linux/fs/overlayfs/super.c

1320 lines
30 KiB
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 <uapi/linux/magic.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/xattr.h>
#include <linux/mount.h>
#include <linux/parser.h>
#include <linux/module.h>
#include <linux/statfs.h>
#include <linux/seq_file.h>
#include <linux/posix_acl_xattr.h>
#include "overlayfs.h"
MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
MODULE_DESCRIPTION("Overlay filesystem");
MODULE_LICENSE("GPL");
struct ovl_dir_cache;
#define OVL_MAX_STACK 500
static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
MODULE_PARM_DESC(ovl_redirect_dir_def,
"Default to on or off for the redirect_dir feature");
static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
module_param_named(index, ovl_index_def, bool, 0644);
MODULE_PARM_DESC(ovl_index_def,
"Default to on or off for the inodes index feature");
static void ovl_entry_stack_free(struct ovl_entry *oe)
{
unsigned int i;
for (i = 0; i < oe->numlower; i++)
dput(oe->lowerstack[i].dentry);
}
static void ovl_dentry_release(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
if (oe) {
ovl_entry_stack_free(oe);
kfree_rcu(oe, rcu);
}
}
static int ovl_check_append_only(struct inode *inode, int flag)
{
/*
* This test was moot in vfs may_open() because overlay inode does
* not have the S_APPEND flag, so re-check on real upper inode
*/
if (IS_APPEND(inode)) {
if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
return -EPERM;
if (flag & O_TRUNC)
return -EPERM;
}
return 0;
}
static struct dentry *ovl_d_real(struct dentry *dentry,
const struct inode *inode,
unsigned int open_flags, unsigned int flags)
{
struct dentry *real;
int err;
if (flags & D_REAL_UPPER)
return ovl_dentry_upper(dentry);
if (!d_is_reg(dentry)) {
if (!inode || inode == d_inode(dentry))
return dentry;
goto bug;
}
if (open_flags) {
err = ovl_open_maybe_copy_up(dentry, open_flags);
if (err)
return ERR_PTR(err);
}
real = ovl_dentry_upper(dentry);
if (real && (!inode || inode == d_inode(real))) {
if (!inode) {
err = ovl_check_append_only(d_inode(real), open_flags);
if (err)
return ERR_PTR(err);
}
return real;
}
real = ovl_dentry_lower(dentry);
if (!real)
goto bug;
/* Handle recursion */
real = d_real(real, inode, open_flags, 0);
if (!inode || inode == d_inode(real))
return real;
bug:
WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
return dentry;
}
static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
{
struct ovl_entry *oe = dentry->d_fsdata;
unsigned int i;
int ret = 1;
for (i = 0; i < oe->numlower; i++) {
struct dentry *d = oe->lowerstack[i].dentry;
if (d->d_flags & DCACHE_OP_REVALIDATE) {
ret = d->d_op->d_revalidate(d, flags);
if (ret < 0)
return ret;
if (!ret) {
if (!(flags & LOOKUP_RCU))
d_invalidate(d);
return -ESTALE;
}
}
}
return 1;
}
static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
{
struct ovl_entry *oe = dentry->d_fsdata;
unsigned int i;
int ret = 1;
for (i = 0; i < oe->numlower; i++) {
struct dentry *d = oe->lowerstack[i].dentry;
if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
