// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2002,2003 by Andreas Gruenbacher <a.gruenbacher@computer.org>
 *
 * Fixes from William Schumacher incorporated on 15 March 2001.
 *    (Reported by Charles Bertsch, <CBertsch@microtest.com>).
 */

/*
 *  This file contains generic functions for manipulating
 *  POSIX 1003.1e draft standard 17 ACLs.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/atomic.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/posix_acl.h>
#include <linux/posix_acl_xattr.h>
#include <linux/xattr.h>
#include <linux/export.h>
#include <linux/user_namespace.h>
#include <linux/namei.h>
#include <linux/mnt_idmapping.h>

static struct posix_acl **acl_by_type(struct inode *inode, int type)
{
        switch (type) {
        case ACL_TYPE_ACCESS:
                return &inode->i_acl;
        case ACL_TYPE_DEFAULT:
                return &inode->i_default_acl;
        default:
                BUG();
        }
}

struct posix_acl *get_cached_acl(struct inode *inode, int type)
{
        struct posix_acl **p = acl_by_type(inode, type);
        struct posix_acl *acl;

        for (;;) {
                rcu_read_lock();
                acl = rcu_dereference(*p);
                if (!acl || is_uncached_acl(acl) ||
                    refcount_inc_not_zero(&acl->a_refcount))
                        break;
                rcu_read_unlock();
                cpu_relax();
        }
        rcu_read_unlock();
        return acl;
}
EXPORT_SYMBOL(get_cached_acl);

struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
{
        struct posix_acl *acl = rcu_dereference(*acl_by_type(inode, type));

        if (acl == ACL_DONT_CACHE) {
                struct posix_acl *ret;

                ret = inode->i_op->get_acl(inode, type, LOOKUP_RCU);
                if (!IS_ERR(ret))
                        acl = ret;
        }

        return acl;
}
EXPORT_SYMBOL(get_cached_acl_rcu);

void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
{
        struct posix_acl **p = acl_by_type(inode, type);
        struct posix_acl *old;

        old = xchg(p, posix_acl_dup(acl));
        if (!is_uncached_acl(old))
                posix_acl_release(old);
}
EXPORT_SYMBOL(set_cached_acl);

static void __forget_cached_acl(struct posix_acl **p)
{
        struct posix_acl *old;

        old = xchg(p, ACL_NOT_CACHED);
        if (!is_uncached_acl(old))
                posix_acl_release(old);
}

void forget_cached_acl(struct inode *inode, int type)
{
        __forget_cached_acl(acl_by_type(inode, type));
}
EXPORT_SYMBOL(forget_cached_acl);

void forget_all_cached_acls(struct inode *inode)
{
        __forget_cached_acl(&inode->i_acl);
        __forget_cached_acl(&inode->i_default_acl);
}
EXPORT_SYMBOL(forget_all_cached_acls);

struct posix_acl *get_acl(struct inode *inode, int type)
{
        void *sentinel;
        struct posix_acl **p;
        struct posix_acl *acl;

        /*
         * The sentinel is used to detect when another operation like
         * set_cached_acl() or forget_cached_acl() races with get_acl().
         * It is guaranteed that is_uncached_acl(sentinel) is true.
         */

        acl = get_cached_acl(inode, type);
        if (!is_uncached_acl(acl))
                return acl;

        if (!IS_POSIXACL(inode))
                return NULL;

        sentinel = uncached_acl_sentinel(current);
        p = acl_by_type(inode, type);

        /*
         * If the ACL isn't being read yet, set our sentinel.  Otherwise, the
         * current value of the ACL will not be ACL_NOT_CACHED and so our own
         * sentinel will not be set; another task will update the cache.  We
         * could wait for that other task to complete its job, but it's easier
         * to just call ->get_acl to fetch the ACL ourself.  (This is going to
         * be an unlikely race.)
         */
        cmpxchg(p, ACL_NOT_CACHED, sentinel);

