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android-kvm / linux / f05fb508ec3bb2d4b6006682d76d380d50a6fc42 / . / fs / overlayfs / super.c
blob: 178daa5e82c9ddac45f0a972976ba90afeab4af8 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-only
/*
*
* Copyright (C) 2011 Novell Inc.
*/
#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 <linux/exportfs.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(redirect_dir,
"Default to on or off for the redirect_dir feature");
static bool ovl_redirect_always_follow =
IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
module_param_named(redirect_always_follow, ovl_redirect_always_follow,
bool, 0644);
MODULE_PARM_DESC(redirect_always_follow,
"Follow redirects even if redirect_dir feature is turned off");
static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
module_param_named(index, ovl_index_def, bool, 0644);
MODULE_PARM_DESC(index,
"Default to on or off for the inodes index feature");
static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
MODULE_PARM_DESC(nfs_export,
"Default to on or off for the NFS export feature");
static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO);
module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
MODULE_PARM_DESC(xino_auto,
"Auto enable xino 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 bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
MODULE_PARM_DESC(metacopy,
"Default to on or off for the metadata only copy up feature");
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 struct dentry *ovl_d_real(struct dentry *dentry,
const struct inode *inode)
{
struct dentry *real = NULL, *lower;
/* It's an overlay file */
if (inode && d_inode(dentry) == inode)
return dentry;
if (!d_is_reg(dentry)) {
if (!inode || inode == d_inode(dentry))
return dentry;
goto bug;
}
real = ovl_dentry_upper(dentry);
if (real && (inode == d_inode(real)))
return real;
if (real && !inode && ovl_has_upperdata(d_inode(dentry)))
return real;
lower = ovl_dentry_lowerdata(dentry);
if (!lower)
goto bug;
real = lower;
/* Handle recursion */
real = d_real(real, inode);
if (!inode || inode == d_inode(real))
return real;
bug:
WARN(1, "%s(%pd4, %s:%lu): real dentry (%p/%lu) not found\n",
__func__, dentry, inode ? inode->i_sb->s_id : "NULL",
inode ? inode->i_ino : 0, real,
real && d_inode(real) ? d_inode(real)->i_ino : 0);
return dentry;
}
static int ovl_revalidate_real(struct dentry *d, unsigned int flags, bool weak)
{
int ret = 1;
if (weak) {
if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE)
ret = d->d_op->d_weak_revalidate(d, flags);
} else if (d->d_flags & DCACHE_OP_REVALIDATE) {
ret = d->d_op->d_revalidate(d, flags);
if (!ret) {
if (!(flags & LOOKUP_RCU))
d_invalidate(d);
ret = -ESTALE;
}
}
return ret;
}
static int ovl_dentry_revalidate_common(struct dentry *dentry,
unsigned int flags, bool weak)
{
struct ovl_entry *oe = dentry->d_fsdata;
struct dentry *upper;
unsigned int i;
int ret = 1;
upper = ovl_dentry_upper(dentry);
if (upper)
ret = ovl_revalidate_real(upper, flags, weak);
for (i = 0; ret > 0 && i < oe->numlower; i++) {
ret = ovl_revalidate_real(oe->lowerstack[i].dentry, flags,
weak);
}
return ret;
}
static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
{
return ovl_dentry_revalidate_common(dentry, flags, false);
}
static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
{
return ovl_dentry_revalidate_common(dentry, flags, true);
}
static const struct dentry_operations ovl_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;
oi->lowerdata = NULL;
mutex_init(&oi->lock);
return &oi->vfs_inode;
}
static void ovl_free_inode(struct inode *inode)
{
struct ovl_inode *oi = OVL_I(inode);
kfree(oi->redirect);
mutex_destroy(&oi->lock);
kmem_cache_free(ovl_inode_cachep, oi);
}
static void ovl_destroy_inode(struct inode *inode)
{
struct ovl_inode *oi = OVL_I(inode);
dput(oi->__upperdentry);
iput(oi->lower);
if (S_ISDIR(inode->i_mode))
ovl_dir_cache_free(inode);
else
iput(oi->lowerdata);
}
static void ovl_free_fs(struct ovl_fs *ofs)
{
struct vfsmount **mounts;
unsigned i;
iput(ofs->workbasedir_trap);
iput(ofs->indexdir_trap);
iput(ofs->workdir_trap);
dput(ofs->whiteout);
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(ovl_upper_mnt(ofs)->mnt_root);
/* Hack! Reuse ofs->layers as a vfsmount array before freeing it */
mounts = (struct vfsmount **) ofs->layers;
for (i = 0; i < ofs->numlayer; i++) {
iput(ofs->layers[i].trap);
mounts[i] = ofs->layers[i].mnt;
}
kern_unmount_array(mounts, ofs->numlayer);
kfree(ofs->layers);
for (i = 0; i < ofs->numfs; i++)
free_anon_bdev(ofs->fs[i].pseudo_dev);
kfree(ofs->fs);
kfree(ofs->config.lowerdir);
kfree(ofs->config.upperdir);
kfree(ofs->config.workdir);
kfree(ofs->config.redirect_mode);
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);
}
/* Sync real dirty inodes in upper filesystem (if it exists) */
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;
ret = ovl_sync_status(ofs);
/*
* We have to always set the err, because the return value isn't
* checked in syncfs, and instead indirectly return an error via
* the sb's writeback errseq, which VFS inspects after this call.
