path: root/fs/cifs/cifsacl.c

/*
 *   fs/cifs/cifsacl.c
 *
 *   Copyright (C) International Business Machines  Corp., 2007,2008
 *   Author(s): Steve French (sfrench@us.ibm.com)
 *
 *   Contains the routines for mapping CIFS/NTFS ACLs
 *
 *   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/slab.h>
#include "cifspdu.h"
#include "cifsglob.h"
#include "cifsacl.h"
#include "cifsproto.h"
#include "cifs_debug.h"


static struct cifs_wksid wksidarr[NUM_WK_SIDS] = {
	{{1, 0, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0} }, "null user"},
	{{1, 1, {0, 0, 0, 0, 0, 1}, {0, 0, 0, 0, 0} }, "nobody"},
	{{1, 1, {0, 0, 0, 0, 0, 5}, {__constant_cpu_to_le32(11), 0, 0, 0, 0} }, "net-users"},
	{{1, 1, {0, 0, 0, 0, 0, 5}, {__constant_cpu_to_le32(18), 0, 0, 0, 0} }, "sys"},
	{{1, 2, {0, 0, 0, 0, 0, 5}, {__constant_cpu_to_le32(32), __constant_cpu_to_le32(544), 0, 0, 0} }, "root"},
	{{1, 2, {0, 0, 0, 0, 0, 5}, {__constant_cpu_to_le32(32), __constant_cpu_to_le32(545), 0, 0, 0} }, "users"},
	{{1, 2, {0, 0, 0, 0, 0, 5}, {__constant_cpu_to_le32(32), __constant_cpu_to_le32(546), 0, 0, 0} }, "guest"} }
;


/* security id for everyone/world system group */
static const struct cifs_sid sid_everyone = {
	1, 1, {0, 0, 0, 0, 0, 1}, {0} };
/* security id for Authenticated Users system group */
static const struct cifs_sid sid_authusers = {
	1, 1, {0, 0, 0, 0, 0, 5}, {11} };
/* group users */
static const struct cifs_sid sid_user = {1, 2 , {0, 0, 0, 0, 0, 5}, {} };


int match_sid(struct cifs_sid *ctsid)
{
	int i, j;
	int num_subauth, num_sat, num_saw;
	struct cifs_sid *cwsid;

	if (!ctsid)
		return -1;

	for (i = 0; i < NUM_WK_SIDS; ++i) {
		cwsid = &(wksidarr[i].cifssid);

		/* compare the revision */
		if (ctsid->revision != cwsid->revision)
			continue;

		/* compare all of the six auth values */
		for (j = 0; j < 6; ++j) {
			if (ctsid->authority[j] != cwsid->authority[j])
				break;
		}
		if (j < 6)
			continue; /* all of the auth values did not match */

		/* compare all of the subauth values if any */
		num_sat = ctsid->num_subauth;
		num_saw = cwsid->num_subauth;
		num_subauth = num_sat < num_saw ? num_sat : num_saw;
		if (num_subauth) {
			for (j = 0; j < num_subauth; ++j) {
				if (ctsid->sub_auth[j] != cwsid->sub_auth[j])
					break;
			}
			if (j < num_subauth)
				continue; /* all sub_auth values do not match */
		}

		cFYI(1, "matching sid: %s\n", wksidarr[i].sidname);
		return 0; /* sids compare/match */
	}

	cFYI(1, "No matching sid");
	return -1;
}

/* if the two SIDs (roughly equivalent to a UUID for a user or group) are
   the same returns 1, if they do not match returns 0 */
int compare_sids(const struct cifs_sid *ctsid, const struct cifs_sid *cwsid)
{
	int i;
	int num_subauth, num_sat, num_saw;

	if ((!ctsid) || (!cwsid))
		return 0;

	/* compare the revision */
	if (ctsid->revision != cwsid->revision)
		return 0;

	/* compare all of the six auth values */
	for (i = 0; i < 6; ++i) {
		if (ctsid->authority[i] != cwsid->authority[i])
			return 0;
	}