        /*
         * Normally, the ACL returned by ->get_acl will be cached.
         * A filesystem can prevent that by calling
         * forget_cached_acl(inode, type) in ->get_acl.
         *
         * If the filesystem doesn't have a get_acl() function at all, we'll
         * just create the negative cache entry.
         */
        if (!inode->i_op->get_acl) {
                set_cached_acl(inode, type, NULL);
                return NULL;
        }
        acl = inode->i_op->get_acl(inode, type, false);

        if (IS_ERR(acl)) {
                /*
                 * Remove our sentinel so that we don't block future attempts
                 * to cache the ACL.
                 */
                cmpxchg(p, sentinel, ACL_NOT_CACHED);
                return acl;
        }

        /*
         * Cache the result, but only if our sentinel is still in place.
         */
        posix_acl_dup(acl);
        if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))
                posix_acl_release(acl);
        return acl;
}
EXPORT_SYMBOL(get_acl);

/*
 * Init a fresh posix_acl
 */
void
posix_acl_init(struct posix_acl *acl, int count)
{
        refcount_set(&acl->a_refcount, 1);
        acl->a_count = count;
}
EXPORT_SYMBOL(posix_acl_init);

/*
 * Allocate a new ACL with the specified number of entries.
 */
struct posix_acl *
posix_acl_alloc(int count, gfp_t flags)
{
        const size_t size = sizeof(struct posix_acl) +
                            count * sizeof(struct posix_acl_entry);
        struct posix_acl *acl = kmalloc(size, flags);
        if (acl)
                posix_acl_init(acl, count);
        return acl;
}
EXPORT_SYMBOL(posix_acl_alloc);

/*
 * Clone an ACL.
 */
static struct posix_acl *
posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
{
        struct posix_acl *clone = NULL;

        if (acl) {
                int size = sizeof(struct posix_acl) + acl->a_count *
                           sizeof(struct posix_acl_entry);
                clone = kmemdup(acl, size, flags);
                if (clone)
                        refcount_set(&clone->a_refcount, 1);
        }
        return clone;
}

/*
 * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
 */
int
posix_acl_valid(struct user_namespace *user_ns, const struct posix_acl *acl)
{
        const struct posix_acl_entry *pa, *pe;
        int state = ACL_USER_OBJ;
        int needs_mask = 0;

        FOREACH_ACL_ENTRY(pa, acl, pe) {
                if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
                        return -EINVAL;
                switch (pa->e_tag) {
                        case ACL_USER_OBJ:
                                if (state == ACL_USER_OBJ) {
                                        state = ACL_USER;
                                        break;
                                }
                                return -EINVAL;

                        case ACL_USER:
                                if (state != ACL_USER)
                                        return -EINVAL;
                                if (!kuid_has_mapping(user_ns, pa->e_uid))
                                        return -EINVAL;
                                needs_mask = 1;
                                break;

                        case ACL_GROUP_OBJ:
                                if (state == ACL_USER) {
                                        state = ACL_GROUP;
                                        break;
                                }
                                return -EINVAL;

                        case ACL_GROUP:
                                if (state != ACL_GROUP)
                                        return -EINVAL;
                                if (!kgid_has_mapping(user_ns, pa->e_gid))
                                        return -EINVAL;
                                needs_mask = 1;
                                break;

                        case ACL_MASK:
                                if (state != ACL_GROUP)
                                        return -EINVAL;
                                state = ACL_OTHER;
                                break;

                        case ACL_OTHER:
                                if (state == ACL_OTHER ||
                                    (state == ACL_GROUP && !needs_mask)) {
                                        state = 0;
                                        break;
                                }
                                return -EINVAL;

                        default:
                                return -EINVAL;
                }
        }
        if (state == 0)
                return 0;
        return -EINVAL;
}
EXPORT_SYMBOL(posix_acl_valid);

/*
 * Returns 0 if the acl can be exactly represented in the traditional
 * file mode permission bits, or else 1. Returns -E... on error.
 */
int
posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
{
        const struct posix_acl_entry *pa, *pe;
        umode_t mode = 0;
        int not_equiv = 0;

        /*
         * A null ACL can always be presented as mode bits.
         */
        if (!acl)
                return 0;

