inode.c
/*
*
* Copyright (C) 2011 Novell Inc.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published by
* the Free Software Foundation.
*/
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include <linux/ratelimit.h>
#include "overlayfs.h"
static dev_t ovl_get_pseudo_dev(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
return oe->lowerstack[0].layer->pseudo_dev;
}
int ovl_setattr(struct dentry *dentry, struct iattr *attr)
{
int err;
struct dentry *upperdentry;
const struct cred *old_cred;
/*
* Check for permissions before trying to copy-up. This is redundant
* since it will be rechecked later by ->setattr() on upper dentry. But
* without this, copy-up can be triggered by just about anybody.
*
* We don't initialize inode->size, which just means that
* inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
* check for a swapfile (which this won't be anyway).
*/
err = setattr_prepare(dentry, attr);
if (err)
return err;
err = ovl_want_write(dentry);
if (err)
goto out;
err = ovl_copy_up(dentry);
if (!err) {
upperdentry = ovl_dentry_upper(dentry);
if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
attr->ia_valid &= ~ATTR_MODE;
inode_lock(upperdentry->d_inode);
old_cred = ovl_override_creds(dentry->d_sb);
err = notify_change(upperdentry, attr, NULL);
revert_creds(old_cred);
if (!err)
ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
inode_unlock(upperdentry->d_inode);
}
ovl_drop_write(dentry);
out:
return err;
}
int ovl_getattr(const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int flags)
{
struct dentry *dentry = path->dentry;
enum ovl_path_type type;
struct path realpath;
const struct cred *old_cred;
bool is_dir = S_ISDIR(dentry->d_inode->i_mode);
bool samefs = ovl_same_sb(dentry->d_sb);
int err;
type = ovl_path_real(dentry, &realpath);
old_cred = ovl_override_creds(dentry->d_sb);
err = vfs_getattr(&realpath, stat, request_mask, flags);
if (err)
goto out;
/*
* For non-dir or same fs, we use st_ino of the copy up origin, if we
* know it. This guaranties constant st_dev/st_ino across copy up.
*
* If filesystem supports NFS export ops, this also guaranties
* persistent st_ino across mount cycle.
*/
if (!is_dir || samefs) {
if (OVL_TYPE_ORIGIN(type)) {
struct kstat lowerstat;
u32 lowermask = STATX_INO | (!is_dir ? STATX_NLINK : 0);
ovl_path_lower(dentry, &realpath);
err = vfs_getattr(&realpath, &lowerstat,
lowermask, flags);
if (err)
goto out;
/*
* Lower hardlinks may be broken on copy up to different
* upper files, so we cannot use the lower origin st_ino
* for those different files, even for the same fs case.
*
* Similarly, several redirected dirs can point to the
* same dir on a lower layer. With the "verify_lower"
* feature, we do not use the lower origin st_ino, if
* we haven't verified that this redirect is unique.
*
* With inodes index enabled, it is safe to use st_ino
* of an indexed origin. The index validates that the
* upper hardlink is not broken and that a redirected
* dir is the only redirect to that origin.
*/
if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) ||
(!ovl_verify_lower(dentry->d_sb) &&
(is_dir || lowerstat.nlink == 1)))
stat->ino = lowerstat.ino;
if (samefs)
WARN_ON_ONCE(stat->dev != lowerstat.dev);
else
stat->dev = ovl_get_pseudo_dev(dentry);
}
if (samefs) {
/*
* When all layers are on the same fs, all real inode
* number are unique, so we use the overlay st_dev,
* which is friendly to du -x.
*/
stat->dev = dentry->d_sb->s_dev;
} else if (!OVL_TYPE_UPPER(type)) {
/*
* For non-samefs setup, to make sure that st_dev/st_ino
* pair is unique across the system, we use a unique
* anonymous st_dev for lower layer inode.
*/
stat->dev = ovl_get_pseudo_dev(dentry);
}
} else {
/*
* Always use the overlay st_dev for directories, so 'find
* -xdev' will scan the entire overlay mount and won't cross the
* overlay mount boundaries.
*
* If not all layers are on the same fs the pair {real st_ino;
* overlay st_dev} is not unique, so use the non persistent
* overlay st_ino for directories.
*/
stat->dev = dentry->d_sb->s_dev;
stat->ino = dentry->d_inode->i_ino;
}
/*
* It's probably not worth it to count subdirs to get the
* correct link count. nlink=1 seems to pacify 'find' and
* other utilities.
*/
if (is_dir && OVL_TYPE_MERGE(type))
stat->nlink = 1;
/*
* Return the overlay inode nlinks for indexed upper inodes.
* Overlay inode nlink counts the union of the upper hardlinks
* and non-covered lower hardlinks. It does not include the upper
* index hardlink.