ret = d->d_op->d_weak_revalidate(d, flags);
if (ret <= 0)
break;
}
}
return ret;
}
static const struct dentry_operations ovl_dentry_operations = {
.d_release = ovl_dentry_release,
.d_real = ovl_d_real,
};
static const struct dentry_operations ovl_reval_dentry_operations = {
.d_release = ovl_dentry_release,
.d_real = ovl_d_real,
.d_revalidate = ovl_dentry_revalidate,
.d_weak_revalidate = ovl_dentry_weak_revalidate,
};
static struct kmem_cache *ovl_inode_cachep;
static struct inode *ovl_alloc_inode(struct super_block *sb)
{
struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
if (!oi)
return NULL;
oi->cache = NULL;
oi->redirect = NULL;
oi->version = 0;
oi->flags = 0;
oi->__upperdentry = NULL;
oi->lower = NULL;
mutex_init(&oi->lock);
return &oi->vfs_inode;
}
static void ovl_i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
kmem_cache_free(ovl_inode_cachep, OVL_I(inode));
}
static void ovl_destroy_inode(struct inode *inode)
{
struct ovl_inode *oi = OVL_I(inode);
dput(oi->__upperdentry);
kfree(oi->redirect);
ovl_dir_cache_free(inode);
mutex_destroy(&oi->lock);
call_rcu(&inode->i_rcu, ovl_i_callback);
}
static void ovl_free_fs(struct ovl_fs *ofs)
{
unsigned i;
dput(ofs->indexdir);
dput(ofs->workdir);
if (ofs->workdir_locked)
ovl_inuse_unlock(ofs->workbasedir);
dput(ofs->workbasedir);
if (ofs->upperdir_locked)
ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
mntput(ofs->upper_mnt);
for (i = 0; i < ofs->numlower; i++) {
mntput(ofs->lower_layers[i].mnt);
free_anon_bdev(ofs->lower_layers[i].pseudo_dev);
}
kfree(ofs->lower_layers);
kfree(ofs->config.lowerdir);
kfree(ofs->config.upperdir);
kfree(ofs->config.workdir);
if (ofs->creator_cred)
put_cred(ofs->creator_cred);
kfree(ofs);
}
static void ovl_put_super(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
ovl_free_fs(ofs);
}
static int ovl_sync_fs(struct super_block *sb, int wait)
{
struct ovl_fs *ofs = sb->s_fs_info;
struct super_block *upper_sb;
int ret;
if (!ofs->upper_mnt)
return 0;
upper_sb = ofs->upper_mnt->mnt_sb;
if (!upper_sb->s_op->sync_fs)
return 0;
/* real inodes have already been synced by sync_filesystem(ovl_sb) */
down_read(&upper_sb->s_umount);
ret = upper_sb->s_op->sync_fs(upper_sb, wait);
up_read(&upper_sb->s_umount);
return ret;
}
/**
* ovl_statfs
* @sb: The overlayfs super block
* @buf: The struct kstatfs to fill in with stats
*
* Get the filesystem statistics. As writes always target the upper layer
* filesystem pass the statfs to the upper filesystem (if it exists)
*/
static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
struct dentry *root_dentry = dentry->d_sb->s_root;
struct path path;
int err;
ovl_path_real(root_dentry, &path);
err = vfs_statfs(&path, buf);
if (!err) {
buf->f_namelen = ofs->namelen;
buf->f_type = OVERLAYFS_SUPER_MAGIC;
}
return err;
}
/* Will this overlay be forced to mount/remount ro? */
static bool ovl_force_readonly(struct ovl_fs *ofs)
{
return (!ofs->upper_mnt || !ofs->workdir);
}
/**
* ovl_show_options
*
* Prints the mount options for a given superblock.
* Returns zero; does not fail.
