SLOB: fix bogus ksize calculation fix

[linux-2.6/zen-sources.git] / fs / xfs / xfs_acl.c

/*
 * Copyright (c) 2001-2002,2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * 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.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_bit.h"
#include "xfs_inum.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_acl.h"
#include "xfs_attr.h"
#include "xfs_vnodeops.h"

#include <linux/capability.h>
#include <linux/posix_acl_xattr.h>

STATIC int      xfs_acl_setmode(struct inode *, xfs_acl_t *, int *);
STATIC void     xfs_acl_filter_mode(mode_t, xfs_acl_t *);
STATIC void     xfs_acl_get_endian(xfs_acl_t *);
STATIC int      xfs_acl_access(uid_t, gid_t, xfs_acl_t *, mode_t, cred_t *);
STATIC int      xfs_acl_invalid(xfs_acl_t *);
STATIC void     xfs_acl_sync_mode(mode_t, xfs_acl_t *);
STATIC void     xfs_acl_get_attr(struct inode *, xfs_acl_t *, int, int, int *);
STATIC void     xfs_acl_set_attr(struct inode *, xfs_acl_t *, int, int *);
STATIC int      xfs_acl_allow_set(struct inode *, int);

kmem_zone_t *xfs_acl_zone;


/*
 * Test for existence of access ACL attribute as efficiently as possible.
 */
int
xfs_acl_vhasacl_access(
        struct inode    *vp)
{
        int             error;

        xfs_acl_get_attr(vp, NULL, _ACL_TYPE_ACCESS, ATTR_KERNOVAL, &error);
        return (error == 0);
}

/*
 * Test for existence of default ACL attribute as efficiently as possible.
 */
int
xfs_acl_vhasacl_default(
        struct inode    *vp)
{
        int             error;

        if (!S_ISDIR(vp->i_mode))
                return 0;
        xfs_acl_get_attr(vp, NULL, _ACL_TYPE_DEFAULT, ATTR_KERNOVAL, &error);
        return (error == 0);
}

/*
 * Convert from extended attribute representation to in-memory for XFS.
 */
STATIC int
posix_acl_xattr_to_xfs(
        posix_acl_xattr_header  *src,
        size_t                  size,
        xfs_acl_t               *dest)
{
        posix_acl_xattr_entry   *src_entry;
        xfs_acl_entry_t         *dest_entry;
        int                     n;

        if (!src || !dest)
                return EINVAL;

        if (size < sizeof(posix_acl_xattr_header))
                return EINVAL;

        if (src->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
                return EOPNOTSUPP;

        memset(dest, 0, sizeof(xfs_acl_t));
        dest->acl_cnt = posix_acl_xattr_count(size);
        if (dest->acl_cnt < 0 || dest->acl_cnt > XFS_ACL_MAX_ENTRIES)
                return EINVAL;

        /*
         * acl_set_file(3) may request that we set default ACLs with
         * zero length -- defend (gracefully) against that here.
         */
        if (!dest->acl_cnt)
                return 0;

        src_entry = (posix_acl_xattr_entry *)((char *)src + sizeof(*src));
        dest_entry = &dest->acl_entry[0];

        for (n = 0; n < dest->acl_cnt; n++, src_entry++, dest_entry++) {
                dest_entry->ae_perm = le16_to_cpu(src_entry->e_perm);
                if (_ACL_PERM_INVALID(dest_entry->ae_perm))
                        return EINVAL;
                dest_entry->ae_tag  = le16_to_cpu(src_entry->e_tag);
                switch(dest_entry->ae_tag) {
                case ACL_USER:
                case ACL_GROUP:
                        dest_entry->ae_id = le32_to_cpu(src_entry->e_id);
                        break;
                case ACL_USER_OBJ:
                case ACL_GROUP_OBJ:
                case ACL_MASK:
                case ACL_OTHER:
                        dest_entry->ae_id = ACL_UNDEFINED_ID;
                        break;
                default:
                        return EINVAL;
                }
        }
        if (xfs_acl_invalid(dest))
                return EINVAL;

        return 0;
}

/*
 * Comparison function called from xfs_sort().
 * Primary key is ae_tag, secondary key is ae_id.
 */
STATIC int
xfs_acl_entry_compare(
        const void      *va,
        const void      *vb)
{
        xfs_acl_entry_t *a = (xfs_acl_entry_t *)va,
                        *b = (xfs_acl_entry_t *)vb;

        if (a->ae_tag == b->ae_tag)
                return (a->ae_id - b->ae_id);
        return (a->ae_tag - b->ae_tag);
}