*/
if (ret < 0) {
errseq_set(&sb->s_wb_err, -EIO);
return -EIO;
}
if (!ret)
return ret;
/*
* Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
* All the super blocks will be iterated, including upper_sb.
*
* If this is a syncfs(2) call, then we do need to call
* sync_filesystem() on upper_sb, but enough if we do it when being
* called with wait == 1.
*/
if (!wait)
return 0;
upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
down_read(&upper_sb->s_umount);
ret = sync_filesystem(upper_sb);
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 (!ovl_upper_mnt(ofs) || !ofs->workdir);
}
static const char *ovl_redirect_mode_def(void)
{
return ovl_redirect_dir_def ? "on" : "off";
}
static const char * const ovl_xino_str[] = {
"off",
"auto",
"on",
};
static inline int ovl_xino_def(void)
{
return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
}
/**
* 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 (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
if (ofs->config.index != ovl_index_def)
seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
if (!ofs->config.uuid)
seq_puts(m, ",uuid=off");
if (ofs->config.nfs_export != ovl_nfs_export_def)
seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
"on" : "off");
if (ofs->config.xino != ovl_xino_def() && !ovl_same_fs(sb))
seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
if (ofs->config.metacopy != ovl_metacopy_def)
seq_printf(m, ",metacopy=%s",
ofs->config.metacopy ? "on" : "off");
if (ofs->config.ovl_volatile)
seq_puts(m, ",volatile");
if (ofs->config.userxattr)
seq_puts(m, ",userxattr");
return 0;
}
static int ovl_remount(struct super_block *sb, int *flags, char *data)
{
struct ovl_fs *ofs = sb->s_fs_info;
struct super_block *upper_sb;
int ret = 0;
if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
return -EROFS;
if (*flags & SB_RDONLY && !sb_rdonly(sb)) {
upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
if (ovl_should_sync(ofs)) {
down_read(&upper_sb->s_umount);
ret = sync_filesystem(upper_sb);
up_read(&upper_sb->s_umount);
}
}
return ret;
}
static const struct super_operations ovl_super_operations = {
.alloc_inode = ovl_alloc_inode,
.free_inode = ovl_free_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,
OPT_INDEX_ON,
OPT_INDEX_OFF,
OPT_UUID_ON,
OPT_UUID_OFF,
OPT_NFS_EXPORT_ON,
OPT_USERXATTR,
OPT_NFS_EXPORT_OFF,
OPT_XINO_ON,
OPT_XINO_OFF,
OPT_XINO_AUTO,
OPT_METACOPY_ON,
OPT_METACOPY_OFF,
OPT_VOLATILE,
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, "redirect_dir=%s"},
{OPT_INDEX_ON, "index=on"},
{OPT_INDEX_OFF, "index=off"},
{OPT_USERXATTR, "userxattr"},
{OPT_UUID_ON, "uuid=on"},
{OPT_UUID_OFF, "uuid=off"},
{OPT_NFS_EXPORT_ON, "nfs_export=on"},
{OPT_NFS_EXPORT_OFF, "nfs_export=off"},
{OPT_XINO_ON, "xino=on"},
{OPT_XINO_OFF, "xino=off"},
{OPT_XINO_AUTO, "xino=auto"},
{OPT_METACOPY_ON, "metacopy=on"},
{OPT_METACOPY_OFF, "metacopy=off"},
{OPT_VOLATILE, "volatile"},
{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_redirect_mode(struct ovl_config *config, const char *mode)
{
if (strcmp(mode, "on") == 0) {
config->redirect_dir = true;
/*
* Does not make sense to have redirect creation without
* redirect following.
