xref: /linux/fs/overlayfs/overlayfs.h (revision c21c839b8448dd4b1e37ffc1bde928f57d34c0db)

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 *
 * Copyright (C) 2011 Novell Inc.
 */

#include <linux/kernel.h>
#include <linux/uuid.h>
#include <linux/fs.h>
#include "ovl_entry.h"

#undef pr_fmt
#define pr_fmt(fmt) "overlayfs: " fmt

enum ovl_path_type {
	__OVL_PATH_UPPER	= (1 << 0),
	__OVL_PATH_MERGE	= (1 << 1),
	__OVL_PATH_ORIGIN	= (1 << 2),
};

#define OVL_TYPE_UPPER(type)	((type) & __OVL_PATH_UPPER)
#define OVL_TYPE_MERGE(type)	((type) & __OVL_PATH_MERGE)
#define OVL_TYPE_ORIGIN(type)	((type) & __OVL_PATH_ORIGIN)

#define OVL_XATTR_PREFIX XATTR_TRUSTED_PREFIX "overlay."
#define OVL_XATTR_OPAQUE OVL_XATTR_PREFIX "opaque"
#define OVL_XATTR_REDIRECT OVL_XATTR_PREFIX "redirect"
#define OVL_XATTR_ORIGIN OVL_XATTR_PREFIX "origin"
#define OVL_XATTR_IMPURE OVL_XATTR_PREFIX "impure"
#define OVL_XATTR_NLINK OVL_XATTR_PREFIX "nlink"
#define OVL_XATTR_UPPER OVL_XATTR_PREFIX "upper"
#define OVL_XATTR_METACOPY OVL_XATTR_PREFIX "metacopy"

enum ovl_inode_flag {
	/* Pure upper dir that may contain non pure upper entries */
	OVL_IMPURE,
	/* Non-merge dir that may contain whiteout entries */
	OVL_WHITEOUTS,
	OVL_INDEX,
	OVL_UPPERDATA,
	/* Inode number will remain constant over copy up. */
	OVL_CONST_INO,
};

enum ovl_entry_flag {
	OVL_E_UPPER_ALIAS,
	OVL_E_OPAQUE,
	OVL_E_CONNECTED,
};

enum {
	OVL_XINO_OFF,
	OVL_XINO_AUTO,
	OVL_XINO_ON,
};

/*
 * The tuple (fh,uuid) is a universal unique identifier for a copy up origin,
 * where:
 * origin.fh	- exported file handle of the lower file
 * origin.uuid	- uuid of the lower filesystem
 */
#define OVL_FH_VERSION	0
#define OVL_FH_MAGIC	0xfb

/* CPU byte order required for fid decoding:  */
#define OVL_FH_FLAG_BIG_ENDIAN	(1 << 0)
#define OVL_FH_FLAG_ANY_ENDIAN	(1 << 1)
/* Is the real inode encoded in fid an upper inode? */
#define OVL_FH_FLAG_PATH_UPPER	(1 << 2)

#define OVL_FH_FLAG_ALL (OVL_FH_FLAG_BIG_ENDIAN | OVL_FH_FLAG_ANY_ENDIAN | \
			 OVL_FH_FLAG_PATH_UPPER)

#if defined(__LITTLE_ENDIAN)
#define OVL_FH_FLAG_CPU_ENDIAN 0
#elif defined(__BIG_ENDIAN)
#define OVL_FH_FLAG_CPU_ENDIAN OVL_FH_FLAG_BIG_ENDIAN
#else
#error Endianness not defined
#endif

/* The type used to be returned by overlay exportfs for misaligned fid */
#define OVL_FILEID_V0	0xfb
/* The type returned by overlay exportfs for 32bit aligned fid */
#define OVL_FILEID_V1	0xf8

/* On-disk format for "origin" file handle */
struct ovl_fb {
	u8 version;	/* 0 */
	u8 magic;	/* 0xfb */
	u8 len;		/* size of this header + size of fid */
	u8 flags;	/* OVL_FH_FLAG_* */
	u8 type;	/* fid_type of fid */
	uuid_t uuid;	/* uuid of filesystem */
	u32 fid[];	/* file identifier should be 32bit aligned in-memory */
} __packed;

