![Amir Goldstein](/assets/img/avatar_default.png)
commit 31747eda41
upstream.
fsnotify pins a watched directory inode in cache, but if directory dentry
is released, new lookup will allocate a new dentry and a new inode.
Directory events will be notified on the new inode, while fsnotify listener
is watching the old pinned inode.
Hash all directory inodes to reuse the pinned inode on lookup. Pure upper
dirs are hashes by real upper inode, merge and lower dirs are hashed by
real lower inode.
The reference to lower inode was being held by the lower dentry object
in the overlay dentry (oe->lowerstack[0]). Releasing the overlay dentry
may drop lower inode refcount to zero. Add a refcount on behalf of the
overlay inode to prevent that.
As a by-product, hashing directory inodes also detects multiple
redirected dirs to the same lower dir and uncovered redirected dir
target on and returns -ESTALE on lookup.
The reported issue dates back to initial version of overlayfs, but this
patch depends on ovl_inode code that was introduced in kernel v4.13.
Cc: <stable@vger.kernel.org> #v4.13
Reported-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Tested-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
686 lines
18 KiB
C
686 lines
18 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/cred.h>
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#include <linux/xattr.h>
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#include <linux/posix_acl.h>
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#include <linux/ratelimit.h>
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#include "overlayfs.h"
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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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err = ovl_copy_up(dentry);
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if (!err) {
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upperdentry = ovl_dentry_upper(dentry);
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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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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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}
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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_getattr(const struct path *path, struct kstat *stat,
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u32 request_mask, unsigned int flags)
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{
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struct dentry *dentry = path->dentry;
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enum ovl_path_type type;
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struct path realpath;
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const struct cred *old_cred;
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bool is_dir = S_ISDIR(dentry->d_inode->i_mode);
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int err;
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type = 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, request_mask, flags);
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if (err)
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goto out;
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/*
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* When all layers are on the same fs, all real inode number are
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* unique, so we use the overlay st_dev, which is friendly to du -x.
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*
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* We also use st_ino of the copy up origin, if we know it.
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* This guaranties constant st_dev/st_ino across copy up.
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*
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* If filesystem supports NFS export ops, this also guaranties
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* persistent st_ino across mount cycle.
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*/
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if (ovl_same_sb(dentry->d_sb)) {
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if (OVL_TYPE_ORIGIN(type)) {
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struct kstat lowerstat;
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u32 lowermask = STATX_INO | (!is_dir ? STATX_NLINK : 0);
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ovl_path_lower(dentry, &realpath);
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err = vfs_getattr(&realpath, &lowerstat,
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lowermask, flags);
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if (err)
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goto out;
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WARN_ON_ONCE(stat->dev != lowerstat.dev);
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/*
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* Lower hardlinks may be broken on copy up to different
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* upper files, so we cannot use the lower origin st_ino
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* for those different files, even for the same fs case.
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* With inodes index enabled, it is safe to use st_ino
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* of an indexed hardlinked origin. The index validates
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* that the upper hardlink is not broken.
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*/
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if (is_dir || lowerstat.nlink == 1 ||
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ovl_test_flag(OVL_INDEX, d_inode(dentry)))
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stat->ino = lowerstat.ino;
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}
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stat->dev = dentry->d_sb->s_dev;
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} else if (is_dir) {
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/*
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* If not all layers are on the same fs the pair {real st_ino;
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* overlay st_dev} is not unique, so use the non persistent
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* overlay st_ino.
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*
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* Always use the overlay st_dev for directories, so 'find
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* -xdev' will scan the entire overlay mount and won't cross the
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* overlay mount boundaries.
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*/
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stat->dev = dentry->d_sb->s_dev;
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stat->ino = dentry->d_inode->i_ino;
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}
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/*
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* It's probably not worth it to count subdirs to get the
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* correct link count. nlink=1 seems to pacify 'find' and
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* other utilities.
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*/
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if (is_dir && OVL_TYPE_MERGE(type))
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stat->nlink = 1;
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/*
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* Return the overlay inode nlinks for indexed upper inodes.
