fs/cifs/link.c - kernel/msm-5.4 - Gitiles

 /*
  *   fs/cifs/link.c
  *
  *   Copyright (C) International Business Machines  Corp., 2002,2008
  *   Author(s): Steve French (sfrench@us.ibm.com)
  *
  *   This library is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU Lesser General Public License as published
  *   by the Free Software Foundation; either version 2.1 of the License, or
  *   (at your option) any later version.
  *
  *   This library is distributed in the hope that it will be useful,
  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
  *   the GNU Lesser General Public License for more details.
  *
  *   You should have received a copy of the GNU Lesser General Public License
  *   along with this library; if not, write to the Free Software
  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  */
 #include <linux/fs.h>
 #include <linux/stat.h>
 #include <linux/slab.h>
 #include <linux/namei.h>
 #include "cifsfs.h"
 #include "cifspdu.h"
 #include "cifsglob.h"
 #include "cifsproto.h"
 #include "cifs_debug.h"
 #include "cifs_fs_sb.h"

 #define CIFS_MF_SYMLINK_LEN_OFFSET (4+1)
 #define CIFS_MF_SYMLINK_MD5_OFFSET (CIFS_MF_SYMLINK_LEN_OFFSET+(4+1))
 #define CIFS_MF_SYMLINK_LINK_OFFSET (CIFS_MF_SYMLINK_MD5_OFFSET+(32+1))
 #define CIFS_MF_SYMLINK_LINK_MAXLEN (1024)
 #define CIFS_MF_SYMLINK_FILE_SIZE \
 	(CIFS_MF_SYMLINK_LINK_OFFSET + CIFS_MF_SYMLINK_LINK_MAXLEN)

 #define CIFS_MF_SYMLINK_LEN_FORMAT "XSym\n%04u\n"
 #define CIFS_MF_SYMLINK_MD5_FORMAT \
 	"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x\n"
 #define CIFS_MF_SYMLINK_MD5_ARGS(md5_hash) \
 	md5_hash[0],  md5_hash[1],  md5_hash[2],  md5_hash[3], \
 	md5_hash[4],  md5_hash[5],  md5_hash[6],  md5_hash[7], \
 	md5_hash[8],  md5_hash[9],  md5_hash[10], md5_hash[11],\
 	md5_hash[12], md5_hash[13], md5_hash[14], md5_hash[15]

 static int
 symlink_hash(unsigned int link_len, const char *link_str, u8 *md5_hash)
 {
 	int rc;
 	unsigned int size;
 	struct crypto_shash *md5;
 	struct sdesc *sdescmd5;

 	md5 = crypto_alloc_shash("md5", 0, 0);
 	if (IS_ERR(md5)) {
 		rc = PTR_ERR(md5);
 		cifs_dbg(VFS, "%s: Crypto md5 allocation error %d\n",
 			 __func__, rc);
 		return rc;
 	}
 	size = sizeof(struct shash_desc) + crypto_shash_descsize(md5);
 	sdescmd5 = kmalloc(size, GFP_KERNEL);
 	if (!sdescmd5) {
 		rc = -ENOMEM;
 		goto symlink_hash_err;
 	}
 	sdescmd5->shash.tfm = md5;
 	sdescmd5->shash.flags = 0x0;

 	rc = crypto_shash_init(&sdescmd5->shash);
 	if (rc) {
 		cifs_dbg(VFS, "%s: Could not init md5 shash\n", __func__);
 		goto symlink_hash_err;
 	}
 	rc = crypto_shash_update(&sdescmd5->shash, link_str, link_len);
 	if (rc) {
 		cifs_dbg(VFS, "%s: Could not update with link_str\n", __func__);
 		goto symlink_hash_err;
 	}
 	rc = crypto_shash_final(&sdescmd5->shash, md5_hash);
 	if (rc)
 		cifs_dbg(VFS, "%s: Could not generate md5 hash\n", __func__);

 symlink_hash_err:
 	crypto_free_shash(md5);
 	kfree(sdescmd5);

 	return rc;
 }

 static int
 CIFSParseMFSymlink(const u8 *buf,
 		   unsigned int buf_len,
 		   unsigned int *_link_len,
 		   char **_link_str)
 {
 	int rc;
 	unsigned int link_len;
 	const char *md5_str1;
 	const char *link_str;
 	u8 md5_hash[16];
 	char md5_str2[34];

 	if (buf_len != CIFS_MF_SYMLINK_FILE_SIZE)
 		return -EINVAL;

 	md5_str1 = (const char *)&buf[CIFS_MF_SYMLINK_MD5_OFFSET];
 	link_str = (const char *)&buf[CIFS_MF_SYMLINK_LINK_OFFSET];

 	rc = sscanf(buf, CIFS_MF_SYMLINK_LEN_FORMAT, &link_len);
 	if (rc != 1)
 		return -EINVAL;

 	rc = symlink_hash(link_len, link_str, md5_hash);
 	if (rc) {
 		cifs_dbg(FYI, "%s: MD5 hash failure: %d\n", __func__, rc);
 		return rc;
 	}

 	snprintf(md5_str2, sizeof(md5_str2),
 		 CIFS_MF_SYMLINK_MD5_FORMAT,
 		 CIFS_MF_SYMLINK_MD5_ARGS(md5_hash));

 	if (strncmp(md5_str1, md5_str2, 17) != 0)
 		return -EINVAL;

 	if (_link_str) {
 		*_link_str = kstrndup(link_str, link_len, GFP_KERNEL);
 		if (!*_link_str)
 			return -ENOMEM;
 	}

