Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1254 insertions, 0 deletions

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
new file mode 100644
index 000000000..74dc0f571
--- /dev/null
+++ b/fs/posix_acl.c
@@ -0,0 +1,1254 @@
+// 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>
+#include <linux/iversion.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.
+ */
+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;
+}
+EXPORT_SYMBOL_GPL(posix_acl_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;
+	struct user_namespace *fs_userns = i_user_ns(inode);
+	int found = 0;
+	vfsuid_t vfsuid;
+	vfsgid_t vfsgid;
+
+	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) */
+				vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
+				if (vfsuid_eq_kuid(vfsuid, current_fsuid()))
+                                        goto check_perm;
+                                break;
+                        case ACL_USER:
+				vfsuid = make_vfsuid(mnt_userns, fs_userns,
+						     pa->e_uid);
+				if (vfsuid_eq_kuid(vfsuid, current_fsuid()))
+                                        goto mask;
+				break;
+                        case ACL_GROUP_OBJ:
+				vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
+				if (vfsgid_in_group_p(vfsgid)) {
+					found = 1;
+					if ((pa->e_perm & want) == want)
+						goto mask;
+                                }
+				break;
+                        case ACL_GROUP:
+				vfsgid = make_vfsgid(mnt_userns, fs_userns,
+						     pa->e_gid);
+				if (vfsgid_in_group_p(vfsgid)) {
+					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 (!vfsgid_in_group_p(i_gid_into_vfsgid(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 int posix_acl_fix_xattr_common(const void *value, size_t size)
+{
+	const struct posix_acl_xattr_header *header = value;
+	int count;
+
+	if (!header)
+		return -EINVAL;
+	if (size < sizeof(struct posix_acl_xattr_header))
+		return -EINVAL;
+	if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
+		return -EOPNOTSUPP;
+
+	count = posix_acl_xattr_count(size);
+	if (count < 0)
+		return -EINVAL;
+	if (count == 0)
+		return 0;
+
+	return count;
+}
+
+void posix_acl_getxattr_idmapped_mnt(struct user_namespace *mnt_userns,
+				     const struct inode *inode,
+				     void *value, size_t size)
+{
+	struct posix_acl_xattr_header *header = value;
+	struct posix_acl_xattr_entry *entry = (void *)(header + 1), *end;
+	struct user_namespace *fs_userns = i_user_ns(inode);
+	int count;
+	vfsuid_t vfsuid;
+	vfsgid_t vfsgid;
+	kuid_t uid;
+	kgid_t gid;
+
+	if (no_idmapping(mnt_userns, i_user_ns(inode)))
+		return;
+
+	count = posix_acl_fix_xattr_common(value, size);
+	if (count <= 0)
+		return;
+
+	for (end = entry + count; entry != end; entry++) {
+		switch (le16_to_cpu(entry->e_tag)) {
+		case ACL_USER:
+			uid = make_kuid(&init_user_ns, le32_to_cpu(entry->e_id));
+			vfsuid = make_vfsuid(mnt_userns, fs_userns, uid);
+			entry->e_id = cpu_to_le32(from_kuid(&init_user_ns,
+						vfsuid_into_kuid(vfsuid)));
+			break;
+		case ACL_GROUP:
+			gid = make_kgid(&init_user_ns, le32_to_cpu(entry->e_id));
+			vfsgid = make_vfsgid(mnt_userns, fs_userns, gid);
+			entry->e_id = cpu_to_le32(from_kgid(&init_user_ns,
+						vfsgid_into_kgid(vfsgid)));
+			break;
+		default:
+			break;
+		}
+	}
+}
+
+static void posix_acl_fix_xattr_userns(
+	struct user_namespace *to, struct user_namespace *from,
+	void *value, size_t size)
+{
+	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;
+
+	count = posix_acl_fix_xattr_common(value, size);
