[linux-block.git] / fs / cifs / cifs_dfs_ref.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *   Contains the CIFS DFS referral mounting routines used for handling
 *   traversal via DFS junction point
 *
 *   Copyright (c) 2007 Igor Mammedov
 *   Copyright (C) International Business Machines  Corp., 2008
 *   Author(s): Igor Mammedov (niallain@gmail.com)
 *		Steve French (sfrench@us.ibm.com)
 */

#include <linux/dcache.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/slab.h>
#include <linux/vfs.h>
#include <linux/fs.h>
#include <linux/inet.h>
#include "cifsglob.h"
#include "cifsproto.h"
#include "cifsfs.h"
#include "dns_resolve.h"
#include "cifs_debug.h"
#include "cifs_unicode.h"
#include "dfs_cache.h"
#include "fs_context.h"

static LIST_HEAD(cifs_dfs_automount_list);

static void cifs_dfs_expire_automounts(struct work_struct *work);
static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
			    cifs_dfs_expire_automounts);
static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;

static void cifs_dfs_expire_automounts(struct work_struct *work)
{
	struct list_head *list = &cifs_dfs_automount_list;

	mark_mounts_for_expiry(list);
	if (!list_empty(list))
		schedule_delayed_work(&cifs_dfs_automount_task,
				      cifs_dfs_mountpoint_expiry_timeout);
}

void cifs_dfs_release_automount_timer(void)
{
	BUG_ON(!list_empty(&cifs_dfs_automount_list));
	cancel_delayed_work_sync(&cifs_dfs_automount_task);
}

/**
 * cifs_build_devname - build a devicename from a UNC and optional prepath
 * @nodename:	pointer to UNC string
 * @prepath:	pointer to prefixpath (or NULL if there isn't one)
 *
 * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
 * big enough to hold the final thing. Copy the UNC from the nodename, and
 * concatenate the prepath onto the end of it if there is one.
 *
 * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
 * for freeing the returned string.
 */
static char *
cifs_build_devname(char *nodename, const char *prepath)
{
	size_t pplen;
	size_t unclen;
	char *dev;
	char *pos;

	/* skip over any preceding delimiters */
	nodename += strspn(nodename, "\\");
	if (!*nodename)
		return ERR_PTR(-EINVAL);

	/* get length of UNC and set pos to last char */
	unclen = strlen(nodename);
	pos = nodename + unclen - 1;

	/* trim off any trailing delimiters */
	while (*pos == '\\') {
		--pos;
		--unclen;
	}

	/* allocate a buffer:
	 * +2 for preceding "//"
	 * +1 for delimiter between UNC and prepath
	 * +1 for trailing NULL
	 */
	pplen = prepath ? strlen(prepath) : 0;
	dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
	if (!dev)
		return ERR_PTR(-ENOMEM);

	pos = dev;
	/* add the initial "//" */
	*pos = '/';
	++pos;
	*pos = '/';
	++pos;

	/* copy in the UNC portion from referral */
	memcpy(pos, nodename, unclen);
	pos += unclen;

	/* copy the prefixpath remainder (if there is one) */
	if (pplen) {
		*pos = '/';
		++pos;
		memcpy(pos, prepath, pplen);
		pos += pplen;
	}

	/* NULL terminator */
	*pos = '\0';

	convert_delimiter(dev, '/');
	return dev;
}


/**
 * cifs_compose_mount_options	-	creates mount options for referral
 * @sb_mountdata:	parent/root DFS mount options (template)
 * @fullpath:		full path in UNC format
 * @ref:		optional server's referral
 * @devname:		return the built cifs device name if passed pointer not NULL
 * creates mount options for submount based on template options sb_mountdata
 * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
 *
 * Returns: pointer to new mount options or ERR_PTR.
 * Caller is responsible for freeing returned value if it is not error.
 */
char *cifs_compose_mount_options(const char *sb_mountdata,
				 const char *fullpath,
				 const struct dfs_info3_param *ref,
				 char **devname)
{
	int rc;
	char *name;
	char *mountdata = NULL;
	const char *prepath = NULL;
	int md_len;
	char *tkn_e;
	char *srvIP = NULL;
	char sep = ',';
	int off, noff;