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* Overlay inode nlink counts the union of the upper hardlinks
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* and non-covered lower hardlinks. It does not include the upper
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* index hardlink.
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*/
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if (!is_dir && ovl_test_flag(OVL_INDEX, d_inode(dentry)))
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stat->nlink = dentry->d_inode->i_nlink;
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out:
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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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struct inode *upperinode = ovl_inode_upper(inode);
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struct inode *realinode = upperinode ?: ovl_inode_lower(inode);
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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 (!upperinode &&
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!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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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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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, struct inode *inode, 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 = ovl_i_dentry_upper(inode);
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struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry);
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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 && !upperdentry) {
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err = vfs_getxattr(realdentry, 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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if (!upperdentry) {
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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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realdentry = ovl_dentry_upper(dentry);
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}
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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(realdentry, 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(realdentry, name);
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}
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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, struct inode *inode, const char *name,
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void *value, size_t size)
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{
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ssize_t res;
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const struct cred *old_cred;
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struct dentry *realdentry =
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ovl_i_dentry_upper(inode) ?: ovl_dentry_lower(dentry);
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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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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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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);
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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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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(struct dentry *dentry, int flags)
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{
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if (ovl_dentry_upper(dentry) &&
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ovl_dentry_has_upper_alias(dentry))
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return false;
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if (special_file(d_inode(dentry)->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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if (ovl_open_need_copy_up(dentry, file_flags)) {
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err = ovl_want_write(dentry);
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if (!err) {
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err = ovl_copy_up_flags(dentry, file_flags);
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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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.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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/*
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* It is possible to stack overlayfs instance on top of another
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* overlayfs instance as lower layer. We need to annonate the
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* stackable i_mutex locks according to stack level of the super
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* block instance. An overlayfs instance can never be in stack
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* depth 0 (there is always a real fs below it). An overlayfs
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* inode lock will use the lockdep annotaion ovl_i_mutex_key[depth].
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*
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* For example, here is a snip from /proc/lockdep_chains after
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* dir_iterate of nested overlayfs:
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*
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* [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2)
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* [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1)
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* [...] &type->i_mutex_dir_key (stack_depth=0)
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*/
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#define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH
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static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
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{
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#ifdef CONFIG_LOCKDEP
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static struct lock_class_key ovl_i_mutex_key[OVL_MAX_NESTING];
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static struct lock_class_key ovl_i_mutex_dir_key[OVL_MAX_NESTING];
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int depth = inode->i_sb->s_stack_depth - 1;
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if (WARN_ON_ONCE(depth < 0 || depth >= OVL_MAX_NESTING))
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depth = 0;
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if (S_ISDIR(inode->i_mode))
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lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_dir_key[depth]);
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else
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lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_key[depth]);
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#endif
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}
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static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
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{
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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_NOCMTIME;
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#ifdef CONFIG_FS_POSIX_ACL
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inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
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#endif
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ovl_lockdep_annotate_inode_mutex_key(inode);
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switch (mode & S_IFMT) {
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case S_IFREG:
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inode->i_op = &ovl_file_inode_operations;
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break;
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case S_IFDIR:
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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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default:
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inode->i_op = &ovl_file_inode_operations;
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init_special_inode(inode, mode, rdev);
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break;
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}
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}
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/*
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* With inodes index enabled, an overlay inode nlink counts the union of upper
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* hardlinks and non-covered lower hardlinks. During the lifetime of a non-pure
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* upper inode, the following nlink modifying operations can happen:
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*
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* 1. Lower hardlink copy up
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* 2. Upper hardlink created, unlinked or renamed over
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* 3. Lower hardlink whiteout or renamed over
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*
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* For the first, copy up case, the union nlink does not change, whether the
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* operation succeeds or fails, but the upper inode nlink may change.
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* Therefore, before copy up, we store the union nlink value relative to the
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* lower inode nlink in the index inode xattr trusted.overlay.nlink.
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*
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* For the second, upper hardlink case, the union nlink should be incremented
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* or decremented IFF the operation succeeds, aligned with nlink change of the
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* upper inode. Therefore, before link/unlink/rename, we store the union nlink
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* value relative to the upper inode nlink in the index inode.