*/
config->redirect_follow = true;
} else if (strcmp(mode, "follow") == 0) {
config->redirect_follow = true;
} else if (strcmp(mode, "off") == 0) {
if (ovl_redirect_always_follow)
config->redirect_follow = true;
} else if (strcmp(mode, "nofollow") != 0) {
pr_err("bad mount option \"redirect_dir=%s\"\n",
mode);
return -EINVAL;
}
return 0;
}
static int ovl_parse_opt(char *opt, struct ovl_config *config)
{
char *p;
int err;
bool metacopy_opt = false, redirect_opt = false;
bool nfs_export_opt = false, index_opt = false;
config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
if (!config->redirect_mode)
return -ENOMEM;
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:
kfree(config->redirect_mode);
config->redirect_mode = match_strdup(&args[0]);
if (!config->redirect_mode)
return -ENOMEM;
redirect_opt = true;
break;
case OPT_INDEX_ON:
config->index = true;
index_opt = true;
break;
case OPT_INDEX_OFF:
config->index = false;
index_opt = true;
break;
case OPT_UUID_ON:
config->uuid = true;
break;
case OPT_UUID_OFF:
config->uuid = false;
break;
case OPT_NFS_EXPORT_ON:
config->nfs_export = true;
nfs_export_opt = true;
break;
case OPT_NFS_EXPORT_OFF:
config->nfs_export = false;
nfs_export_opt = true;
break;
case OPT_XINO_ON:
config->xino = OVL_XINO_ON;
break;
case OPT_XINO_OFF:
config->xino = OVL_XINO_OFF;
break;
case OPT_XINO_AUTO:
config->xino = OVL_XINO_AUTO;
break;
case OPT_METACOPY_ON:
config->metacopy = true;
metacopy_opt = true;
break;
case OPT_METACOPY_OFF:
config->metacopy = false;
metacopy_opt = true;
break;
case OPT_VOLATILE:
config->ovl_volatile = true;
break;
case OPT_USERXATTR:
config->userxattr = true;
break;
default:
pr_err("unrecognized mount option \"%s\" or missing value\n",
p);
return -EINVAL;
}
}
/* Workdir/index are useless in non-upper mount */
if (!config->upperdir) {
if (config->workdir) {
pr_info("option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
config->workdir);
kfree(config->workdir);
config->workdir = NULL;
}
if (config->index && index_opt) {
pr_info("option \"index=on\" is useless in a non-upper mount, ignore\n");
index_opt = false;
}
config->index = false;
}
if (!config->upperdir && config->ovl_volatile) {
pr_info("option \"volatile\" is meaningless in a non-upper mount, ignoring it.\n");
config->ovl_volatile = false;
}
err = ovl_parse_redirect_mode(config, config->redirect_mode);
if (err)
return err;
/*
* This is to make the logic below simpler. It doesn't make any other
* difference, since config->redirect_dir is only used for upper.
*/
if (!config->upperdir && config->redirect_follow)
config->redirect_dir = true;
/* Resolve metacopy -> redirect_dir dependency */
if (config->metacopy && !config->redirect_dir) {
if (metacopy_opt && redirect_opt) {
pr_err("conflicting options: metacopy=on,redirect_dir=%s\n",
config->redirect_mode);
return -EINVAL;
}
if (redirect_opt) {
/*
* There was an explicit redirect_dir=... that resulted
* in this conflict.
*/
pr_info("disabling metacopy due to redirect_dir=%s\n",
config->redirect_mode);
config->metacopy = false;
} else {
/* Automatically enable redirect otherwise. */
config->redirect_follow = config->redirect_dir = true;
}
}
/* Resolve nfs_export -> index dependency */
if (config->nfs_export && !config->index) {
if (!config->upperdir && config->redirect_follow) {
pr_info("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
config->nfs_export = false;
} else if (nfs_export_opt && index_opt) {
pr_err("conflicting options: nfs_export=on,index=off\n");
return -EINVAL;
} else if (index_opt) {
/*
* There was an explicit index=off that resulted
* in this conflict.
*/
pr_info("disabling nfs_export due to index=off\n");
config->nfs_export = false;
} else {
/* Automatically enable index otherwise. */
config->index = true;
}
}
/* Resolve nfs_export -> !metacopy dependency */
if (config->nfs_export && config->metacopy) {
if (nfs_export_opt && metacopy_opt) {
pr_err("conflicting options: nfs_export=on,metacopy=on\n");
return -EINVAL;
}
if (metacopy_opt) {
/*
* There was an explicit metacopy=on that resulted
* in this conflict.
*/
pr_info("disabling nfs_export due to metacopy=on\n");
config->nfs_export = false;
} else {
/*
* There was an explicit nfs_export=on that resulted
* in this conflict.
*/
pr_info("disabling metacopy due to nfs_export=on\n");
config->metacopy = false;
}
}
/* Resolve userxattr -> !redirect && !metacopy dependency */
if (config->userxattr) {
if (config->redirect_follow && redirect_opt) {
pr_err("conflicting options: userxattr,redirect_dir=%s\n",
config->redirect_mode);
return -EINVAL;
}
if (config->metacopy && metacopy_opt) {
pr_err("conflicting options: userxattr,metacopy=on\n");
return -EINVAL;
}
/*
* Silently disable default setting of redirect and metacopy.
* This shall be the default in the future as well: these
* options must be explicitly enabled if used together with
* userxattr.
*/
config->redirect_dir = config->redirect_follow = false;
config->metacopy = false;
}
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 = ovl_upper_mnt(ofs);
struct dentry *work;
int err;
bool retried = false;
inode_lock_nested(dir, I_MUTEX_PARENT);
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;
err = ovl_workdir_cleanup(dir, mnt, work, 0);
dput(work);
if (err == -EINVAL) {
work = ERR_PTR(err);
goto out_unlock;
}
goto retry;
}
work = ovl_create_real(dir, work, OVL_CATTR(attr.ia_mode));
err = PTR_ERR(work);
if (IS_ERR(work))
goto out_err;
/*
* 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(&init_user_ns, work,
XATTR_NAME_POSIX_ACL_DEFAULT);
if (err && err != -ENODATA && err != -EOPNOTSUPP)
goto out_dput;
err = vfs_removexattr(&init_user_ns, 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(&init_user_ns, work, &attr, NULL);
inode_unlock(work->d_inode);
if (err)
goto out_dput;
} else {
err = PTR_ERR(work);
goto out_err;
}
out_unlock:
inode_unlock(dir);
return work;
out_dput:
dput(work);
out_err:
pr_warn("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("empty lowerdir\n");
goto out;
}
err = kern_path(name, LOOKUP_FOLLOW, path);
if (err) {
pr_err("failed to resolve '%s': %i\n", name, err);
goto out;
}
err = -EINVAL;
if (ovl_dentry_weird(path->dentry)) {
pr_err("filesystem on '%s' not supported\n", name);
goto out_put;
}
if (mnt_user_ns(path->mnt) != &init_user_ns) {
pr_err("idmapped layers are currently not supported\n");
goto out_put;
}
if (!d_is_dir(path->dentry)) {
pr_err("'%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 && path->dentry->d_flags & DCACHE_OP_REAL) {
pr_err("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("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)
{
int fh_type;
int err;
err = ovl_mount_dir_noesc(name, path);
if (err)
return err;
err = ovl_check_namelen(path, ofs, name);
if (err)
return err;
*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
/*
* The inodes index feature and NFS export need to encode and decode
* file handles, so they require that all layers support them.