	if (sb_mountdata == NULL)
		return ERR_PTR(-EINVAL);

	if (ref) {
		if (WARN_ON_ONCE(!ref->node_name || ref->path_consumed < 0))
			return ERR_PTR(-EINVAL);

		if (strlen(fullpath) - ref->path_consumed) {
			prepath = fullpath + ref->path_consumed;
			/* skip initial delimiter */
			if (*prepath == '/' || *prepath == '\\')
				prepath++;
		}

		name = cifs_build_devname(ref->node_name, prepath);
		if (IS_ERR(name)) {
			rc = PTR_ERR(name);
			name = NULL;
			goto compose_mount_options_err;
		}
	} else {
		name = cifs_build_devname((char *)fullpath, NULL);
		if (IS_ERR(name)) {
			rc = PTR_ERR(name);
			name = NULL;
			goto compose_mount_options_err;
		}
	}

	rc = dns_resolve_server_name_to_ip(name, &srvIP, NULL);
	if (rc < 0) {
		cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
			 __func__, name, rc);
		goto compose_mount_options_err;
	}

	/*
	 * In most cases, we'll be building a shorter string than the original,
	 * but we do have to assume that the address in the ip= option may be
	 * much longer than the original. Add the max length of an address
	 * string to the length of the original string to allow for worst case.
	 */
	md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
	mountdata = kzalloc(md_len + sizeof("ip=") + 1, GFP_KERNEL);
	if (mountdata == NULL) {
		rc = -ENOMEM;
		goto compose_mount_options_err;
	}

	/* copy all options except of unc,ip,prefixpath */
	off = 0;
	if (strncmp(sb_mountdata, "sep=", 4) == 0) {
			sep = sb_mountdata[4];
			strncpy(mountdata, sb_mountdata, 5);
			off += 5;
	}

	do {
		tkn_e = strchr(sb_mountdata + off, sep);
		if (tkn_e == NULL)
			noff = strlen(sb_mountdata + off);
		else
			noff = tkn_e - (sb_mountdata + off) + 1;

		if (strncasecmp(sb_mountdata + off, "cruid=", 6) == 0) {
			off += noff;
			continue;
		}
		if (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
			off += noff;
			continue;
		}
		if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
			off += noff;
			continue;
		}
		if (strncasecmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
			off += noff;
			continue;
		}
		strncat(mountdata, sb_mountdata + off, noff);
		off += noff;
	} while (tkn_e);
	strcat(mountdata, sb_mountdata + off);
	mountdata[md_len] = '\0';

	/* copy new IP and ref share name */
	if (mountdata[strlen(mountdata) - 1] != sep)
		strncat(mountdata, &sep, 1);
	strcat(mountdata, "ip=");
	strcat(mountdata, srvIP);

	if (devname)
		*devname = name;
	else
		kfree(name);

	/*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
	/*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/

compose_mount_options_out:
	kfree(srvIP);
	return mountdata;

compose_mount_options_err:
	kfree(mountdata);
	mountdata = ERR_PTR(rc);
	kfree(name);
	goto compose_mount_options_out;
}

/**
 * cifs_dfs_do_mount - mounts specified path using DFS full path
 *
 * Always pass down @fullpath to smb3_do_mount() so we can use the root server
 * to perform failover in case we failed to connect to the first target in the
 * referral.
 *
 * @mntpt:		directory entry for the path we are trying to automount
 * @cifs_sb:		parent/root superblock
 * @fullpath:		full path in UNC format
 */
static struct vfsmount *cifs_dfs_do_mount(struct dentry *mntpt,
					  struct cifs_sb_info *cifs_sb,
					  const char *fullpath)
{
	struct vfsmount *mnt;
	char *mountdata;
	char *devname;

	devname = kstrdup(fullpath, GFP_KERNEL);
	if (!devname)
		return ERR_PTR(-ENOMEM);

	convert_delimiter(devname, '/');