+	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));
+			entry->e_id = cpu_to_le32(from_kuid(to, uid));
+			break;
+		case ACL_GROUP:
+			gid = make_kgid(from, le32_to_cpu(entry->e_id));
+			entry->e_id = cpu_to_le32(from_kgid(to, gid));
+			break;
+		default:
+			break;
+		}
+	}
+}
+
+void posix_acl_fix_xattr_from_user(void *value, size_t size)
+{
+	struct user_namespace *user_ns = current_user_ns();
+	if (user_ns == &init_user_ns)
+		return;
+	posix_acl_fix_xattr_userns(&init_user_ns, user_ns, value, size);
+}
+
+void posix_acl_fix_xattr_to_user(void *value, size_t size)
+{
+	struct user_namespace *user_ns = current_user_ns();
+	if (user_ns == &init_user_ns)
+		return;
+	posix_acl_fix_xattr_userns(user_ns, &init_user_ns, value, size);
+}
+
+/**
+ * make_posix_acl - convert POSIX ACLs from uapi to VFS format using the
+ *                  provided callbacks to map ACL_{GROUP,USER} entries into the
+ *                  appropriate format
+ * @mnt_userns: the mount's idmapping
+ * @fs_userns: the filesystem's idmapping
+ * @value: the uapi representation of POSIX ACLs
+ * @size: the size of @void
+ * @uid_cb: callback to use for mapping the uid stored in ACL_USER entries
+ * @gid_cb: callback to use for mapping the gid stored in ACL_GROUP entries
+ *
+ * The make_posix_acl() helper is an abstraction to translate from uapi format
+ * into the VFS format allowing the caller to specific callbacks to map
+ * ACL_{GROUP,USER} entries into the expected format. This is used in
+ * posix_acl_from_xattr() and vfs_set_acl_prepare() and avoids pointless code
+ * duplication.
+ *
+ * Return: Allocated struct posix_acl on success, NULL for a valid header but
+ *         without actual POSIX ACL entries, or ERR_PTR() encoded error code.
+ */
+static struct posix_acl *make_posix_acl(struct user_namespace *mnt_userns,
+	struct user_namespace *fs_userns, const void *value, size_t size,
+	kuid_t (*uid_cb)(struct user_namespace *, struct user_namespace *,
+			 const struct posix_acl_xattr_entry *),
+	kgid_t (*gid_cb)(struct user_namespace *, struct user_namespace *,
+			 const struct posix_acl_xattr_entry *))
+{
+	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;
+
+	count = posix_acl_fix_xattr_common(value, size);
+	if (count < 0)
+		return ERR_PTR(count);
+	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 = uid_cb(mnt_userns, fs_userns, entry);
+				if (!uid_valid(acl_e->e_uid))
+					goto fail;
+				break;
+			case ACL_GROUP:
+				acl_e->e_gid = gid_cb(mnt_userns, fs_userns, entry);
+				if (!gid_valid(acl_e->e_gid))
+					goto fail;
+				break;
+
+			default:
+				goto fail;
+		}
+	}
+	return acl;
+
+fail:
+	posix_acl_release(acl);
+	return ERR_PTR(-EINVAL);
+}
+
+/**
+ * vfs_set_acl_prepare_kuid - map ACL_USER uid according to mount- and
+ *                            filesystem idmapping
+ * @mnt_userns: the mount's idmapping
+ * @fs_userns: the filesystem's idmapping
+ * @e: a ACL_USER entry in POSIX ACL uapi format
+ *
+ * The uid stored as ACL_USER entry in @e is a kuid_t stored as a raw {g,u}id
+ * value. The vfs_set_acl_prepare_kuid() will recover the kuid_t through
+ * KUIDT_INIT() and then map it according to the idmapped mount. The resulting
+ * kuid_t is the value which the filesystem can map up into a raw backing store
+ * id in the filesystem's idmapping.
+ *
+ * This is used in vfs_set_acl_prepare() to generate the proper VFS
+ * representation of POSIX ACLs with ACL_USER entries during setxattr().
+ *
+ * Return: A kuid in @fs_userns for the uid stored in @e.