/* In-memory and on-wire format for overlay file handle */
struct ovl_fh {
	u8 padding[3];	/* make sure fb.fid is 32bit aligned */
	union {
		struct ovl_fb fb;
		u8 buf[0];
	};
} __packed;

#define OVL_FH_WIRE_OFFSET	offsetof(struct ovl_fh, fb)
#define OVL_FH_LEN(fh)		(OVL_FH_WIRE_OFFSET + (fh)->fb.len)
#define OVL_FH_FID_OFFSET	(OVL_FH_WIRE_OFFSET + \
				 offsetof(struct ovl_fb, fid))

static inline int ovl_do_rmdir(struct inode *dir, struct dentry *dentry)
{
	int err = vfs_rmdir(dir, dentry);

	pr_debug("rmdir(%pd2) = %i\n", dentry, err);
	return err;
}

static inline int ovl_do_unlink(struct inode *dir, struct dentry *dentry)
{
	int err = vfs_unlink(dir, dentry, NULL);

	pr_debug("unlink(%pd2) = %i\n", dentry, err);
	return err;
}

static inline int ovl_do_link(struct dentry *old_dentry, struct inode *dir,
			      struct dentry *new_dentry)
{
	int err = vfs_link(old_dentry, dir, new_dentry, NULL);

	pr_debug("link(%pd2, %pd2) = %i\n", old_dentry, new_dentry, err);
	return err;
}

static inline int ovl_do_create(struct inode *dir, struct dentry *dentry,
				umode_t mode)
{
	int err = vfs_create(dir, dentry, mode, true);

	pr_debug("create(%pd2, 0%o) = %i\n", dentry, mode, err);
	return err;
}

static inline int ovl_do_mkdir(struct inode *dir, struct dentry *dentry,
			       umode_t mode)
{
	int err = vfs_mkdir(dir, dentry, mode);
	pr_debug("mkdir(%pd2, 0%o) = %i\n", dentry, mode, err);
	return err;
}

static inline int ovl_do_mknod(struct inode *dir, struct dentry *dentry,
			       umode_t mode, dev_t dev)
{
	int err = vfs_mknod(dir, dentry, mode, dev);

	pr_debug("mknod(%pd2, 0%o, 0%o) = %i\n", dentry, mode, dev, err);
	return err;
}

static inline int ovl_do_symlink(struct inode *dir, struct dentry *dentry,
				 const char *oldname)
{
	int err = vfs_symlink(dir, dentry, oldname);

	pr_debug("symlink(\"%s\", %pd2) = %i\n", oldname, dentry, err);
	return err;
}

static inline int ovl_do_setxattr(struct dentry *dentry, const char *name,
				  const void *value, size_t size, int flags)
{
	int err = vfs_setxattr(dentry, name, value, size, flags);
	pr_debug("setxattr(%pd2, \"%s\", \"%*pE\", %zu, 0x%x) = %i\n",
		 dentry, name, min((int)size, 48), value, size, flags, err);
	return err;
}

static inline int ovl_do_removexattr(struct dentry *dentry, const char *name)
{
	int err = vfs_removexattr(dentry, name);
	pr_debug("removexattr(%pd2, \"%s\") = %i\n", dentry, name, err);
	return err;
}

static inline int ovl_do_rename(struct inode *olddir, struct dentry *olddentry,
				struct inode *newdir, struct dentry *newdentry,
				unsigned int flags)
{
	int err;

	pr_debug("rename(%pd2, %pd2, 0x%x)\n", olddentry, newdentry, flags);
	err = vfs_rename(olddir, olddentry, newdir, newdentry, NULL, flags);
	if (err) {
		pr_debug("...rename(%pd2, %pd2, ...) = %i\n",
			 olddentry, newdentry, err);
	}
	return err;
}