	/* TODO: change to call fs_context_for_mount(), fill in context directly, call fc_mount */

	/* See afs_mntpt_do_automount in fs/afs/mntpt.c for an example */

	/* strip first '\' from fullpath */
	mountdata = cifs_compose_mount_options(cifs_sb->ctx->mount_options,
					       fullpath + 1, NULL, NULL);
	if (IS_ERR(mountdata)) {
		kfree(devname);
		return (struct vfsmount *)mountdata;
	}

	mnt = vfs_submount(mntpt, &cifs_fs_type, devname, mountdata);
	kfree(mountdata);
	kfree(devname);
	return mnt;
}

/*
 * Create a vfsmount that we can automount
 */
static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
{
	struct cifs_sb_info *cifs_sb;
	struct cifs_ses *ses;
	struct cifs_tcon *tcon;
	void *page;
	char *full_path, *root_path;
	unsigned int xid;
	int rc;
	struct vfsmount *mnt;

	cifs_dbg(FYI, "in %s\n", __func__);
	BUG_ON(IS_ROOT(mntpt));

	/*
	 * The MSDFS spec states that paths in DFS referral requests and
	 * responses must be prefixed by a single '\' character instead of
	 * the double backslashes usually used in the UNC. This function
	 * gives us the latter, so we must adjust the result.
	 */
	mnt = ERR_PTR(-ENOMEM);

	cifs_sb = CIFS_SB(mntpt->d_sb);
	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) {
		mnt = ERR_PTR(-EREMOTE);
		goto cdda_exit;
	}

	page = alloc_dentry_path();
	/* always use tree name prefix */
	full_path = build_path_from_dentry_optional_prefix(mntpt, page, true);
	if (IS_ERR(full_path)) {
		mnt = ERR_CAST(full_path);
		goto free_full_path;
	}

	convert_delimiter(full_path, '\\');

	cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);

	if (!cifs_sb_master_tlink(cifs_sb)) {
		cifs_dbg(FYI, "%s: master tlink is NULL\n", __func__);
		goto free_full_path;
	}

	tcon = cifs_sb_master_tcon(cifs_sb);
	if (!tcon) {
		cifs_dbg(FYI, "%s: master tcon is NULL\n", __func__);
		goto free_full_path;
	}

	root_path = kstrdup(tcon->treeName, GFP_KERNEL);
	if (!root_path) {
		mnt = ERR_PTR(-ENOMEM);
		goto free_full_path;
	}
	cifs_dbg(FYI, "%s: root path: %s\n", __func__, root_path);

	ses = tcon->ses;
	xid = get_xid();

	/*
	 * If DFS root has been expired, then unconditionally fetch it again to
	 * refresh DFS referral cache.
	 */
	rc = dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
			    root_path + 1, NULL, NULL);
	if (!rc) {
		rc = dfs_cache_find(xid, ses, cifs_sb->local_nls,
				    cifs_remap(cifs_sb), full_path + 1,
				    NULL, NULL);
	}

	free_xid(xid);

	if (rc) {
		mnt = ERR_PTR(rc);
		goto free_root_path;
	}
	/*
	 * OK - we were able to get and cache a referral for @full_path.
	 *
	 * Now, pass it down to cifs_mount() and it will retry every available
	 * node server in case of failures - no need to do it here.
	 */
	mnt = cifs_dfs_do_mount(mntpt, cifs_sb, full_path);
	cifs_dbg(FYI, "%s: cifs_dfs_do_mount:%s , mnt:%p\n", __func__,
		 full_path + 1, mnt);

free_root_path:
	kfree(root_path);
free_full_path:
	free_dentry_path(page);
cdda_exit:
	cifs_dbg(FYI, "leaving %s\n" , __func__);
	return mnt;
}