*/
static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
{
struct super_block *sb = dentry->d_sb;
struct ovl_fs *ofs = sb->s_fs_info;
seq_show_option(m, "lowerdir", ofs->config.lowerdir);
if (ofs->config.upperdir) {
seq_show_option(m, "upperdir", ofs->config.upperdir);
seq_show_option(m, "workdir", ofs->config.workdir);
}
if (ofs->config.default_permissions)
seq_puts(m, ",default_permissions");
if (ofs->config.redirect_dir != ovl_redirect_dir_def)
seq_printf(m, ",redirect_dir=%s",
ofs->config.redirect_dir ? "on" : "off");
if (ofs->config.index != ovl_index_def)
seq_printf(m, ",index=%s",
ofs->config.index ? "on" : "off");
return 0;
}
static int ovl_remount(struct super_block *sb, int *flags, char *data)
{
struct ovl_fs *ofs = sb->s_fs_info;
if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
return -EROFS;
return 0;
}
static const struct super_operations ovl_super_operations = {
.alloc_inode = ovl_alloc_inode,
.destroy_inode = ovl_destroy_inode,
.drop_inode = generic_delete_inode,
.put_super = ovl_put_super,
.sync_fs = ovl_sync_fs,
.statfs = ovl_statfs,
.show_options = ovl_show_options,
.remount_fs = ovl_remount,
};
enum {
OPT_LOWERDIR,
OPT_UPPERDIR,
OPT_WORKDIR,
OPT_DEFAULT_PERMISSIONS,
OPT_REDIRECT_DIR_ON,
OPT_REDIRECT_DIR_OFF,
OPT_INDEX_ON,
OPT_INDEX_OFF,
OPT_ERR,
};
static const match_table_t ovl_tokens = {
{OPT_LOWERDIR, "lowerdir=%s"},
{OPT_UPPERDIR, "upperdir=%s"},
{OPT_WORKDIR, "workdir=%s"},
{OPT_DEFAULT_PERMISSIONS, "default_permissions"},
{OPT_REDIRECT_DIR_ON, "redirect_dir=on"},
{OPT_REDIRECT_DIR_OFF, "redirect_dir=off"},
{OPT_INDEX_ON, "index=on"},
{OPT_INDEX_OFF, "index=off"},
{OPT_ERR, NULL}
};
static char *ovl_next_opt(char **s)
{
char *sbegin = *s;
char *p;
if (sbegin == NULL)
return NULL;
for (p = sbegin; *p; p++) {
if (*p == '\\') {
p++;
if (!*p)
break;
} else if (*p == ',') {
*p = '\0';
*s = p + 1;
return sbegin;
}
}
*s = NULL;
return sbegin;
}
static int ovl_parse_opt(char *opt, struct ovl_config *config)
{
char *p;
while ((p = ovl_next_opt(&opt)) != NULL) {
int token;
substring_t args[MAX_OPT_ARGS];
if (!*p)
continue;
token = match_token(p, ovl_tokens, args);
switch (token) {
case OPT_UPPERDIR:
kfree(config->upperdir);
config->upperdir = match_strdup(&args[0]);
if (!config->upperdir)
return -ENOMEM;
break;
case OPT_LOWERDIR:
kfree(config->lowerdir);
config->lowerdir = match_strdup(&args[0]);
if (!config->lowerdir)
return -ENOMEM;
break;
case OPT_WORKDIR:
kfree(config->workdir);
config->workdir = match_strdup(&args[0]);
if (!config->workdir)
return -ENOMEM;
break;
case OPT_DEFAULT_PERMISSIONS:
config->default_permissions = true;
break;
case OPT_REDIRECT_DIR_ON:
config->redirect_dir = true;
break;
case OPT_REDIRECT_DIR_OFF:
config->redirect_dir = false;
break;
case OPT_INDEX_ON:
config->index = true;
break;
case OPT_INDEX_OFF:
config->index = false;
break;
default:
pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
return -EINVAL;
}
}
/* Workdir is useless in non-upper mount */
if (!config->upperdir && config->workdir) {
pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
config->workdir);
kfree(config->workdir);
config->workdir = NULL;
}
return 0;
}
#define OVL_WORKDIR_NAME "work"
#define OVL_INDEXDIR_NAME "index"
static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
const char *name, bool persist)
{
struct inode *dir = ofs->workbasedir->d_inode;
struct vfsmount *mnt = ofs->upper_mnt;
struct dentry *work;
int err;
bool retried = false;
bool locked = false;
err = mnt_want_write(mnt);
if (err)
goto out_err;
inode_lock_nested(dir, I_MUTEX_PARENT);
locked = true;
retry:
work = lookup_one_len(name, ofs->workbasedir, strlen(name));
if (!IS_ERR(work)) {
struct iattr attr = {
.ia_valid = ATTR_MODE,
.ia_mode = S_IFDIR | 0,
};
if (work->d_inode) {
err = -EEXIST;
if (retried)
goto out_dput;
if (persist)
goto out_unlock;
retried = true;
ovl_workdir_cleanup(dir, mnt, work, 0);
dput(work);
goto retry;
}
err = ovl_create_real(dir, work,
&(struct cattr){.mode = S_IFDIR | 0},
NULL, true);
if (err)
goto out_dput;
/*
* Try to remove POSIX ACL xattrs from workdir. We are good if:
*
* a) success (there was a POSIX ACL xattr and was removed)
* b) -ENODATA (there was no POSIX ACL xattr)
* c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
*
* There are various other error values that could effectively
* mean that the xattr doesn't exist (e.g. -ERANGE is returned
* if the xattr name is too long), but the set of filesystems
* allowed as upper are limited to "normal" ones, where checking
* for the above two errors is sufficient.