	/* compare all of the subauth values if any */
	num_sat = ctsid->num_subauth;
	num_saw = cwsid->num_subauth;
	num_subauth = num_sat < num_saw ? num_sat : num_saw;
	if (num_subauth) {
		for (i = 0; i < num_subauth; ++i) {
			if (ctsid->sub_auth[i] != cwsid->sub_auth[i])
				return 0;
		}
	}

	return 1; /* sids compare/match */
}


/* copy ntsd, owner sid, and group sid from a security descriptor to another */
static void copy_sec_desc(const struct cifs_ntsd *pntsd,
				struct cifs_ntsd *pnntsd, __u32 sidsoffset)
{
	int i;

	struct cifs_sid *owner_sid_ptr, *group_sid_ptr;
	struct cifs_sid *nowner_sid_ptr, *ngroup_sid_ptr;

	/* copy security descriptor control portion */
	pnntsd->revision = pntsd->revision;
	pnntsd->type = pntsd->type;
	pnntsd->dacloffset = cpu_to_le32(sizeof(struct cifs_ntsd));
	pnntsd->sacloffset = 0;
	pnntsd->osidoffset = cpu_to_le32(sidsoffset);
	pnntsd->gsidoffset = cpu_to_le32(sidsoffset + sizeof(struct cifs_sid));

	/* copy owner sid */
	owner_sid_ptr = (struct cifs_sid *)((char *)pntsd +
				le32_to_cpu(pntsd->osidoffset));
	nowner_sid_ptr = (struct cifs_sid *)((char *)pnntsd + sidsoffset);

	nowner_sid_ptr->revision = owner_sid_ptr->revision;
	nowner_sid_ptr->num_subauth = owner_sid_ptr->num_subauth;
	for (i = 0; i < 6; i++)
		nowner_sid_ptr->authority[i] = owner_sid_ptr->authority[i];
	for (i = 0; i < 5; i++)
		nowner_sid_ptr->sub_auth[i] = owner_sid_ptr->sub_auth[i];

	/* copy group sid */
	group_sid_ptr = (struct cifs_sid *)((char *)pntsd +
				le32_to_cpu(pntsd->gsidoffset));
	ngroup_sid_ptr = (struct cifs_sid *)((char *)pnntsd + sidsoffset +
					sizeof(struct cifs_sid));

	ngroup_sid_ptr->revision = group_sid_ptr->revision;
	ngroup_sid_ptr->num_subauth = group_sid_ptr->num_subauth;
	for (i = 0; i < 6; i++)
		ngroup_sid_ptr->authority[i] = group_sid_ptr->authority[i];
	for (i = 0; i < 5; i++)
		ngroup_sid_ptr->sub_auth[i] = group_sid_ptr->sub_auth[i];

	return;
}


/*
   change posix mode to reflect permissions
   pmode is the existing mode (we only want to overwrite part of this
   bits to set can be: S_IRWXU, S_IRWXG or S_IRWXO ie 00700 or 00070 or 00007
*/
static void access_flags_to_mode(__le32 ace_flags, int type, umode_t *pmode,
				 umode_t *pbits_to_set)
{
	__u32 flags = le32_to_cpu(ace_flags);
	/* the order of ACEs is important.  The canonical order is to begin with
	   DENY entries followed by ALLOW, otherwise an allow entry could be
	   encountered first, making the subsequent deny entry like "dead code"
	   which would be superflous since Windows stops when a match is made
	   for the operation you are trying to perform for your user */

	/* For deny ACEs we change the mask so that subsequent allow access
	   control entries do not turn on the bits we are denying */
	if (type == ACCESS_DENIED) {
		if (flags & GENERIC_ALL)
			*pbits_to_set &= ~S_IRWXUGO;

		if ((flags & GENERIC_WRITE) ||
			((flags & FILE_WRITE_RIGHTS) == FILE_WRITE_RIGHTS))
			*pbits_to_set &= ~S_IWUGO;
		if ((flags & GENERIC_READ) ||
			((flags & FILE_READ_RIGHTS) == FILE_READ_RIGHTS))
			*pbits_to_set &= ~S_IRUGO;
		if ((flags & GENERIC_EXECUTE) ||
			((flags & FILE_EXEC_RIGHTS) == FILE_EXEC_RIGHTS))
			*pbits_to_set &= ~S_IXUGO;
		return;
	} else if (type != ACCESS_ALLOWED) {
		cERROR(1, "unknown access control type %d", type);
		return;
	}
	/* else ACCESS_ALLOWED type */

