226	if (MSG_CMSG_COMPAT & msg->msg_flags)
	227	return put_cmsg_compat(msg, level, type, len, data);
	228
	229	if (cm==NULL \|\| msg->msg_controllen < sizeof(*cm)) {
	230	msg->msg_flags \|= MSG_CTRUNC;
	231	return 0; /* XXX: return error? check spec. */
	232	}
	233	if (msg->msg_controllen < cmlen) {
	234	msg->msg_flags \|= MSG_CTRUNC;
	235	cmlen = msg->msg_controllen;
	236	}
	237	cmhdr.cmsg_level = level;
	238	cmhdr.cmsg_type = type;
	239	cmhdr.cmsg_len = cmlen;
	240
	241	err = -EFAULT;
	242	if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
4ec93edb	243	goto out;
1da177e4 LT	244	if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
	245	goto out;
	246	cmlen = CMSG_SPACE(len);
1ac70e7a WY	247	if (msg->msg_controllen < cmlen)
1ac70e7a WY	248	cmlen = msg->msg_controllen;
1da177e4 LT	249	msg->msg_control += cmlen;
	250	msg->msg_controllen -= cmlen;
	251	err = 0;
	252	out:
	253	return err;
	254	}
9e34a5b5	255	EXPORT_SYMBOL(put_cmsg);
1da177e4 LT	256
	257	void scm_detach_fds(struct msghdr msg, struct scm_cookie scm)
	258	{
cfcabdcc SH	259	struct cmsghdr __user *cm
cfcabdcc SH	260	= (__force struct cmsghdr __user*)msg->msg_control;
1da177e4 LT	261
	262	int fdmax = 0;
	263	int fdnum = scm->fp->count;
	264	struct file **fp = scm->fp->fp;
	265	int __user *cmfptr;
	266	int err = 0, i;
	267
	268	if (MSG_CMSG_COMPAT & msg->msg_flags) {
	269	scm_detach_fds_compat(msg, scm);
	270	return;
	271	}
	272
	273	if (msg->msg_controllen > sizeof(struct cmsghdr))
	274	fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
	275	/ sizeof(int));
	276
	277	if (fdnum < fdmax)
	278	fdmax = fdnum;
	279
cfcabdcc SH	280	for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
cfcabdcc SH	281	i++, cmfptr++)
1da177e4 LT	282	{
	283	int new_fd;
	284	err = security_file_receive(fp[i]);
	285	if (err)
	286	break;
4a19542e UD	287	err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
4a19542e UD	288	? O_CLOEXEC : 0);
1da177e4 LT	289	if (err < 0)
	290	break;
	291	new_fd = err;
	292	err = put_user(new_fd, cmfptr);
	293	if (err) {
	294	put_unused_fd(new_fd);
	295	break;
	296	}
	297	/* Bump the usage count and install the file. */
	298	get_file(fp[i]);
	299	fd_install(new_fd, fp[i]);
	300	}
	301
	302	if (i > 0)
	303	{
	304	int cmlen = CMSG_LEN(i*sizeof(int));
effee6a0	305	err = put_user(SOL_SOCKET, &cm->cmsg_level);
1da177e4 LT	306	if (!err)
	307	err = put_user(SCM_RIGHTS, &cm->cmsg_type);
	308	if (!err)
	309	err = put_user(cmlen, &cm->cmsg_len);
	310	if (!err) {
	311	cmlen = CMSG_SPACE(i*sizeof(int));
	312	msg->msg_control += cmlen;
	313	msg->msg_controllen -= cmlen;
	314	}
	315	}
	316	if (i < fdnum \|\| (fdnum && fdmax <= 0))
	317	msg->msg_flags \|= MSG_CTRUNC;
	318
	319	/*
	320	* All of the files that fit in the message have had their
	321	* usage counts incremented, so we just free the list.
	322	*/
	323	__scm_destroy(scm);
	324	}
9e34a5b5	325	EXPORT_SYMBOL(scm_detach_fds);
1da177e4 LT	326
	327	struct scm_fp_list scm_fp_dup(struct scm_fp_list fpl)
	328	{
	329	struct scm_fp_list *new_fpl;
	330	int i;
	331
	332	if (!fpl)
	333	return NULL;
	334
bba14de9 ED	335	new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
bba14de9 ED	336	GFP_KERNEL);
1da177e4	337	if (new_fpl) {
bba14de9	338	for (i = 0; i < fpl->count; i++)
1da177e4	339	get_file(fpl->fp[i]);
bba14de9	340	new_fpl->max = new_fpl->count;
1da177e4 LT	341	}
	342	return new_fpl;
	343	}
1da177e4	344	EXPORT_SYMBOL(scm_fp_dup);