/*
 * Attempt to automount the referral
 */
struct vfsmount *cifs_dfs_d_automount(struct path *path)
{
	struct vfsmount *newmnt;

	cifs_dbg(FYI, "in %s\n", __func__);

	newmnt = cifs_dfs_do_automount(path->dentry);
	if (IS_ERR(newmnt)) {
		cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
		return newmnt;
	}

	mntget(newmnt); /* prevent immediate expiration */
	mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
	schedule_delayed_work(&cifs_dfs_automount_task,
			      cifs_dfs_mountpoint_expiry_timeout);
	cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
	return newmnt;
}

const struct inode_operations cifs_dfs_referral_inode_operations = {
};
Commit	Line	Data
2874c5fd	1	// SPDX-License-Identifier: GPL-2.0-or-later
6d5ae0de IM	2	/*
	3	* Contains the CIFS DFS referral mounting routines used for handling
	4	* traversal via DFS junction point
	5	*
	6	* Copyright (c) 2007 Igor Mammedov
366781c1	7	* Copyright (C) International Business Machines Corp., 2008
6d5ae0de	8	* Author(s): Igor Mammedov (niallain@gmail.com)
366781c1	9	* Steve French (sfrench@us.ibm.com)
6d5ae0de IM	10	*/
	11
	12	#include <linux/dcache.h>
	13	#include <linux/mount.h>
	14	#include <linux/namei.h>
5a0e3ad6	15	#include <linux/slab.h>
6d5ae0de IM	16	#include <linux/vfs.h>
6d5ae0de IM	17	#include <linux/fs.h>
166faf21	18	#include <linux/inet.h>
6d5ae0de IM	19	#include "cifsglob.h"
	20	#include "cifsproto.h"
	21	#include "cifsfs.h"
	22	#include "dns_resolve.h"
	23	#include "cifs_debug.h"
bc8ebdc4	24	#include "cifs_unicode.h"
1c780228	25	#include "dfs_cache.h"
a2a52a8a	26	#include "fs_context.h"
6d5ae0de	27
8d142137	28	static LIST_HEAD(cifs_dfs_automount_list);
6d5ae0de	29
78d31a3a IM	30	static void cifs_dfs_expire_automounts(struct work_struct *work);
	31	static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
	32	cifs_dfs_expire_automounts);
	33	static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
	34
	35	static void cifs_dfs_expire_automounts(struct work_struct *work)
	36	{
	37	struct list_head *list = &cifs_dfs_automount_list;
	38
	39	mark_mounts_for_expiry(list);
	40	if (!list_empty(list))
	41	schedule_delayed_work(&cifs_dfs_automount_task,
	42	cifs_dfs_mountpoint_expiry_timeout);
	43	}
6d5ae0de	44
78d31a3a	45	void cifs_dfs_release_automount_timer(void)
6d5ae0de	46	{
78d31a3a	47	BUG_ON(!list_empty(&cifs_dfs_automount_list));
3e24e132	48	cancel_delayed_work_sync(&cifs_dfs_automount_task);
6d5ae0de IM	49	}
	50
	51	/**
d9deef0a JL	52	* cifs_build_devname - build a devicename from a UNC and optional prepath
	53	* @nodename: pointer to UNC string
	54	* @prepath: pointer to prefixpath (or NULL if there isn't one)
6d5ae0de	55	*
d9deef0a JL	56	* Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
	57	* big enough to hold the final thing. Copy the UNC from the nodename, and
	58	* concatenate the prepath onto the end of it if there is one.
	59	*
	60	* Returns pointer to the built string, or a ERR_PTR. Caller is responsible
	61	* for freeing the returned string.