	if (flags & GENERIC_ALL) {
		*pmode |= (S_IRWXUGO & (*pbits_to_set));
		cFYI(DBG2, "all perms");
		return;
	}
	if ((flags & GENERIC_WRITE) ||
			((flags & FILE_WRITE_RIGHTS) == FILE_WRITE_RIGHTS))
		*pmode |= (S_IWUGO & (*pbits_to_set));
	if ((flags & GENERIC_READ) ||
			((flags & FILE_READ_RIGHTS) == FILE_READ_RIGHTS))
		*pmode |= (S_IRUGO & (*pbits_to_set));
	if ((flags & GENERIC_EXECUTE) ||
			((flags & FILE_EXEC_RIGHTS) == FILE_EXEC_RIGHTS))
		*pmode |= (S_IXUGO & (*pbits_to_set));

	cFYI(DBG2, "access flags 0x%x mode now 0x%x", flags, *pmode);
	return;
}

/*
   Generate access flags to reflect permissions mode is the existing mode.
   This function is called for every ACE in the DACL whose SID matches
   with either owner or group or everyone.
*/

static void mode_to_access_flags(umode_t mode, umode_t bits_to_use,
				__u32 *pace_flags)
{
	/* reset access mask */
	*pace_flags = 0x0;

	/* bits to use are either S_IRWXU or S_IRWXG or S_IRWXO */
	mode &= bits_to_use;

	/* check for R/W/X UGO since we do not know whose flags
	   is this but we have cleared all the bits sans RWX for
	   either user or group or other as per bits_to_use */
	if (mode & S_IRUGO)
		*pace_flags |= SET_FILE_READ_RIGHTS;
	if (mode & S_IWUGO)
		*pace_flags |= SET_FILE_WRITE_RIGHTS;
	if (mode & S_IXUGO)
		*pace_flags |= SET_FILE_EXEC_RIGHTS;

	cFYI(DBG2, "mode: 0x%x, access flags now 0x%x", mode, *pace_flags);
	return;
}

static __u16 fill_ace_for_sid(struct cifs_ace *pntace,
			const struct cifs_sid *psid, __u64 nmode, umode_t bits)
{
	int i;
	__u16 size = 0;
	__u32 access_req = 0;

	pntace->type = ACCESS_ALLOWED;
	pntace->flags = 0x0;
	mode_to_access_flags(nmode, bits, &access_req);
	if (!access_req)
		access_req = SET_MINIMUM_RIGHTS;
	pntace->access_req = cpu_to_le32(access_req);

	pntace->sid.revision = psid->revision;
	pntace->sid.num_subauth = psid->num_subauth;
	for (i = 0; i < 6; i++)
		pntace->sid.authority[i] = psid->authority[i];
	for (i = 0; i < psid->num_subauth; i++)
		pntace->sid.sub_auth[i] = psid->sub_auth[i];

	size = 1 + 1 + 2 + 4 + 1 + 1 + 6 + (psid->num_subauth * 4);
	pntace->size = cpu_to_le16(size);

	return size;
}


#ifdef CONFIG_CIFS_DEBUG2
static void dump_ace(struct cifs_ace *pace, char *end_of_acl)
{
	int num_subauth;

	/* validate that we do not go past end of acl */

	if (le16_to_cpu(pace->size) < 16) {
		cERROR(1, "ACE too small %d", le16_to_cpu(pace->size));
		return;
	}

	if (end_of_acl < (char *)pace + le16_to_cpu(pace->size)) {
		cERROR(1, "ACL too small to parse ACE");
		return;
	}

	num_subauth = pace->sid.num_subauth;
	if (num_subauth) {
		int i;
		cFYI(1, "ACE revision %d num_auth %d type %d flags %d size %d",
			pace->sid.revision, pace->sid.num_subauth, pace->type,
			pace->flags, le16_to_cpu(pace->size));
		for (i = 0; i < num_subauth; ++i) {
			cFYI(1, "ACE sub_auth[%d]: 0x%x", i,
				le32_to_cpu(pace->sid.sub_auth[i]));
		}