*/
fh_type = ovl_can_decode_fh(path->dentry->d_sb);
if ((ofs->config.nfs_export ||
(ofs->config.index && ofs->config.upperdir)) && !fh_type) {
ofs->config.index = false;
ofs->config.nfs_export = false;
pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
name);
}
/*
* Decoding origin file handle is required for persistent st_ino.
* Without persistent st_ino, xino=auto falls back to xino=off.
*/
if (ofs->config.xino == OVL_XINO_AUTO &&
ofs->config.upperdir && !fh_type) {
ofs->config.xino = OVL_XINO_OFF;
pr_warn("fs on '%s' does not support file handles, falling back to xino=off.\n",
name);
}
/* Check if lower fs has 32bit inode numbers */
if (fh_type != FILEID_INO32_GEN)
ofs->xino_mode = -1;
return 0;
}
/* 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 user_namespace *mnt_userns,
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(&init_user_ns, 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(&init_user_ns, inode, CAP_FSETID)) {
struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
err = ovl_setattr(&init_user_ns, dentry, &iattr);
if (err)
return err;
}
err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
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 user_namespace *mnt_userns,
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 user_namespace *mnt_userns,
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_trusted_xattr_handler = {
.prefix = OVL_XATTR_TRUSTED_PREFIX,
.get = ovl_own_xattr_get,
.set = ovl_own_xattr_set,
};
static const struct xattr_handler ovl_own_user_xattr_handler = {
.prefix = OVL_XATTR_USER_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_trusted_xattr_handlers[] = {
#ifdef CONFIG_FS_POSIX_ACL
&ovl_posix_acl_access_xattr_handler,
&ovl_posix_acl_default_xattr_handler,
#endif
&ovl_own_trusted_xattr_handler,
&ovl_other_xattr_handler,
NULL
};
static const struct xattr_handler *ovl_user_xattr_handlers[] = {
#ifdef CONFIG_FS_POSIX_ACL
&ovl_posix_acl_access_xattr_handler,
&ovl_posix_acl_default_xattr_handler,
#endif
&ovl_own_user_xattr_handler,
&ovl_other_xattr_handler,
NULL
};
static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
struct inode **ptrap, const char *name)
{
struct inode *trap;
int err;
trap = ovl_get_trap_inode(sb, dir);
err = PTR_ERR_OR_ZERO(trap);
if (err) {
if (err == -ELOOP)
pr_err("conflicting %s path\n", name);
return err;
}
*ptrap = trap;
return 0;
}
/*
* Determine how we treat concurrent use of upperdir/workdir based on the
* index feature. This is papering over mount leaks of container runtimes,
* for example, an old overlay mount is leaked and now its upperdir is
* attempted to be used as a lower layer in a new overlay mount.
*/
static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
{
if (ofs->config.index) {
pr_err("%s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n",
name);
return -EBUSY;
} else {
pr_warn("%s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n",
name);
return 0;
}
}
static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
struct ovl_layer *upper_layer, struct path *upperpath)
{
struct vfsmount *upper_mnt;
int err;
err = ovl_mount_dir(ofs->config.upperdir, upperpath);
if (err)
goto out;
/* Upperdir path should not be r/o */
if (__mnt_is_readonly(upperpath->mnt)) {
pr_err("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 = ovl_setup_trap(sb, upperpath->dentry, &upper_layer->trap,
"upperdir");
if (err)
goto out;
upper_mnt = clone_private_mount(upperpath);
err = PTR_ERR(upper_mnt);
if (IS_ERR(upper_mnt)) {
pr_err("failed to clone upperpath\n");
goto out;
}
/* Don't inherit atime flags */
upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
upper_layer->mnt = upper_mnt;
upper_layer->idx = 0;
upper_layer->fsid = 0;
/*
* Inherit SB_NOSEC flag from upperdir.
*
* This optimization changes behavior when a security related attribute
* (suid/sgid/security.*) is changed on an underlying layer. This is
* okay because we don't yet have guarantees in that case, but it will
* need careful treatment once we want to honour changes to underlying
* filesystems.
*/
if (upper_mnt->mnt_sb->s_flags & SB_NOSEC)
sb->s_flags |= SB_NOSEC;
if (ovl_inuse_trylock(ovl_upper_mnt(ofs)->mnt_root)) {
ofs->upperdir_locked = true;
} else {
err = ovl_report_in_use(ofs, "upperdir");
if (err)
goto out;
}
err = 0;
out:
return err;
}
/*
* Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and
* negative values if error is encountered.