*/
if (!is_dir && ovl_test_flag(OVL_INDEX, d_inode(dentry)))
stat->nlink = dentry->d_inode->i_nlink;
out:
revert_creds(old_cred);
return err;
}
int ovl_permission(struct inode *inode, int mask)
{
struct inode *upperinode = ovl_inode_upper(inode);
struct inode *realinode = upperinode ?: ovl_inode_lower(inode);
const struct cred *old_cred;
int err;
/* Careful in RCU walk mode */
if (!realinode) {
WARN_ON(!(mask & MAY_NOT_BLOCK));
return -ECHILD;
}
/*
* Check overlay inode with the creds of task and underlying inode
* with creds of mounter
*/
err = generic_permission(inode, mask);
if (err)
return err;
old_cred = ovl_override_creds(inode->i_sb);
if (!upperinode &&
!special_file(realinode->i_mode) && mask & MAY_WRITE) {
mask &= ~(MAY_WRITE | MAY_APPEND);
/* Make sure mounter can read file for copy up later */
mask |= MAY_READ;
}
err = inode_permission(realinode, mask);
revert_creds(old_cred);
return err;
}
static const char *ovl_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
const struct cred *old_cred;
const char *p;
if (!dentry)
return ERR_PTR(-ECHILD);
old_cred = ovl_override_creds(dentry->d_sb);
p = vfs_get_link(ovl_dentry_real(dentry), done);
revert_creds(old_cred);
return p;
}
bool ovl_is_private_xattr(const char *name)
{
return strncmp(name, OVL_XATTR_PREFIX,
sizeof(OVL_XATTR_PREFIX) - 1) == 0;
}
int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
const void *value, size_t size, int flags)
{
int err;
struct dentry *upperdentry = ovl_i_dentry_upper(inode);
struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry);
const struct cred *old_cred;
err = ovl_want_write(dentry);
if (err)
goto out;
if (!value && !upperdentry) {
err = vfs_getxattr(realdentry, name, NULL, 0);
if (err < 0)
goto out_drop_write;
}
if (!upperdentry) {
err = ovl_copy_up(dentry);
if (err)
goto out_drop_write;
realdentry = ovl_dentry_upper(dentry);
}
old_cred = ovl_override_creds(dentry->d_sb);
if (value)
err = vfs_setxattr(realdentry, name, value, size, flags);
else {
WARN_ON(flags != XATTR_REPLACE);
err = vfs_removexattr(realdentry, name);
}
revert_creds(old_cred);
out_drop_write:
ovl_drop_write(dentry);
out:
return err;
}
int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
void *value, size_t size)
{
ssize_t res;
const struct cred *old_cred;
struct dentry *realdentry =
ovl_i_dentry_upper(inode) ?: ovl_dentry_lower(dentry);
old_cred = ovl_override_creds(dentry->d_sb);
res = vfs_getxattr(realdentry, name, value, size);
revert_creds(old_cred);
return res;
}
static bool ovl_can_list(const char *s)
{
/* List all non-trusted xatts */
if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0)
return true;
/* Never list trusted.overlay, list other trusted for superuser only */
return !ovl_is_private_xattr(s) && capable(CAP_SYS_ADMIN);
}
ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
{
struct dentry *realdentry = ovl_dentry_real(dentry);
ssize_t res;
size_t len;
char *s;
const struct cred *old_cred;
old_cred = ovl_override_creds(dentry->d_sb);
res = vfs_listxattr(realdentry, list, size);
revert_creds(old_cred);
if (res <= 0 || size == 0)
return res;
/* filter out private xattrs */
for (s = list, len = res; len;) {
size_t slen = strnlen(s, len) + 1;
/* underlying fs providing us with an broken xattr list? */
if (WARN_ON(slen > len))
return -EIO;
len -= slen;
if (!ovl_can_list(s)) {
res -= slen;
memmove(s, s + slen, len);
} else {
s += slen;
}
}
return res;
}
struct posix_acl *ovl_get_acl(struct inode *inode, int type)
{
struct inode *realinode = ovl_inode_real(inode);
const struct cred *old_cred;
struct posix_acl *acl;
if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
return NULL;
old_cred = ovl_override_creds(inode->i_sb);
acl = get_acl(realinode, type);
revert_creds(old_cred);
return acl;
}
static bool ovl_open_need_copy_up(struct dentry *dentry, int flags)
{
/* Copy up of disconnected dentry does not set upper alias */
if (ovl_dentry_upper(dentry) &&
(ovl_dentry_has_upper_alias(dentry) ||
(dentry->d_flags & DCACHE_DISCONNECTED)))
return false;
if (special_file(d_inode(dentry)->i_mode))
return false;
if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
return false;
return true;
}
int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
{
int err = 0;
if (ovl_open_need_copy_up(dentry, file_flags)) {
err = ovl_want_write(dentry);
if (!err) {
err = ovl_copy_up_flags(dentry, file_flags);
ovl_drop_write(dentry);
}
}
return err;
}
int ovl_update_time(struct inode *inode, struct timespec *ts, int flags)
{
struct dentry *alias;
struct path upperpath;
if (!(flags & S_ATIME))
return 0;
alias = d_find_any_alias(inode);
if (!alias)
return 0;
ovl_path_upper(alias, &upperpath);
if (upperpath.dentry) {
touch_atime(&upperpath);
inode->i_atime = d_inode(upperpath.dentry)->i_atime;
}
dput(alias);
return 0;
}
static const struct inode_operations ovl_file_inode_operations = {
.setattr = ovl_setattr,
.permission = ovl_permission,
.getattr = ovl_getattr,
.listxattr = ovl_listxattr,
.get_acl = ovl_get_acl,
.update_time = ovl_update_time,
};
static const struct inode_operations ovl_symlink_inode_operations = {
.setattr = ovl_setattr,
.get_link = ovl_get_link,
.getattr = ovl_getattr,
.listxattr = ovl_listxattr,
.update_time = ovl_update_time,
};
/*
* It is possible to stack overlayfs instance on top of another
* overlayfs instance as lower layer. We need to annonate the
* stackable i_mutex locks according to stack level of the super
* block instance. An overlayfs instance can never be in stack
* depth 0 (there is always a real fs below it). An overlayfs
* inode lock will use the lockdep annotaion ovl_i_mutex_key[depth].