 	*_link_len = link_len;
 	return 0;
 }

 static int
 CIFSFormatMFSymlink(u8 *buf, unsigned int buf_len, const char *link_str)
 {
 	int rc;
 	unsigned int link_len;
 	unsigned int ofs;
 	u8 md5_hash[16];

 	if (buf_len != CIFS_MF_SYMLINK_FILE_SIZE)
 		return -EINVAL;

 	link_len = strlen(link_str);

 	if (link_len > CIFS_MF_SYMLINK_LINK_MAXLEN)
 		return -ENAMETOOLONG;

 	rc = symlink_hash(link_len, link_str, md5_hash);
 	if (rc) {
 		cifs_dbg(FYI, "%s: MD5 hash failure: %d\n", __func__, rc);
 		return rc;
 	}

 	snprintf(buf, buf_len,
 		 CIFS_MF_SYMLINK_LEN_FORMAT CIFS_MF_SYMLINK_MD5_FORMAT,
 		 link_len,
 		 CIFS_MF_SYMLINK_MD5_ARGS(md5_hash));

 	ofs = CIFS_MF_SYMLINK_LINK_OFFSET;
 	memcpy(buf + ofs, link_str, link_len);

 	ofs += link_len;
 	if (ofs < CIFS_MF_SYMLINK_FILE_SIZE) {
 		buf[ofs] = '\n';
 		ofs++;
 	}

 	while (ofs < CIFS_MF_SYMLINK_FILE_SIZE) {
 		buf[ofs] = ' ';
 		ofs++;
 	}

 	return 0;
 }

 static int
 CIFSCreateMFSymLink(const unsigned int xid, struct cifs_tcon *tcon,
 		    const char *fromName, const char *toName,
 		    struct cifs_sb_info *cifs_sb)
 {
 	int rc;
 	int oplock = 0;
 	int remap;
 	int create_options = CREATE_NOT_DIR;
 	__u16 netfid = 0;
 	u8 *buf;
 	unsigned int bytes_written = 0;
 	struct cifs_io_parms io_parms;
 	struct nls_table *nls_codepage;

 	nls_codepage = cifs_sb->local_nls;
 	remap = cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR;

 	buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;

 	rc = CIFSFormatMFSymlink(buf, CIFS_MF_SYMLINK_FILE_SIZE, toName);
 	if (rc != 0) {
 		kfree(buf);
 		return rc;
 	}

 	if (backup_cred(cifs_sb))
 		create_options |= CREATE_OPEN_BACKUP_INTENT;

 	rc = CIFSSMBOpen(xid, tcon, fromName, FILE_CREATE, GENERIC_WRITE,
 			 create_options, &netfid, &oplock, NULL,
 			 nls_codepage, remap);
 	if (rc != 0) {
 		kfree(buf);
 		return rc;
 	}

 	io_parms.netfid = netfid;
 	io_parms.pid = current->tgid;
 	io_parms.tcon = tcon;
 	io_parms.offset = 0;
 	io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;

 	rc = CIFSSMBWrite(xid, &io_parms, &bytes_written, buf, NULL, 0);
 	CIFSSMBClose(xid, tcon, netfid);
 	kfree(buf);
 	if (rc != 0)
 		return rc;

 	if (bytes_written != CIFS_MF_SYMLINK_FILE_SIZE)
 		return -EIO;

 	return 0;
 }

 static int
 CIFSQueryMFSymLink(const unsigned int xid, struct cifs_tcon *tcon,
 		   const unsigned char *searchName, char **symlinkinfo,
 		   const struct nls_table *nls_codepage, int remap)
 {
 	int rc;
 	int oplock = 0;
 	__u16 netfid = 0;
 	u8 *buf;
 	char *pbuf;
 	unsigned int bytes_read = 0;
 	int buf_type = CIFS_NO_BUFFER;
 	unsigned int link_len = 0;
 	struct cifs_io_parms io_parms;
 	FILE_ALL_INFO file_info;

 	rc = CIFSSMBOpen(xid, tcon, searchName, FILE_OPEN, GENERIC_READ,
 			 CREATE_NOT_DIR, &netfid, &oplock, &file_info,
 			 nls_codepage, remap);
 	if (rc != 0)
 		return rc;

 	if (file_info.EndOfFile != cpu_to_le64(CIFS_MF_SYMLINK_FILE_SIZE)) {
 		CIFSSMBClose(xid, tcon, netfid);
 		/* it's not a symlink */
 		return -EINVAL;
 	}

 	buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;
 	pbuf = buf;
 	io_parms.netfid = netfid;
 	io_parms.pid = current->tgid;
 	io_parms.tcon = tcon;
 	io_parms.offset = 0;
 	io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;

 	rc = CIFSSMBRead(xid, &io_parms, &bytes_read, &pbuf, &buf_type);
 	CIFSSMBClose(xid, tcon, netfid);
 	if (rc != 0) {
 		kfree(buf);
 		return rc;
 	}

 	rc = CIFSParseMFSymlink(buf, bytes_read, &link_len, symlinkinfo);
 	kfree(buf);
 	if (rc != 0)
 		return rc;

 	return 0;
 }

 bool
 CIFSCouldBeMFSymlink(const struct cifs_fattr *fattr)
 {
 	if (!(fattr->cf_mode & S_IFREG))
 		/* it's not a symlink */
 		return false;

