[linux.git] / net / core / scm.c

/* scm.c - Socket level control messages processing.
 *
 * Author:	Alexey Kuznetsov, <[email protected]>
 *              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 <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;
	}
	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;
		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;
		}
	}
}

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
		= (__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;
}

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);
}

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);
Commit	Line	Data
1da177e4 LT	1	/* scm.c - Socket level control messages processing.
	2	*
	3	* Author: Alexey Kuznetsov, <[email protected]>
	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>
1da177e4 LT	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	/*
4ec93edb	41	* Only allow a user to send credentials, that they could set with
1da177e4 LT	42	* setu(g)id.
	43	*/
	44
	45	static __inline__ int scm_check_creds(struct ucred *creds)
	46	{
86a264ab	47	const struct cred *cred = current_cred();
b6dff3ec	48
b488893a	49	if ((creds->pid == task_tgid_vnr(current) \|\| capable(CAP_SYS_ADMIN)) &&
b6dff3ec DH	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))) {
1da177e4 LT	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;
4ec93edb	86
1da177e4 LT	87	/*
	88	* Verify the descriptors and increment the usage count.
	89	*/
4ec93edb	90
1da177e4 LT	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;
f8d570a4 DM	111	if (current->scm_work_list) {
	112	list_add_tail(&fpl->list, current->scm_work_list);
	113	} else {
	114	LIST_HEAD(work_list);
	115
	116	current->scm_work_list = &work_list;
	117
	118	list_add(&fpl->list, &work_list);
	119	while (!list_empty(&work_list)) {
	120	fpl = list_first_entry(&work_list, struct scm_fp_list, list);
	121
	122	list_del(&fpl->list);
	123	for (i=fpl->count-1; i>=0; i--)
	124	fput(fpl->fp[i]);
	125	kfree(fpl);
	126	}
	127
	128	current->scm_work_list = NULL;
	129	}
1da177e4 LT	130	}
	131	}
	132
	133	int __scm_send(struct socket sock, struct msghdr msg, struct scm_cookie *p)
	134	{
	135	struct cmsghdr *cmsg;
	136	int err;
	137
	138	for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
	139	{
	140	err = -EINVAL;
	141
	142	/* Verify that cmsg_len is at least sizeof(struct cmsghdr) */
	143	/* The first check was omitted in <= 2.2.5. The reasoning was
	144	that parser checks cmsg_len in any case, so that
	145	additional check would be work duplication.
4ec93edb	146	But if cmsg_level is not SOL_SOCKET, we do not check
1da177e4 LT	147	for too short ancillary data object at all! Oops.
	148	OK, let's add it...
	149	*/
	150	if (!CMSG_OK(msg, cmsg))
	151	goto error;
	152
	153	if (cmsg->cmsg_level != SOL_SOCKET)
	154	continue;
	155
	156	switch (cmsg->cmsg_type)
	157	{
	158	case SCM_RIGHTS:
	159	err=scm_fp_copy(cmsg, &p->fp);
	160	if (err<0)
	161	goto error;
	162	break;
	163	case SCM_CREDENTIALS:
	164	if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
	165	goto error;
	166	memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
	167	err = scm_check_creds(&p->creds);
	168	if (err)
	169	goto error;
	170	break;
	171	default:
	172	goto error;
	173	}
	174	}
	175
	176	if (p->fp && !p->fp->count)
	177	{
	178	kfree(p->fp);
	179	p->fp = NULL;
	180	}
	181	return 0;
4ec93edb	182
1da177e4 LT	183	error:
	184	scm_destroy(p);
	185	return err;
	186	}
	187
	188	int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
	189	{
cfcabdcc SH	190	struct cmsghdr __user *cm