*/
static int ovl_check_rename_whiteout(struct dentry *workdir)
{
struct inode *dir = d_inode(workdir);
struct dentry *temp;
struct dentry *dest;
struct dentry *whiteout;
struct name_snapshot name;
int err;
inode_lock_nested(dir, I_MUTEX_PARENT);
temp = ovl_create_temp(workdir, OVL_CATTR(S_IFREG | 0));
err = PTR_ERR(temp);
if (IS_ERR(temp))
goto out_unlock;
dest = ovl_lookup_temp(workdir);
err = PTR_ERR(dest);
if (IS_ERR(dest)) {
dput(temp);
goto out_unlock;
}
/* Name is inline and stable - using snapshot as a copy helper */
take_dentry_name_snapshot(&name, temp);
err = ovl_do_rename(dir, temp, dir, dest, RENAME_WHITEOUT);
if (err) {
if (err == -EINVAL)
err = 0;
goto cleanup_temp;
}
whiteout = lookup_one_len(name.name.name, workdir, name.name.len);
err = PTR_ERR(whiteout);
if (IS_ERR(whiteout))
goto cleanup_temp;
err = ovl_is_whiteout(whiteout);
/* Best effort cleanup of whiteout and temp file */
if (err)
ovl_cleanup(dir, whiteout);
dput(whiteout);
cleanup_temp:
ovl_cleanup(dir, temp);
release_dentry_name_snapshot(&name);
dput(temp);
dput(dest);
out_unlock:
inode_unlock(dir);
return err;
}
static struct dentry *ovl_lookup_or_create(struct dentry *parent,
const char *name, umode_t mode)
{
size_t len = strlen(name);
struct dentry *child;
inode_lock_nested(parent->d_inode, I_MUTEX_PARENT);
child = lookup_one_len(name, parent, len);
if (!IS_ERR(child) && !child->d_inode)
child = ovl_create_real(parent->d_inode, child,
OVL_CATTR(mode));
inode_unlock(parent->d_inode);
dput(parent);
return child;
}
/*
* Creates $workdir/work/incompat/volatile/dirty file if it is not already
* present.
*/
static int ovl_create_volatile_dirty(struct ovl_fs *ofs)
{
unsigned int ctr;
struct dentry *d = dget(ofs->workbasedir);
static const char *const volatile_path[] = {
OVL_WORKDIR_NAME, "incompat", "volatile", "dirty"
};
const char *const *name = volatile_path;
for (ctr = ARRAY_SIZE(volatile_path); ctr; ctr--, name++) {
d = ovl_lookup_or_create(d, *name, ctr > 1 ? S_IFDIR : S_IFREG);
if (IS_ERR(d))
return PTR_ERR(d);
}
dput(d);
return 0;
}
static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
struct path *workpath)
{
struct vfsmount *mnt = ovl_upper_mnt(ofs);
struct dentry *temp, *workdir;
bool rename_whiteout;
bool d_type;
int fh_type;
int err;
err = mnt_want_write(mnt);
if (err)
return err;
workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
err = PTR_ERR(workdir);
if (IS_ERR_OR_NULL(workdir))
goto out;
ofs->workdir = workdir;
err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
if (err)
goto out;
/*
* 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)
goto out;
d_type = err;
if (!d_type)
pr_warn("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("upper fs does not support tmpfile.\n");
/* Check if upper/work fs supports RENAME_WHITEOUT */
err = ovl_check_rename_whiteout(ofs->workdir);
if (err < 0)
goto out;
rename_whiteout = err;
if (!rename_whiteout)
pr_warn("upper fs does not support RENAME_WHITEOUT.\n");
/*
* Check if upper/work fs supports (trusted|user).overlay.* xattr
*/
err = ovl_do_setxattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE, "0", 1);
if (err) {
ofs->noxattr = true;
if (ofs->config.index || ofs->config.metacopy) {
ofs->config.index = false;
ofs->config.metacopy = false;
pr_warn("upper fs does not support xattr, falling back to index=off,metacopy=off.\n");
}
/*
* xattr support is required for persistent st_ino.
* Without persistent st_ino, xino=auto falls back to xino=off.
*/
if (ofs->config.xino == OVL_XINO_AUTO) {
ofs->config.xino = OVL_XINO_OFF;
pr_warn("upper fs does not support xattr, falling back to xino=off.\n");
}
err = 0;
} else {
ovl_do_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE);
}
/*
* We allowed sub-optimal upper fs configuration and don't want to break
* users over kernel upgrade, but we never allowed remote upper fs, so
* we can enforce strict requirements for remote upper fs.
*/
if (ovl_dentry_remote(ofs->workdir) &&
(!d_type || !rename_whiteout || ofs->noxattr)) {
pr_err("upper fs missing required features.\n");
err = -EINVAL;
goto out;
}
/*
* For volatile mount, create a incompat/volatile/dirty file to keep
* track of it.