*/
err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
if (err && err != -ENODATA && err != -EOPNOTSUPP)
goto out_dput;
err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
if (err && err != -ENODATA && err != -EOPNOTSUPP)
goto out_dput;
/* Clear any inherited mode bits */
inode_lock(work->d_inode);
err = notify_change(work, &attr, NULL);
inode_unlock(work->d_inode);
if (err)
goto out_dput;
} else {
err = PTR_ERR(work);
goto out_err;
}
out_unlock:
mnt_drop_write(mnt);
if (locked)
inode_unlock(dir);
return work;
out_dput:
dput(work);
out_err:
pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
ofs->config.workdir, name, -err);
work = NULL;
goto out_unlock;
}
static void ovl_unescape(char *s)
{
char *d = s;
for (;; s++, d++) {
if (*s == '\\')
s++;
*d = *s;
if (!*s)
break;
}
}
static int ovl_mount_dir_noesc(const char *name, struct path *path)
{
int err = -EINVAL;
if (!*name) {
pr_err("overlayfs: empty lowerdir\n");
goto out;
}
err = kern_path(name, LOOKUP_FOLLOW, path);
if (err) {
pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
goto out;
}
err = -EINVAL;
if (ovl_dentry_weird(path->dentry)) {
pr_err("overlayfs: filesystem on '%s' not supported\n", name);
goto out_put;
}
if (!d_is_dir(path->dentry)) {
pr_err("overlayfs: '%s' not a directory\n", name);
goto out_put;
}
return 0;
out_put:
path_put_init(path);
out:
return err;
}
static int ovl_mount_dir(const char *name, struct path *path)
{
int err = -ENOMEM;
char *tmp = kstrdup(name, GFP_KERNEL);
if (tmp) {
ovl_unescape(tmp);
err = ovl_mount_dir_noesc(tmp, path);
if (!err)
if (ovl_dentry_remote(path->dentry)) {
pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
tmp);
path_put_init(path);
err = -EINVAL;
}
kfree(tmp);
}
return err;
}
static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
const char *name)
{
struct kstatfs statfs;
int err = vfs_statfs(path, &statfs);
if (err)
pr_err("overlayfs: statfs failed on '%s'\n", name);
else
ofs->namelen = max(ofs->namelen, statfs.f_namelen);
return err;
}
static int ovl_lower_dir(const char *name, struct path *path,
struct ovl_fs *ofs, int *stack_depth, bool *remote)
{
int err;
err = ovl_mount_dir_noesc(name, path);
if (err)
goto out;
err = ovl_check_namelen(path, ofs, name);
if (err)
goto out_put;
*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
if (ovl_dentry_remote(path->dentry))
*remote = true;
/*
* The inodes index feature needs to encode and decode file
* handles, so it requires that all layers support them.