 	if (fattr->cf_eof != CIFS_MF_SYMLINK_FILE_SIZE)
 		/* it's not a symlink */
 		return false;

 	return true;
 }

 int
 open_query_close_cifs_symlink(const unsigned char *path, char *pbuf,
 			unsigned int *pbytes_read, struct cifs_sb_info *cifs_sb,
 			unsigned int xid)
 {
 	int rc;
 	int oplock = 0;
 	__u16 netfid = 0;
 	struct tcon_link *tlink;
 	struct cifs_tcon *ptcon;
 	struct cifs_io_parms io_parms;
 	int buf_type = CIFS_NO_BUFFER;
 	FILE_ALL_INFO file_info;

 	tlink = cifs_sb_tlink(cifs_sb);
 	if (IS_ERR(tlink))
 		return PTR_ERR(tlink);
 	ptcon = tlink_tcon(tlink);

 	rc = CIFSSMBOpen(xid, ptcon, path, FILE_OPEN, GENERIC_READ,
 			 CREATE_NOT_DIR, &netfid, &oplock, &file_info,
 			 cifs_sb->local_nls,
 			 cifs_sb->mnt_cifs_flags &
 				CIFS_MOUNT_MAP_SPECIAL_CHR);
 	if (rc != 0) {
 		cifs_put_tlink(tlink);
 		return rc;
 	}

 	if (file_info.EndOfFile != cpu_to_le64(CIFS_MF_SYMLINK_FILE_SIZE)) {
 		CIFSSMBClose(xid, ptcon, netfid);
 		cifs_put_tlink(tlink);
 		/* it's not a symlink */
 		return rc;
 	}

 	io_parms.netfid = netfid;
 	io_parms.pid = current->tgid;
 	io_parms.tcon = ptcon;
 	io_parms.offset = 0;
 	io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;

 	rc = CIFSSMBRead(xid, &io_parms, pbytes_read, &pbuf, &buf_type);
 	CIFSSMBClose(xid, ptcon, netfid);
 	cifs_put_tlink(tlink);
 	return rc;
 }


 int
 CIFSCheckMFSymlink(struct cifs_fattr *fattr,
 		   const unsigned char *path,
 		   struct cifs_sb_info *cifs_sb, unsigned int xid)
 {
 	int rc = 0;
 	u8 *buf = NULL;
 	unsigned int link_len = 0;
 	unsigned int bytes_read = 0;
 	struct cifs_tcon *ptcon;

 	if (!CIFSCouldBeMFSymlink(fattr))
 		/* it's not a symlink */
 		return 0;

 	buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
 	if (!buf) {
 		rc = -ENOMEM;
 		goto out;
 	}

 	ptcon = tlink_tcon(cifs_sb_tlink(cifs_sb));
 	if ((ptcon->ses) && (ptcon->ses->server->ops->query_mf_symlink))
 		rc = ptcon->ses->server->ops->query_mf_symlink(path, buf,
 						 &bytes_read, cifs_sb, xid);
 	else
 		goto out;

 	if (rc != 0)
 		goto out;

 	if (bytes_read == 0) /* not a symlink */
 		goto out;

 	rc = CIFSParseMFSymlink(buf, bytes_read, &link_len, NULL);
 	if (rc == -EINVAL) {
 		/* it's not a symlink */
 		rc = 0;
 		goto out;
 	}

 	if (rc != 0)
 		goto out;

 	/* it is a symlink */
 	fattr->cf_eof = link_len;
 	fattr->cf_mode &= ~S_IFMT;
 	fattr->cf_mode |= S_IFLNK | S_IRWXU | S_IRWXG | S_IRWXO;
 	fattr->cf_dtype = DT_LNK;
 out:
 	kfree(buf);
 	return rc;
 }

 int
 cifs_hardlink(struct dentry *old_file, struct inode *inode,
 	      struct dentry *direntry)
 {
 	int rc = -EACCES;
 	unsigned int xid;
 	char *from_name = NULL;
 	char *to_name = NULL;
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 	struct tcon_link *tlink;
 	struct cifs_tcon *tcon;
 	struct TCP_Server_Info *server;
 	struct cifsInodeInfo *cifsInode;

 	tlink = cifs_sb_tlink(cifs_sb);
 	if (IS_ERR(tlink))
 		return PTR_ERR(tlink);
 	tcon = tlink_tcon(tlink);

 	xid = get_xid();

 	from_name = build_path_from_dentry(old_file);
 	to_name = build_path_from_dentry(direntry);
 	if ((from_name == NULL) || (to_name == NULL)) {
 		rc = -ENOMEM;
 		goto cifs_hl_exit;
 	}

 	if (tcon->unix_ext)
 		rc = CIFSUnixCreateHardLink(xid, tcon, from_name, to_name,
 					    cifs_sb->local_nls,
 					    cifs_sb->mnt_cifs_flags &
 						CIFS_MOUNT_MAP_SPECIAL_CHR);
 	else {
 		server = tcon->ses->server;
 		if (!server->ops->create_hardlink)
 			return -ENOSYS;
 		rc = server->ops->create_hardlink(xid, tcon, from_name, to_name,
 						  cifs_sb);
 		if ((rc == -EIO) || (rc == -EINVAL))
 			rc = -EOPNOTSUPP;
 	}