*/
if (ofs->config.ovl_volatile) {
err = ovl_create_volatile_dirty(ofs);
if (err < 0) {
pr_err("Failed to create volatile/dirty file.\n");
goto out;
}
}
/* Check if upper/work fs supports file handles */
fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
if (ofs->config.index && !fh_type) {
ofs->config.index = false;
pr_warn("upper fs does not support file handles, falling back to index=off.\n");
}
/* Check if upper fs has 32bit inode numbers */
if (fh_type != FILEID_INO32_GEN)
ofs->xino_mode = -1;
/* NFS export of r/w mount depends on index */
if (ofs->config.nfs_export && !ofs->config.index) {
pr_warn("NFS export requires \"index=on\", falling back to nfs_export=off.\n");
ofs->config.nfs_export = false;
}
out:
mnt_drop_write(mnt);
return err;
}
static int ovl_get_workdir(struct super_block *sb, 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("workdir and upperdir must reside under the same mount\n");
goto out;
}
if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
pr_err("workdir and upperdir must be separate subtrees\n");
goto out;
}
ofs->workbasedir = dget(workpath.dentry);
if (ovl_inuse_trylock(ofs->workbasedir)) {
ofs->workdir_locked = true;
} else {
err = ovl_report_in_use(ofs, "workdir");
if (err)
goto out;
}
err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap,
"workdir");
if (err)
goto out;
err = ovl_make_workdir(sb, ofs, &workpath);
out:
path_put(&workpath);
return err;
}
static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
struct ovl_entry *oe, struct path *upperpath)
{
struct vfsmount *mnt = ovl_upper_mnt(ofs);
struct dentry *indexdir;
int err;
err = mnt_want_write(mnt);
if (err)
return err;
/* Verify lower root is upper root origin */
err = ovl_verify_origin(ofs, upperpath->dentry,
oe->lowerstack[0].dentry, true);
if (err) {
pr_err("failed to verify upper root origin\n");
goto out;
}
/* index dir will act also as workdir */
iput(ofs->workdir_trap);
ofs->workdir_trap = NULL;
dput(ofs->workdir);
ofs->workdir = NULL;
indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
if (IS_ERR(indexdir)) {
err = PTR_ERR(indexdir);
} else if (indexdir) {
ofs->indexdir = indexdir;
ofs->workdir = dget(indexdir);
err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
"indexdir");
if (err)
goto out;
/*
* Verify upper root is exclusively associated with index dir.
* Older kernels stored upper fh in ".overlay.origin"
* xattr. If that xattr exists, verify that it is a match to
* upper dir file handle. In any case, verify or set xattr
* ".overlay.upper" to indicate that index may have
* directory entries.
*/
if (ovl_check_origin_xattr(ofs, ofs->indexdir)) {
err = ovl_verify_set_fh(ofs, ofs->indexdir,
OVL_XATTR_ORIGIN,
upperpath->dentry, true, false);
if (err)
pr_err("failed to verify index dir 'origin' xattr\n");
}
err = ovl_verify_upper(ofs, ofs->indexdir, upperpath->dentry,
true);
if (err)
pr_err("failed to verify index dir 'upper' xattr\n");
/* Cleanup bad/stale/orphan index entries */
if (!err)
err = ovl_indexdir_cleanup(ofs);
}
if (err || !ofs->indexdir)
pr_warn("try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
out:
mnt_drop_write(mnt);
return err;
}
static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
{
unsigned int i;
if (!ofs->config.nfs_export && !ovl_upper_mnt(ofs))
return true;
/*
* We allow using single lower with null uuid for index and nfs_export
* for example to support those features with single lower squashfs.
* To avoid regressions in setups of overlay with re-formatted lower
* squashfs, do not allow decoding origin with lower null uuid unless
* user opted-in to one of the new features that require following the
* lower inode of non-dir upper.
*/
if (ovl_allow_offline_changes(ofs) && uuid_is_null(uuid))
return false;
for (i = 0; i < ofs->numfs; i++) {
/*
* We use uuid to associate an overlay lower file handle with a
* lower layer, so we can accept lower fs with null uuid as long
* as all lower layers with null uuid are on the same fs.
* if we detect multiple lower fs with the same uuid, we
* disable lower file handle decoding on all of them.
*/
if (ofs->fs[i].is_lower &&
uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) {
ofs->fs[i].bad_uuid = true;
return false;
}
}
return true;
}
/* Get a unique fsid for the layer */
static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
{
struct super_block *sb = path->mnt->mnt_sb;
unsigned int i;
dev_t dev;
int err;
bool bad_uuid = false;
bool warn = false;
for (i = 0; i < ofs->numfs; i++) {
if (ofs->fs[i].sb == sb)
return i;
}
if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
bad_uuid = true;
if (ofs->config.xino == OVL_XINO_AUTO) {
ofs->config.xino = OVL_XINO_OFF;
warn = true;
}
if (ofs->config.index || ofs->config.nfs_export) {
ofs->config.index = false;
ofs->config.nfs_export = false;
warn = true;
}
if (warn) {
pr_warn("%s uuid detected in lower fs '%pd2', falling back to xino=%s,index=off,nfs_export=off.\n",
uuid_is_null(&sb->s_uuid) ? "null" :
"conflicting",
path->dentry, ovl_xino_str[ofs->config.xino]);
}
}
err = get_anon_bdev(&dev);
if (err) {
pr_err("failed to get anonymous bdev for lowerpath\n");
return err;
}
ofs->fs[ofs->numfs].sb = sb;
ofs->fs[ofs->numfs].pseudo_dev = dev;
ofs->fs[ofs->numfs].bad_uuid = bad_uuid;
return ofs->numfs++;
}
static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
struct path *stack, unsigned int numlower,
struct ovl_layer *layers)
{
int err;
unsigned int i;
err = -ENOMEM;
ofs->fs = kcalloc(numlower + 1, sizeof(struct ovl_sb), GFP_KERNEL);
if (ofs->fs == NULL)
goto out;
/* idx/fsid 0 are reserved for upper fs even with lower only overlay */
ofs->numfs++;
/*
* All lower layers that share the same fs as upper layer, use the same
* pseudo_dev as upper layer. Allocate fs[0].pseudo_dev even for lower
* only overlay to simplify ovl_fs_free().
