linux/fs/overlayfs/namei.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2011 Novell Inc.
 * Copyright (C) 2016 Red Hat, Inc.
 */

#include <linux/fs.h>
#include <linux/cred.h>
#include <linux/ctype.h>
#include <linux/namei.h>
#include <linux/xattr.h>
#include <linux/ratelimit.h>
#include <linux/mount.h>
#include <linux/exportfs.h>
#include "overlayfs.h"

#include "../internal.h"	/* for vfs_path_lookup */

struct ovl_lookup_data { … };

static int ovl_check_redirect(const struct path *path, struct ovl_lookup_data *d,
			      size_t prelen, const char *post)
{ … }

static int ovl_acceptable(void *ctx, struct dentry *dentry)
{ … }

/*
 * Check validity of an overlay file handle buffer.
 *
 * Return 0 for a valid file handle.
 * Return -ENODATA for "origin unknown".
 * Return <0 for an invalid file handle.
 */
int ovl_check_fb_len(struct ovl_fb *fb, int fb_len)
{ … }

static struct ovl_fh *ovl_get_fh(struct ovl_fs *ofs, struct dentry *upperdentry,
				 enum ovl_xattr ox)
{ … }

struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh,
				  struct vfsmount *mnt, bool connected)
{ … }

static struct dentry *ovl_lookup_positive_unlocked(struct ovl_lookup_data *d,
						   const char *name,
						   struct dentry *base, int len,
						   bool drop_negative)
{ … }

static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
			     const char *name, unsigned int namelen,
			     size_t prelen, const char *post,
			     struct dentry **ret, bool drop_negative)
{ … }

static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
			    struct dentry **ret, bool drop_negative)
{ … }

static int ovl_lookup_data_layer(struct dentry *dentry, const char *redirect,
				 const struct ovl_layer *layer,
				 struct path *datapath)
{ … }

/* Lookup in data-only layers by absolute redirect to layer root */
static int ovl_lookup_data_layers(struct dentry *dentry, const char *redirect,
				  struct ovl_path *lowerdata)
{ … }

int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
			struct dentry *upperdentry, struct ovl_path **stackp)
{ … }

static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry,
			    struct ovl_path **stackp)
{ … }

/*
 * Verify that @fh matches the file handle stored in xattr @name.
 * Return 0 on match, -ESTALE on mismatch, < 0 on error.
 */
static int ovl_verify_fh(struct ovl_fs *ofs, struct dentry *dentry,
			 enum ovl_xattr ox, const struct ovl_fh *fh)
{ … }

int ovl_verify_set_fh(struct ovl_fs *ofs, struct dentry *dentry,
		      enum ovl_xattr ox, const struct ovl_fh *fh,
		      bool is_upper, bool set)
{ … }

/*
 * Verify that @real dentry matches the file handle stored in xattr @name.
 *
 * If @set is true and there is no stored file handle, encode @real and store
 * file handle in xattr @name.
 *
 * Return 0 on match, -ESTALE on mismatch, -ENODATA on no xattr, < 0 on error.
 */
int ovl_verify_origin_xattr(struct ovl_fs *ofs, struct dentry *dentry,
			    enum ovl_xattr ox, struct dentry *real,
			    bool is_upper, bool set)
{ … }


/* Get upper dentry from index */
struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index,
			       bool connected)
{ … }

/*
 * Verify that an index entry name matches the origin file handle stored in
 * OVL_XATTR_ORIGIN and that origin file handle can be decoded to lower path.
 * Return 0 on match, -ESTALE on mismatch or stale origin, < 0 on error.
 */
int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index)
{ … }

int ovl_get_index_name_fh(const struct ovl_fh *fh, struct qstr *name)
{ … }

/*
 * Lookup in indexdir for the index entry of a lower real inode or a copy up
 * origin inode. The index entry name is the hex representation of the lower
 * inode file handle.
 *
 * If the index dentry in negative, then either no lower aliases have been
 * copied up yet, or aliases have been copied up in older kernels and are
 * not indexed.
 *
 * If the index dentry for a copy up origin inode is positive, but points
 * to an inode different than the upper inode, then either the upper inode
 * has been copied up and not indexed or it was indexed, but since then
 * index dir was cleared. Either way, that index cannot be used to identify
 * the overlay inode.
 */
int ovl_get_index_name(struct ovl_fs *ofs, struct dentry *origin,
		       struct qstr *name)
{ … }

/* Lookup index by file handle for NFS export */
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)
{ … }

/*
 * Returns next layer in stack starting from top.
 * Returns -1 if this is the last layer.
 */
int ovl_path_next(int idx, struct dentry *dentry, struct path *path,
		  const struct ovl_layer **layer)
{ … }

/* Fix missing 'origin' xattr */
static int ovl_fix_origin(struct ovl_fs *ofs, struct dentry *dentry,
			  struct dentry *lower, struct dentry *upper)
{ … }

static int ovl_maybe_validate_verity(struct dentry *dentry)
{ … }

/* Lazy lookup of lowerdata */
static int ovl_maybe_lookup_lowerdata(struct dentry *dentry)
{ … }

int ovl_verify_lowerdata(struct dentry *dentry)
{ … }

struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
			  unsigned int flags)
{ … }

bool ovl_lower_positive(struct dentry *dentry)
{ … }