		/* BB add length check to make sure that we do not have huge
			num auths and therefore go off the end */
	}

	return;
}
#endif


static void parse_dacl(struct cifs_acl *pdacl, char *end_of_acl,
		       struct cifs_sid *pownersid, struct cifs_sid *pgrpsid,
		       struct cifs_fattr *fattr)
{
	int i;
	int num_aces = 0;
	int acl_size;
	char *acl_base;
	struct cifs_ace **ppace;

	/* BB need to add parm so we can store the SID BB */

	if (!pdacl) {
		/* no DACL in the security descriptor, set
		   all the permissions for user/group/other */
		fattr->cf_mode |= S_IRWXUGO;
		return;
	}

	/* validate that we do not go past end of acl */
	if (end_of_acl < (char *)pdacl + le16_to_cpu(pdacl->size)) {
		cERROR(1, "ACL too small to parse DACL");
		return;
	}

	cFYI(DBG2, "DACL revision %d size %d num aces %d",
		le16_to_cpu(pdacl->revision), le16_to_cpu(pdacl->size),
		le32_to_cpu(pdacl->num_aces));

	/* reset rwx permissions for user/group/other.
	   Also, if num_aces is 0 i.e. DACL has no ACEs,
	   user/group/other have no permissions */
	fattr->cf_mode &= ~(S_IRWXUGO);

	acl_base = (char *)pdacl;
	acl_size = sizeof(struct cifs_acl);

	num_aces = le32_to_cpu(pdacl->num_aces);
	if (num_aces  > 0) {
		umode_t user_mask = S_IRWXU;
		umode_t group_mask = S_IRWXG;
		umode_t other_mask = S_IRWXU | S_IRWXG | S_IRWXO;

		ppace = kmalloc(num_aces * sizeof(struct cifs_ace *),
				GFP_KERNEL);

		for (i = 0; i < num_aces; ++i) {
			ppace[i] = (struct cifs_ace *) (acl_base + acl_size);
#ifdef CONFIG_CIFS_DEBUG2
			dump_ace(ppace[i], end_of_acl);
#endif
			if (compare_sids(&(ppace[i]->sid), pownersid))
				access_flags_to_mode(ppace[i]->access_req,
						     ppace[i]->type,
						     &fattr->cf_mode,
						     &user_mask);
			if (compare_sids(&(ppace[i]->sid), pgrpsid))
				access_flags_to_mode(ppace[i]->access_req,
						     ppace[i]->type,
						     &fattr->cf_mode,
						     &group_mask);
			if (compare_sids(&(ppace[i]->sid), &sid_everyone))
				access_flags_to_mode(ppace[i]->access_req,
						     ppace[i]->type,
						     &fattr->cf_mode,
						     &other_mask);
			if (compare_sids(&(ppace[i]->sid), &sid_authusers))
				access_flags_to_mode(ppace[i]->access_req,
						     ppace[i]->type,
						     &fattr->cf_mode,
						     &other_mask);


/*			memcpy((void *)(&(cifscred->aces[i])),
				(void *)ppace[i],
				sizeof(struct cifs_ace)); */

			acl_base = (char *)ppace[i];
			acl_size = le16_to_cpu(ppace[i]->size);
		}

		kfree(ppace);
	}

	return;
}


static int set_chmod_dacl(struct cifs_acl *pndacl, struct cifs_sid *pownersid,
			struct cifs_sid *pgrpsid, __u64 nmode)
{
	u16 size = 0;
	struct cifs_acl *pnndacl;

	pnndacl = (struct cifs_acl *)((char *)pndacl + sizeof(struct cifs_acl));

	size += fill_ace_for_sid((struct cifs_ace *) ((char *)pnndacl + size),
					pownersid, nmode, S_IRWXU);
	size += fill_ace_for_sid((struct cifs_ace *)((char *)pnndacl + size),
					pgrpsid, nmode, S_IRWXG);
	size += fill_ace_for_sid((struct cifs_ace *)((char *)pnndacl + size),
					 &sid_everyone, nmode, S_IRWXO);

	pndacl->size = cpu_to_le16(size + sizeof(struct cifs_acl));
	pndacl->num_aces = cpu_to_le32(3);

	return 0;
}


static int parse_sid(struct cifs_sid *psid, char *end_of_acl)
{
	/* BB need to add parm so we can store the SID BB */