6d5ae0de	62	*/
d9deef0a JL	63	static char *
d9deef0a JL	64	cifs_build_devname(char nodename, const char prepath)
6d5ae0de	65	{
d9deef0a JL	66	size_t pplen;
	67	size_t unclen;
	68	char *dev;
	69	char *pos;
6d5ae0de	70
d9deef0a JL	71	/* skip over any preceding delimiters */
	72	nodename += strspn(nodename, "\\");
	73	if (!*nodename)
7b91e266	74	return ERR_PTR(-EINVAL);
d9deef0a JL	75
	76	/* get length of UNC and set pos to last char */
	77	unclen = strlen(nodename);
	78	pos = nodename + unclen - 1;
	79
	80	/* trim off any trailing delimiters */
	81	while (*pos == '\\') {
	82	--pos;
	83	--unclen;
6d5ae0de IM	84	}
6d5ae0de IM	85
d9deef0a JL	86	/* allocate a buffer:
	87	* +2 for preceding "//"
	88	* +1 for delimiter between UNC and prepath
	89	* +1 for trailing NULL
	90	*/
	91	pplen = prepath ? strlen(prepath) : 0;
	92	dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
	93	if (!dev)
	94	return ERR_PTR(-ENOMEM);
	95
	96	pos = dev;
	97	/* add the initial "//" */
	98	*pos = '/';
	99	++pos;
	100	*pos = '/';
	101	++pos;
	102
	103	/* copy in the UNC portion from referral */
	104	memcpy(pos, nodename, unclen);
	105	pos += unclen;
	106
	107	/* copy the prefixpath remainder (if there is one) */
	108	if (pplen) {
	109	*pos = '/';
	110	++pos;
	111	memcpy(pos, prepath, pplen);
	112	pos += pplen;
6d5ae0de	113	}
6d5ae0de	114
d9deef0a JL	115	/* NULL terminator */
	116	*pos = '\0';
	117
	118	convert_delimiter(dev, '/');
	119	return dev;
6d5ae0de IM	120	}
	121
	122
	123	/**
5739375e	124	* cifs_compose_mount_options - creates mount options for referral
6d5ae0de	125	* @sb_mountdata: parent/root DFS mount options (template)
c6c00919	126	* @fullpath: full path in UNC format
5739375e	127	* @ref: optional server's referral
aaf36df3	128	* @devname: return the built cifs device name if passed pointer not NULL
6d5ae0de IM	129	* creates mount options for submount based on template options sb_mountdata
	130	* and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
	131	*
	132	* Returns: pointer to new mount options or ERR_PTR.
5739375e	133	* Caller is responsible for freeing returned value if it is not error.
6d5ae0de	134	*/
c6c00919	135	char cifs_compose_mount_options(const char sb_mountdata,
0d4873f9 RS	136	const char *fullpath,
	137	const struct dfs_info3_param *ref,
	138	char **devname)
6d5ae0de IM	139	{
6d5ae0de IM	140	int rc;
d9345e0a	141	char *name;
c6fbba05	142	char *mountdata = NULL;
d9deef0a	143	const char *prepath = NULL;
6d5ae0de IM	144	int md_len;
	145	char *tkn_e;
	146	char *srvIP = NULL;
	147	char sep = ',';
	148	int off, noff;
	149
	150	if (sb_mountdata == NULL)
	151	return ERR_PTR(-EINVAL);
	152
5739375e	153	if (ref) {
03313d1c PA	154	if (WARN_ON_ONCE(!ref->node_name \|\| ref->path_consumed < 0))
	155	return ERR_PTR(-EINVAL);
	156
5739375e PAS	157	if (strlen(fullpath) - ref->path_consumed) {
	158	prepath = fullpath + ref->path_consumed;
	159	/* skip initial delimiter */
	160	if (prepath == '/' \|\| prepath == '\\')
	161	prepath++;
	162	}
d9deef0a	163
