![Linus Torvalds](/assets/img/avatar_default.png)
Pull overlayfs updates from Miklos Szeredi: "This update contains fixes to the "use mounter's permission to access underlying layers" area, and miscellaneous other fixes and cleanups. No new features this time" * 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs: ovl: use vfs_get_link() vfs: add vfs_get_link() helper ovl: use generic_readlink ovl: explain error values when removing acl from workdir ovl: Fix info leak in ovl_lookup_temp() ovl: during copy up, switch to mounter's creds early ovl: lookup: do getxattr with mounter's permission ovl: copy_up_xattr(): use strnlen
426 lines
9.4 KiB
C
426 lines
9.4 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/module.h>
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#include <linux/fs.h>
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#include <linux/slab.h>
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#include <linux/file.h>
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#include <linux/splice.h>
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#include <linux/xattr.h>
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#include <linux/security.h>
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#include <linux/uaccess.h>
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#include <linux/sched.h>
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#include <linux/namei.h>
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#include <linux/fdtable.h>
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#include <linux/ratelimit.h>
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#include "overlayfs.h"
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#define OVL_COPY_UP_CHUNK_SIZE (1 << 20)
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static bool __read_mostly ovl_check_copy_up;
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module_param_named(check_copy_up, ovl_check_copy_up, bool,
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S_IWUSR | S_IRUGO);
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MODULE_PARM_DESC(ovl_check_copy_up,
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"Warn on copy-up when causing process also has a R/O fd open");
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static int ovl_check_fd(const void *data, struct file *f, unsigned int fd)
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{
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const struct dentry *dentry = data;
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if (f->f_inode == d_inode(dentry))
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pr_warn_ratelimited("overlayfs: Warning: Copying up %pD, but open R/O on fd %u which will cease to be coherent [pid=%d %s]\n",
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f, fd, current->pid, current->comm);
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return 0;
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}
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/*
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* Check the fds open by this process and warn if something like the following
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* scenario is about to occur:
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*
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* fd1 = open("foo", O_RDONLY);
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* fd2 = open("foo", O_RDWR);
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*/
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static void ovl_do_check_copy_up(struct dentry *dentry)
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{
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if (ovl_check_copy_up)
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iterate_fd(current->files, 0, ovl_check_fd, dentry);
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}
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int ovl_copy_xattr(struct dentry *old, struct dentry *new)
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{
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ssize_t list_size, size, value_size = 0;
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char *buf, *name, *value = NULL;
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int uninitialized_var(error);
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size_t slen;
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if (!(old->d_inode->i_opflags & IOP_XATTR) ||
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!(new->d_inode->i_opflags & IOP_XATTR))
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return 0;
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list_size = vfs_listxattr(old, NULL, 0);
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if (list_size <= 0) {
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if (list_size == -EOPNOTSUPP)
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return 0;
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return list_size;
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}
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buf = kzalloc(list_size, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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list_size = vfs_listxattr(old, buf, list_size);
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if (list_size <= 0) {
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error = list_size;
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goto out;
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}
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for (name = buf; list_size; name += slen) {
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slen = strnlen(name, list_size) + 1;
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/* underlying fs providing us with an broken xattr list? */
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if (WARN_ON(slen > list_size)) {
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error = -EIO;
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break;
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}
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list_size -= slen;
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if (ovl_is_private_xattr(name))
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continue;
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retry:
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size = vfs_getxattr(old, name, value, value_size);
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if (size == -ERANGE)
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size = vfs_getxattr(old, name, NULL, 0);
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if (size < 0) {
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error = size;
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break;
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}
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if (size > value_size) {
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void *new;
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new = krealloc(value, size, GFP_KERNEL);
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if (!new) {
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error = -ENOMEM;
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break;
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}
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value = new;
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value_size = size;
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goto retry;
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}
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error = security_inode_copy_up_xattr(name);
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if (error < 0 && error != -EOPNOTSUPP)
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break;
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if (error == 1) {
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error = 0;
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continue; /* Discard */
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}
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error = vfs_setxattr(new, name, value, size, 0);
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if (error)
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break;
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}
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kfree(value);
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out:
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kfree(buf);
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return error;
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}
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static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
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{
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struct file *old_file;
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struct file *new_file;
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loff_t old_pos = 0;
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loff_t new_pos = 0;
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int error = 0;
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if (len == 0)
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return 0;
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old_file = ovl_path_open(old, O_LARGEFILE | O_RDONLY);