	/* validate that we do not go past end of ACL - sid must be at least 8
	   bytes long (assuming no sub-auths - e.g. the null SID */
	if (end_of_acl < (char *)psid + 8) {
		cERROR(1, "ACL too small to parse SID %p", psid);
		return -EINVAL;
	}

	if (psid->num_subauth) {
#ifdef CONFIG_CIFS_DEBUG2
		int i;
		cFYI(1, "SID revision %d num_auth %d",
			psid->revision, psid->num_subauth);

		for (i = 0; i < psid->num_subauth; i++) {
			cFYI(1, "SID sub_auth[%d]: 0x%x ", i,
				le32_to_cpu(psid->sub_auth[i]));
		}

		/* BB add length check to make sure that we do not have huge
			num auths and therefore go off the end */
		cFYI(1, "RID 0x%x",
			le32_to_cpu(psid->sub_auth[psid->num_subauth-1]));
#endif
	}

	return 0;
}


/* Convert CIFS ACL to POSIX form */
static int parse_sec_desc(struct cifs_ntsd *pntsd, int acl_len,
			  struct cifs_fattr *fattr)
{
	int rc;
	struct cifs_sid *owner_sid_ptr, *group_sid_ptr;
	struct cifs_acl *dacl_ptr; /* no need for SACL ptr */
	char *end_of_acl = ((char *)pntsd) + acl_len;
	__u32 dacloffset;

	if (pntsd == NULL)
		return -EIO;

	owner_sid_ptr = (struct cifs_sid *)((char *)pntsd +
				le32_to_cpu(pntsd->osidoffset));
	group_sid_ptr = (struct cifs_sid *)((char *)pntsd +
				le32_to_cpu(pntsd->gsidoffset));
	dacloffset = le32_to_cpu(pntsd->dacloffset);
	dacl_ptr = (struct cifs_acl *)((char *)pntsd + dacloffset);
	cFYI(DBG2, "revision %d type 0x%x ooffset 0x%x goffset 0x%x "
		 "sacloffset 0x%x dacloffset 0x%x",
		 pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset),
		 le32_to_cpu(pntsd->gsidoffset),
		 le32_to_cpu(pntsd->sacloffset), dacloffset);
/*	cifs_dump_mem("owner_sid: ", owner_sid_ptr, 64); */
	rc = parse_sid(owner_sid_ptr, end_of_acl);
	if (rc)
		return rc;

	rc = parse_sid(group_sid_ptr, end_of_acl);
	if (rc)
		return rc;

	if (dacloffset)
		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
			   group_sid_ptr, fattr);
	else
		cFYI(1, "no ACL"); /* BB grant all or default perms? */

/*	cifscred->uid = owner_sid_ptr->rid;
	cifscred->gid = group_sid_ptr->rid;
	memcpy((void *)(&(cifscred->osid)), (void *)owner_sid_ptr,
			sizeof(struct cifs_sid));
	memcpy((void *)(&(cifscred->gsid)), (void *)group_sid_ptr,
			sizeof(struct cifs_sid)); */

	return 0;
}


/* Convert permission bits from mode to equivalent CIFS ACL */
static int build_sec_desc(struct cifs_ntsd *pntsd, struct cifs_ntsd *pnntsd,
				struct inode *inode, __u64 nmode)
{
	int rc = 0;
	__u32 dacloffset;
	__u32 ndacloffset;
	__u32 sidsoffset;
	struct cifs_sid *owner_sid_ptr, *group_sid_ptr;
	struct cifs_acl *dacl_ptr = NULL;  /* no need for SACL ptr */
	struct cifs_acl *ndacl_ptr = NULL; /* no need for SACL ptr */

	if ((inode == NULL) || (pntsd == NULL) || (pnntsd == NULL))
		return -EIO;

	owner_sid_ptr = (struct cifs_sid *)((char *)pntsd +
				le32_to_cpu(pntsd->osidoffset));
	group_sid_ptr = (struct cifs_sid *)((char *)pntsd +
				le32_to_cpu(pntsd->gsidoffset));

	dacloffset = le32_to_cpu(pntsd->dacloffset);
	dacl_ptr = (struct cifs_acl *)((char *)pntsd + dacloffset);

	ndacloffset = sizeof(struct cifs_ntsd);
	ndacl_ptr = (struct cifs_acl *)((char *)pnntsd + ndacloffset);
	ndacl_ptr->revision = dacl_ptr->revision;
	ndacl_ptr->size = 0;
	ndacl_ptr->num_aces = 0;

	rc = set_chmod_dacl(ndacl_ptr, owner_sid_ptr, group_sid_ptr, nmode);

	sidsoffset = ndacloffset + le16_to_cpu(ndacl_ptr->size);

