402 lines
8.4 KiB
C
402 lines
8.4 KiB
C
/*
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* Copyright (C) 2011 Novell Inc.
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* Copyright (C) 2016 Red Hat, Inc.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*/
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#include <linux/fs.h>
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#include <linux/namei.h>
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#include <linux/xattr.h>
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#include <linux/ratelimit.h>
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#include "overlayfs.h"
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#include "ovl_entry.h"
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struct ovl_lookup_data {
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struct qstr name;
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bool is_dir;
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bool opaque;
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bool stop;
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bool last;
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char *redirect;
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};
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static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
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size_t prelen, const char *post)
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{
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int res;
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char *s, *next, *buf = NULL;
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res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0);
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if (res < 0) {
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if (res == -ENODATA || res == -EOPNOTSUPP)
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return 0;
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goto fail;
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}
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buf = kzalloc(prelen + res + strlen(post) + 1, GFP_TEMPORARY);
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if (!buf)
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return -ENOMEM;
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if (res == 0)
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goto invalid;
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res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res);
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if (res < 0)
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goto fail;
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if (res == 0)
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goto invalid;
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if (buf[0] == '/') {
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for (s = buf; *s++ == '/'; s = next) {
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next = strchrnul(s, '/');
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if (s == next)
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goto invalid;
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}
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} else {
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if (strchr(buf, '/') != NULL)
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goto invalid;
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memmove(buf + prelen, buf, res);
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memcpy(buf, d->name.name, prelen);
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}
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strcat(buf, post);
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kfree(d->redirect);
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d->redirect = buf;
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d->name.name = d->redirect;
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d->name.len = strlen(d->redirect);
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return 0;
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err_free:
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kfree(buf);
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return 0;
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fail:
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pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res);
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goto err_free;
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invalid:
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pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf);
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goto err_free;
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}
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static bool ovl_is_opaquedir(struct dentry *dentry)
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{
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int res;
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char val;
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if (!d_is_dir(dentry))
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return false;
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res = vfs_getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1);
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if (res == 1 && val == 'y')
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return true;
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return false;
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}
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static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
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const char *name, unsigned int namelen,
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size_t prelen, const char *post,
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struct dentry **ret)
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{
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struct dentry *this;
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int err;
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this = lookup_one_len_unlocked(name, base, namelen);
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if (IS_ERR(this)) {
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err = PTR_ERR(this);
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this = NULL;
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if (err == -ENOENT || err == -ENAMETOOLONG)
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goto out;
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goto out_err;
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}
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if (!this->d_inode)
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goto put_and_out;
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if (ovl_dentry_weird(this)) {
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/* Don't support traversing automounts and other weirdness */
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err = -EREMOTE;
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goto out_err;
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}
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if (ovl_is_whiteout(this)) {
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d->stop = d->opaque = true;
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goto put_and_out;
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}
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if (!d_can_lookup(this)) {
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d->stop = true;
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if (d->is_dir)
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goto put_and_out;
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goto out;
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}
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d->is_dir = true;
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if (!d->last && ovl_is_opaquedir(this)) {
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d->stop = d->opaque = true;
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goto out;
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}
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err = ovl_check_redirect(this, d, prelen, post);
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if (err)
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goto out_err;
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out:
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*ret = this;
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return 0;
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put_and_out:
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dput(this);
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this = NULL;
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goto out;
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out_err:
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dput(this);
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return err;
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}
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static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
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struct dentry **ret)
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{
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const char *s = d->name.name;
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struct dentry *dentry = NULL;
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int err;
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if (*s != '/')
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return ovl_lookup_single(base, d, d->name.name, d->name.len,
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0, "", ret);
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while (*s++ == '/' && !IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
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const char *next = strchrnul(s, '/');
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size_t slen = strlen(s);
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if (WARN_ON(slen > d->name.len) ||
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WARN_ON(strcmp(d->name.name + d->name.len - slen, s)))
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return -EIO;
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err = ovl_lookup_single(base, d, s, next - s,
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d->name.len - slen, next, &base);
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dput(dentry);
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if (err)
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return err;
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dentry = base;
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s = next;
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}
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*ret = dentry;
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return 0;
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}
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/*
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* Returns next layer in stack starting from top.
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* Returns -1 if this is the last layer.