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*
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* For the last, lower cover up case, we simplify things by preceding the
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* whiteout or cover up with copy up. This makes sure that there is an index
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* upper inode where the nlink xattr can be stored before the copied up upper
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* entry is unlink.
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*/
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#define OVL_NLINK_ADD_UPPER (1 << 0)
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/*
|
|
* On-disk format for indexed nlink:
|
|
*
|
|
* nlink relative to the upper inode - "U[+-]NUM"
|
|
* nlink relative to the lower inode - "L[+-]NUM"
|
|
*/
|
|
|
|
static int ovl_set_nlink_common(struct dentry *dentry,
|
|
struct dentry *realdentry, const char *format)
|
|
{
|
|
struct inode *inode = d_inode(dentry);
|
|
struct inode *realinode = d_inode(realdentry);
|
|
char buf[13];
|
|
int len;
|
|
|
|
len = snprintf(buf, sizeof(buf), format,
|
|
(int) (inode->i_nlink - realinode->i_nlink));
|
|
|
|
if (WARN_ON(len >= sizeof(buf)))
|
|
return -EIO;
|
|
|
|
return ovl_do_setxattr(ovl_dentry_upper(dentry),
|
|
OVL_XATTR_NLINK, buf, len, 0);
|
|
}
|
|
|
|
int ovl_set_nlink_upper(struct dentry *dentry)
|
|
{
|
|
return ovl_set_nlink_common(dentry, ovl_dentry_upper(dentry), "U%+i");
|
|
}
|
|
|
|
int ovl_set_nlink_lower(struct dentry *dentry)
|
|
{
|
|
return ovl_set_nlink_common(dentry, ovl_dentry_lower(dentry), "L%+i");
|
|
}
|
|
|
|
unsigned int ovl_get_nlink(struct dentry *lowerdentry,
|
|
struct dentry *upperdentry,
|
|
unsigned int fallback)
|
|
{
|
|
int nlink_diff;
|
|
int nlink;
|
|
char buf[13];
|
|
int err;
|
|
|
|
if (!lowerdentry || !upperdentry || d_inode(lowerdentry)->i_nlink == 1)
|
|
return fallback;
|
|
|
|
err = vfs_getxattr(upperdentry, OVL_XATTR_NLINK, &buf, sizeof(buf) - 1);
|
|
if (err < 0)
|
|
goto fail;
|
|
|
|
buf[err] = '\0';
|
|
if ((buf[0] != 'L' && buf[0] != 'U') ||
|
|
(buf[1] != '+' && buf[1] != '-'))
|
|
goto fail;
|
|
|
|
err = kstrtoint(buf + 1, 10, &nlink_diff);
|
|
if (err < 0)
|
|
goto fail;
|
|
|
|
nlink = d_inode(buf[0] == 'L' ? lowerdentry : upperdentry)->i_nlink;
|
|
nlink += nlink_diff;
|
|
|
|
if (nlink <= 0)
|
|
goto fail;
|
|
|
|
return nlink;
|
|
|
|
fail:
|
|
pr_warn_ratelimited("overlayfs: failed to get index nlink (%pd2, err=%i)\n",
|
|
upperdentry, err);
|
|
return fallback;
|
|
}
|
|
|
|
struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev)
|
|
{
|
|
struct inode *inode;
|
|
|
|
inode = new_inode(sb);
|
|
if (inode)
|
|
ovl_fill_inode(inode, mode, rdev);
|
|
|
|
return inode;
|
|
}
|
|
|
|
static int ovl_inode_test(struct inode *inode, void *data)
|
|
{
|
|
return inode->i_private == data;
|
|
}
|
|
|
|
static int ovl_inode_set(struct inode *inode, void *data)
|
|
{
|
|
inode->i_private = data;
|
|
return 0;
|
|
}
|
|
|
|
static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
|
|
struct dentry *upperdentry)
|
|
{
|
|
if (S_ISDIR(inode->i_mode)) {
|
|
/* Real lower dir moved to upper layer under us? */
|
|
if (!lowerdentry && ovl_inode_lower(inode))
|
|
return false;
|
|
|
|
/* Lookup of an uncovered redirect origin? */
|
|
if (!upperdentry && ovl_inode_upper(inode))
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Allow non-NULL lower inode in ovl_inode even if lowerdentry is NULL.