        FOREACH_ACL_ENTRY(pa, acl, pe) {
                switch (pa->e_tag) {
                        case ACL_USER_OBJ:
                                mode |= (pa->e_perm & S_IRWXO) << 6;
                                break;
                        case ACL_GROUP_OBJ:
                                mode |= (pa->e_perm & S_IRWXO) << 3;
                                break;
                        case ACL_OTHER:
                                mode |= pa->e_perm & S_IRWXO;
                                break;
                        case ACL_MASK:
                                mode = (mode & ~S_IRWXG) |
                                       ((pa->e_perm & S_IRWXO) << 3);
                                not_equiv = 1;
                                break;
                        case ACL_USER:
                        case ACL_GROUP:
                                not_equiv = 1;
                                break;
                        default:
                                return -EINVAL;
                }
        }
        if (mode_p)
                *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
        return not_equiv;
}
EXPORT_SYMBOL(posix_acl_equiv_mode);

/*
 * Create an ACL representing the file mode permission bits of an inode.
 */
struct posix_acl *
posix_acl_from_mode(umode_t mode, gfp_t flags)
{
        struct posix_acl *acl = posix_acl_alloc(3, flags);
        if (!acl)
                return ERR_PTR(-ENOMEM);

        acl->a_entries[0].e_tag  = ACL_USER_OBJ;
        acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;

        acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
        acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;

        acl->a_entries[2].e_tag  = ACL_OTHER;
        acl->a_entries[2].e_perm = (mode & S_IRWXO);
        return acl;
}
EXPORT_SYMBOL(posix_acl_from_mode);

/*
 * Return 0 if current is granted want access to the inode
 * by the acl. Returns -E... otherwise.
 */
int
posix_acl_permission(struct user_namespace *mnt_userns, struct inode *inode,
                     const struct posix_acl *acl, int want)
{
        const struct posix_acl_entry *pa, *pe, *mask_obj;
        int found = 0;
        kuid_t uid;
        kgid_t gid;

        want &= MAY_READ | MAY_WRITE | MAY_EXEC;

        FOREACH_ACL_ENTRY(pa, acl, pe) {
                switch(pa->e_tag) {
                        case ACL_USER_OBJ:
                                /* (May have been checked already) */
                                uid = i_uid_into_mnt(mnt_userns, inode);
                                if (uid_eq(uid, current_fsuid()))
                                        goto check_perm;
                                break;
                        case ACL_USER:
                                uid = mapped_kuid_fs(mnt_userns,
                                                     i_user_ns(inode),
                                                     pa->e_uid);
                                if (uid_eq(uid, current_fsuid()))
                                        goto mask;
                                break;
                        case ACL_GROUP_OBJ:
                                gid = i_gid_into_mnt(mnt_userns, inode);
                                if (in_group_p(gid)) {
                                        found = 1;
                                        if ((pa->e_perm & want) == want)
                                                goto mask;
                                }
                                break;
                        case ACL_GROUP:
                                gid = mapped_kgid_fs(mnt_userns,
                                                     i_user_ns(inode),
                                                     pa->e_gid);
                                if (in_group_p(gid)) {
                                        found = 1;
                                        if ((pa->e_perm & want) == want)
                                                goto mask;
                                }
                                break;
                        case ACL_MASK:
                                break;
                        case ACL_OTHER:
                                if (found)
                                        return -EACCES;
                                else
                                        goto check_perm;
                        default:
                                return -EIO;
                }
        }
        return -EIO;

mask:
        for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
                if (mask_obj->e_tag == ACL_MASK) {
                        if ((pa->e_perm & mask_obj->e_perm & want) == want)
                                return 0;
                        return -EACCES;
                }
        }

check_perm:
        if ((pa->e_perm & want) == want)
                return 0;
        return -EACCES;
}

/*
 * Modify acl when creating a new inode. The caller must ensure the acl is
 * only referenced once.
 *
 * mode_p initially must contain the mode parameter to the open() / creat()
 * system calls. All permissions that are not granted by the acl are removed.
 * The permissions in the acl are changed to reflect the mode_p parameter.
 */
static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
{
        struct posix_acl_entry *pa, *pe;
        struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
        umode_t mode = *mode_p;
        int not_equiv = 0;