static inline int ovl_do_whiteout(struct inode *dir, struct dentry *dentry)
{
	int err = vfs_whiteout(dir, dentry);
	pr_debug("whiteout(%pd2) = %i\n", dentry, err);
	return err;
}

static inline struct dentry *ovl_do_tmpfile(struct dentry *dentry, umode_t mode)
{
	struct dentry *ret = vfs_tmpfile(dentry, mode, 0);
	int err = PTR_ERR_OR_ZERO(ret);

	pr_debug("tmpfile(%pd2, 0%o) = %i\n", dentry, mode, err);
	return ret;
}

static inline bool ovl_open_flags_need_copy_up(int flags)
{
	if (!flags)
		return false;

	return ((OPEN_FMODE(flags) & FMODE_WRITE) || (flags & O_TRUNC));
}

/* util.c */
int ovl_want_write(struct dentry *dentry);
void ovl_drop_write(struct dentry *dentry);
struct dentry *ovl_workdir(struct dentry *dentry);
const struct cred *ovl_override_creds(struct super_block *sb);
int ovl_can_decode_fh(struct super_block *sb);
struct dentry *ovl_indexdir(struct super_block *sb);
bool ovl_index_all(struct super_block *sb);
bool ovl_verify_lower(struct super_block *sb);
struct ovl_entry *ovl_alloc_entry(unsigned int numlower);
bool ovl_dentry_remote(struct dentry *dentry);
void ovl_dentry_update_reval(struct dentry *dentry, struct dentry *upperdentry,
			     unsigned int mask);
bool ovl_dentry_weird(struct dentry *dentry);
enum ovl_path_type ovl_path_type(struct dentry *dentry);
void ovl_path_upper(struct dentry *dentry, struct path *path);
void ovl_path_lower(struct dentry *dentry, struct path *path);
void ovl_path_lowerdata(struct dentry *dentry, struct path *path);
enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
struct dentry *ovl_dentry_upper(struct dentry *dentry);
struct dentry *ovl_dentry_lower(struct dentry *dentry);
struct dentry *ovl_dentry_lowerdata(struct dentry *dentry);
const struct ovl_layer *ovl_layer_lower(struct dentry *dentry);
struct dentry *ovl_dentry_real(struct dentry *dentry);
struct dentry *ovl_i_dentry_upper(struct inode *inode);
struct inode *ovl_inode_upper(struct inode *inode);
struct inode *ovl_inode_lower(struct inode *inode);
struct inode *ovl_inode_lowerdata(struct inode *inode);
struct inode *ovl_inode_real(struct inode *inode);
struct inode *ovl_inode_realdata(struct inode *inode);
struct ovl_dir_cache *ovl_dir_cache(struct inode *inode);
void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache);
void ovl_dentry_set_flag(unsigned long flag, struct dentry *dentry);
void ovl_dentry_clear_flag(unsigned long flag, struct dentry *dentry);
bool ovl_dentry_test_flag(unsigned long flag, struct dentry *dentry);
bool ovl_dentry_is_opaque(struct dentry *dentry);
bool ovl_dentry_is_whiteout(struct dentry *dentry);
void ovl_dentry_set_opaque(struct dentry *dentry);
bool ovl_dentry_has_upper_alias(struct dentry *dentry);
void ovl_dentry_set_upper_alias(struct dentry *dentry);
bool ovl_dentry_needs_data_copy_up(struct dentry *dentry, int flags);
bool ovl_dentry_needs_data_copy_up_locked(struct dentry *dentry, int flags);
bool ovl_has_upperdata(struct inode *inode);
void ovl_set_upperdata(struct inode *inode);
bool ovl_redirect_dir(struct super_block *sb);
const char *ovl_dentry_get_redirect(struct dentry *dentry);
void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect);
void ovl_inode_update(struct inode *inode, struct dentry *upperdentry);
void ovl_dir_modified(struct dentry *dentry, bool impurity);
u64 ovl_dentry_version_get(struct dentry *dentry);
bool ovl_is_whiteout(struct dentry *dentry);
struct file *ovl_path_open(struct path *path, int flags);
int ovl_copy_up_start(struct dentry *dentry, int flags);
void ovl_copy_up_end(struct dentry *dentry);
bool ovl_already_copied_up(struct dentry *dentry, int flags);
bool ovl_check_origin_xattr(struct dentry *dentry);
bool ovl_check_dir_xattr(struct dentry *dentry, const char *name);
int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
		       const char *name, const void *value, size_t size,
		       int xerr);
int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry);
void ovl_set_flag(unsigned long flag, struct inode *inode);
void ovl_clear_flag(unsigned long flag, struct inode *inode);
bool ovl_test_flag(unsigned long flag, struct inode *inode);
bool ovl_inuse_trylock(struct dentry *dentry);
void ovl_inuse_unlock(struct dentry *dentry);
bool ovl_is_inuse(struct dentry *dentry);
bool ovl_need_index(struct dentry *dentry);
int ovl_nlink_start(struct dentry *dentry);
void ovl_nlink_end(struct dentry *dentry);
int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir);
int ovl_check_metacopy_xattr(struct dentry *dentry);
bool ovl_is_metacopy_dentry(struct dentry *dentry);
char *ovl_get_redirect_xattr(struct dentry *dentry, int padding);
ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value,
		     size_t padding);