* is_lower will be set if upper fs is shared with a lower layer.
*/
err = get_anon_bdev(&ofs->fs[0].pseudo_dev);
if (err) {
pr_err("failed to get anonymous bdev for upper fs\n");
goto out;
}
if (ovl_upper_mnt(ofs)) {
ofs->fs[0].sb = ovl_upper_mnt(ofs)->mnt_sb;
ofs->fs[0].is_lower = false;
}
for (i = 0; i < numlower; i++) {
struct vfsmount *mnt;
struct inode *trap;
int fsid;
err = fsid = ovl_get_fsid(ofs, &stack[i]);
if (err < 0)
goto out;
/*
* Check if lower root conflicts with this overlay layers before
* checking if it is in-use as upperdir/workdir of "another"
* mount, because we do not bother to check in ovl_is_inuse() if
* the upperdir/workdir is in fact in-use by our
* upperdir/workdir.
*/
err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
if (err)
goto out;
if (ovl_is_inuse(stack[i].dentry)) {
err = ovl_report_in_use(ofs, "lowerdir");
if (err) {
iput(trap);
goto out;
}
}
mnt = clone_private_mount(&stack[i]);
err = PTR_ERR(mnt);
if (IS_ERR(mnt)) {
pr_err("failed to clone lowerpath\n");
iput(trap);
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;
layers[ofs->numlayer].trap = trap;
layers[ofs->numlayer].mnt = mnt;
layers[ofs->numlayer].idx = ofs->numlayer;
layers[ofs->numlayer].fsid = fsid;
layers[ofs->numlayer].fs = &ofs->fs[fsid];
ofs->numlayer++;
ofs->fs[fsid].is_lower = true;
}
/*
* When all layers on same fs, overlay can use real inode numbers.
* With mount option "xino=<on|auto>", mounter declares that there are
* enough free high bits in underlying fs to hold the unique fsid.
* If overlayfs does encounter underlying inodes using the high xino
* bits reserved for fsid, it emits a warning and uses the original
* inode number or a non persistent inode number allocated from a
* dedicated range.
*/
if (ofs->numfs - !ovl_upper_mnt(ofs) == 1) {
if (ofs->config.xino == OVL_XINO_ON)
pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n");
ofs->xino_mode = 0;
} else if (ofs->config.xino == OVL_XINO_OFF) {
ofs->xino_mode = -1;
} else if (ofs->xino_mode < 0) {
/*
* This is a roundup of number of bits needed for encoding
* fsid, where fsid 0 is reserved for upper fs (even with
* lower only overlay) +1 extra bit is reserved for the non
* persistent inode number range that is used for resolving
* xino lower bits overflow.
*/
BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 30);
ofs->xino_mode = ilog2(ofs->numfs - 1) + 2;
}
if (ofs->xino_mode > 0) {
pr_info("\"xino\" feature enabled using %d upper inode bits.\n",
ofs->xino_mode);
}
err = 0;
out:
return err;
}
static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
const char *lower, unsigned int numlower,
struct ovl_fs *ofs, struct ovl_layer *layers)
{
int err;
struct path *stack = NULL;
unsigned int i;
struct ovl_entry *oe;
if (!ofs->config.upperdir && numlower == 1) {
pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
return ERR_PTR(-EINVAL);
}
stack = kcalloc(numlower, sizeof(struct path), GFP_KERNEL);
if (!stack)
return ERR_PTR(-ENOMEM);
err = -EINVAL;
for (i = 0; i < numlower; i++) {
err = ovl_lower_dir(lower, &stack[i], ofs, &sb->s_stack_depth);
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("maximum fs stacking depth exceeded\n");
goto out_err;
}
err = ovl_get_layers(sb, ofs, stack, numlower, layers);
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->layers[i+1];
}
out:
for (i = 0; i < numlower; i++)
path_put(&stack[i]);
kfree(stack);
return oe;
out_err:
oe = ERR_PTR(err);
goto out;
}
/*
* Check if this layer root is a descendant of:
* - another layer of this overlayfs instance
* - upper/work dir of any overlayfs instance
*/
static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
struct dentry *dentry, const char *name,
bool is_lower)
{
struct dentry *next = dentry, *parent;
int err = 0;
if (!dentry)
return 0;
parent = dget_parent(next);
/* Walk back ancestors to root (inclusive) looking for traps */
while (!err && parent != next) {
if (is_lower && ovl_lookup_trap_inode(sb, parent)) {
err = -ELOOP;
pr_err("overlapping %s path\n", name);
} else if (ovl_is_inuse(parent)) {
err = ovl_report_in_use(ofs, name);
}
next = parent;
parent = dget_parent(next);
dput(next);
}
dput(parent);
return err;
}
/*
* Check if any of the layers or work dirs overlap.