/*
 * Convert from in-memory XFS to extended attribute representation.
 */
STATIC int
posix_acl_xfs_to_xattr(
        xfs_acl_t               *src,
        posix_acl_xattr_header  *dest,
        size_t                  size)
{
        int                     n;
        size_t                  new_size = posix_acl_xattr_size(src->acl_cnt);
        posix_acl_xattr_entry   *dest_entry;
        xfs_acl_entry_t         *src_entry;

        if (size < new_size)
                return -ERANGE;

        /* Need to sort src XFS ACL by <ae_tag,ae_id> */
        xfs_sort(src->acl_entry, src->acl_cnt, sizeof(src->acl_entry[0]),
                 xfs_acl_entry_compare);

        dest->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
        dest_entry = &dest->a_entries[0];
        src_entry = &src->acl_entry[0];
        for (n = 0; n < src->acl_cnt; n++, dest_entry++, src_entry++) {
                dest_entry->e_perm = cpu_to_le16(src_entry->ae_perm);
                if (_ACL_PERM_INVALID(src_entry->ae_perm))
                        return -EINVAL;
                dest_entry->e_tag  = cpu_to_le16(src_entry->ae_tag);
                switch (src_entry->ae_tag) {
                case ACL_USER:
                case ACL_GROUP:
                        dest_entry->e_id = cpu_to_le32(src_entry->ae_id);
                                break;
                case ACL_USER_OBJ:
                case ACL_GROUP_OBJ:
                case ACL_MASK:
                case ACL_OTHER:
                        dest_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
                        break;
                default:
                        return -EINVAL;
                }
        }
        return new_size;
}

int
xfs_acl_vget(
        struct inode    *vp,
        void            *acl,
        size_t          size,
        int             kind)
{
        int                     error;
        xfs_acl_t               *xfs_acl = NULL;
        posix_acl_xattr_header  *ext_acl = acl;
        int                     flags = 0;

        if(size) {
                if (!(_ACL_ALLOC(xfs_acl))) {
                        error = ENOMEM;
                        goto out;
                }
                memset(xfs_acl, 0, sizeof(xfs_acl_t));
        } else
                flags = ATTR_KERNOVAL;

        xfs_acl_get_attr(vp, xfs_acl, kind, flags, &error);
        if (error)
                goto out;

        if (!size) {
                error = -posix_acl_xattr_size(XFS_ACL_MAX_ENTRIES);
        } else {
                if (xfs_acl_invalid(xfs_acl)) {
                        error = EINVAL;
                        goto out;
                }
                if (kind == _ACL_TYPE_ACCESS)
                        xfs_acl_sync_mode(XFS_I(vp)->i_d.di_mode, xfs_acl);
                error = -posix_acl_xfs_to_xattr(xfs_acl, ext_acl, size);
        }
out:
        if(xfs_acl)
                _ACL_FREE(xfs_acl);
        return -error;
}

int
xfs_acl_vremove(
        struct inode    *vp,
        int             kind)
{
        int             error;

        error = xfs_acl_allow_set(vp, kind);
        if (!error) {
                error = xfs_attr_remove(XFS_I(vp),
                                                kind == _ACL_TYPE_DEFAULT?
                                                SGI_ACL_DEFAULT: SGI_ACL_FILE,
                                                ATTR_ROOT);
                if (error == ENOATTR)
                        error = 0;      /* 'scool */
        }
        return -error;
}