	/* copy security descriptor control portion and owner and group sid */
	copy_sec_desc(pntsd, pnntsd, sidsoffset);

	return rc;
}

static struct cifs_ntsd *get_cifs_acl_by_fid(struct cifs_sb_info *cifs_sb,
		__u16 fid, u32 *pacllen)
{
	struct cifs_ntsd *pntsd = NULL;
	int xid, rc;
	struct tcon_link *tlink = cifs_sb_tlink(cifs_sb);

	if (IS_ERR(tlink))
		return ERR_CAST(tlink);

	xid = GetXid();
	rc = CIFSSMBGetCIFSACL(xid, tlink_tcon(tlink), fid, &pntsd, pacllen);
	FreeXid(xid);

	cifs_put_tlink(tlink);

	cFYI(1, "%s: rc = %d ACL len %d", __func__, rc, *pacllen);
	if (rc)
		return ERR_PTR(rc);
	return pntsd;
}

static struct cifs_ntsd *get_cifs_acl_by_path(struct cifs_sb_info *cifs_sb,
		const char *path, u32 *pacllen)
{
	struct cifs_ntsd *pntsd = NULL;
	int oplock = 0;
	int xid, rc;
	__u16 fid;
	struct cifsTconInfo *tcon;
	struct tcon_link *tlink = cifs_sb_tlink(cifs_sb);

	if (IS_ERR(tlink))
		return ERR_CAST(tlink);

	tcon = tlink_tcon(tlink);
	xid = GetXid();

	rc = CIFSSMBOpen(xid, tcon, path, FILE_OPEN, READ_CONTROL, 0,
			 &fid, &oplock, NULL, cifs_sb->local_nls,
			 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
	if (!rc) {
		rc = CIFSSMBGetCIFSACL(xid, tcon, fid, &pntsd, pacllen);
		CIFSSMBClose(xid, tcon, fid);
	}

	cifs_put_tlink(tlink);
	FreeXid(xid);

	cFYI(1, "%s: rc = %d ACL len %d", __func__, rc, *pacllen);
	if (rc)
		return ERR_PTR(rc);
	return pntsd;
}

/* Retrieve an ACL from the server */
struct cifs_ntsd *get_cifs_acl(struct cifs_sb_info *cifs_sb,
				      struct inode *inode, const char *path,
				      u32 *pacllen)
{
	struct cifs_ntsd *pntsd = NULL;
	struct cifsFileInfo *open_file = NULL;

	if (inode)
		open_file = find_readable_file(CIFS_I(inode), true);
	if (!open_file)
		return get_cifs_acl_by_path(cifs_sb, path, pacllen);

	pntsd = get_cifs_acl_by_fid(cifs_sb, open_file->netfid, pacllen);
	cifsFileInfo_put(open_file);
	return pntsd;
}

static int set_cifs_acl_by_fid(struct cifs_sb_info *cifs_sb, __u16 fid,
		struct cifs_ntsd *pnntsd, u32 acllen)
{
	int xid, rc;
	struct tcon_link *tlink = cifs_sb_tlink(cifs_sb);

	if (IS_ERR(tlink))
		return PTR_ERR(tlink);

	xid = GetXid();
	rc = CIFSSMBSetCIFSACL(xid, tlink_tcon(tlink), fid, pnntsd, acllen);
	FreeXid(xid);
	cifs_put_tlink(tlink);

	cFYI(DBG2, "SetCIFSACL rc = %d", rc);
	return rc;
}

static int set_cifs_acl_by_path(struct cifs_sb_info *cifs_sb, const char *path,
		struct cifs_ntsd *pnntsd, u32 acllen)
{
	int oplock = 0;
	int xid, rc;
	__u16 fid;
	struct cifsTconInfo *tcon;
	struct tcon_link *tlink = cifs_sb_tlink(cifs_sb);

	if (IS_ERR(tlink))
		return PTR_ERR(tlink);

	tcon = tlink_tcon(tlink);
	xid = GetXid();

	rc = CIFSSMBOpen(xid, tcon, path, FILE_OPEN, WRITE_DAC, 0,
			 &fid, &oplock, NULL, cifs_sb->local_nls,
			 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
	if (rc) {
		cERROR(1, "Unable to open file to set ACL");
		goto out;
	}

	rc = CIFSSMBSetCIFSACL(xid, tcon, fid, pnntsd, acllen);
	cFYI(DBG2, "SetCIFSACL rc = %d", rc);