        /* assert(atomic_read(acl->a_refcount) == 1); */

        FOREACH_ACL_ENTRY(pa, acl, pe) {
                switch(pa->e_tag) {
                        case ACL_USER_OBJ:
                                pa->e_perm &= (mode >> 6) | ~S_IRWXO;
                                mode &= (pa->e_perm << 6) | ~S_IRWXU;
                                break;

                        case ACL_USER:
                        case ACL_GROUP:
                                not_equiv = 1;
                                break;

                        case ACL_GROUP_OBJ:
                                group_obj = pa;
                                break;

                        case ACL_OTHER:
                                pa->e_perm &= mode | ~S_IRWXO;
                                mode &= pa->e_perm | ~S_IRWXO;
                                break;

                        case ACL_MASK:
                                mask_obj = pa;
                                not_equiv = 1;
                                break;

                        default:
                                return -EIO;
                }
        }

        if (mask_obj) {
                mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
                mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
        } else {
                if (!group_obj)
                        return -EIO;
                group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
                mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
        }

        *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
        return not_equiv;
}

/*
 * Modify the ACL for the chmod syscall.
 */
static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
{
        struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
        struct posix_acl_entry *pa, *pe;

        /* assert(atomic_read(acl->a_refcount) == 1); */

        FOREACH_ACL_ENTRY(pa, acl, pe) {
                switch(pa->e_tag) {
                        case ACL_USER_OBJ:
                                pa->e_perm = (mode & S_IRWXU) >> 6;
                                break;

                        case ACL_USER:
                        case ACL_GROUP:
                                break;

                        case ACL_GROUP_OBJ:
                                group_obj = pa;
                                break;

                        case ACL_MASK:
                                mask_obj = pa;
                                break;

                        case ACL_OTHER:
                                pa->e_perm = (mode & S_IRWXO);
                                break;

                        default:
                                return -EIO;
                }
        }

        if (mask_obj) {
                mask_obj->e_perm = (mode & S_IRWXG) >> 3;
        } else {
                if (!group_obj)
                        return -EIO;
                group_obj->e_perm = (mode & S_IRWXG) >> 3;
        }

        return 0;
}

int
__posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
{
        struct posix_acl *clone = posix_acl_clone(*acl, gfp);
        int err = -ENOMEM;
        if (clone) {
                err = posix_acl_create_masq(clone, mode_p);
                if (err < 0) {
                        posix_acl_release(clone);
                        clone = NULL;
                }
        }
        posix_acl_release(*acl);
        *acl = clone;
        return err;
}
EXPORT_SYMBOL(__posix_acl_create);

int
__posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
{
        struct posix_acl *clone = posix_acl_clone(*acl, gfp);
        int err = -ENOMEM;
        if (clone) {
                err = __posix_acl_chmod_masq(clone, mode);
                if (err) {
                        posix_acl_release(clone);
                        clone = NULL;
                }
        }
        posix_acl_release(*acl);
        *acl = clone;
        return err;
}
EXPORT_SYMBOL(__posix_acl_chmod);

/**
 * posix_acl_chmod - chmod a posix acl
 *
 * @mnt_userns: user namespace of the mount @inode was found from
 * @inode:      inode to check permissions on
 * @mode:       the new mode of @inode
 *
 * If the inode has been found through an idmapped mount the user namespace of
 * the vfsmount must be passed through @mnt_userns. This function will then
 * take care to map the inode according to @mnt_userns before checking
 * permissions. On non-idmapped mounts or if permission checking is to be
 * performed on the raw inode simply passs init_user_ns.
 */
int
 posix_acl_chmod(struct user_namespace *mnt_userns, struct inode *inode,
                    umode_t mode)
{
        struct posix_acl *acl;
        int ret = 0;

        if (!IS_POSIXACL(inode))
                return 0;
        if (!inode->i_op->set_acl)
                return -EOPNOTSUPP;

        acl = get_acl(inode, ACL_TYPE_ACCESS);
        if (IS_ERR_OR_NULL(acl)) {
                if (acl == ERR_PTR(-EOPNOTSUPP))
                        return 0;
                return PTR_ERR(acl);
        }

        ret = __posix_acl_chmod(&acl, GFP_KERNEL, mode);
        if (ret)
                return ret;
        ret = inode->i_op->set_acl(mnt_userns, inode, acl, ACL_TYPE_ACCESS);
        posix_acl_release(acl);
        return ret;
}
EXPORT_SYMBOL(posix_acl_chmod);

int
posix_acl_create(struct inode *dir, umode_t *mode,
                struct posix_acl **default_acl, struct posix_acl **acl)
{
        struct posix_acl *p;
        struct posix_acl *clone;
        int ret;