 	d_drop(direntry);	/* force new lookup from server of target */

 	/*
 	 * if source file is cached (oplocked) revalidate will not go to server
 	 * until the file is closed or oplock broken so update nlinks locally
 	 */
 	if (old_file->d_inode) {
 		cifsInode = CIFS_I(old_file->d_inode);
 		if (rc == 0) {
 			spin_lock(&old_file->d_inode->i_lock);
 			inc_nlink(old_file->d_inode);
 			spin_unlock(&old_file->d_inode->i_lock);
 			/*
 			 * BB should we make this contingent on superblock flag
 			 * NOATIME?
 			 */
 			/* old_file->d_inode->i_ctime = CURRENT_TIME; */
 			/*
 			 * parent dir timestamps will update from srv within a
 			 * second, would it really be worth it to set the parent
 			 * dir cifs inode time to zero to force revalidate
 			 * (faster) for it too?
 			 */
 		}
 		/*
 		 * if not oplocked will force revalidate to get info on source
 		 * file from srv
 		 */
 		cifsInode->time = 0;

 		/*
 		 * Will update parent dir timestamps from srv within a second.
 		 * Would it really be worth it to set the parent dir (cifs
 		 * inode) time field to zero to force revalidate on parent
 		 * directory faster ie
 		 *
 		 * CIFS_I(inode)->time = 0;
 		 */
 	}

 cifs_hl_exit:
 	kfree(from_name);
 	kfree(to_name);
 	free_xid(xid);
 	cifs_put_tlink(tlink);
 	return rc;
 }

 void *
 cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
 {
 	struct inode *inode = direntry->d_inode;
 	int rc = -ENOMEM;
 	unsigned int xid;
 	char *full_path = NULL;
 	char *target_path = NULL;
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 	struct tcon_link *tlink = NULL;
 	struct cifs_tcon *tcon;

 	xid = get_xid();

 	tlink = cifs_sb_tlink(cifs_sb);
 	if (IS_ERR(tlink)) {
 		rc = PTR_ERR(tlink);
 		tlink = NULL;
 		goto out;
 	}
 	tcon = tlink_tcon(tlink);

 	/*
 	 * For now, we just handle symlinks with unix extensions enabled.
 	 * Eventually we should handle NTFS reparse points, and MacOS
 	 * symlink support. For instance...
 	 *
 	 * rc = CIFSSMBQueryReparseLinkInfo(...)
 	 *
 	 * For now, just return -EACCES when the server doesn't support posix
 	 * extensions. Note that we still allow querying symlinks when posix
 	 * extensions are manually disabled. We could disable these as well
 	 * but there doesn't seem to be any harm in allowing the client to
 	 * read them.
 	 */
 	if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) &&
 	    !cap_unix(tcon->ses)) {
 		rc = -EACCES;
 		goto out;
 	}

 	full_path = build_path_from_dentry(direntry);
 	if (!full_path)
 		goto out;

 	cifs_dbg(FYI, "Full path: %s inode = 0x%p\n", full_path, inode);

 	rc = -EACCES;
 	/*
 	 * First try Minshall+French Symlinks, if configured
 	 * and fallback to UNIX Extensions Symlinks.
 	 */
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
 		rc = CIFSQueryMFSymLink(xid, tcon, full_path, &target_path,
 					cifs_sb->local_nls,
 					cifs_sb->mnt_cifs_flags &
 						CIFS_MOUNT_MAP_SPECIAL_CHR);

 	if ((rc != 0) && cap_unix(tcon->ses))
 		rc = CIFSSMBUnixQuerySymLink(xid, tcon, full_path, &target_path,
 					     cifs_sb->local_nls);

 	kfree(full_path);
 out:
 	if (rc != 0) {
 		kfree(target_path);
 		target_path = ERR_PTR(rc);
 	}

 	free_xid(xid);
 	if (tlink)
 		cifs_put_tlink(tlink);
 	nd_set_link(nd, target_path);
 	return NULL;
 }

 int
 cifs_symlink(struct inode *inode, struct dentry *direntry, const char *symname)
 {
 	int rc = -EOPNOTSUPP;
 	unsigned int xid;
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 	struct tcon_link *tlink;
 	struct cifs_tcon *pTcon;
 	char *full_path = NULL;
 	struct inode *newinode = NULL;

 	xid = get_xid();

 	tlink = cifs_sb_tlink(cifs_sb);
 	if (IS_ERR(tlink)) {
 		rc = PTR_ERR(tlink);
 		goto symlink_exit;
 	}
 	pTcon = tlink_tcon(tlink);

 	full_path = build_path_from_dentry(direntry);
 	if (full_path == NULL) {
 		rc = -ENOMEM;
 		goto symlink_exit;
 	}

 	cifs_dbg(FYI, "Full path: %s\n", full_path);
 	cifs_dbg(FYI, "symname is %s\n", symname);