*/
if (ofs->config.index && !ovl_can_decode_fh(path->dentry->d_sb)) {
ofs->config.index = false;
pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name);
}
return 0;
out_put:
path_put_init(path);
out:
return err;
}
/* Workdir should not be subdir of upperdir and vice versa */
static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
{
bool ok = false;
if (workdir != upperdir) {
ok = (lock_rename(workdir, upperdir) == NULL);
unlock_rename(workdir, upperdir);
}
return ok;
}
static unsigned int ovl_split_lowerdirs(char *str)
{
unsigned int ctr = 1;
char *s, *d;
for (s = d = str;; s++, d++) {
if (*s == '\\') {
s++;
} else if (*s == ':') {
*d = '\0';
ctr++;
continue;
}
*d = *s;
if (!*s)
break;
}
return ctr;
}
static int __maybe_unused
ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
struct dentry *dentry, struct inode *inode,
const char *name, void *buffer, size_t size)
{
return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
}
static int __maybe_unused
ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
struct dentry *dentry, struct inode *inode,
const char *name, const void *value,
size_t size, int flags)
{
struct dentry *workdir = ovl_workdir(dentry);
struct inode *realinode = ovl_inode_real(inode);
struct posix_acl *acl = NULL;
int err;
/* Check that everything is OK before copy-up */
if (value) {
acl = posix_acl_from_xattr(&init_user_ns, value, size);
if (IS_ERR(acl))
return PTR_ERR(acl);
}
err = -EOPNOTSUPP;
if (!IS_POSIXACL(d_inode(workdir)))
goto out_acl_release;
if (!realinode->i_op->set_acl)
goto out_acl_release;
if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
err = acl ? -EACCES : 0;
goto out_acl_release;
}
err = -EPERM;
if (!inode_owner_or_capable(inode))
goto out_acl_release;
posix_acl_release(acl);
/*
* Check if sgid bit needs to be cleared (actual setacl operation will
* be done with mounter's capabilities and so that won't do it for us).
*/
if (unlikely(inode->i_mode & S_ISGID) &&
handler->flags == ACL_TYPE_ACCESS &&
!in_group_p(inode->i_gid) &&
!capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
err = ovl_setattr(dentry, &iattr);
if (err)
return err;
}
err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
if (!err)
ovl_copyattr(ovl_inode_real(inode), inode);
return err;
out_acl_release:
posix_acl_release(acl);
return err;
}
static int ovl_own_xattr_get(const struct xattr_handler *handler,
struct dentry *dentry, struct inode *inode,
const char *name, void *buffer, size_t size)
{
return -EOPNOTSUPP;
}
static int ovl_own_xattr_set(const struct xattr_handler *handler,
struct dentry *dentry, struct inode *inode,
const char *name, const void *value,
size_t size, int flags)
{
return -EOPNOTSUPP;
}
static int ovl_other_xattr_get(const struct xattr_handler *handler,
struct dentry *dentry, struct inode *inode,
const char *name, void *buffer, size_t size)
{
return ovl_xattr_get(dentry, inode, name, buffer, size);
}
static int ovl_other_xattr_set(const struct xattr_handler *handler,
struct dentry *dentry, struct inode *inode,
const char *name, const void *value,
size_t size, int flags)
{
return ovl_xattr_set(dentry, inode, name, value, size, flags);
}
static const struct xattr_handler __maybe_unused
ovl_posix_acl_access_xattr_handler = {
.name = XATTR_NAME_POSIX_ACL_ACCESS,
.flags = ACL_TYPE_ACCESS,
.get = ovl_posix_acl_xattr_get,
.set = ovl_posix_acl_xattr_set,
};
static const struct xattr_handler __maybe_unused
ovl_posix_acl_default_xattr_handler = {
.name = XATTR_NAME_POSIX_ACL_DEFAULT,
.flags = ACL_TYPE_DEFAULT,
.get = ovl_posix_acl_xattr_get,
.set = ovl_posix_acl_xattr_set,
};
static const struct xattr_handler ovl_own_xattr_handler = {
.prefix = OVL_XATTR_PREFIX,
.get = ovl_own_xattr_get,
.set = ovl_own_xattr_set,
};
static const struct xattr_handler ovl_other_xattr_handler = {
.prefix = "", /* catch all */
.get = ovl_other_xattr_get,
.set = ovl_other_xattr_set,
};
static const struct xattr_handler *ovl_xattr_handlers[] = {
#ifdef CONFIG_FS_POSIX_ACL
&ovl_posix_acl_access_xattr_handler,
&ovl_posix_acl_default_xattr_handler,
#endif
&ovl_own_xattr_handler,
&ovl_other_xattr_handler,
NULL
};
static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
{
struct vfsmount *upper_mnt;
int err;
err = ovl_mount_dir(ofs->config.upperdir, upperpath);
if (err)
goto out;
/* Upper fs should not be r/o */