int
xfs_acl_vset(
        struct inode            *vp,
        void                    *acl,
        size_t                  size,
        int                     kind)
{
        posix_acl_xattr_header  *ext_acl = acl;
        xfs_acl_t               *xfs_acl;
        int                     error;
        int                     basicperms = 0; /* more than std unix perms? */

        if (!acl)
                return -EINVAL;

        if (!(_ACL_ALLOC(xfs_acl)))
                return -ENOMEM;

        error = posix_acl_xattr_to_xfs(ext_acl, size, xfs_acl);
        if (error) {
                _ACL_FREE(xfs_acl);
                return -error;
        }
        if (!xfs_acl->acl_cnt) {
                _ACL_FREE(xfs_acl);
                return 0;
        }

        error = xfs_acl_allow_set(vp, kind);

        /* Incoming ACL exists, set file mode based on its value */
        if (!error && kind == _ACL_TYPE_ACCESS)
                error = xfs_acl_setmode(vp, xfs_acl, &basicperms);

        if (error)
                goto out;

        /*
         * If we have more than std unix permissions, set up the actual attr.
         * Otherwise, delete any existing attr.  This prevents us from
         * having actual attrs for permissions that can be stored in the
         * standard permission bits.
         */
        if (!basicperms) {
                xfs_acl_set_attr(vp, xfs_acl, kind, &error);
        } else {
                error = -xfs_acl_vremove(vp, _ACL_TYPE_ACCESS);
        }

out:
        _ACL_FREE(xfs_acl);
        return -error;
}

int
xfs_acl_iaccess(
        xfs_inode_t     *ip,
        mode_t          mode,
        cred_t          *cr)
{
        xfs_acl_t       *acl;
        int             rval;
        struct xfs_name acl_name = {SGI_ACL_FILE, SGI_ACL_FILE_SIZE};

        if (!(_ACL_ALLOC(acl)))
                return -1;

        /* If the file has no ACL return -1. */
        rval = sizeof(xfs_acl_t);
        if (xfs_attr_fetch(ip, &acl_name, (char *)acl, &rval, ATTR_ROOT)) {
                _ACL_FREE(acl);
                return -1;
        }
        xfs_acl_get_endian(acl);

        /* If the file has an empty ACL return -1. */
        if (acl->acl_cnt == XFS_ACL_NOT_PRESENT) {
                _ACL_FREE(acl);
                return -1;
        }

        /* Synchronize ACL with mode bits */
        xfs_acl_sync_mode(ip->i_d.di_mode, acl);

        rval = xfs_acl_access(ip->i_d.di_uid, ip->i_d.di_gid, acl, mode, cr);
        _ACL_FREE(acl);
        return rval;
}

STATIC int
xfs_acl_allow_set(
        struct inode    *vp,
        int             kind)
{
        if (vp->i_flags & (S_IMMUTABLE|S_APPEND))
                return EPERM;
        if (kind == _ACL_TYPE_DEFAULT && !S_ISDIR(vp->i_mode))
                return ENOTDIR;
        if (vp->i_sb->s_flags & MS_RDONLY)
                return EROFS;
        if (XFS_I(vp)->i_d.di_uid != current->fsuid && !capable(CAP_FOWNER))
                return EPERM;
        return 0;
}

/*
 * Note: cr is only used here for the capability check if the ACL test fails.
 *       It is not used to find out the credentials uid or groups etc, as was
 *       done in IRIX. It is assumed that the uid and groups for the current
 *       thread are taken from "current" instead of the cr parameter.
 */
STATIC int
xfs_acl_access(
        uid_t           fuid,
        gid_t           fgid,
        xfs_acl_t       *fap,
        mode_t          md,
        cred_t          *cr)
{
        xfs_acl_entry_t matched;
        int             i, allows;
        int             maskallows = -1;        /* true, but not 1, either */
        int             seen_userobj = 0;

        matched.ae_tag = 0;     /* Invalid type */
        matched.ae_perm = 0;