        *acl = NULL;
        *default_acl = NULL;

        if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
                return 0;

        p = get_acl(dir, ACL_TYPE_DEFAULT);
        if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
                *mode &= ~current_umask();
                return 0;
        }
        if (IS_ERR(p))
                return PTR_ERR(p);

        ret = -ENOMEM;
        clone = posix_acl_clone(p, GFP_NOFS);
        if (!clone)
                goto err_release;

        ret = posix_acl_create_masq(clone, mode);
        if (ret < 0)
                goto err_release_clone;

        if (ret == 0)
                posix_acl_release(clone);
        else
                *acl = clone;

        if (!S_ISDIR(*mode))
                posix_acl_release(p);
        else
                *default_acl = p;

        return 0;

err_release_clone:
        posix_acl_release(clone);
err_release:
        posix_acl_release(p);
        return ret;
}
EXPORT_SYMBOL_GPL(posix_acl_create);

/**
 * posix_acl_update_mode  -  update mode in set_acl
 * @mnt_userns: user namespace of the mount @inode was found from
 * @inode:      target inode
 * @mode_p:     mode (pointer) for update
 * @acl:        acl pointer
 *
 * Update the file mode when setting an ACL: compute the new file permission
 * bits based on the ACL.  In addition, if the ACL is equivalent to the new
 * file mode, set *@acl to NULL to indicate that no ACL should be set.
 *
 * As with chmod, clear the setgid bit if the caller is not in the owning group
 * or capable of CAP_FSETID (see inode_change_ok).
 *
 * If the inode has been found through an idmapped mount the user namespace of
 * the vfsmount must be passed through @mnt_userns. This function will then
 * take care to map the inode according to @mnt_userns before checking
 * permissions. On non-idmapped mounts or if permission checking is to be
 * performed on the raw inode simply passs init_user_ns.
 *
 * Called from set_acl inode operations.
 */
int posix_acl_update_mode(struct user_namespace *mnt_userns,
                          struct inode *inode, umode_t *mode_p,
                          struct posix_acl **acl)
{
        umode_t mode = inode->i_mode;
        int error;

        error = posix_acl_equiv_mode(*acl, &mode);
        if (error < 0)
                return error;
        if (error == 0)
                *acl = NULL;
        if (!in_group_p(i_gid_into_mnt(mnt_userns, inode)) &&
            !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
                mode &= ~S_ISGID;
        *mode_p = mode;
        return 0;
}
EXPORT_SYMBOL(posix_acl_update_mode);

/*
 * Fix up the uids and gids in posix acl extended attributes in place.
 */
static void posix_acl_fix_xattr_userns(
        struct user_namespace *to, struct user_namespace *from,
        struct user_namespace *mnt_userns,
        void *value, size_t size, bool from_user)
{
        struct posix_acl_xattr_header *header = value;
        struct posix_acl_xattr_entry *entry = (void *)(header + 1), *end;
        int count;
        kuid_t uid;
        kgid_t gid;

        if (!value)
                return;
        if (size < sizeof(struct posix_acl_xattr_header))
                return;
        if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
                return;

        count = posix_acl_xattr_count(size);
        if (count < 0)
                return;
        if (count == 0)
                return;

        for (end = entry + count; entry != end; entry++) {
                switch(le16_to_cpu(entry->e_tag)) {
                case ACL_USER:
                        uid = make_kuid(from, le32_to_cpu(entry->e_id));
                        if (from_user)
                                uid = mapped_kuid_user(mnt_userns, &init_user_ns, uid);
                        else
                                uid = mapped_kuid_fs(mnt_userns, &init_user_ns, uid);
                        entry->e_id = cpu_to_le32(from_kuid(to, uid));
                        break;
                case ACL_GROUP:
                        gid = make_kgid(from, le32_to_cpu(entry->e_id));
                        if (from_user)
                                gid = mapped_kgid_user(mnt_userns, &init_user_ns, gid);
                        else
                                gid = mapped_kgid_fs(mnt_userns, &init_user_ns, gid);
                        entry->e_id = cpu_to_le32(from_kgid(to, gid));
                        break;
                default:
                        break;
                }
        }
}

void posix_acl_fix_xattr_from_user(struct user_namespace *mnt_userns,
                                   struct inode *inode,
                                   void *value, size_t size)
{
        struct user_namespace *user_ns = current_user_ns();