5739375e PAS	164	name = cifs_build_devname(ref->node_name, prepath);
	165	if (IS_ERR(name)) {
	166	rc = PTR_ERR(name);
	167	name = NULL;
	168	goto compose_mount_options_err;
	169	}
	170	} else {
	171	name = cifs_build_devname((char *)fullpath, NULL);
	172	if (IS_ERR(name)) {
	173	rc = PTR_ERR(name);
	174	name = NULL;
	175	goto compose_mount_options_err;
	176	}
7b91e266 JL	177	}
7b91e266 JL	178
506c1da4	179	rc = dns_resolve_server_name_to_ip(name, &srvIP, NULL);
67b7626a	180	if (rc < 0) {
f96637be	181	cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
d9345e0a	182	__func__, name, rc);
c6fbba05	183	goto compose_mount_options_err;
6d5ae0de	184	}
b8028983	185
d9deef0a JL	186	/*
	187	* In most cases, we'll be building a shorter string than the original,
	188	* but we do have to assume that the address in the ip= option may be
	189	* much longer than the original. Add the max length of an address
	190	* string to the length of the original string to allow for worst case.
2c55608f	191	*/
d9deef0a	192	md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
f34d69c3	193	mountdata = kzalloc(md_len + sizeof("ip=") + 1, GFP_KERNEL);
6d5ae0de	194	if (mountdata == NULL) {
c6fbba05 SF	195	rc = -ENOMEM;
c6fbba05 SF	196	goto compose_mount_options_err;
6d5ae0de IM	197	}
	198
	199	/* copy all options except of unc,ip,prefixpath */
	200	off = 0;
	201	if (strncmp(sb_mountdata, "sep=", 4) == 0) {
	202	sep = sb_mountdata[4];
	203	strncpy(mountdata, sb_mountdata, 5);
	204	off += 5;
	205	}
2c55608f IM	206
	207	do {
	208	tkn_e = strchr(sb_mountdata + off, sep);
	209	if (tkn_e == NULL)
	210	noff = strlen(sb_mountdata + off);
	211	else
	212	noff = tkn_e - (sb_mountdata + off) + 1;
	213
50630b3f RS	214	if (strncasecmp(sb_mountdata + off, "cruid=", 6) == 0) {
	215	off += noff;
	216	continue;
	217	}
87e747cd	218	if (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
6d5ae0de IM	219	off += noff;
	220	continue;
	221	}
87e747cd	222	if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
6d5ae0de IM	223	off += noff;
	224	continue;
	225	}
87e747cd	226	if (strncasecmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
6d5ae0de IM	227	off += noff;
	228	continue;
	229	}
2c55608f	230	strncat(mountdata, sb_mountdata + off, noff);
6d5ae0de	231	off += noff;
2c55608f IM	232	} while (tkn_e);
2c55608f IM	233	strcat(mountdata, sb_mountdata + off);
6d5ae0de IM	234	mountdata[md_len] = '\0';
	235
	236	/* copy new IP and ref share name */
2c55608f IM	237	if (mountdata[strlen(mountdata) - 1] != sep)
	238	strncat(mountdata, &sep, 1);
	239	strcat(mountdata, "ip=");
6d5ae0de	240	strcat(mountdata, srvIP);
6d5ae0de	241
0d4873f9 RS	242	if (devname)
	243	*devname = name;
	244	else
	245	kfree(name);
d9345e0a	246
f96637be JP	247	/cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);/
f96637be JP	248	/cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );/
6d5ae0de IM	249
	250	compose_mount_options_out:
	251	kfree(srvIP);
	252	return mountdata;
c6fbba05 SF	253
	254	compose_mount_options_err:
