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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * Copyright (C) 2002,2003 by Andreas Gruenbacher <[email protected]>
- *
- * Fixes from William Schumacher incorporated on 15 March 2001.
- * (Reported by Charles Bertsch, <[email protected]>).
- */
- /*
- * 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;
- }
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