        for (i = 0; i < fap->acl_cnt; i++) {
                /*
                 * Break out if we've got a user_obj entry or
                 * a user entry and the mask (and have processed USER_OBJ)
                 */
                if (matched.ae_tag == ACL_USER_OBJ)
                        break;
                if (matched.ae_tag == ACL_USER) {
                        if (maskallows != -1 && seen_userobj)
                                break;
                        if (fap->acl_entry[i].ae_tag != ACL_MASK &&
                            fap->acl_entry[i].ae_tag != ACL_USER_OBJ)
                                continue;
                }
                /* True if this entry allows the requested access */
                allows = ((fap->acl_entry[i].ae_perm & md) == md);

                switch (fap->acl_entry[i].ae_tag) {
                case ACL_USER_OBJ:
                        seen_userobj = 1;
                        if (fuid != current->fsuid)
                                continue;
                        matched.ae_tag = ACL_USER_OBJ;
                        matched.ae_perm = allows;
                        break;
                case ACL_USER:
                        if (fap->acl_entry[i].ae_id != current->fsuid)
                                continue;
                        matched.ae_tag = ACL_USER;
                        matched.ae_perm = allows;
                        break;
                case ACL_GROUP_OBJ:
                        if ((matched.ae_tag == ACL_GROUP_OBJ ||
                            matched.ae_tag == ACL_GROUP) && !allows)
                                continue;
                        if (!in_group_p(fgid))
                                continue;
                        matched.ae_tag = ACL_GROUP_OBJ;
                        matched.ae_perm = allows;
                        break;
                case ACL_GROUP:
                        if ((matched.ae_tag == ACL_GROUP_OBJ ||
                            matched.ae_tag == ACL_GROUP) && !allows)
                                continue;
                        if (!in_group_p(fap->acl_entry[i].ae_id))
                                continue;
                        matched.ae_tag = ACL_GROUP;
                        matched.ae_perm = allows;
                        break;
                case ACL_MASK:
                        maskallows = allows;
                        break;
                case ACL_OTHER:
                        if (matched.ae_tag != 0)
                                continue;
                        matched.ae_tag = ACL_OTHER;
                        matched.ae_perm = allows;
                        break;
                }
        }
        /*
         * First possibility is that no matched entry allows access.
         * The capability to override DAC may exist, so check for it.
         */
        switch (matched.ae_tag) {
        case ACL_OTHER:
        case ACL_USER_OBJ:
                if (matched.ae_perm)
                        return 0;
                break;
        case ACL_USER:
        case ACL_GROUP_OBJ:
        case ACL_GROUP:
                if (maskallows && matched.ae_perm)
                        return 0;
                break;
        case 0:
                break;
        }

        /* EACCES tells generic_permission to check for capability overrides */
        return EACCES;
}

/*
 * ACL validity checker.
 *   This acl validation routine checks each ACL entry read in makes sense.
 */
STATIC int
xfs_acl_invalid(
        xfs_acl_t       *aclp)
{
        xfs_acl_entry_t *entry, *e;
        int             user = 0, group = 0, other = 0, mask = 0;
        int             mask_required = 0;
        int             i, j;

        if (!aclp)
                goto acl_invalid;

        if (aclp->acl_cnt > XFS_ACL_MAX_ENTRIES)
                goto acl_invalid;

        for (i = 0; i < aclp->acl_cnt; i++) {
                entry = &aclp->acl_entry[i];
                switch (entry->ae_tag) {
                case ACL_USER_OBJ:
                        if (user++)
                                goto acl_invalid;
                        break;
                case ACL_GROUP_OBJ:
                        if (group++)
                                goto acl_invalid;
                        break;
                case ACL_OTHER:
                        if (other++)
                                goto acl_invalid;
                        break;
                case ACL_USER:
                case ACL_GROUP:
                        for (j = i + 1; j < aclp->acl_cnt; j++) {
                                e = &aclp->acl_entry[j];
                                if (e->ae_id == entry->ae_id &&
                                    e->ae_tag == entry->ae_tag)
                                        goto acl_invalid;
                        }
                        mask_required++;
                        break;
                case ACL_MASK:
                        if (mask++)
                                goto acl_invalid;
                        break;
                default:
                        goto acl_invalid;
                }
        }
        if (!user || !group || !other || (mask_required && !mask))
                goto acl_invalid;
        else
                return 0;
acl_invalid:
        return EINVAL;
}