if (sb_rdonly(upperpath->mnt->mnt_sb)) {
pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
err = -EINVAL;
goto out;
}
err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
if (err)
goto out;
err = -EBUSY;
if (ovl_inuse_trylock(upperpath->dentry)) {
ofs->upperdir_locked = true;
} else if (ofs->config.index) {
pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
goto out;
} else {
pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
}
upper_mnt = clone_private_mount(upperpath);
err = PTR_ERR(upper_mnt);
if (IS_ERR(upper_mnt)) {
pr_err("overlayfs: failed to clone upperpath\n");
goto out;
}
/* Don't inherit atime flags */
upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
ofs->upper_mnt = upper_mnt;
err = 0;
out:
return err;
}
static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
{
struct dentry *temp;
int err;
ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
if (!ofs->workdir)
return 0;
/*
* Upper should support d_type, else whiteouts are visible. Given
* workdir and upper are on same fs, we can do iterate_dir() on
* workdir. This check requires successful creation of workdir in
* previous step.
*/
err = ovl_check_d_type_supported(workpath);
if (err < 0)
return err;
/*
* We allowed this configuration and don't want to break users over
* kernel upgrade. So warn instead of erroring out.
*/
if (!err)
pr_warn("overlayfs: upper fs needs to support d_type.\n");
/* Check if upper/work fs supports O_TMPFILE */
temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
ofs->tmpfile = !IS_ERR(temp);
if (ofs->tmpfile)
dput(temp);
else
pr_warn("overlayfs: upper fs does not support tmpfile.\n");
/*
* Check if upper/work fs supports trusted.overlay.* xattr
*/
err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
if (err) {
ofs->noxattr = true;
pr_warn("overlayfs: upper fs does not support xattr.\n");
} else {
vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
}
/* Check if upper/work fs supports file handles */
if (ofs->config.index &&
!ovl_can_decode_fh(ofs->workdir->d_sb)) {
ofs->config.index = false;
pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
}
return 0;
}
static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
{
int err;
struct path workpath = { };
err = ovl_mount_dir(ofs->config.workdir, &workpath);
if (err)
goto out;
err = -EINVAL;
if (upperpath->mnt != workpath.mnt) {
pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
goto out;
}
if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
goto out;
}
err = -EBUSY;
if (ovl_inuse_trylock(workpath.dentry)) {
ofs->workdir_locked = true;
} else if (ofs->config.index) {
pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
goto out;
} else {
pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
}
ofs->workbasedir = dget(workpath.dentry);
err = ovl_make_workdir(ofs, &workpath);
if (err)
goto out;
err = 0;
out:
path_put(&workpath);
return err;
}
static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
struct path *upperpath)
{
int err;
/* Verify lower root is upper root origin */
err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
false, true);
if (err) {
pr_err("overlayfs: failed to verify upper root origin\n");
goto out;
}
ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
if (ofs->indexdir) {
/* Verify upper root is index dir origin */
err = ovl_verify_origin(ofs->indexdir, upperpath->dentry,
true, true);
if (err)
pr_err("overlayfs: failed to verify index dir origin\n");
/* Cleanup bad/stale/orphan index entries */
if (!err)
err = ovl_indexdir_cleanup(ofs->indexdir,
ofs->upper_mnt,
oe->lowerstack,
oe->numlower);
}
if (err || !ofs->indexdir)
pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
out:
return err;
}
static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
unsigned int numlower)
{
int err;
unsigned int i;
err = -ENOMEM;
ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
GFP_KERNEL);
if (ofs->lower_layers == NULL)
goto out;
for (i = 0; i < numlower; i++) {
struct vfsmount *mnt;
dev_t dev;
err = get_anon_bdev(&dev);
if (err) {
pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
goto out;
}
mnt = clone_private_mount(&stack[i]);
err = PTR_ERR(mnt);
if (IS_ERR(mnt)) {
pr_err("overlayfs: failed to clone lowerpath\n");
free_anon_bdev(dev);
goto out;
}
/*
* Make lower layers R/O. That way fchmod/fchown on lower file
* will fail instead of modifying lower fs.