 	/* BB what if DFS and this volume is on different share? BB */
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
 		rc = CIFSCreateMFSymLink(xid, pTcon, full_path, symname,
 					cifs_sb);
 	else if (pTcon->unix_ext)
 		rc = CIFSUnixCreateSymLink(xid, pTcon, full_path, symname,
 					   cifs_sb->local_nls);
 	/* else
 	   rc = CIFSCreateReparseSymLink(xid, pTcon, fromName, toName,
 					cifs_sb_target->local_nls); */

 	if (rc == 0) {
 		if (pTcon->unix_ext)
 			rc = cifs_get_inode_info_unix(&newinode, full_path,
 						      inode->i_sb, xid);
 		else
 			rc = cifs_get_inode_info(&newinode, full_path, NULL,
 						 inode->i_sb, xid, NULL);

 		if (rc != 0) {
 			cifs_dbg(FYI, "Create symlink ok, getinodeinfo fail rc = %d\n",
 				 rc);
 		} else {
 			d_instantiate(direntry, newinode);
 		}
 	}
 symlink_exit:
 	kfree(full_path);
 	cifs_put_tlink(tlink);
 	free_xid(xid);
 	return rc;
 }

 void cifs_put_link(struct dentry *direntry, struct nameidata *nd, void *cookie)
 {
 	char *p = nd_get_link(nd);
 	if (!IS_ERR(p))
 		kfree(p);
 }
	/*
	* fs/cifs/link.c
	*
	* Copyright (C) International Business Machines Corp., 2002,2008
	* Author(s): Steve French (sfrench@us.ibm.com)
	*
	* This library is free software; you can redistribute it and/or modify
	* it under the terms of the GNU Lesser General Public License as published
	* by the Free Software Foundation; either version 2.1 of the License, or
	* (at your option) any later version.
	*
	* This library is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
	* the GNU Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public License
	* along with this library; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*/
	#include <linux/fs.h>
	#include <linux/stat.h>
	#include <linux/slab.h>
	#include <linux/namei.h>
	#include "cifsfs.h"
	#include "cifspdu.h"
	#include "cifsglob.h"
	#include "cifsproto.h"
	#include "cifs_debug.h"
	#include "cifs_fs_sb.h"

	#define CIFS_MF_SYMLINK_LEN_OFFSET (4+1)
	#define CIFS_MF_SYMLINK_MD5_OFFSET (CIFS_MF_SYMLINK_LEN_OFFSET+(4+1))
	#define CIFS_MF_SYMLINK_LINK_OFFSET (CIFS_MF_SYMLINK_MD5_OFFSET+(32+1))
	#define CIFS_MF_SYMLINK_LINK_MAXLEN (1024)
	#define CIFS_MF_SYMLINK_FILE_SIZE \
	(CIFS_MF_SYMLINK_LINK_OFFSET + CIFS_MF_SYMLINK_LINK_MAXLEN)

	#define CIFS_MF_SYMLINK_LEN_FORMAT "XSym\n%04u\n"
	#define CIFS_MF_SYMLINK_MD5_FORMAT \
	"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x\n"
	#define CIFS_MF_SYMLINK_MD5_ARGS(md5_hash) \
	md5_hash[0], md5_hash[1], md5_hash[2], md5_hash[3], \
	md5_hash[4], md5_hash[5], md5_hash[6], md5_hash[7], \
	md5_hash[8], md5_hash[9], md5_hash[10], md5_hash[11],\
	md5_hash[12], md5_hash[13], md5_hash[14], md5_hash[15]

	static int
	symlink_hash(unsigned int link_len, const char link_str, u8 md5_hash)
	{
	int rc;
	unsigned int size;
	struct crypto_shash *md5;
	struct sdesc *sdescmd5;

	md5 = crypto_alloc_shash("md5", 0, 0);
	if (IS_ERR(md5)) {
	rc = PTR_ERR(md5);
	cifs_dbg(VFS, "%s: Crypto md5 allocation error %d\n",
	__func__, rc);
	return rc;
	}
	size = sizeof(struct shash_desc) + crypto_shash_descsize(md5);
	sdescmd5 = kmalloc(size, GFP_KERNEL);
	if (!sdescmd5) {
	rc = -ENOMEM;
	goto symlink_hash_err;
	}
	sdescmd5->shash.tfm = md5;
	sdescmd5->shash.flags = 0x0;

	rc = crypto_shash_init(&sdescmd5->shash);
	if (rc) {
	cifs_dbg(VFS, "%s: Could not init md5 shash\n", __func__);
	goto symlink_hash_err;
	}
	rc = crypto_shash_update(&sdescmd5->shash, link_str, link_len);
	if (rc) {
	cifs_dbg(VFS, "%s: Could not update with link_str\n", __func__);
	goto symlink_hash_err;
	}
	rc = crypto_shash_final(&sdescmd5->shash, md5_hash);
	if (rc)
	cifs_dbg(VFS, "%s: Could not generate md5 hash\n", __func__);

	symlink_hash_err:
	crypto_free_shash(md5);
	kfree(sdescmd5);

	return rc;
	}

	static int
	CIFSParseMFSymlink(const u8 *buf,
	unsigned int buf_len,
	unsigned int *_link_len,
	char **_link_str)
	{
	int rc;
	unsigned int link_len;
	const char *md5_str1;
	const char *link_str;
	u8 md5_hash[16];
	char md5_str2[34];

	if (buf_len != CIFS_MF_SYMLINK_FILE_SIZE)
	return -EINVAL;

	md5_str1 = (const char *)&buf[CIFS_MF_SYMLINK_MD5_OFFSET];
	link_str = (const char *)&buf[CIFS_MF_SYMLINK_LINK_OFFSET];

	rc = sscanf(buf, CIFS_MF_SYMLINK_LEN_FORMAT, &link_len);
	if (rc != 1)
	return -EINVAL;

	rc = symlink_hash(link_len, link_str, md5_hash);
	if (rc) {
	cifs_dbg(FYI, "%s: MD5 hash failure: %d\n", __func__, rc);
	return rc;
	}

	snprintf(md5_str2, sizeof(md5_str2),
	CIFS_MF_SYMLINK_MD5_FORMAT,
	CIFS_MF_SYMLINK_MD5_ARGS(md5_hash));

	if (strncmp(md5_str1, md5_str2, 17) != 0)
	return -EINVAL;

	if (_link_str) {
	*_link_str = kstrndup(link_str, link_len, GFP_KERNEL);
	if (!*_link_str)
	return -ENOMEM;
	}