+ */
+static inline kuid_t
+vfs_set_acl_prepare_kuid(struct user_namespace *mnt_userns,
+			 struct user_namespace *fs_userns,
+			 const struct posix_acl_xattr_entry *e)
+{
+	kuid_t kuid = KUIDT_INIT(le32_to_cpu(e->e_id));
+	return from_vfsuid(mnt_userns, fs_userns, VFSUIDT_INIT(kuid));
+}
+
+/**
+ * vfs_set_acl_prepare_kgid - map ACL_GROUP gid according to mount- and
+ *                            filesystem idmapping
+ * @mnt_userns: the mount's idmapping
+ * @fs_userns: the filesystem's idmapping
+ * @e: a ACL_GROUP entry in POSIX ACL uapi format
+ *
+ * The gid stored as ACL_GROUP entry in @e is a kgid_t stored as a raw {g,u}id
+ * value. The vfs_set_acl_prepare_kgid() will recover the kgid_t through
+ * KGIDT_INIT() and then map it according to the idmapped mount. The resulting
+ * kgid_t is the value which the filesystem can map up into a raw backing store
+ * id in the filesystem's idmapping.
+ *
+ * This is used in vfs_set_acl_prepare() to generate the proper VFS
+ * representation of POSIX ACLs with ACL_GROUP entries during setxattr().
+ *
+ * Return: A kgid in @fs_userns for the gid stored in @e.
+ */
+static inline kgid_t
+vfs_set_acl_prepare_kgid(struct user_namespace *mnt_userns,
+			 struct user_namespace *fs_userns,
+			 const struct posix_acl_xattr_entry *e)
+{
+	kgid_t kgid = KGIDT_INIT(le32_to_cpu(e->e_id));
+	return from_vfsgid(mnt_userns, fs_userns, VFSGIDT_INIT(kgid));
+}
+
+/**
+ * vfs_set_acl_prepare - convert POSIX ACLs from uapi to VFS format taking
+ *                       mount and filesystem idmappings into account
+ * @mnt_userns: the mount's idmapping
+ * @fs_userns: the filesystem's idmapping
+ * @value: the uapi representation of POSIX ACLs
+ * @size: the size of @void
+ *
+ * When setting POSIX ACLs with ACL_{GROUP,USER} entries they need to be
+ * mapped according to the relevant mount- and filesystem idmapping. It is
+ * important that the ACL_{GROUP,USER} entries in struct posix_acl will be
+ * mapped into k{g,u}id_t that are supposed to be mapped up in the filesystem
+ * idmapping. This is crucial since the resulting struct posix_acl might be
+ * cached filesystem wide. The vfs_set_acl_prepare() function will take care to
+ * perform all necessary idmappings.
+ *
+ * Note, that since basically forever the {g,u}id values encoded as
+ * ACL_{GROUP,USER} entries in the uapi POSIX ACLs passed via @value contain
+ * values that have been mapped according to the caller's idmapping. In other
+ * words, POSIX ACLs passed in uapi format as @value during setxattr() contain
+ * {g,u}id values in their ACL_{GROUP,USER} entries that should actually have
+ * been stored as k{g,u}id_t.
+ *
+ * This means, vfs_set_acl_prepare() needs to first recover the k{g,u}id_t by
+ * calling K{G,U}IDT_INIT(). Afterwards they can be interpreted as vfs{g,u}id_t
+ * through from_vfs{g,u}id() to account for any idmapped mounts. The
+ * vfs_set_acl_prepare_k{g,u}id() helpers will take care to generate the
+ * correct k{g,u}id_t.
+ *
+ * The filesystem will then receive the POSIX ACLs ready to be cached
+ * filesystem wide and ready to be written to the backing store taking the
+ * filesystem's idmapping into account.
+ *
+ * Return: Allocated struct posix_acl on success, NULL for a valid header but
+ *         without actual POSIX ACL entries, or ERR_PTR() encoded error code.
+ */
+struct posix_acl *vfs_set_acl_prepare(struct user_namespace *mnt_userns,
+				      struct user_namespace *fs_userns,
+				      const void *value, size_t size)
+{
+	return make_posix_acl(mnt_userns, fs_userns, value, size,
+			      vfs_set_acl_prepare_kuid,
+			      vfs_set_acl_prepare_kgid);
+}
+EXPORT_SYMBOL(vfs_set_acl_prepare);
+
+/**
+ * posix_acl_from_xattr_kuid - map ACL_USER uid into filesystem idmapping
+ * @mnt_userns: unused
+ * @fs_userns: the filesystem's idmapping
+ * @e: a ACL_USER entry in POSIX ACL uapi format
+ *
+ * Map the uid stored as ACL_USER entry in @e into the filesystem's idmapping.