static inline bool ovl_is_impuredir(struct dentry *dentry)
{
	return ovl_check_dir_xattr(dentry, OVL_XATTR_IMPURE);
}

/*
 * With xino=auto, we do best effort to keep all inodes on same st_dev and
 * d_ino consistent with st_ino.
 * With xino=on, we do the same effort but we warn if we failed.
 */
static inline bool ovl_xino_warn(struct super_block *sb)
{
	return OVL_FS(sb)->config.xino == OVL_XINO_ON;
}

/* All layers on same fs? */
static inline bool ovl_same_fs(struct super_block *sb)
{
	return OVL_FS(sb)->xino_mode == 0;
}

/* All overlay inodes have same st_dev? */
static inline bool ovl_same_dev(struct super_block *sb)
{
	return OVL_FS(sb)->xino_mode >= 0;
}

static inline unsigned int ovl_xino_bits(struct super_block *sb)
{
	return ovl_same_dev(sb) ? OVL_FS(sb)->xino_mode : 0;
}

static inline void ovl_inode_lock(struct inode *inode)
{
	mutex_lock(&OVL_I(inode)->lock);
}

static inline int ovl_inode_lock_interruptible(struct inode *inode)
{
	return mutex_lock_interruptible(&OVL_I(inode)->lock);
}

static inline void ovl_inode_unlock(struct inode *inode)
{
	mutex_unlock(&OVL_I(inode)->lock);
}


/* namei.c */
int ovl_check_fb_len(struct ovl_fb *fb, int fb_len);

static inline int ovl_check_fh_len(struct ovl_fh *fh, int fh_len)
{
	return ovl_check_fb_len(&fh->fb, fh_len - OVL_FH_WIRE_OFFSET);
}

struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt,
				  bool connected);
int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
			struct dentry *upperdentry, struct ovl_path **stackp);
int ovl_verify_set_fh(struct dentry *dentry, const char *name,
		      struct dentry *real, bool is_upper, bool set);
struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index);
int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index);
int ovl_get_index_name(struct dentry *origin, struct qstr *name);
struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh);
struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
				struct dentry *origin, bool verify);
int ovl_path_next(int idx, struct dentry *dentry, struct path *path);
struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
			  unsigned int flags);
bool ovl_lower_positive(struct dentry *dentry);

static inline int ovl_verify_origin(struct dentry *upper,
				    struct dentry *origin, bool set)
{
	return ovl_verify_set_fh(upper, OVL_XATTR_ORIGIN, origin, false, set);
}

static inline int ovl_verify_upper(struct dentry *index,
				    struct dentry *upper, bool set)
{
	return ovl_verify_set_fh(index, OVL_XATTR_UPPER, upper, true, set);
}