*/
mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
ofs->lower_layers[ofs->numlower].mnt = mnt;
ofs->lower_layers[ofs->numlower].pseudo_dev = dev;
ofs->numlower++;
/* Check if all lower layers are on same sb */
if (i == 0)
ofs->same_sb = mnt->mnt_sb;
else if (ofs->same_sb != mnt->mnt_sb)
ofs->same_sb = NULL;
}
err = 0;
out:
return err;
}
static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
struct ovl_fs *ofs)
{
int err;
char *lowertmp, *lower;
struct path *stack = NULL;
unsigned int stacklen, numlower = 0, i;
bool remote = false;
struct ovl_entry *oe;
err = -ENOMEM;
lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
if (!lowertmp)
goto out_err;
err = -EINVAL;
stacklen = ovl_split_lowerdirs(lowertmp);
if (stacklen > OVL_MAX_STACK) {
pr_err("overlayfs: too many lower directories, limit is %d\n",
OVL_MAX_STACK);
goto out_err;
} else if (!ofs->config.upperdir && stacklen == 1) {
pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
goto out_err;
}
err = -ENOMEM;
stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
if (!stack)
goto out_err;
err = -EINVAL;
lower = lowertmp;
for (numlower = 0; numlower < stacklen; numlower++) {
err = ovl_lower_dir(lower, &stack[numlower], ofs,
&sb->s_stack_depth, &remote);
if (err)
goto out_err;
lower = strchr(lower, '\0') + 1;
}
err = -EINVAL;
sb->s_stack_depth++;
if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
pr_err("overlayfs: maximum fs stacking depth exceeded\n");
goto out_err;
}
err = ovl_get_lower_layers(ofs, stack, numlower);
if (err)
goto out_err;
err = -ENOMEM;
oe = ovl_alloc_entry(numlower);
if (!oe)
goto out_err;
for (i = 0; i < numlower; i++) {
oe->lowerstack[i].dentry = dget(stack[i].dentry);
oe->lowerstack[i].layer = &ofs->lower_layers[i];
}
if (remote)
sb->s_d_op = &ovl_reval_dentry_operations;
else
sb->s_d_op = &ovl_dentry_operations;
out:
for (i = 0; i < numlower; i++)
path_put(&stack[i]);
kfree(stack);
kfree(lowertmp);
return oe;
out_err:
oe = ERR_PTR(err);
goto out;
}
static int ovl_fill_super(struct super_block *sb, void *data, int silent)
{
struct path upperpath = { };
struct dentry *root_dentry;
struct ovl_entry *oe;
struct ovl_fs *ofs;
struct cred *cred;
int err;
err = -ENOMEM;
ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
if (!ofs)
goto out;
ofs->creator_cred = cred = prepare_creds();
if (!cred)
goto out_err;
ofs->config.redirect_dir = ovl_redirect_dir_def;
ofs->config.index = ovl_index_def;
err = ovl_parse_opt((char *) data, &ofs->config);
if (err)
goto out_err;
err = -EINVAL;
if (!ofs->config.lowerdir) {
if (!silent)
pr_err("overlayfs: missing 'lowerdir'\n");
goto out_err;
}
sb->s_stack_depth = 0;
sb->s_maxbytes = MAX_LFS_FILESIZE;
if (ofs->config.upperdir) {
if (!ofs->config.workdir) {
