461 lines
10 KiB
C
461 lines
10 KiB
C
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/*
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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 <linux/posix_acl.h>
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#include "overlayfs.h"
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#include <linux/security.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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const struct cred *old_cred;
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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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old_cred = ovl_override_creds(dentry->d_sb);
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err = vfs_getattr(&lowerpath, &stat);
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if (!err) {
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stat.size = 0;
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err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
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}
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ovl_revert_creds(old_cred);
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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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const struct cred *old_cred;
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/*
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* Check for permissions before trying to copy-up. This is redundant
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* since it will be rechecked later by ->setattr() on upper dentry. But
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* without this, copy-up can be triggered by just about anybody.
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*
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* We don't initialize inode->size, which just means that
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* inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
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* check for a swapfile (which this won't be anyway).
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*/
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err = setattr_prepare(dentry, attr);
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if (err)
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return err;
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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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if (attr->ia_valid & ATTR_SIZE) {
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struct inode *realinode = d_inode(ovl_dentry_real(dentry));
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err = -ETXTBSY;
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if (atomic_read(&realinode->i_writecount) < 0)
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goto out_drop_write;
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}
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err = ovl_copy_up(dentry);
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if (!err) {
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struct inode *winode = NULL;
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upperdentry = ovl_dentry_upper(dentry);
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if (attr->ia_valid & ATTR_SIZE) {
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winode = d_inode(upperdentry);
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err = get_write_access(winode);
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if (err)
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goto out_drop_write;
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}
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if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
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attr->ia_valid &= ~ATTR_MODE;
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inode_lock(upperdentry->d_inode);
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old_cred = ovl_override_creds(dentry->d_sb);
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err = notify_change(upperdentry, attr, NULL);
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ovl_revert_creds(old_cred);
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if (!err)
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ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
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inode_unlock(upperdentry->d_inode);
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if (winode)
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put_write_access(winode);
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}
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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 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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const struct cred *old_cred;
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int err;
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ovl_path_real(dentry, &realpath);
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old_cred = ovl_override_creds(dentry->d_sb);
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err = vfs_getattr(&realpath, stat);
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ovl_revert_creds(old_cred);
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return err;
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}
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int ovl_permission(struct inode *inode, int mask)
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{
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bool is_upper;
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struct inode *realinode = ovl_inode_real(inode, &is_upper);
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const struct cred *old_cred;
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int err;
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/* Careful in RCU walk mode */
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if (!realinode) {
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WARN_ON(!(mask & MAY_NOT_BLOCK));
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return -ECHILD;
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}
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/*
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* Check overlay inode with the creds of task and underlying inode
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* with creds of mounter
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*/
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err = generic_permission(inode, mask);
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if (err)
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return err;
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old_cred = ovl_override_creds(inode->i_sb);
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if (!is_upper && !special_file(realinode->i_mode) && mask & MAY_WRITE) {
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mask &= ~(MAY_WRITE | MAY_APPEND);
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/* Make sure mounter can read file for copy up later */
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mask |= MAY_READ;
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}
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err = inode_permission(realinode, mask);
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ovl_revert_creds(old_cred);
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return err;
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}
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static const char *ovl_get_link(struct dentry *dentry,
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struct inode *inode,
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struct delayed_call *done)
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{
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const struct cred *old_cred;
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const char *p;
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if (!dentry)
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return ERR_PTR(-ECHILD);
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old_cred = ovl_override_creds(dentry->d_sb);
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p = vfs_get_link(ovl_dentry_real(dentry), done);
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ovl_revert_creds(old_cred);
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return p;
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}
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bool ovl_is_private_xattr(const char *name)
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{
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return strncmp(name, OVL_XATTR_PREFIX,
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sizeof(OVL_XATTR_PREFIX) - 1) == 0;
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}
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int ovl_xattr_set(struct dentry *dentry, const char *name, const void *value,
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size_t size, int 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 = ovl_path_real(dentry, &realpath);
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const struct cred *old_cred;
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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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if (!value && !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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}
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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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if (!OVL_TYPE_UPPER(type))
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ovl_path_upper(dentry, &realpath);
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old_cred = ovl_override_creds(dentry->d_sb);
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if (value)
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err = vfs_setxattr(realpath.dentry, name, value, size, flags);
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else {
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WARN_ON(flags != XATTR_REPLACE);
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err = vfs_removexattr(realpath.dentry, name);
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}
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ovl_revert_creds(old_cred);