	255	kfree(mountdata);
	256	mountdata = ERR_PTR(rc);
d9345e0a	257	kfree(name);
c6fbba05	258	goto compose_mount_options_out;
6d5ae0de IM	259	}
6d5ae0de IM	260
f67909cf	261	/**
5739375e PAS	262	* cifs_dfs_do_mount - mounts specified path using DFS full path
	263	*
	264	* Always pass down @fullpath to smb3_do_mount() so we can use the root server
	265	* to perform failover in case we failed to connect to the first target in the
	266	* referral.
	267	*
607dfc79	268	* @mntpt: directory entry for the path we are trying to automount
f67909cf SF	269	* @cifs_sb: parent/root superblock
f67909cf SF	270	* @fullpath: full path in UNC format
f67909cf	271	*/
5739375e PAS	272	static struct vfsmount cifs_dfs_do_mount(struct dentry mntpt,
	273	struct cifs_sb_info *cifs_sb,
	274	const char *fullpath)
6d5ae0de	275	{
6d5ae0de IM	276	struct vfsmount *mnt;
6d5ae0de IM	277	char *mountdata;
4a367dc0 PA	278	char *devname;
4a367dc0 PA	279
8d767223	280	devname = kstrdup(fullpath, GFP_KERNEL);
4a367dc0 PA	281	if (!devname)
	282	return ERR_PTR(-ENOMEM);
	283
	284	convert_delimiter(devname, '/');
c6c00919	285
24e0a1ef RS	286	/* TODO: change to call fs_context_for_mount(), fill in context directly, call fc_mount */
	287
	288	/* See afs_mntpt_do_automount in fs/afs/mntpt.c for an example */
	289
f67909cf	290	/* strip first '\' from fullpath */
a2a52a8a	291	mountdata = cifs_compose_mount_options(cifs_sb->ctx->mount_options,
0d4873f9	292	fullpath + 1, NULL, NULL);
4a367dc0 PA	293	if (IS_ERR(mountdata)) {
4a367dc0 PA	294	kfree(devname);
6d5ae0de	295	return (struct vfsmount *)mountdata;
4a367dc0	296	}
6d5ae0de	297
93faccbb	298	mnt = vfs_submount(mntpt, &cifs_fs_type, devname, mountdata);
6d5ae0de IM	299	kfree(mountdata);
	300	kfree(devname);
	301	return mnt;
6d5ae0de IM	302	}
6d5ae0de IM	303
01c64fea DH	304	/*
	305	* Create a vfsmount that we can automount
	306	*/
	307	static struct vfsmount cifs_dfs_do_automount(struct dentry mntpt)
6d5ae0de	308	{
6d5ae0de	309	struct cifs_sb_info *cifs_sb;
96daf2b0	310	struct cifs_ses *ses;
1c780228	311	struct cifs_tcon *tcon;
f6a9bc33	312	void *page;
1c780228	313	char full_path, root_path;
6d5786a3	314	unsigned int xid;
01c64fea DH	315	int rc;
01c64fea DH	316	struct vfsmount *mnt;
6d5ae0de	317
f96637be	318	cifs_dbg(FYI, "in %s\n", __func__);
01c64fea	319	BUG_ON(IS_ROOT(mntpt));
6d5ae0de	320
c6fbba05 SF	321	/*
	322	* The MSDFS spec states that paths in DFS referral requests and
	323	* responses must be prefixed by a single '\' character instead of
	324	* the double backslashes usually used in the UNC. This function
	325	* gives us the latter, so we must adjust the result.
	326	*/
01c64fea	327	mnt = ERR_PTR(-ENOMEM);
268a635d	328
8393072b AA	329	cifs_sb = CIFS_SB(mntpt->d_sb);
	330	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) {
	331	mnt = ERR_PTR(-EREMOTE);
	332	goto cdda_exit;
	333	}
	334
f6a9bc33	335	page = alloc_dentry_path();
268a635d	336	/* always use tree name prefix */
f6a9bc33 AV	337	full_path = build_path_from_dentry_optional_prefix(mntpt, page, true);