|
|
* This happens when finding a copied up overlay inode for a renamed
|
|
* or hardlinked overlay dentry and lower dentry cannot be followed
|
|
* by origin because lower fs does not support file handles.
|
|
*/
|
|
if (lowerdentry && ovl_inode_lower(inode) != d_inode(lowerdentry))
|
|
return false;
|
|
|
|
/*
|
|
* Allow non-NULL __upperdentry in inode even if upperdentry is NULL.
|
|
* This happens when finding a lower alias for a copied up hard link.
|
|
*/
|
|
if (upperdentry && ovl_inode_upper(inode) != d_inode(upperdentry))
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry,
|
|
struct dentry *index)
|
|
{
|
|
struct dentry *lowerdentry = ovl_dentry_lower(dentry);
|
|
struct inode *realinode = upperdentry ? d_inode(upperdentry) : NULL;
|
|
struct inode *inode;
|
|
/* Already indexed or could be indexed on copy up? */
|
|
bool indexed = (index || (ovl_indexdir(dentry->d_sb) && !upperdentry));
|
|
struct dentry *origin = indexed ? lowerdentry : NULL;
|
|
bool is_dir;
|
|
|
|
if (WARN_ON(upperdentry && indexed && !lowerdentry))
|
|
return ERR_PTR(-EIO);
|
|
|
|
if (!realinode)
|
|
realinode = d_inode(lowerdentry);
|
|
|
|
/*
|
|
* Copy up origin (lower) may exist for non-indexed non-dir upper, but
|
|
* we must not use lower as hash key in that case.
|
|
* Hash non-dir that is or could be indexed by origin inode.
|
|
* Hash dir that is or could be merged by origin inode.
|
|
* Hash pure upper and non-indexed non-dir by upper inode.
|
|
*/
|
|
is_dir = S_ISDIR(realinode->i_mode);
|
|
if (is_dir)
|
|
origin = lowerdentry;
|
|
|
|
if (upperdentry || origin) {
|
|
struct inode *key = d_inode(origin ?: upperdentry);
|
|
unsigned int nlink = is_dir ? 1 : realinode->i_nlink;
|
|
|
|
inode = iget5_locked(dentry->d_sb, (unsigned long) key,
|
|
ovl_inode_test, ovl_inode_set, key);
|
|
if (!inode)
|
|
goto out_nomem;
|
|
if (!(inode->i_state & I_NEW)) {
|
|
/*
|
|
* Verify that the underlying files stored in the inode
|
|
* match those in the dentry.
|
|
*/
|
|
if (!ovl_verify_inode(inode, lowerdentry, upperdentry)) {
|
|
iput(inode);
|
|
inode = ERR_PTR(-ESTALE);
|
|
goto out;
|
|
}
|
|
|
|
dput(upperdentry);
|
|
goto out;
|
|
}
|
|
|
|
/* Recalculate nlink for non-dir due to indexing */
|
|
if (!is_dir)
|
|
nlink = ovl_get_nlink(lowerdentry, upperdentry, nlink);
|
|
set_nlink(inode, nlink);
|
|
} else {
|
|
inode = new_inode(dentry->d_sb);
|
|
if (!inode)
|
|
goto out_nomem;
|
|
}
|
|
ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
|
|
ovl_inode_init(inode, upperdentry, lowerdentry);
|
|
|
|
if (upperdentry && ovl_is_impuredir(upperdentry))
|
|
ovl_set_flag(OVL_IMPURE, inode);
|
|
|
|
if (inode->i_state & I_NEW)
|
|
unlock_new_inode(inode);
|
|
out:
|
|
return inode;
|
|
|
|
out_nomem:
|
|
inode = ERR_PTR(-ENOMEM);
|
|
goto out;
|
|
}
|