433 lines
8.9 KiB
C
433 lines
8.9 KiB
C
/*
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*
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* Copyright (C) 2011 Novell 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/slab.h>
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#include <linux/xattr.h>
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#include "overlayfs.h"
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static int ovl_copy_up_truncate(struct dentry *dentry)
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{
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int err;
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struct dentry *parent;
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struct kstat stat;
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struct path lowerpath;
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parent = dget_parent(dentry);
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err = ovl_copy_up(parent);
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if (err)
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goto out_dput_parent;
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ovl_path_lower(dentry, &lowerpath);
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err = vfs_getattr(&lowerpath, &stat);
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if (err)
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goto out_dput_parent;
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stat.size = 0;
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err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
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out_dput_parent:
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dput(parent);
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return err;
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}
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int ovl_setattr(struct dentry *dentry, struct iattr *attr)
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{
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int err;
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struct dentry *upperdentry;
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err = ovl_want_write(dentry);
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if (err)
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goto out;
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err = ovl_copy_up(dentry);
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if (!err) {
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upperdentry = ovl_dentry_upper(dentry);
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mutex_lock(&upperdentry->d_inode->i_mutex);
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err = notify_change(upperdentry, attr, NULL);
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mutex_unlock(&upperdentry->d_inode->i_mutex);
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}
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ovl_drop_write(dentry);
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out:
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return err;
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}
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static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
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struct kstat *stat)
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{
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struct path realpath;
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ovl_path_real(dentry, &realpath);
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return vfs_getattr(&realpath, stat);
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}
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int ovl_permission(struct inode *inode, int mask)
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{
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struct ovl_entry *oe;
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struct dentry *alias = NULL;
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struct inode *realinode;
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struct dentry *realdentry;
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bool is_upper;
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int err;
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if (S_ISDIR(inode->i_mode)) {
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oe = inode->i_private;
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} else if (mask & MAY_NOT_BLOCK) {
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return -ECHILD;
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} else {
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/*
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* For non-directories find an alias and get the info
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* from there.
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*/
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alias = d_find_any_alias(inode);
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if (WARN_ON(!alias))
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return -ENOENT;
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oe = alias->d_fsdata;
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}
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realdentry = ovl_entry_real(oe, &is_upper);
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/* Careful in RCU walk mode */
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realinode = ACCESS_ONCE(realdentry->d_inode);
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if (!realinode) {
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WARN_ON(!(mask & MAY_NOT_BLOCK));
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err = -ENOENT;
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goto out_dput;
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}
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if (mask & MAY_WRITE) {
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umode_t mode = realinode->i_mode;
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/*
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* Writes will always be redirected to upper layer, so
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* ignore lower layer being read-only.
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*
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* If the overlay itself is read-only then proceed
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* with the permission check, don't return EROFS.
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* This will only happen if this is the lower layer of
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* another overlayfs.
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*
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* If upper fs becomes read-only after the overlay was
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* constructed return EROFS to prevent modification of
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* upper layer.
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*/
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err = -EROFS;
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if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
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(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
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goto out_dput;
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}
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err = __inode_permission(realinode, mask);
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out_dput:
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dput(alias);
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return err;
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}
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struct ovl_link_data {
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struct dentry *realdentry;
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void *cookie;
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};
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static const char *ovl_follow_link(struct dentry *dentry, void **cookie)
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{
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struct dentry *realdentry;
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struct inode *realinode;
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struct ovl_link_data *data = NULL;
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const char *ret;
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realdentry = ovl_dentry_real(dentry);
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realinode = realdentry->d_inode;
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if (WARN_ON(!realinode->i_op->follow_link))
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return ERR_PTR(-EPERM);
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if (realinode->i_op->put_link) {
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data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
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if (!data)
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return ERR_PTR(-ENOMEM);
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data->realdentry = realdentry;
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}
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ret = realinode->i_op->follow_link(realdentry, cookie);
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if (IS_ERR_OR_NULL(ret)) {
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kfree(data);
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return ret;
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}
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if (data)
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data->cookie = *cookie;
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*cookie = data;
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return ret;
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}
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static void ovl_put_link(struct inode *unused, void *c)
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{
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struct inode *realinode;
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struct ovl_link_data *data = c;
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if (!data)
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return;
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realinode = data->realdentry->d_inode;
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realinode->i_op->put_link(realinode, data->cookie);
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kfree(data);
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}
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static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
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{
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struct path realpath;
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struct inode *realinode;
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ovl_path_real(dentry, &realpath);
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realinode = realpath.dentry->d_inode;
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if (!realinode->i_op->readlink)
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return -EINVAL;
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touch_atime(&realpath);
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return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
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}
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static bool ovl_is_private_xattr(const char *name)
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{
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return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0;
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}
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int ovl_setxattr(struct dentry *dentry, const char *name,
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const void *value, size_t size, int flags)
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{
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int err;
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struct dentry *upperdentry;
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err = ovl_want_write(dentry);
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if (err)
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goto out;
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err = -EPERM;
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if (ovl_is_private_xattr(name))