	*_link_len = link_len;
	return 0;
	}

	static int
	CIFSFormatMFSymlink(u8 buf, unsigned int buf_len, const char link_str)
	{
	int rc;
	unsigned int link_len;
	unsigned int ofs;
	u8 md5_hash[16];

	if (buf_len != CIFS_MF_SYMLINK_FILE_SIZE)
	return -EINVAL;

	link_len = strlen(link_str);

	if (link_len > CIFS_MF_SYMLINK_LINK_MAXLEN)
	return -ENAMETOOLONG;

	rc = symlink_hash(link_len, link_str, md5_hash);
	if (rc) {
	cifs_dbg(FYI, "%s: MD5 hash failure: %d\n", __func__, rc);
	return rc;
	}

	snprintf(buf, buf_len,
	CIFS_MF_SYMLINK_LEN_FORMAT CIFS_MF_SYMLINK_MD5_FORMAT,
	link_len,
	CIFS_MF_SYMLINK_MD5_ARGS(md5_hash));

	ofs = CIFS_MF_SYMLINK_LINK_OFFSET;
	memcpy(buf + ofs, link_str, link_len);

	ofs += link_len;
	if (ofs < CIFS_MF_SYMLINK_FILE_SIZE) {
	buf[ofs] = '\n';
	ofs++;
	}

	while (ofs < CIFS_MF_SYMLINK_FILE_SIZE) {
	buf[ofs] = ' ';
	ofs++;
	}

	return 0;
	}

	static int
	CIFSCreateMFSymLink(const unsigned int xid, struct cifs_tcon *tcon,
	const char fromName, const char toName,
	struct cifs_sb_info *cifs_sb)
	{
	int rc;
	int oplock = 0;
	int remap;
	int create_options = CREATE_NOT_DIR;
	__u16 netfid = 0;
	u8 *buf;
	unsigned int bytes_written = 0;
	struct cifs_io_parms io_parms;
	struct nls_table *nls_codepage;

	nls_codepage = cifs_sb->local_nls;
	remap = cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR;

	buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
	if (!buf)
	return -ENOMEM;

	rc = CIFSFormatMFSymlink(buf, CIFS_MF_SYMLINK_FILE_SIZE, toName);
	if (rc != 0) {
	kfree(buf);
	return rc;
	}

	if (backup_cred(cifs_sb))
	create_options \|= CREATE_OPEN_BACKUP_INTENT;

	rc = CIFSSMBOpen(xid, tcon, fromName, FILE_CREATE, GENERIC_WRITE,
	create_options, &netfid, &oplock, NULL,
	nls_codepage, remap);
	if (rc != 0) {
	kfree(buf);
	return rc;
	}

	io_parms.netfid = netfid;
	io_parms.pid = current->tgid;
	io_parms.tcon = tcon;
	io_parms.offset = 0;
	io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;

	rc = CIFSSMBWrite(xid, &io_parms, &bytes_written, buf, NULL, 0);
	CIFSSMBClose(xid, tcon, netfid);
	kfree(buf);
	if (rc != 0)
	return rc;

	if (bytes_written != CIFS_MF_SYMLINK_FILE_SIZE)
	return -EIO;

	return 0;
	}

	static int
	CIFSQueryMFSymLink(const unsigned int xid, struct cifs_tcon *tcon,
	const unsigned char searchName, char *symlinkinfo,
	const struct nls_table *nls_codepage, int remap)
	{
	int rc;
	int oplock = 0;
	__u16 netfid = 0;
	u8 *buf;
	char *pbuf;
	unsigned int bytes_read = 0;
	int buf_type = CIFS_NO_BUFFER;
	unsigned int link_len = 0;
	struct cifs_io_parms io_parms;
	FILE_ALL_INFO file_info;

	rc = CIFSSMBOpen(xid, tcon, searchName, FILE_OPEN, GENERIC_READ,
	CREATE_NOT_DIR, &netfid, &oplock, &file_info,
	nls_codepage, remap);
	if (rc != 0)
	return rc;

	if (file_info.EndOfFile != cpu_to_le64(CIFS_MF_SYMLINK_FILE_SIZE)) {
	CIFSSMBClose(xid, tcon, netfid);
	/* it's not a symlink */
	return -EINVAL;
	}

	buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
	if (!buf)
	return -ENOMEM;
	pbuf = buf;
	io_parms.netfid = netfid;
	io_parms.pid = current->tgid;
	io_parms.tcon = tcon;
	io_parms.offset = 0;
	io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;

	rc = CIFSSMBRead(xid, &io_parms, &bytes_read, &pbuf, &buf_type);
	CIFSSMBClose(xid, tcon, netfid);
	if (rc != 0) {
	kfree(buf);
	return rc;
	}

	rc = CIFSParseMFSymlink(buf, bytes_read, &link_len, symlinkinfo);
	kfree(buf);
	if (rc != 0)
	return rc;

	return 0;
	}

	bool
	CIFSCouldBeMFSymlink(const struct cifs_fattr *fattr)
	{
	if (!(fattr->cf_mode & S_IFREG))
	/* it's not a symlink */
	return false;