pr_err("overlayfs: missing 'workdir'\n");
goto out_err;
}
err = ovl_get_upper(ofs, &upperpath);
if (err)
goto out_err;
err = ovl_get_workdir(ofs, &upperpath);
if (err)
goto out_err;
if (!ofs->workdir)
sb->s_flags |= SB_RDONLY;
sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
}
oe = ovl_get_lowerstack(sb, ofs);
err = PTR_ERR(oe);
if (IS_ERR(oe))
goto out_err;
/* If the upper fs is nonexistent, we mark overlayfs r/o too */
if (!ofs->upper_mnt)
sb->s_flags |= SB_RDONLY;
else if (ofs->upper_mnt->mnt_sb != ofs->same_sb)
ofs->same_sb = NULL;
if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
err = ovl_get_indexdir(ofs, oe, &upperpath);
if (err)
goto out_free_oe;
if (!ofs->indexdir)
sb->s_flags |= SB_RDONLY;
}
/* Show index=off/on in /proc/mounts for any of the reasons above */
if (!ofs->indexdir)
ofs->config.index = false;
/* Never override disk quota limits or use reserved space */
cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
sb->s_magic = OVERLAYFS_SUPER_MAGIC;
sb->s_op = &ovl_super_operations;
sb->s_xattr = ovl_xattr_handlers;
sb->s_fs_info = ofs;
sb->s_flags |= SB_POSIXACL | SB_NOREMOTELOCK;
err = -ENOMEM;
root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
if (!root_dentry)
goto out_free_oe;
mntput(upperpath.mnt);
if (upperpath.dentry) {
oe->has_upper = true;
if (ovl_is_impuredir(upperpath.dentry))
ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
}
root_dentry->d_fsdata = oe;
/* Root is always merge -> can have whiteouts */
ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
ovl_dentry_lower(root_dentry));
sb->s_root = root_dentry;
return 0;
out_free_oe:
ovl_entry_stack_free(oe);
kfree(oe);
out_err:
path_put(&upperpath);
ovl_free_fs(ofs);
out:
return err;
}
static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
const char *dev_name, void *raw_data)
{
return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
}
static struct file_system_type ovl_fs_type = {
.owner = THIS_MODULE,
.name = "overlay",
.mount = ovl_mount,
.kill_sb = kill_anon_super,
};
MODULE_ALIAS_FS("overlay");
static void ovl_inode_init_once(void *foo)
{
struct ovl_inode *oi = foo;
inode_init_once(&oi->vfs_inode);
}
static int __init ovl_init(void)
{
int err;
ovl_inode_cachep = kmem_cache_create("ovl_inode",
sizeof(struct ovl_inode), 0,
(SLAB_RECLAIM_ACCOUNT|
SLAB_MEM_SPREAD|SLAB_ACCOUNT),
ovl_inode_init_once);
if (ovl_inode_cachep == NULL)
return -ENOMEM;
err = register_filesystem(&ovl_fs_type);
if (err)
kmem_cache_destroy(ovl_inode_cachep);
return err;
}
static void __exit ovl_exit(void)
{
unregister_filesystem(&ovl_fs_type);
/*
* Make sure all delayed rcu free inodes are flushed before we
* destroy cache.
*/
rcu_barrier();
kmem_cache_destroy(ovl_inode_cachep);
}
module_init(ovl_init);
module_exit(ovl_exit);