*
* For example, here is a snip from /proc/lockdep_chains after
* dir_iterate of nested overlayfs:
*
* [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2)
* [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1)
* [...] &type->i_mutex_dir_key (stack_depth=0)
*/
#define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH
static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
{
#ifdef CONFIG_LOCKDEP
static struct lock_class_key ovl_i_mutex_key[OVL_MAX_NESTING];
static struct lock_class_key ovl_i_mutex_dir_key[OVL_MAX_NESTING];
static struct lock_class_key ovl_i_lock_key[OVL_MAX_NESTING];
int depth = inode->i_sb->s_stack_depth - 1;
if (WARN_ON_ONCE(depth < 0 || depth >= OVL_MAX_NESTING))
depth = 0;
if (S_ISDIR(inode->i_mode))
lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_dir_key[depth]);
else
lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_key[depth]);
lockdep_set_class(&OVL_I(inode)->lock, &ovl_i_lock_key[depth]);
#endif
}
static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
{
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
ovl_lockdep_annotate_inode_mutex_key(inode);
switch (mode & S_IFMT) {
case S_IFREG:
inode->i_op = &ovl_file_inode_operations;
break;
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:
inode->i_op = &ovl_file_inode_operations;
init_special_inode(inode, mode, rdev);
break;
}
}
/*
* With inodes index enabled, an overlay inode nlink counts the union of upper
* hardlinks and non-covered lower hardlinks. During the lifetime of a non-pure
* upper inode, the following nlink modifying operations can happen:
*
* 1. Lower hardlink copy up
* 2. Upper hardlink created, unlinked or renamed over
* 3. Lower hardlink whiteout or renamed over
*
* For the first, copy up case, the union nlink does not change, whether the
* operation succeeds or fails, but the upper inode nlink may change.
* Therefore, before copy up, we store the union nlink value relative to the
* lower inode nlink in the index inode xattr trusted.overlay.nlink.
*
* For the second, upper hardlink case, the union nlink should be incremented
* or decremented IFF the operation succeeds, aligned with nlink change of the
* upper inode. Therefore, before link/unlink/rename, we store the union nlink
* value relative to the upper inode nlink in the index inode.
*
* For the last, lower cover up case, we simplify things by preceding the
* whiteout or cover up with copy up. This makes sure that there is an index
* upper inode where the nlink xattr can be stored before the copied up upper
* entry is unlink.
*/
#define OVL_NLINK_ADD_UPPER (1 << 0)
/*
* 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, bool strict)
{
/*
* For directories, @strict verify from lookup path performs consistency
* checks, so NULL lower/upper in dentry must match NULL lower/upper in
* inode. Non @strict verify from NFS handle decode path passes NULL for
* 'unknown' lower/upper.
*/
if (S_ISDIR(inode->i_mode) && strict) {
/* 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_lookup_inode(struct super_block *sb, struct dentry *real,
bool is_upper)
{
struct inode *inode, *key = d_inode(real);
inode = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
if (!inode)
return NULL;
if (!ovl_verify_inode(inode, is_upper ? NULL : real,
is_upper ? real : NULL, false)) {
iput(inode);
return ERR_PTR(-ESTALE);
}
return inode;
}
struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
struct dentry *lowerdentry, struct dentry *index,
unsigned int numlower)
{
struct ovl_fs *ofs = sb->s_fs_info;
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(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.
* Hash non-indexed dir by upper inode for NFS export.
*/
is_dir = S_ISDIR(realinode->i_mode);
if (is_dir && (indexed || !sb->s_export_op || !ofs->upper_mnt))
origin = lowerdentry;
if (upperdentry || origin) {
struct inode *key = d_inode(origin ?: upperdentry);
unsigned int nlink = is_dir ? 1 : realinode->i_nlink;
inode = iget5_locked(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,
true)) {
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(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);
/* Check for non-merge dir that may have whiteouts */
if (is_dir) {
if (((upperdentry && lowerdentry) || numlower > 1) ||
ovl_check_origin_xattr(upperdentry ?: lowerdentry)) {
ovl_set_flag(OVL_WHITEOUTS, inode);
}
}
if (inode->i_state & I_NEW)
unlock_new_inode(inode);
out:
return inode;
out_nomem:
inode = ERR_PTR(-ENOMEM);
goto out;
}