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if (IS_ERR(old_file))
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return PTR_ERR(old_file);
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new_file = ovl_path_open(new, O_LARGEFILE | O_WRONLY);
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if (IS_ERR(new_file)) {
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error = PTR_ERR(new_file);
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goto out_fput;
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}
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/* FIXME: copy up sparse files efficiently */
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while (len) {
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size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
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long bytes;
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if (len < this_len)
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this_len = len;
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if (signal_pending_state(TASK_KILLABLE, current)) {
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error = -EINTR;
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break;
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}
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bytes = do_splice_direct(old_file, &old_pos,
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new_file, &new_pos,
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this_len, SPLICE_F_MOVE);
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if (bytes <= 0) {
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error = bytes;
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break;
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}
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WARN_ON(old_pos != new_pos);
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len -= bytes;
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}
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fput(new_file);
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out_fput:
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fput(old_file);
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return error;
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}
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static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat)
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{
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struct iattr attr = {
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.ia_valid =
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ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET,
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.ia_atime = stat->atime,
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.ia_mtime = stat->mtime,
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};
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return notify_change(upperdentry, &attr, NULL);
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}
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int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat)
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{
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int err = 0;
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if (!S_ISLNK(stat->mode)) {
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struct iattr attr = {
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.ia_valid = ATTR_MODE,
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.ia_mode = stat->mode,
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};
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err = notify_change(upperdentry, &attr, NULL);
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}
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if (!err) {
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struct iattr attr = {
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.ia_valid = ATTR_UID | ATTR_GID,
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.ia_uid = stat->uid,
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.ia_gid = stat->gid,
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};
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err = notify_change(upperdentry, &attr, NULL);
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}
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if (!err)
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ovl_set_timestamps(upperdentry, stat);
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return err;
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}
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static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
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struct dentry *dentry, struct path *lowerpath,
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struct kstat *stat, const char *link)
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{
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struct inode *wdir = workdir->d_inode;
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struct inode *udir = upperdir->d_inode;
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struct dentry *newdentry = NULL;
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struct dentry *upper = NULL;
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umode_t mode = stat->mode;
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int err;
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const struct cred *old_creds = NULL;
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struct cred *new_creds = NULL;
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newdentry = ovl_lookup_temp(workdir, dentry);
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err = PTR_ERR(newdentry);
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if (IS_ERR(newdentry))
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goto out;
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upper = lookup_one_len(dentry->d_name.name, upperdir,
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dentry->d_name.len);
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err = PTR_ERR(upper);
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if (IS_ERR(upper))
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goto out1;
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err = security_inode_copy_up(dentry, &new_creds);
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if (err < 0)
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goto out2;
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if (new_creds)
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old_creds = override_creds(new_creds);
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/* Can't properly set mode on creation because of the umask */
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stat->mode &= S_IFMT;
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err = ovl_create_real(wdir, newdentry, stat, link, NULL, true);
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stat->mode = mode;
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if (new_creds) {
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revert_creds(old_creds);
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put_cred(new_creds);
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}
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if (err)
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goto out2;
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if (S_ISREG(stat->mode)) {
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struct path upperpath;
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ovl_path_upper(dentry, &upperpath);
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BUG_ON(upperpath.dentry != NULL);
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upperpath.dentry = newdentry;
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err = ovl_copy_up_data(lowerpath, &upperpath, stat->size);
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if (err)
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goto out_cleanup;
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}
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err = ovl_copy_xattr(lowerpath->dentry, newdentry);
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if (err)
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goto out_cleanup;
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inode_lock(newdentry->d_inode);
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err = ovl_set_attr(newdentry, stat);
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inode_unlock(newdentry->d_inode);
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if (err)
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goto out_cleanup;
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err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
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if (err)
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goto out_cleanup;
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ovl_dentry_update(dentry, newdentry);
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ovl_inode_update(d_inode(dentry), d_inode(newdentry));
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newdentry = NULL;
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/*
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* Non-directores become opaque when copied up.