	338	if (IS_ERR(full_path)) {
	339	mnt = ERR_CAST(full_path);
	340	goto free_full_path;
	341	}
6d5ae0de	342
15425523 PAS	343	convert_delimiter(full_path, '\\');
15425523 PAS	344
1c780228 PA	345	cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);
	346
	347	if (!cifs_sb_master_tlink(cifs_sb)) {
	348	cifs_dbg(FYI, "%s: master tlink is NULL\n", __func__);
	349	goto free_full_path;
	350	}
	351
	352	tcon = cifs_sb_master_tcon(cifs_sb);
	353	if (!tcon) {
	354	cifs_dbg(FYI, "%s: master tcon is NULL\n", __func__);
01c64fea	355	goto free_full_path;
7ffec372	356	}
7ffec372	357
1c780228 PA	358	root_path = kstrdup(tcon->treeName, GFP_KERNEL);
	359	if (!root_path) {
	360	mnt = ERR_PTR(-ENOMEM);
	361	goto free_full_path;
	362	}
	363	cifs_dbg(FYI, "%s: root path: %s\n", __func__, root_path);
	364
	365	ses = tcon->ses;
6d5786a3	366	xid = get_xid();
6d5ae0de	367
1c780228 PA	368	/*
	369	* If DFS root has been expired, then unconditionally fetch it again to
	370	* refresh DFS referral cache.
	371	*/
	372	rc = dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
	373	root_path + 1, NULL, NULL);
	374	if (!rc) {
	375	rc = dfs_cache_find(xid, ses, cifs_sb->local_nls,
	376	cifs_remap(cifs_sb), full_path + 1,
5739375e	377	NULL, NULL);
6d5ae0de IM	378	}
6d5ae0de IM	379
1c780228 PA	380	free_xid(xid);
	381
	382	if (rc) {
01c64fea	383	mnt = ERR_PTR(rc);
1c780228 PA	384	goto free_root_path;
1c780228 PA	385	}
1c780228	386	/*
5739375e PAS	387	* OK - we were able to get and cache a referral for @full_path.
	388	*
	389	* Now, pass it down to cifs_mount() and it will retry every available
	390	* node server in case of failures - no need to do it here.
1c780228	391	*/
5739375e PAS	392	mnt = cifs_dfs_do_mount(mntpt, cifs_sb, full_path);
	393	cifs_dbg(FYI, "%s: cifs_dfs_do_mount:%s , mnt:%p\n", __func__,
	394	full_path + 1, mnt);
1c780228	395
1c780228 PA	396	free_root_path:
1c780228 PA	397	kfree(root_path);
01c64fea	398	free_full_path:
f6a9bc33	399	free_dentry_path(page);
31c2659d	400	cdda_exit:
f96637be	401	cifs_dbg(FYI, "leaving %s\n" , __func__);
01c64fea DH	402	return mnt;
	403	}
	404
	405	/*
	406	* Attempt to automount the referral
	407	*/
	408	struct vfsmount cifs_dfs_d_automount(struct path path)
	409	{
	410	struct vfsmount *newmnt;
01c64fea	411
f96637be	412	cifs_dbg(FYI, "in %s\n", __func__);
01c64fea DH	413
	414	newmnt = cifs_dfs_do_automount(path->dentry);
	415	if (IS_ERR(newmnt)) {
f96637be	416	cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
01c64fea DH	417	return newmnt;
	418	}
	419
ea5b778a DH	420	mntget(newmnt); /* prevent immediate expiration */
	421	mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
	422	schedule_delayed_work(&cifs_dfs_automount_task,
	423	cifs_dfs_mountpoint_expiry_timeout);
f96637be	424	cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
ea5b778a	425	return newmnt;
6d5ae0de IM	426	}
6d5ae0de IM	427
6e1d5dcc	428	const struct inode_operations cifs_dfs_referral_inode_operations = {
6d5ae0de	429	};