posix_acl.c | Explore in Territory

// 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>
#include <linux/security.h>
#include <linux/fsnotify.h>
#include <linux/filelock.h>

#include "internal.h"

static struct posix_acl **acl_by_type(struct inode *inode, int type)
{ … }

struct posix_acl *get_cached_acl(struct inode *inode, int type)
{ … }
EXPORT_SYMBOL(…);

struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
{ … }
EXPORT_SYMBOL(…);

void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
{ … }
EXPORT_SYMBOL(…);

static void __forget_cached_acl(struct posix_acl **p)
{ … }

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

void forget_all_cached_acls(struct inode *inode)
{ … }
EXPORT_SYMBOL(…);

static struct posix_acl *__get_acl(struct mnt_idmap *idmap,
				   struct dentry *dentry, struct inode *inode,
				   int type)
{ … }

struct posix_acl *get_inode_acl(struct inode *inode, int type)
{ … }
EXPORT_SYMBOL(…);

/*
 * Init a fresh posix_acl
 */
void
posix_acl_init(struct posix_acl *acl, int count)
{ … }
EXPORT_SYMBOL(…);

/*
 * Allocate a new ACL with the specified number of entries.
 */
struct posix_acl *
posix_acl_alloc(int count, gfp_t flags)
{ … }
EXPORT_SYMBOL(…);

/*
 * Clone an ACL.
 */
struct posix_acl *
posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * 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)
{ … }
EXPORT_SYMBOL(…);

/*
 * 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)
{ … }
EXPORT_SYMBOL(…);

/*
 * 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)
{ … }
EXPORT_SYMBOL(…);

/*
 * Return 0 if current is granted want access to the inode
 * by the acl. Returns -E... otherwise.
 */
int
posix_acl_permission(struct mnt_idmap *idmap, struct inode *inode,
		     const struct posix_acl *acl, int want)
{ … }

/*
 * 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)
{ … }

/*
 * Modify the ACL for the chmod syscall.
 */
static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
{ … }

int
__posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
{ … }
EXPORT_SYMBOL(…);

int
__posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
{ … }
EXPORT_SYMBOL(…);

/**
 * posix_acl_chmod - chmod a posix acl
 *
 * @idmap:	idmap of the mount @inode was found from
 * @dentry:	dentry to check permissions on
 * @mode:	the new mode of @inode
 *
 * If the dentry has been found through an idmapped mount the idmap of
 * the vfsmount must be passed through @idmap. This function will then
 * take care to map the inode according to @idmap before checking
 * permissions. On non-idmapped mounts or if permission checking is to be
 * performed on the raw inode simply pass @nop_mnt_idmap.
 */
int
 posix_acl_chmod(struct mnt_idmap *idmap, struct dentry *dentry,
		    umode_t mode)
{ … }
EXPORT_SYMBOL(…);

int
posix_acl_create(struct inode *dir, umode_t *mode,
		struct posix_acl **default_acl, struct posix_acl **acl)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * posix_acl_update_mode  -  update mode in set_acl
 * @idmap:	idmap 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 idmap of
 * the vfsmount must be passed through @idmap. This function will then
 * take care to map the inode according to @idmap before checking
 * permissions. On non-idmapped mounts or if permission checking is to be
 * performed on the raw inode simply pass @nop_mnt_idmap.
 *
 * Called from set_acl inode operations.
 */
int posix_acl_update_mode(struct mnt_idmap *idmap,
			  struct inode *inode, umode_t *mode_p,
			  struct posix_acl **acl)
{ … }
EXPORT_SYMBOL(…);

/*
 * 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)
{ … }

/**
 * posix_acl_from_xattr - convert POSIX ACLs from backing store to VFS format
 * @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 acl inode operation.
 *
 * The posix_acl_from_xattr() function will map the raw {g,u}id values stored
 * in ACL_{GROUP,USER} entries into idmapping in @userns.
 *
 * Note that posix_acl_from_xattr() does not take idmapped mounts into account.
 * If it did it calling it 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 *userns,
				       const void *value, size_t size)
{ … }
EXPORT_SYMBOL(…);