	if (fattr->cf_eof != CIFS_MF_SYMLINK_FILE_SIZE)
	/* it's not a symlink */
	return false;

	return true;
	}

	int
	open_query_close_cifs_symlink(const unsigned char path, char pbuf,
	unsigned int pbytes_read, struct cifs_sb_info cifs_sb,
	unsigned int xid)
	{
	int rc;
	int oplock = 0;
	__u16 netfid = 0;
	struct tcon_link *tlink;
	struct cifs_tcon *ptcon;
	struct cifs_io_parms io_parms;
	int buf_type = CIFS_NO_BUFFER;
	FILE_ALL_INFO file_info;

	tlink = cifs_sb_tlink(cifs_sb);
	if (IS_ERR(tlink))
	return PTR_ERR(tlink);
	ptcon = tlink_tcon(tlink);

	rc = CIFSSMBOpen(xid, ptcon, path, FILE_OPEN, GENERIC_READ,
	CREATE_NOT_DIR, &netfid, &oplock, &file_info,
	cifs_sb->local_nls,
	cifs_sb->mnt_cifs_flags &
	CIFS_MOUNT_MAP_SPECIAL_CHR);
	if (rc != 0) {
	cifs_put_tlink(tlink);
	return rc;
	}

	if (file_info.EndOfFile != cpu_to_le64(CIFS_MF_SYMLINK_FILE_SIZE)) {
	CIFSSMBClose(xid, ptcon, netfid);
	cifs_put_tlink(tlink);
	/* it's not a symlink */
	return rc;
	}

	io_parms.netfid = netfid;
	io_parms.pid = current->tgid;
	io_parms.tcon = ptcon;
	io_parms.offset = 0;
	io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;

	rc = CIFSSMBRead(xid, &io_parms, pbytes_read, &pbuf, &buf_type);
	CIFSSMBClose(xid, ptcon, netfid);
	cifs_put_tlink(tlink);
	return rc;
	}


	int
	CIFSCheckMFSymlink(struct cifs_fattr *fattr,
	const unsigned char *path,
	struct cifs_sb_info *cifs_sb, unsigned int xid)
	{
	int rc = 0;
	u8 *buf = NULL;
	unsigned int link_len = 0;
	unsigned int bytes_read = 0;
	struct cifs_tcon *ptcon;

	if (!CIFSCouldBeMFSymlink(fattr))
	/* it's not a symlink */
	return 0;

	buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
	if (!buf) {
	rc = -ENOMEM;
	goto out;
	}

	ptcon = tlink_tcon(cifs_sb_tlink(cifs_sb));
	if ((ptcon->ses) && (ptcon->ses->server->ops->query_mf_symlink))
	rc = ptcon->ses->server->ops->query_mf_symlink(path, buf,
	&bytes_read, cifs_sb, xid);
	else
	goto out;

	if (rc != 0)
	goto out;

	if (bytes_read == 0) /* not a symlink */
	goto out;

	rc = CIFSParseMFSymlink(buf, bytes_read, &link_len, NULL);
	if (rc == -EINVAL) {
	/* it's not a symlink */
	rc = 0;
	goto out;
	}

	if (rc != 0)
	goto out;

	/* it is a symlink */
	fattr->cf_eof = link_len;
	fattr->cf_mode &= ~S_IFMT;
	fattr->cf_mode \|= S_IFLNK \| S_IRWXU \| S_IRWXG \| S_IRWXO;
	fattr->cf_dtype = DT_LNK;
	out:
	kfree(buf);
	return rc;
	}

	int
	cifs_hardlink(struct dentry old_file, struct inode inode,
	struct dentry *direntry)
	{
	int rc = -EACCES;
	unsigned int xid;
	char *from_name = NULL;
	char *to_name = NULL;
	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
	struct tcon_link *tlink;
	struct cifs_tcon *tcon;
	struct TCP_Server_Info *server;
	struct cifsInodeInfo *cifsInode;

	tlink = cifs_sb_tlink(cifs_sb);
	if (IS_ERR(tlink))
	return PTR_ERR(tlink);
	tcon = tlink_tcon(tlink);

	xid = get_xid();

	from_name = build_path_from_dentry(old_file);
	to_name = build_path_from_dentry(direntry);
	if ((from_name == NULL) \|\| (to_name == NULL)) {
	rc = -ENOMEM;
	goto cifs_hl_exit;
	}

	if (tcon->unix_ext)
	rc = CIFSUnixCreateHardLink(xid, tcon, from_name, to_name,
	cifs_sb->local_nls,
	cifs_sb->mnt_cifs_flags &
	CIFS_MOUNT_MAP_SPECIAL_CHR);
	else {
	server = tcon->ses->server;
	if (!server->ops->create_hardlink)
	return -ENOSYS;
	rc = server->ops->create_hardlink(xid, tcon, from_name, to_name,
	cifs_sb);
	if ((rc == -EIO) \|\| (rc == -EINVAL))
	rc = -EOPNOTSUPP;
	}

	d_drop(direntry); /* force new lookup from server of target */

	/*
	* if source file is cached (oplocked) revalidate will not go to server
	* until the file is closed or oplock broken so update nlinks locally
	*/
	if (old_file->d_inode) {
	cifsInode = CIFS_I(old_file->d_inode);
	if (rc == 0) {
	spin_lock(&old_file->d_inode->i_lock);
	inc_nlink(old_file->d_inode);
	spin_unlock(&old_file->d_inode->i_lock);
	/*
	* BB should we make this contingent on superblock flag
	* NOATIME?
	*/
	/* old_file->d_inode->i_ctime = CURRENT_TIME; */
	/*
	* parent dir timestamps will update from srv within a
	* second, would it really be worth it to set the parent
	* dir cifs inode time to zero to force revalidate
	* (faster) for it too?
	*/
	}
	/*
	* if not oplocked will force revalidate to get info on source
	* file from srv
	*/
	cifsInode->time = 0;