cfcabdcc SH	191	= (__force struct cmsghdr __user *)msg->msg_control;
1da177e4 LT	192	struct cmsghdr cmhdr;
	193	int cmlen = CMSG_LEN(len);
	194	int err;
	195
	196	if (MSG_CMSG_COMPAT & msg->msg_flags)
	197	return put_cmsg_compat(msg, level, type, len, data);
	198
	199	if (cm==NULL \|\| msg->msg_controllen < sizeof(*cm)) {
	200	msg->msg_flags \|= MSG_CTRUNC;
	201	return 0; /* XXX: return error? check spec. */
	202	}
	203	if (msg->msg_controllen < cmlen) {
	204	msg->msg_flags \|= MSG_CTRUNC;
	205	cmlen = msg->msg_controllen;
	206	}
	207	cmhdr.cmsg_level = level;
	208	cmhdr.cmsg_type = type;
	209	cmhdr.cmsg_len = cmlen;
	210
	211	err = -EFAULT;
	212	if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
4ec93edb	213	goto out;
1da177e4 LT	214	if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
	215	goto out;
	216	cmlen = CMSG_SPACE(len);
1ac70e7a WY	217	if (msg->msg_controllen < cmlen)
1ac70e7a WY	218	cmlen = msg->msg_controllen;
1da177e4 LT	219	msg->msg_control += cmlen;
	220	msg->msg_controllen -= cmlen;
	221	err = 0;
	222	out:
	223	return err;
	224	}
	225
	226	void scm_detach_fds(struct msghdr msg, struct scm_cookie scm)
	227	{
cfcabdcc SH	228	struct cmsghdr __user *cm
cfcabdcc SH	229	= (__force struct cmsghdr __user*)msg->msg_control;
1da177e4 LT	230
	231	int fdmax = 0;
	232	int fdnum = scm->fp->count;
	233	struct file **fp = scm->fp->fp;
	234	int __user *cmfptr;
	235	int err = 0, i;
	236
	237	if (MSG_CMSG_COMPAT & msg->msg_flags) {
	238	scm_detach_fds_compat(msg, scm);
	239	return;
	240	}
	241
	242	if (msg->msg_controllen > sizeof(struct cmsghdr))
	243	fdmax = ((msg->msg_controllen - sizeof(struct cmsghdr))
	244	/ sizeof(int));
	245
	246	if (fdnum < fdmax)
	247	fdmax = fdnum;
	248
cfcabdcc SH	249	for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
cfcabdcc SH	250	i++, cmfptr++)
1da177e4 LT	251	{
	252	int new_fd;
	253	err = security_file_receive(fp[i]);
	254	if (err)
	255	break;
4a19542e UD	256	err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & msg->msg_flags
4a19542e UD	257	? O_CLOEXEC : 0);
1da177e4 LT	258	if (err < 0)
	259	break;
	260	new_fd = err;
	261	err = put_user(new_fd, cmfptr);
	262	if (err) {
	263	put_unused_fd(new_fd);
	264	break;
	265	}
	266	/* Bump the usage count and install the file. */
	267	get_file(fp[i]);
	268	fd_install(new_fd, fp[i]);
	269	}
	270
	271	if (i > 0)
	272	{
	273	int cmlen = CMSG_LEN(i*sizeof(int));
effee6a0	274	err = put_user(SOL_SOCKET, &cm->cmsg_level);
1da177e4 LT	275	if (!err)
	276	err = put_user(SCM_RIGHTS, &cm->cmsg_type);
	277	if (!err)
	278	err = put_user(cmlen, &cm->cmsg_len);
	279	if (!err) {
	280	cmlen = CMSG_SPACE(i*sizeof(int));
	281	msg->msg_control += cmlen;
	282	msg->msg_controllen -= cmlen;
	283	}
	284	}
	285	if (i < fdnum \|\| (fdnum && fdmax <= 0))
	286	msg->msg_flags \|= MSG_CTRUNC;
	287
	288	/*
	289	* All of the files that fit in the message have had their
	290	* usage counts incremented, so we just free the list.
	291	*/
	292	__scm_destroy(scm);
	293	}
	294
	295	struct scm_fp_list scm_fp_dup(struct scm_fp_list fpl)
	296	{
	297	struct scm_fp_list *new_fpl;
	298	int i;
	299
	300	if (!fpl)
	301	return NULL;
	302
	303	new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL);
	304	if (new_fpl) {
	305	for (i=fpl->count-1; i>=0; i--)
	306	get_file(fpl->fp[i]);
	307	memcpy(new_fpl, fpl, sizeof(*fpl));
	308	}
	309	return new_fpl;
	310	}
	311
	312	EXPORT_SYMBOL(__scm_destroy);
	313	EXPORT_SYMBOL(__scm_send);
	314	EXPORT_SYMBOL(put_cmsg);
	315	EXPORT_SYMBOL(scm_detach_fds);
	316	EXPORT_SYMBOL(scm_fp_dup);