/*
 * 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)
{ … }
EXPORT_SYMBOL(…);

/**
 * vfs_posix_acl_to_xattr - convert from kernel to userspace representation
 * @idmap: idmap of the mount
 * @inode: inode the posix acls are set on
 * @acl: the posix acls as represented by the vfs
 * @buffer: the buffer into which to convert @acl
 * @size: size of @buffer
 *
 * This converts @acl from the VFS representation in the filesystem idmapping
 * to the uapi form reportable to userspace. And mount and caller idmappings
 * are handled appropriately.
 *
 * Return: On success, the size of the stored uapi posix acls, on error a
 * negative errno.
 */
static ssize_t vfs_posix_acl_to_xattr(struct mnt_idmap *idmap,
				      struct inode *inode,
				      const struct posix_acl *acl, void *buffer,
				      size_t size)

{ … }

int
set_posix_acl(struct mnt_idmap *idmap, struct dentry *dentry,
	      int type, struct posix_acl *acl)
{ … }
EXPORT_SYMBOL(…);

int posix_acl_listxattr(struct inode *inode, char **buffer,
			ssize_t *remaining_size)
{ … }

static bool
posix_acl_xattr_list(struct dentry *dentry)
{ … }

/*
 * nop_posix_acl_access - legacy xattr handler for access POSIX ACLs
 *
 * This is the legacy POSIX ACL access xattr handler. It is used by some
 * filesystems to implement their ->listxattr() inode operation. New code
 * should never use them.
 */
const struct xattr_handler nop_posix_acl_access = …;
EXPORT_SYMBOL_GPL(…);

/*
 * nop_posix_acl_default - legacy xattr handler for default POSIX ACLs
 *
 * This is the legacy POSIX ACL default xattr handler. It is used by some
 * filesystems to implement their ->listxattr() inode operation. New code
 * should never use them.
 */
const struct xattr_handler nop_posix_acl_default = …;
EXPORT_SYMBOL_GPL(…);

int simple_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
		   struct posix_acl *acl, int type)
{ … }

int simple_acl_create(struct inode *dir, struct inode *inode)
{ … }

static int vfs_set_acl_idmapped_mnt(struct mnt_idmap *idmap,
				    struct user_namespace *fs_userns,
				    struct posix_acl *acl)
{ … }

/**
 * vfs_set_acl - set posix acls
 * @idmap: idmap of the mount
 * @dentry: the dentry based on which to set the posix acls
 * @acl_name: the name of the posix acl
 * @kacl: the posix acls in the appropriate VFS format
 *
 * This function sets @kacl. The caller must all posix_acl_release() on @kacl
 * afterwards.
 *
 * Return: On success 0, on error negative errno.
 */
int vfs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
		const char *acl_name, struct posix_acl *kacl)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * vfs_get_acl - get posix acls
 * @idmap: idmap of the mount
 * @dentry: the dentry based on which to retrieve the posix acls
 * @acl_name: the name of the posix acl
 *
 * This function retrieves @kacl from the filesystem. The caller must all
 * posix_acl_release() on @kacl.
 *
 * Return: On success POSIX ACLs in VFS format, on error negative errno.
 */
struct posix_acl *vfs_get_acl(struct mnt_idmap *idmap,
			      struct dentry *dentry, const char *acl_name)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * vfs_remove_acl - remove posix acls
 * @idmap: idmap of the mount
 * @dentry: the dentry based on which to retrieve the posix acls
 * @acl_name: the name of the posix acl
 *
 * This function removes posix acls.
 *
 * Return: On success 0, on error negative errno.
 */
int vfs_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
		   const char *acl_name)
{ … }
EXPORT_SYMBOL_GPL(…);

int do_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
	       const char *acl_name, const void *kvalue, size_t size)
{ … }

ssize_t do_get_acl(struct mnt_idmap *idmap, struct dentry *dentry,
		   const char *acl_name, void *kvalue, size_t size)
{ … }
linux/fs/posix_acl.c