/*
 * Do ACL endian conversion.
 */
STATIC void
xfs_acl_get_endian(
        xfs_acl_t       *aclp)
{
        xfs_acl_entry_t *ace, *end;

        INT_SET(aclp->acl_cnt, ARCH_CONVERT, aclp->acl_cnt);
        end = &aclp->acl_entry[0]+aclp->acl_cnt;
        for (ace = &aclp->acl_entry[0]; ace < end; ace++) {
                INT_SET(ace->ae_tag, ARCH_CONVERT, ace->ae_tag);
                INT_SET(ace->ae_id, ARCH_CONVERT, ace->ae_id);
                INT_SET(ace->ae_perm, ARCH_CONVERT, ace->ae_perm);
        }
}

/*
 * Get the ACL from the EA and do endian conversion.
 */
STATIC void
xfs_acl_get_attr(
        struct inode    *vp,
        xfs_acl_t       *aclp,
        int             kind,
        int             flags,
        int             *error)
{
        int             len = sizeof(xfs_acl_t);

        ASSERT((flags & ATTR_KERNOVAL) ? (aclp == NULL) : 1);
        flags |= ATTR_ROOT;
        *error = xfs_attr_get(XFS_I(vp),
                                        kind == _ACL_TYPE_ACCESS ?
                                        SGI_ACL_FILE : SGI_ACL_DEFAULT,
                                        (char *)aclp, &len, flags);
        if (*error || (flags & ATTR_KERNOVAL))
                return;
        xfs_acl_get_endian(aclp);
}

/*
 * Set the EA with the ACL and do endian conversion.
 */
STATIC void
xfs_acl_set_attr(
        struct inode    *vp,
        xfs_acl_t       *aclp,
        int             kind,
        int             *error)
{
        xfs_acl_entry_t *ace, *newace, *end;
        xfs_acl_t       *newacl;
        int             len;

        if (!(_ACL_ALLOC(newacl))) {
                *error = ENOMEM;
                return;
        }

        len = sizeof(xfs_acl_t) -
              (sizeof(xfs_acl_entry_t) * (XFS_ACL_MAX_ENTRIES - aclp->acl_cnt));
        end = &aclp->acl_entry[0]+aclp->acl_cnt;
        for (ace = &aclp->acl_entry[0], newace = &newacl->acl_entry[0];
             ace < end;
             ace++, newace++) {
                INT_SET(newace->ae_tag, ARCH_CONVERT, ace->ae_tag);
                INT_SET(newace->ae_id, ARCH_CONVERT, ace->ae_id);
                INT_SET(newace->ae_perm, ARCH_CONVERT, ace->ae_perm);
        }
        INT_SET(newacl->acl_cnt, ARCH_CONVERT, aclp->acl_cnt);
        *error = xfs_attr_set(XFS_I(vp),
                                kind == _ACL_TYPE_ACCESS ?
                                SGI_ACL_FILE: SGI_ACL_DEFAULT,
                                (char *)newacl, len, ATTR_ROOT);
        _ACL_FREE(newacl);
}

int
xfs_acl_vtoacl(
        struct inode    *vp,
        xfs_acl_t       *access_acl,
        xfs_acl_t       *default_acl)
{
        int             error = 0;

        if (access_acl) {
                /*
                 * Get the Access ACL and the mode.  If either cannot
                 * be obtained for some reason, invalidate the access ACL.
                 */
                xfs_acl_get_attr(vp, access_acl, _ACL_TYPE_ACCESS, 0, &error);
                if (error)
                        access_acl->acl_cnt = XFS_ACL_NOT_PRESENT;
                else /* We have a good ACL and the file mode, synchronize. */
                        xfs_acl_sync_mode(XFS_I(vp)->i_d.di_mode, access_acl);
        }

        if (default_acl) {
                xfs_acl_get_attr(vp, default_acl, _ACL_TYPE_DEFAULT, 0, &error);
                if (error)
                        default_acl->acl_cnt = XFS_ACL_NOT_PRESENT;
        }
        return error;
}