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*/
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if (!S_ISDIR(stat->mode))
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ovl_dentry_set_opaque(dentry, true);
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out2:
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dput(upper);
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out1:
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dput(newdentry);
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out:
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return err;
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out_cleanup:
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ovl_cleanup(wdir, newdentry);
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goto out2;
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}
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/*
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* Copy up a single dentry
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*
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* Directory renames only allowed on "pure upper" (already created on
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* upper filesystem, never copied up). Directories which are on lower or
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* are merged may not be renamed. For these -EXDEV is returned and
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* userspace has to deal with it. This means, when copying up a
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* directory we can rely on it and ancestors being stable.
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*
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* Non-directory renames start with copy up of source if necessary. The
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* actual rename will only proceed once the copy up was successful. Copy
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* up uses upper parent i_mutex for exclusion. Since rename can change
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* d_parent it is possible that the copy up will lock the old parent. At
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* that point the file will have already been copied up anyway.
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*/
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int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
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struct path *lowerpath, struct kstat *stat)
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{
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DEFINE_DELAYED_CALL(done);
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struct dentry *workdir = ovl_workdir(dentry);
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int err;
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struct kstat pstat;
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struct path parentpath;
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struct dentry *lowerdentry = lowerpath->dentry;
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struct dentry *upperdir;
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struct dentry *upperdentry;
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const char *link = NULL;
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if (WARN_ON(!workdir))
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return -EROFS;
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ovl_do_check_copy_up(lowerdentry);
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ovl_path_upper(parent, &parentpath);
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upperdir = parentpath.dentry;
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err = vfs_getattr(&parentpath, &pstat);
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if (err)
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return err;
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if (S_ISLNK(stat->mode)) {
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link = vfs_get_link(lowerdentry, &done);
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if (IS_ERR(link))
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return PTR_ERR(link);
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}
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err = -EIO;
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if (lock_rename(workdir, upperdir) != NULL) {
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pr_err("overlayfs: failed to lock workdir+upperdir\n");
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goto out_unlock;
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}
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upperdentry = ovl_dentry_upper(dentry);
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if (upperdentry) {
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/* Raced with another copy-up? Nothing to do, then... */
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err = 0;
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goto out_unlock;
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}
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err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
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stat, link);
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if (!err) {
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/* Restore timestamps on parent (best effort) */
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ovl_set_timestamps(upperdir, &pstat);
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}
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out_unlock:
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unlock_rename(workdir, upperdir);
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do_delayed_call(&done);
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return err;
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}
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int ovl_copy_up(struct dentry *dentry)
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{
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int err = 0;
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const struct cred *old_cred = ovl_override_creds(dentry->d_sb);
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while (!err) {
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struct dentry *next;
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struct dentry *parent;
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struct path lowerpath;
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struct kstat stat;
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enum ovl_path_type type = ovl_path_type(dentry);
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if (OVL_TYPE_UPPER(type))
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break;
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next = dget(dentry);
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/* find the topmost dentry not yet copied up */
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for (;;) {
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parent = dget_parent(next);
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type = ovl_path_type(parent);
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if (OVL_TYPE_UPPER(type))
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break;
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dput(next);
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next = parent;
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}
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ovl_path_lower(next, &lowerpath);
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err = vfs_getattr(&lowerpath, &stat);
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if (!err)
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err = ovl_copy_up_one(parent, next, &lowerpath, &stat);
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dput(parent);
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dput(next);
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}
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revert_creds(old_cred);
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return err;
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}
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