/* readdir.c */
extern const struct file_operations ovl_dir_operations;
int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list);
void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list);
void ovl_cache_free(struct list_head *list);
void ovl_dir_cache_free(struct inode *inode);
int ovl_check_d_type_supported(struct path *realpath);
int ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
			struct dentry *dentry, int level);
int ovl_indexdir_cleanup(struct ovl_fs *ofs);

/* inode.c */
int ovl_set_nlink_upper(struct dentry *dentry);
int ovl_set_nlink_lower(struct dentry *dentry);
unsigned int ovl_get_nlink(struct dentry *lowerdentry,
			   struct dentry *upperdentry,
			   unsigned int fallback);
int ovl_setattr(struct dentry *dentry, struct iattr *attr);
int ovl_getattr(const struct path *path, struct kstat *stat,
		u32 request_mask, unsigned int flags);
int ovl_permission(struct inode *inode, int mask);
int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
		  const void *value, size_t size, int flags);
int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
		  void *value, size_t size);
ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
struct posix_acl *ovl_get_acl(struct inode *inode, int type);
int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags);
bool ovl_is_private_xattr(const char *name);

struct ovl_inode_params {
	struct inode *newinode;
	struct dentry *upperdentry;
	struct ovl_path *lowerpath;
	struct dentry *index;
	unsigned int numlower;
	char *redirect;
	struct dentry *lowerdata;
};
void ovl_inode_init(struct inode *inode, struct ovl_inode_params *oip,
		    unsigned long ino, int fsid);
struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev);
struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
			       bool is_upper);
bool ovl_lookup_trap_inode(struct super_block *sb, struct dentry *dir);
struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir);
struct inode *ovl_get_inode(struct super_block *sb,
			    struct ovl_inode_params *oip);
static inline void ovl_copyattr(struct inode *from, struct inode *to)
{
	to->i_uid = from->i_uid;
	to->i_gid = from->i_gid;
	to->i_mode = from->i_mode;
	to->i_atime = from->i_atime;
	to->i_mtime = from->i_mtime;
	to->i_ctime = from->i_ctime;
	i_size_write(to, i_size_read(from));
}

static inline void ovl_copyflags(struct inode *from, struct inode *to)
{
	unsigned int mask = S_SYNC | S_IMMUTABLE | S_APPEND | S_NOATIME;

	inode_set_flags(to, from->i_flags & mask, mask);
}

/* dir.c */
extern const struct inode_operations ovl_dir_inode_operations;
int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
			     struct dentry *dentry);
struct ovl_cattr {
	dev_t rdev;
	umode_t mode;
	const char *link;
	struct dentry *hardlink;
};

#define OVL_CATTR(m) (&(struct ovl_cattr) { .mode = (m) })

struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
			       struct ovl_cattr *attr);
int ovl_cleanup(struct inode *dir, struct dentry *dentry);
struct dentry *ovl_lookup_temp(struct dentry *workdir);
struct dentry *ovl_create_temp(struct dentry *workdir, struct ovl_cattr *attr);

/* file.c */
extern const struct file_operations ovl_file_operations;
int __init ovl_aio_request_cache_init(void);
void ovl_aio_request_cache_destroy(void);

/* copy_up.c */
int ovl_copy_up(struct dentry *dentry);
int ovl_copy_up_with_data(struct dentry *dentry);
int ovl_copy_up_flags(struct dentry *dentry, int flags);
int ovl_maybe_copy_up(struct dentry *dentry, int flags);
int ovl_copy_xattr(struct dentry *old, struct dentry *new);
int ovl_set_attr(struct dentry *upper, struct kstat *stat);
struct ovl_fh *ovl_encode_real_fh(struct dentry *real, bool is_upper);
int ovl_set_origin(struct dentry *dentry, struct dentry *lower,
		   struct dentry *upper);

/* export.c */
extern const struct export_operations ovl_export_operations;