        /* Leave ids untouched on non-idmapped mounts. */
        if (no_idmapping(mnt_userns, i_user_ns(inode)))
                mnt_userns = &init_user_ns;
        if ((user_ns == &init_user_ns) && (mnt_userns == &init_user_ns))
                return;
        posix_acl_fix_xattr_userns(&init_user_ns, user_ns, mnt_userns, value,
                                   size, true);
}

void posix_acl_fix_xattr_to_user(struct user_namespace *mnt_userns,
                                 struct inode *inode,
                                 void *value, size_t size)
{
        struct user_namespace *user_ns = current_user_ns();

        /* Leave ids untouched on non-idmapped mounts. */
        if (no_idmapping(mnt_userns, i_user_ns(inode)))
                mnt_userns = &init_user_ns;
        if ((user_ns == &init_user_ns) && (mnt_userns == &init_user_ns))
                return;
        posix_acl_fix_xattr_userns(user_ns, &init_user_ns, mnt_userns, value,
                                   size, false);
}

/*
 * Convert from extended attribute to in-memory representation.
 */
struct posix_acl *
posix_acl_from_xattr(struct user_namespace *user_ns,
                     const void *value, size_t size)
{
        const struct posix_acl_xattr_header *header = value;
        const struct posix_acl_xattr_entry *entry = (const void *)(header + 1), *end;
        int count;
        struct posix_acl *acl;
        struct posix_acl_entry *acl_e;

        if (!value)
                return NULL;
        if (size < sizeof(struct posix_acl_xattr_header))
                 return ERR_PTR(-EINVAL);
        if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
                return ERR_PTR(-EOPNOTSUPP);

        count = posix_acl_xattr_count(size);
        if (count < 0)
                return ERR_PTR(-EINVAL);
        if (count == 0)
                return NULL;
        
        acl = posix_acl_alloc(count, GFP_NOFS);
        if (!acl)
                return ERR_PTR(-ENOMEM);
        acl_e = acl->a_entries;
        
        for (end = entry + count; entry != end; acl_e++, entry++) {
                acl_e->e_tag  = le16_to_cpu(entry->e_tag);
                acl_e->e_perm = le16_to_cpu(entry->e_perm);

                switch(acl_e->e_tag) {
                        case ACL_USER_OBJ:
                        case ACL_GROUP_OBJ:
                        case ACL_MASK:
                        case ACL_OTHER:
                                break;

                        case ACL_USER:
                                acl_e->e_uid =
                                        make_kuid(user_ns,
                                                  le32_to_cpu(entry->e_id));
                                if (!uid_valid(acl_e->e_uid))
                                        goto fail;
                                break;
                        case ACL_GROUP:
                                acl_e->e_gid =
                                        make_kgid(user_ns,
                                                  le32_to_cpu(entry->e_id));
                                if (!gid_valid(acl_e->e_gid))
                                        goto fail;
                                break;

                        default:
                                goto fail;
                }
        }
        return acl;

fail:
        posix_acl_release(acl);
        return ERR_PTR(-EINVAL);
}
EXPORT_SYMBOL (posix_acl_from_xattr);