	/*
	* Will update parent dir timestamps from srv within a second.
	* Would it really be worth it to set the parent dir (cifs
	* inode) time field to zero to force revalidate on parent
	* directory faster ie
	*
	* CIFS_I(inode)->time = 0;
	*/
	}

	cifs_hl_exit:
	kfree(from_name);
	kfree(to_name);
	free_xid(xid);
	cifs_put_tlink(tlink);
	return rc;
	}

	void *
	cifs_follow_link(struct dentry direntry, struct nameidata nd)
	{
	struct inode *inode = direntry->d_inode;
	int rc = -ENOMEM;
	unsigned int xid;
	char *full_path = NULL;
	char *target_path = NULL;
	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
	struct tcon_link *tlink = NULL;
	struct cifs_tcon *tcon;

	xid = get_xid();

	tlink = cifs_sb_tlink(cifs_sb);
	if (IS_ERR(tlink)) {
	rc = PTR_ERR(tlink);
	tlink = NULL;
	goto out;
	}
	tcon = tlink_tcon(tlink);

	/*
	* For now, we just handle symlinks with unix extensions enabled.
	* Eventually we should handle NTFS reparse points, and MacOS
	* symlink support. For instance...
	*
	* rc = CIFSSMBQueryReparseLinkInfo(...)
	*
	* For now, just return -EACCES when the server doesn't support posix
	* extensions. Note that we still allow querying symlinks when posix
	* extensions are manually disabled. We could disable these as well
	* but there doesn't seem to be any harm in allowing the client to
	* read them.
	*/
	if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) &&
	!cap_unix(tcon->ses)) {
	rc = -EACCES;
	goto out;
	}

	full_path = build_path_from_dentry(direntry);
	if (!full_path)
	goto out;

	cifs_dbg(FYI, "Full path: %s inode = 0x%p\n", full_path, inode);

	rc = -EACCES;
	/*
	* First try Minshall+French Symlinks, if configured
	* and fallback to UNIX Extensions Symlinks.
	*/
	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
	rc = CIFSQueryMFSymLink(xid, tcon, full_path, &target_path,
	cifs_sb->local_nls,
	cifs_sb->mnt_cifs_flags &
	CIFS_MOUNT_MAP_SPECIAL_CHR);

	if ((rc != 0) && cap_unix(tcon->ses))
	rc = CIFSSMBUnixQuerySymLink(xid, tcon, full_path, &target_path,
	cifs_sb->local_nls);

	kfree(full_path);
	out:
	if (rc != 0) {
	kfree(target_path);
	target_path = ERR_PTR(rc);
	}

	free_xid(xid);
	if (tlink)
	cifs_put_tlink(tlink);
	nd_set_link(nd, target_path);
	return NULL;
	}

	int
	cifs_symlink(struct inode inode, struct dentry direntry, const char *symname)
	{
	int rc = -EOPNOTSUPP;
	unsigned int xid;
	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
	struct tcon_link *tlink;
	struct cifs_tcon *pTcon;
	char *full_path = NULL;
	struct inode *newinode = NULL;

	xid = get_xid();

	tlink = cifs_sb_tlink(cifs_sb);
	if (IS_ERR(tlink)) {
	rc = PTR_ERR(tlink);
	goto symlink_exit;
	}
	pTcon = tlink_tcon(tlink);

	full_path = build_path_from_dentry(direntry);
	if (full_path == NULL) {
	rc = -ENOMEM;
	goto symlink_exit;
	}

	cifs_dbg(FYI, "Full path: %s\n", full_path);
	cifs_dbg(FYI, "symname is %s\n", symname);

	/* BB what if DFS and this volume is on different share? BB */
	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
	rc = CIFSCreateMFSymLink(xid, pTcon, full_path, symname,
	cifs_sb);
	else if (pTcon->unix_ext)
	rc = CIFSUnixCreateSymLink(xid, pTcon, full_path, symname,
	cifs_sb->local_nls);
	/* else
	rc = CIFSCreateReparseSymLink(xid, pTcon, fromName, toName,
	cifs_sb_target->local_nls); */

	if (rc == 0) {
	if (pTcon->unix_ext)
	rc = cifs_get_inode_info_unix(&newinode, full_path,
	inode->i_sb, xid);
	else
	rc = cifs_get_inode_info(&newinode, full_path, NULL,
	inode->i_sb, xid, NULL);

	if (rc != 0) {
	cifs_dbg(FYI, "Create symlink ok, getinodeinfo fail rc = %d\n",
	rc);
	} else {
	d_instantiate(direntry, newinode);
	}
	}
	symlink_exit:
	kfree(full_path);
	cifs_put_tlink(tlink);
	free_xid(xid);
	return rc;
	}

	void cifs_put_link(struct dentry direntry, struct nameidata nd, void *cookie)
	{
	char *p = nd_get_link(nd);
	if (!IS_ERR(p))
	kfree(p);
	}