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goto out_drop_write;
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err = ovl_copy_up(dentry);
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if (err)
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goto out_drop_write;
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upperdentry = ovl_dentry_upper(dentry);
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err = vfs_setxattr(upperdentry, name, value, size, flags);
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out_drop_write:
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ovl_drop_write(dentry);
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out:
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return err;
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}
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static bool ovl_need_xattr_filter(struct dentry *dentry,
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enum ovl_path_type type)
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{
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if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER)
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return S_ISDIR(dentry->d_inode->i_mode);
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else
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return false;
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}
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ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
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void *value, size_t size)
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{
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struct path realpath;
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enum ovl_path_type type = ovl_path_real(dentry, &realpath);
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if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
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return -ENODATA;
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return vfs_getxattr(realpath.dentry, name, value, size);
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}
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ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
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{
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struct path realpath;
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enum ovl_path_type type = ovl_path_real(dentry, &realpath);
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ssize_t res;
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int off;
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res = vfs_listxattr(realpath.dentry, list, size);
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if (res <= 0 || size == 0)
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return res;
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if (!ovl_need_xattr_filter(dentry, type))
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return res;
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/* filter out private xattrs */
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for (off = 0; off < res;) {
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char *s = list + off;
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size_t slen = strlen(s) + 1;
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BUG_ON(off + slen > res);
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if (ovl_is_private_xattr(s)) {
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res -= slen;
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memmove(s, s + slen, res - off);
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} else {
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off += slen;
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}
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}
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return res;
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}
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int ovl_removexattr(struct dentry *dentry, const char *name)
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{
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int err;
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struct path realpath;
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enum ovl_path_type type = ovl_path_real(dentry, &realpath);
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err = ovl_want_write(dentry);
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if (err)
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goto out;
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err = -ENODATA;
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if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
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goto out_drop_write;
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if (!OVL_TYPE_UPPER(type)) {
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err = vfs_getxattr(realpath.dentry, name, NULL, 0);
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if (err < 0)
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goto out_drop_write;
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err = ovl_copy_up(dentry);
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if (err)
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goto out_drop_write;
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ovl_path_upper(dentry, &realpath);
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}
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err = vfs_removexattr(realpath.dentry, name);
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out_drop_write:
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ovl_drop_write(dentry);
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out:
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return err;
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}
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static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
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struct dentry *realdentry)
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{
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if (OVL_TYPE_UPPER(type))
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return false;
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if (special_file(realdentry->d_inode->i_mode))
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return false;
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if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
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return false;
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return true;
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}
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struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags)
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{
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int err;
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struct path realpath;
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enum ovl_path_type type;
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if (d_is_dir(dentry))
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return d_backing_inode(dentry);
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type = ovl_path_real(dentry, &realpath);
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if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
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err = ovl_want_write(dentry);
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if (err)
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return ERR_PTR(err);
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if (file_flags & O_TRUNC)
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err = ovl_copy_up_truncate(dentry);
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else
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err = ovl_copy_up(dentry);
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ovl_drop_write(dentry);
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if (err)
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return ERR_PTR(err);
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ovl_path_upper(dentry, &realpath);
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}
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if (realpath.dentry->d_flags & DCACHE_OP_SELECT_INODE)
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return realpath.dentry->d_op->d_select_inode(realpath.dentry, file_flags);
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return d_backing_inode(realpath.dentry);
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}
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static const struct inode_operations ovl_file_inode_operations = {
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.setattr = ovl_setattr,
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.permission = ovl_permission,
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.getattr = ovl_getattr,
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.setxattr = ovl_setxattr,
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.getxattr = ovl_getxattr,
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.listxattr = ovl_listxattr,
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.removexattr = ovl_removexattr,
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};
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static const struct inode_operations ovl_symlink_inode_operations = {
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.setattr = ovl_setattr,
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.follow_link = ovl_follow_link,
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.put_link = ovl_put_link,
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.readlink = ovl_readlink,
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.getattr = ovl_getattr,
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.setxattr = ovl_setxattr,
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.getxattr = ovl_getxattr,
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.listxattr = ovl_listxattr,
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.removexattr = ovl_removexattr,
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};
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struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
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struct ovl_entry *oe)
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{
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struct inode *inode;
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inode = new_inode(sb);
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if (!inode)
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return NULL;
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mode &= S_IFMT;
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inode->i_ino = get_next_ino();
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inode->i_mode = mode;
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inode->i_flags |= S_NOATIME | S_NOCMTIME;
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switch (mode) {
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case S_IFDIR:
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inode->i_private = oe;
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inode->i_op = &ovl_dir_inode_operations;
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inode->i_fop = &ovl_dir_operations;
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break;
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case S_IFLNK:
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inode->i_op = &ovl_symlink_inode_operations;
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break;
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case S_IFREG:
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case S_IFSOCK:
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case S_IFBLK:
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case S_IFCHR:
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case S_IFIFO:
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inode->i_op = &ovl_file_inode_operations;
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break;
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default:
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WARN(1, "illegal file type: %i\n", mode);
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iput(inode);
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inode = NULL;
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}
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return inode;
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}
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