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*/
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int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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BUG_ON(idx < 0);
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if (idx == 0) {
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ovl_path_upper(dentry, path);
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if (path->dentry)
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return oe->numlower ? 1 : -1;
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idx++;
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}
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BUG_ON(idx > oe->numlower);
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*path = oe->lowerstack[idx - 1];
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return (idx < oe->numlower) ? idx + 1 : -1;
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}
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struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
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unsigned int flags)
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{
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struct ovl_entry *oe;
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const struct cred *old_cred;
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struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
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struct ovl_entry *poe = dentry->d_parent->d_fsdata;
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struct path *stack = NULL;
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struct dentry *upperdir, *upperdentry = NULL;
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unsigned int ctr = 0;
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struct inode *inode = NULL;
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bool upperopaque = false;
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char *upperredirect = NULL;
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struct dentry *this;
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unsigned int i;
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int err;
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struct ovl_lookup_data d = {
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.name = dentry->d_name,
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.is_dir = false,
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.opaque = false,
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.stop = false,
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.last = !poe->numlower,
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.redirect = NULL,
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};
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if (dentry->d_name.len > ofs->namelen)
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return ERR_PTR(-ENAMETOOLONG);
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old_cred = ovl_override_creds(dentry->d_sb);
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upperdir = ovl_upperdentry_dereference(poe);
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if (upperdir) {
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err = ovl_lookup_layer(upperdir, &d, &upperdentry);
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if (err)
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goto out;
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if (upperdentry && unlikely(ovl_dentry_remote(upperdentry))) {
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dput(upperdentry);
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err = -EREMOTE;
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goto out;
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}
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if (d.redirect) {
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upperredirect = kstrdup(d.redirect, GFP_KERNEL);
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if (!upperredirect)
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goto out_put_upper;
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if (d.redirect[0] == '/')
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poe = dentry->d_sb->s_root->d_fsdata;
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}
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upperopaque = d.opaque;
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}
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if (!d.stop && poe->numlower) {
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err = -ENOMEM;
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stack = kcalloc(ofs->numlower, sizeof(struct path),
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GFP_TEMPORARY);
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if (!stack)
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goto out_put_upper;
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}
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for (i = 0; !d.stop && i < poe->numlower; i++) {
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struct path lowerpath = poe->lowerstack[i];
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d.last = i == poe->numlower - 1;
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err = ovl_lookup_layer(lowerpath.dentry, &d, &this);
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if (err)
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goto out_put;
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if (!this)
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continue;
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stack[ctr].dentry = this;
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stack[ctr].mnt = lowerpath.mnt;
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ctr++;
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if (d.stop)
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break;
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if (d.redirect &&
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d.redirect[0] == '/' &&
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poe != dentry->d_sb->s_root->d_fsdata) {
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poe = dentry->d_sb->s_root->d_fsdata;
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/* Find the current layer on the root dentry */
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for (i = 0; i < poe->numlower; i++)
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if (poe->lowerstack[i].mnt == lowerpath.mnt)
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break;
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if (WARN_ON(i == poe->numlower))
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break;
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}
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}
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oe = ovl_alloc_entry(ctr);
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err = -ENOMEM;
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if (!oe)
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goto out_put;
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if (upperdentry || ctr) {
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struct dentry *realdentry;
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struct inode *realinode;
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realdentry = upperdentry ? upperdentry : stack[0].dentry;
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realinode = d_inode(realdentry);
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err = -ENOMEM;
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if (upperdentry && !d_is_dir(upperdentry)) {
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inode = ovl_get_inode(dentry->d_sb, realinode);
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} else {
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inode = ovl_new_inode(dentry->d_sb, realinode->i_mode,
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realinode->i_rdev);
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if (inode)
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ovl_inode_init(inode, realinode, !!upperdentry);
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}
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if (!inode)
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goto out_free_oe;
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ovl_copyattr(realdentry->d_inode, inode);
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}
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revert_creds(old_cred);
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oe->opaque = upperopaque;
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oe->redirect = upperredirect;
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oe->__upperdentry = upperdentry;
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memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
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kfree(stack);
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kfree(d.redirect);
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dentry->d_fsdata = oe;
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d_add(dentry, inode);
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return NULL;
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out_free_oe:
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kfree(oe);
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out_put:
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for (i = 0; i < ctr; i++)
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dput(stack[i].dentry);
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kfree(stack);
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out_put_upper:
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dput(upperdentry);
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kfree(upperredirect);
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out:
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kfree(d.redirect);
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revert_creds(old_cred);
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return ERR_PTR(err);
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}
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bool ovl_lower_positive(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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struct ovl_entry *poe = dentry->d_parent->d_fsdata;
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const struct qstr *name = &dentry->d_name;
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unsigned int i;
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bool positive = false;
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bool done = false;
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/*
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* If dentry is negative, then lower is positive iff this is a
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* whiteout.
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*/
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if (!dentry->d_inode)
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return oe->opaque;
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/* Negative upper -> positive lower */
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if (!oe->__upperdentry)
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return true;
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/* Positive upper -> have to look up lower to see whether it exists */
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for (i = 0; !done && !positive && i < poe->numlower; i++) {
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struct dentry *this;
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struct dentry *lowerdir = poe->lowerstack[i].dentry;
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this = lookup_one_len_unlocked(name->name, lowerdir,
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name->len);
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if (IS_ERR(this)) {
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switch (PTR_ERR(this)) {
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case -ENOENT:
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case -ENAMETOOLONG:
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break;
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default:
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/*
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* Assume something is there, we just couldn't
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* access it.
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*/
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positive = true;
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break;
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}
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} else {
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if (this->d_inode) {
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positive = !ovl_is_whiteout(this);
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done = true;
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}
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dput(this);
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}
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}
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return positive;
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}
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