/*
 * This function retrieves the parent directory's acl, processes it
 * and lets the child inherit the acl(s) that it should.
 */
int
xfs_acl_inherit(
        struct inode    *vp,
        mode_t          mode,
        xfs_acl_t       *pdaclp)
{
        xfs_acl_t       *cacl;
        int             error = 0;
        int             basicperms = 0;

        /*
         * If the parent does not have a default ACL, or it's an
         * invalid ACL, we're done.
         */
        if (!vp)
                return 0;
        if (!pdaclp || xfs_acl_invalid(pdaclp))
                return 0;

        /*
         * Copy the default ACL of the containing directory to
         * the access ACL of the new file and use the mode that
         * was passed in to set up the correct initial values for
         * the u::,g::[m::], and o:: entries.  This is what makes
         * umask() "work" with ACL's.
         */

        if (!(_ACL_ALLOC(cacl)))
                return ENOMEM;

        memcpy(cacl, pdaclp, sizeof(xfs_acl_t));
        xfs_acl_filter_mode(mode, cacl);
        error = xfs_acl_setmode(vp, cacl, &basicperms);
        if (error)
                goto out_error;

        /*
         * Set the Default and Access ACL on the file.  The mode is already
         * set on the file, so we don't need to worry about that.
         *
         * If the new file is a directory, its default ACL is a copy of
         * the containing directory's default ACL.
         */
        if (S_ISDIR(vp->i_mode))
                xfs_acl_set_attr(vp, pdaclp, _ACL_TYPE_DEFAULT, &error);
        if (!error && !basicperms)
                xfs_acl_set_attr(vp, cacl, _ACL_TYPE_ACCESS, &error);
out_error:
        _ACL_FREE(cacl);
        return error;
}

/*
 * Set up the correct mode on the file based on the supplied ACL.  This
 * makes sure that the mode on the file reflects the state of the
 * u::,g::[m::], and o:: entries in the ACL.  Since the mode is where
 * the ACL is going to get the permissions for these entries, we must
 * synchronize the mode whenever we set the ACL on a file.
 */
STATIC int
xfs_acl_setmode(
        struct inode    *vp,
        xfs_acl_t       *acl,
        int             *basicperms)
{
        struct iattr    iattr;
        xfs_acl_entry_t *ap;
        xfs_acl_entry_t *gap = NULL;
        int             i, nomask = 1;

        *basicperms = 1;

        if (acl->acl_cnt == XFS_ACL_NOT_PRESENT)
                return 0;

        /*
         * Copy the u::, g::, o::, and m:: bits from the ACL into the
         * mode.  The m:: bits take precedence over the g:: bits.
         */
        iattr.ia_valid = ATTR_MODE;
        iattr.ia_mode = XFS_I(vp)->i_d.di_mode;
        iattr.ia_mode &= ~(S_IRWXU|S_IRWXG|S_IRWXO);
        ap = acl->acl_entry;
        for (i = 0; i < acl->acl_cnt; ++i) {
                switch (ap->ae_tag) {
                case ACL_USER_OBJ:
                        iattr.ia_mode |= ap->ae_perm << 6;
                        break;
                case ACL_GROUP_OBJ:
                        gap = ap;
                        break;
                case ACL_MASK:  /* more than just standard modes */
                        nomask = 0;
                        iattr.ia_mode |= ap->ae_perm << 3;
                        *basicperms = 0;
                        break;
                case ACL_OTHER:
                        iattr.ia_mode |= ap->ae_perm;
                        break;
                default:        /* more than just standard modes */
                        *basicperms = 0;
                        break;
                }
                ap++;
        }