	CIFSSMBClose(xid, tcon, fid);
out:
	FreeXid(xid);
	cifs_put_tlink(tlink);
	return rc;
}

/* Set an ACL on the server */
static int set_cifs_acl(struct cifs_ntsd *pnntsd, __u32 acllen,
				struct inode *inode, const char *path)
{
	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
	struct cifsFileInfo *open_file;
	int rc;

	cFYI(DBG2, "set ACL for %s from mode 0x%x", path, inode->i_mode);

	open_file = find_readable_file(CIFS_I(inode), true);
	if (!open_file)
		return set_cifs_acl_by_path(cifs_sb, path, pnntsd, acllen);

	rc = set_cifs_acl_by_fid(cifs_sb, open_file->netfid, pnntsd, acllen);
	cifsFileInfo_put(open_file);
	return rc;
}

/* Translate the CIFS ACL (simlar to NTFS ACL) for a file into mode bits */
int
cifs_acl_to_fattr(struct cifs_sb_info *cifs_sb, struct cifs_fattr *fattr,
		  struct inode *inode, const char *path, const __u16 *pfid)
{
	struct cifs_ntsd *pntsd = NULL;
	u32 acllen = 0;
	int rc = 0;

	cFYI(DBG2, "converting ACL to mode for %s", path);

	if (pfid)
		pntsd = get_cifs_acl_by_fid(cifs_sb, *pfid, &acllen);
	else
		pntsd = get_cifs_acl(cifs_sb, inode, path, &acllen);

	/* if we can retrieve the ACL, now parse Access Control Entries, ACEs */
	if (IS_ERR(pntsd)) {
		rc = PTR_ERR(pntsd);
		cERROR(1, "%s: error %d getting sec desc", __func__, rc);
	} else {
		rc = parse_sec_desc(pntsd, acllen, fattr);
		kfree(pntsd);
		if (rc)
			cERROR(1, "parse sec desc failed rc = %d", rc);
	}

	return rc;
}

/* Convert mode bits to an ACL so we can update the ACL on the server */
int mode_to_cifs_acl(struct inode *inode, const char *path, __u64 nmode)
{
	int rc = 0;
	__u32 secdesclen = 0;
	struct cifs_ntsd *pntsd = NULL; /* acl obtained from server */
	struct cifs_ntsd *pnntsd = NULL; /* modified acl to be sent to server */

	cFYI(DBG2, "set ACL from mode for %s", path);

	/* Get the security descriptor */
	pntsd = get_cifs_acl(CIFS_SB(inode->i_sb), inode, path, &secdesclen);

	/* Add three ACEs for owner, group, everyone getting rid of
	   other ACEs as chmod disables ACEs and set the security descriptor */

	if (IS_ERR(pntsd)) {
		rc = PTR_ERR(pntsd);
		cERROR(1, "%s: error %d getting sec desc", __func__, rc);
	} else {
		/* allocate memory for the smb header,
		   set security descriptor request security descriptor
		   parameters, and secuirty descriptor itself */

		secdesclen = secdesclen < DEFSECDESCLEN ?
					DEFSECDESCLEN : secdesclen;
		pnntsd = kmalloc(secdesclen, GFP_KERNEL);
		if (!pnntsd) {
			cERROR(1, "Unable to allocate security descriptor");
			kfree(pntsd);
			return -ENOMEM;
		}

		rc = build_sec_desc(pntsd, pnntsd, inode, nmode);

		cFYI(DBG2, "build_sec_desc rc: %d", rc);

		if (!rc) {
			/* Set the security descriptor */
			rc = set_cifs_acl(pnntsd, secdesclen, inode, path);
			cFYI(DBG2, "set_cifs_acl rc: %d", rc);
		}

		kfree(pnntsd);
		kfree(pntsd);
	}

	return rc;
}