+ * This is used in posix_acl_from_xattr() to generate the proper VFS
+ * representation of POSIX ACLs with ACL_USER entries.
+ *
+ * Return: A kuid in @fs_userns for the uid stored in @e.
+ */
+static inline kuid_t
+posix_acl_from_xattr_kuid(struct user_namespace *mnt_userns,
+			  struct user_namespace *fs_userns,
+			  const struct posix_acl_xattr_entry *e)
+{
+	return make_kuid(fs_userns, le32_to_cpu(e->e_id));
+}
+
+/**
+ * posix_acl_from_xattr_kgid - map ACL_GROUP gid into filesystem idmapping
+ * @mnt_userns: unused
+ * @fs_userns: the filesystem's idmapping
+ * @e: a ACL_GROUP entry in POSIX ACL uapi format
+ *
+ * Map the gid stored as ACL_GROUP entry in @e into the filesystem's idmapping.
+ * This is used in posix_acl_from_xattr() to generate the proper VFS
+ * representation of POSIX ACLs with ACL_GROUP entries.
+ *
+ * Return: A kgid in @fs_userns for the gid stored in @e.
+ */
+static inline kgid_t
+posix_acl_from_xattr_kgid(struct user_namespace *mnt_userns,
+			  struct user_namespace *fs_userns,
+			  const struct posix_acl_xattr_entry *e)
+{
+	return make_kgid(fs_userns, le32_to_cpu(e->e_id));
+}
+
+/**
+ * posix_acl_from_xattr - convert POSIX ACLs from backing store to VFS format
+ * @fs_userns: the filesystem's idmapping
+ * @value: the uapi representation of POSIX ACLs
+ * @size: the size of @void
+ *
+ * Filesystems that store POSIX ACLs in the unaltered uapi format should use
+ * posix_acl_from_xattr() when reading them from the backing store and
+ * converting them into the struct posix_acl VFS format. The helper is
+ * specifically intended to be called from the ->get_acl() inode operation.
+ *
+ * The posix_acl_from_xattr() function will map the raw {g,u}id values stored
+ * in ACL_{GROUP,USER} entries into the filesystem idmapping in @fs_userns. The
+ * posix_acl_from_xattr_k{g,u}id() helpers will take care to generate the
+ * correct k{g,u}id_t. The returned struct posix_acl can be cached.
+ *
+ * Note that posix_acl_from_xattr() does not take idmapped mounts into account.
+ * If it did it calling is from the ->get_acl() inode operation would return
+ * POSIX ACLs mapped according to an idmapped mount which would mean that the
+ * value couldn't be cached for the filesystem. Idmapped mounts are taken into
+ * account on the fly during permission checking or right at the VFS -
+ * userspace boundary before reporting them to the user.
+ *
+ * Return: Allocated struct posix_acl on success, NULL for a valid header but
+ *         without actual POSIX ACL entries, or ERR_PTR() encoded error code.
+ */
+struct posix_acl *
+posix_acl_from_xattr(struct user_namespace *fs_userns,
+		     const void *value, size_t size)
+{
+	return make_posix_acl(&init_user_ns, fs_userns, value, size,
+			      posix_acl_from_xattr_kuid,
+			      posix_acl_from_xattr_kgid);
+}
+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) {
+		/*
+		 * By the time we end up here the {g,u}ids stored in
+		 * ACL_{GROUP,USER} have already been mapped according to the
+		 * caller's idmapping. The vfs_set_acl_prepare() helper will
+		 * recover them and take idmapped mounts into account. The
+		 * filesystem will receive the POSIX ACLs in the correct
+		 * format ready to be cached or written to the backing store
+		 * taking the filesystem idmapping into account.
+		 */
+		acl = vfs_set_acl_prepare(mnt_userns, i_user_ns(inode),
+					  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);
+	if (IS_I_VERSION(inode))
+		inode_inc_iversion(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;
+}