/*
 * Convert from in-memory to extended attribute representation.
 */
int
posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
                   void *buffer, size_t size)
{
        struct posix_acl_xattr_header *ext_acl = buffer;
        struct posix_acl_xattr_entry *ext_entry;
        int real_size, n;

        real_size = posix_acl_xattr_size(acl->a_count);
        if (!buffer)
                return real_size;
        if (real_size > size)
                return -ERANGE;

        ext_entry = (void *)(ext_acl + 1);
        ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);

        for (n=0; n < acl->a_count; n++, ext_entry++) {
                const struct posix_acl_entry *acl_e = &acl->a_entries[n];
                ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
                ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
                switch(acl_e->e_tag) {
                case ACL_USER:
                        ext_entry->e_id =
                                cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
                        break;
                case ACL_GROUP:
                        ext_entry->e_id =
                                cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
                        break;
                default:
                        ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
                        break;
                }
        }
        return real_size;
}
EXPORT_SYMBOL (posix_acl_to_xattr);

static int
posix_acl_xattr_get(const struct xattr_handler *handler,
                    struct dentry *unused, struct inode *inode,
                    const char *name, void *value, size_t size)
{
        struct posix_acl *acl;
        int error;

        if (!IS_POSIXACL(inode))
                return -EOPNOTSUPP;
        if (S_ISLNK(inode->i_mode))
                return -EOPNOTSUPP;

        acl = get_acl(inode, handler->flags);
        if (IS_ERR(acl))
                return PTR_ERR(acl);
        if (acl == NULL)
                return -ENODATA;

        error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
        posix_acl_release(acl);

        return error;
}

int
set_posix_acl(struct user_namespace *mnt_userns, struct inode *inode,
              int type, struct posix_acl *acl)
{
        if (!IS_POSIXACL(inode))
                return -EOPNOTSUPP;
        if (!inode->i_op->set_acl)
                return -EOPNOTSUPP;

        if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
                return acl ? -EACCES : 0;
        if (!inode_owner_or_capable(mnt_userns, inode))
                return -EPERM;

        if (acl) {
                int ret = posix_acl_valid(inode->i_sb->s_user_ns, acl);
                if (ret)
                        return ret;
        }
        return inode->i_op->set_acl(mnt_userns, inode, acl, type);
}
EXPORT_SYMBOL(set_posix_acl);

static int
posix_acl_xattr_set(const struct xattr_handler *handler,
                           struct user_namespace *mnt_userns,
                           struct dentry *unused, struct inode *inode,
                           const char *name, const void *value, size_t size,
                           int flags)
{
        struct posix_acl *acl = NULL;
        int ret;

        if (value) {
                acl = posix_acl_from_xattr(&init_user_ns, value, size);
                if (IS_ERR(acl))
                        return PTR_ERR(acl);
        }
        ret = set_posix_acl(mnt_userns, inode, handler->flags, acl);
        posix_acl_release(acl);
        return ret;
}

static bool
posix_acl_xattr_list(struct dentry *dentry)
{
        return IS_POSIXACL(d_backing_inode(dentry));
}

const struct xattr_handler posix_acl_access_xattr_handler = {
        .name = XATTR_NAME_POSIX_ACL_ACCESS,
        .flags = ACL_TYPE_ACCESS,
        .list = posix_acl_xattr_list,
        .get = posix_acl_xattr_get,
        .set = posix_acl_xattr_set,
};
EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler);

const struct xattr_handler posix_acl_default_xattr_handler = {
        .name = XATTR_NAME_POSIX_ACL_DEFAULT,
        .flags = ACL_TYPE_DEFAULT,
        .list = posix_acl_xattr_list,
        .get = posix_acl_xattr_get,
        .set = posix_acl_xattr_set,
};
EXPORT_SYMBOL_GPL(posix_acl_default_xattr_handler);

int simple_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
                   struct posix_acl *acl, int type)
{
        int error;

        if (type == ACL_TYPE_ACCESS) {
                error = posix_acl_update_mode(mnt_userns, inode,

                                &inode->i_mode, &acl);
                if (error)
                        return error;
        }

        inode->i_ctime = current_time(inode);
        set_cached_acl(inode, type, acl);
        return 0;
}

int simple_acl_create(struct inode *dir, struct inode *inode)
{
        struct posix_acl *default_acl, *acl;
        int error;

        error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
        if (error)
                return error;

        set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl);
        set_cached_acl(inode, ACL_TYPE_ACCESS, acl);

        if (default_acl)
                posix_acl_release(default_acl);
        if (acl)
                posix_acl_release(acl);
        return 0;
}