        /* Set the group bits from ACL_GROUP_OBJ if there's no ACL_MASK */
        if (gap && nomask)
                iattr.ia_mode |= gap->ae_perm << 3;

        return xfs_setattr(XFS_I(vp), &iattr, 0, sys_cred);
}

/*
 * The permissions for the special ACL entries (u::, g::[m::], o::) are
 * actually stored in the file mode (if there is both a group and a mask,
 * the group is stored in the ACL entry and the mask is stored on the file).
 * This allows the mode to remain automatically in sync with the ACL without
 * the need for a call-back to the ACL system at every point where the mode
 * could change.  This function takes the permissions from the specified mode
 * and places it in the supplied ACL.
 *
 * This implementation draws its validity from the fact that, when the ACL
 * was assigned, the mode was copied from the ACL.
 * If the mode did not change, therefore, the mode remains exactly what was
 * taken from the special ACL entries at assignment.
 * If a subsequent chmod() was done, the POSIX spec says that the change in
 * mode must cause an update to the ACL seen at user level and used for
 * access checks.  Before and after a mode change, therefore, the file mode
 * most accurately reflects what the special ACL entries should permit/deny.
 *
 * CAVEAT: If someone sets the SGI_ACL_FILE attribute directly,
 *         the existing mode bits will override whatever is in the
 *         ACL. Similarly, if there is a pre-existing ACL that was
 *         never in sync with its mode (owing to a bug in 6.5 and
 *         before), it will now magically (or mystically) be
 *         synchronized.  This could cause slight astonishment, but
 *         it is better than inconsistent permissions.
 *
 * The supplied ACL is a template that may contain any combination
 * of special entries.  These are treated as place holders when we fill
 * out the ACL.  This routine does not add or remove special entries, it
 * simply unites each special entry with its associated set of permissions.
 */
STATIC void
xfs_acl_sync_mode(
        mode_t          mode,
        xfs_acl_t       *acl)
{
        int             i, nomask = 1;
        xfs_acl_entry_t *ap;
        xfs_acl_entry_t *gap = NULL;

        /*
         * Set ACL entries. POSIX1003.1eD16 requires that the MASK
         * be set instead of the GROUP entry, if there is a MASK.
         */
        for (ap = acl->acl_entry, i = 0; i < acl->acl_cnt; ap++, i++) {
                switch (ap->ae_tag) {
                case ACL_USER_OBJ:
                        ap->ae_perm = (mode >> 6) & 0x7;
                        break;
                case ACL_GROUP_OBJ:
                        gap = ap;
                        break;
                case ACL_MASK:
                        nomask = 0;
                        ap->ae_perm = (mode >> 3) & 0x7;
                        break;
                case ACL_OTHER:
                        ap->ae_perm = mode & 0x7;
                        break;
                default:
                        break;
                }
        }
        /* Set the ACL_GROUP_OBJ if there's no ACL_MASK */
        if (gap && nomask)
                gap->ae_perm = (mode >> 3) & 0x7;
}

/*
 * When inheriting an Access ACL from a directory Default ACL,
 * the ACL bits are set to the intersection of the ACL default
 * permission bits and the file permission bits in mode. If there
 * are no permission bits on the file then we must not give them
 * the ACL. This is what what makes umask() work with ACLs.
 */
STATIC void
xfs_acl_filter_mode(
        mode_t          mode,
        xfs_acl_t       *acl)
{
        int             i, nomask = 1;
        xfs_acl_entry_t *ap;
        xfs_acl_entry_t *gap = NULL;

        /*
         * Set ACL entries. POSIX1003.1eD16 requires that the MASK
         * be merged with GROUP entry, if there is a MASK.
         */
        for (ap = acl->acl_entry, i = 0; i < acl->acl_cnt; ap++, i++) {
                switch (ap->ae_tag) {
                case ACL_USER_OBJ:
                        ap->ae_perm &= (mode >> 6) & 0x7;
                        break;
                case ACL_GROUP_OBJ:
                        gap = ap;
                        break;
                case ACL_MASK:
                        nomask = 0;
                        ap->ae_perm &= (mode >> 3) & 0x7;
                        break;
                case ACL_OTHER:
                        ap->ae_perm &= mode & 0x7;
                        break;
                default:
                        break;
                }
        }
        /* Set the ACL_GROUP_OBJ if there's no ACL_MASK */
        if (gap && nomask)
                gap->ae_perm &= (mode >> 3) & 0x7;
}