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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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int ovl_xattr_get(struct dentry *dentry, const char *name,
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void *value, size_t size)
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{
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struct dentry *realdentry = ovl_dentry_real(dentry);
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ssize_t res;
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const struct cred *old_cred;
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old_cred = ovl_override_creds(dentry->d_sb);
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res = vfs_getxattr(realdentry, name, value, size);
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ovl_revert_creds(old_cred);
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return res;
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}
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static bool ovl_can_list(const char *s)
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{
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/* List all non-trusted xatts */
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if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0)
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return true;
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/* Never list trusted.overlay, list other trusted for superuser only */
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return !ovl_is_private_xattr(s) && capable(CAP_SYS_ADMIN);
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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 dentry *realdentry = ovl_dentry_real(dentry);
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ssize_t res;
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size_t len;
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char *s;
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const struct cred *old_cred;
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old_cred = ovl_override_creds(dentry->d_sb);
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res = vfs_listxattr(realdentry, list, size);
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ovl_revert_creds(old_cred);
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if (res <= 0 || size == 0)
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return res;
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/* filter out private xattrs */
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for (s = list, len = res; len;) {
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size_t slen = strnlen(s, len) + 1;
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/* underlying fs providing us with an broken xattr list? */
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if (WARN_ON(slen > len))
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return -EIO;
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len -= slen;
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if (!ovl_can_list(s)) {
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res -= slen;
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memmove(s, s + slen, len);
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} else {
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s += slen;
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}
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}
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return res;
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}
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struct posix_acl *ovl_get_acl(struct inode *inode, int type)
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{
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struct inode *realinode = ovl_inode_real(inode, NULL);
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const struct cred *old_cred;
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struct posix_acl *acl;
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if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
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return NULL;
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old_cred = ovl_override_creds(inode->i_sb);
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acl = get_acl(realinode, type);
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ovl_revert_creds(old_cred);
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return acl;
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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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int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
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{
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int err = 0;
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struct path realpath;
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enum ovl_path_type type;
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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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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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}
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}
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return err;
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}
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int ovl_update_time(struct inode *inode, struct timespec *ts, int flags)
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{
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struct dentry *alias;
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struct path upperpath;
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if (!(flags & S_ATIME))
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return 0;
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alias = d_find_any_alias(inode);
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if (!alias)
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return 0;
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ovl_path_upper(alias, &upperpath);
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if (upperpath.dentry) {
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touch_atime(&upperpath);
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inode->i_atime = d_inode(upperpath.dentry)->i_atime;
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}
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dput(alias);
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return 0;
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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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.listxattr = ovl_listxattr,
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.get_acl = ovl_get_acl,
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.update_time = ovl_update_time,
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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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.get_link = ovl_get_link,
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.readlink = generic_readlink,
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.getattr = ovl_getattr,
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.listxattr = ovl_listxattr,
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.update_time = ovl_update_time,
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};
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void ovl_copyattr(struct inode *from, struct inode *to)
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{
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#ifdef CONFIG_SECURITY
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void *secctx;
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unsigned int ctxlen;
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int err = -1;
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err = security_inode_getsecctx(from, &secctx, &ctxlen);
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if (!err) {
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err = security_inode_notifysecctx(to, secctx, ctxlen);
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security_release_secctx(secctx, ctxlen);
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}
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if (err)
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WARN(1, "cannot copy up security context err:%d\n", err);
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#endif
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to->i_uid = from->i_uid;
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to->i_gid = from->i_gid;
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|
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 void ovl_fill_inode(struct inode *inode, umode_t mode)
|
||
|
|
{
|
||
|
|
inode->i_ino = get_next_ino();
|
||
|
|
inode->i_mode = mode;
|
||
|
|
inode->i_flags |= S_NOCMTIME;
|
||
|
|
#ifdef CONFIG_FS_POSIX_ACL
|
||
|
|
inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
|
||
|
|
#endif
|
||
|
|
|
||
|
|
mode &= S_IFMT;
|
||
|
|
switch (mode) {
|
||
|
|
case S_IFDIR:
|
||
|
|
inode->i_op = &ovl_dir_inode_operations;
|
||
|
|
inode->i_fop = &ovl_dir_operations;
|
||
|
|
break;
|
||
|
|
|
||
|
|
case S_IFLNK:
|
||
|
|
inode->i_op = &ovl_symlink_inode_operations;
|
||
|
|
break;
|
||
|
|
|
||
|
|
default:
|
||
|
|
WARN(1, "illegal file type: %i\n", mode);
|
||
|
|
/* Fall through */
|
||
|
|
|
||
|
|
case S_IFREG:
|
||
|
|
case S_IFSOCK:
|
||
|
|
case S_IFBLK:
|
||
|
|
case S_IFCHR:
|
||
|
|
case S_IFIFO:
|
||
|
|
inode->i_op = &ovl_file_inode_operations;
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
struct inode *ovl_new_inode(struct super_block *sb, umode_t mode)
|
||
|
|
{
|
||
|
|
struct inode *inode;
|
||
|
|
|
||
|
|
inode = new_inode(sb);
|
||
|
|
if (inode)
|
||
|
|
ovl_fill_inode(inode, mode);
|
||
|
|
|
||
|
|
return inode;
|
||
|
|
}
|
||
|
|
|
||
|
|
static int ovl_inode_test(struct inode *inode, void *data)
|
||
|
|
{
|
||
|
|
return ovl_inode_real(inode, NULL) == data;
|
||
|
|
}
|
||
|
|
|
||
|
|
static int ovl_inode_set(struct inode *inode, void *data)
|
||
|
|
{
|
||
|
|
inode->i_private = (void *) (((unsigned long) data) | OVL_ISUPPER_MASK);
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode)
|
||
|
|
|
||
|
|
{
|
||
|
|
struct inode *inode;
|
||
|
|
|
||
|
|
inode = iget5_locked(sb, (unsigned long) realinode,
|
||
|
|
ovl_inode_test, ovl_inode_set, realinode);
|
||
|
|
if (inode && inode->i_state & I_NEW) {
|
||
|
|
ovl_fill_inode(inode, realinode->i_mode);
|
||
|
|
set_nlink(inode, realinode->i_nlink);
|
||
|
|
unlock_new_inode(inode);
|
||
|
|
}
|
||
|
|
|
||
|
|
return inode;
|
||
|
|
}
|