*/
static int ovl_check_overlapping_layers(struct super_block *sb,
struct ovl_fs *ofs)
{
int i, err;
if (ovl_upper_mnt(ofs)) {
err = ovl_check_layer(sb, ofs, ovl_upper_mnt(ofs)->mnt_root,
"upperdir", false);
if (err)
return err;
/*
* Checking workbasedir avoids hitting ovl_is_inuse(parent) of
* this instance and covers overlapping work and index dirs,
* unless work or index dir have been moved since created inside
* workbasedir. In that case, we already have their traps in
* inode cache and we will catch that case on lookup.
*/
err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir",
false);
if (err)
return err;
}
for (i = 1; i < ofs->numlayer; i++) {
err = ovl_check_layer(sb, ofs,
ofs->layers[i].mnt->mnt_root,
"lowerdir", true);
if (err)
return err;
}
return 0;
}
static struct dentry *ovl_get_root(struct super_block *sb,
struct dentry *upperdentry,
struct ovl_entry *oe)
{
struct dentry *root;
struct ovl_path *lowerpath = &oe->lowerstack[0];
unsigned long ino = d_inode(lowerpath->dentry)->i_ino;
int fsid = lowerpath->layer->fsid;
struct ovl_inode_params oip = {
.upperdentry = upperdentry,
.lowerpath = lowerpath,
};
root = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
if (!root)
return NULL;
root->d_fsdata = oe;
if (upperdentry) {
/* Root inode uses upper st_ino/i_ino */
ino = d_inode(upperdentry)->i_ino;
fsid = 0;
ovl_dentry_set_upper_alias(root);
if (ovl_is_impuredir(sb, upperdentry))
ovl_set_flag(OVL_IMPURE, d_inode(root));
}
/* Root is always merge -> can have whiteouts */
ovl_set_flag(OVL_WHITEOUTS, d_inode(root));
ovl_dentry_set_flag(OVL_E_CONNECTED, root);
ovl_set_upperdata(d_inode(root));
ovl_inode_init(d_inode(root), &oip, ino, fsid);
ovl_dentry_update_reval(root, upperdentry, DCACHE_OP_WEAK_REVALIDATE);
return root;
}
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 ovl_layer *layers;
struct cred *cred;
char *splitlower = NULL;
unsigned int numlower;
int err;
err = -EIO;
if (WARN_ON(sb->s_user_ns != current_user_ns()))
goto out;
sb->s_d_op = &ovl_dentry_operations;
err = -ENOMEM;
ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
if (!ofs)
goto out;
err = -ENOMEM;
ofs->creator_cred = cred = prepare_creds();
if (!cred)
goto out_err;
/* Is there a reason anyone would want not to share whiteouts? */
ofs->share_whiteout = true;
ofs->config.index = ovl_index_def;
ofs->config.uuid = true;
ofs->config.nfs_export = ovl_nfs_export_def;
ofs->config.xino = ovl_xino_def();
ofs->config.metacopy = ovl_metacopy_def;
err = ovl_parse_opt((char *) data, &ofs->config);
if (err)
goto out_err;
err = -EINVAL;
if (!ofs->config.lowerdir) {
if (!silent)
pr_err("missing 'lowerdir'\n");
goto out_err;
}
err = -ENOMEM;
splitlower = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
if (!splitlower)
goto out_err;
err = -EINVAL;
numlower = ovl_split_lowerdirs(splitlower);
if (numlower > OVL_MAX_STACK) {
pr_err("too many lower directories, limit is %d\n",
OVL_MAX_STACK);
goto out_err;
}
err = -ENOMEM;
layers = kcalloc(numlower + 1, sizeof(struct ovl_layer), GFP_KERNEL);
if (!layers)
goto out_err;
ofs->layers = layers;
/* Layer 0 is reserved for upper even if there's no upper */
ofs->numlayer = 1;
sb->s_stack_depth = 0;
sb->s_maxbytes = MAX_LFS_FILESIZE;
atomic_long_set(&ofs->last_ino, 1);
/* Assume underlaying fs uses 32bit inodes unless proven otherwise */
if (ofs->config.xino != OVL_XINO_OFF) {
ofs->xino_mode = BITS_PER_LONG - 32;
if (!ofs->xino_mode) {
pr_warn("xino not supported on 32bit kernel, falling back to xino=off.\n");
ofs->config.xino = OVL_XINO_OFF;
}
}
/* alloc/destroy_inode needed for setting up traps in inode cache */
sb->s_op = &ovl_super_operations;
if (ofs->config.upperdir) {
struct super_block *upper_sb;
err = -EINVAL;
if (!ofs->config.workdir) {
pr_err("missing 'workdir'\n");
goto out_err;
}
err = ovl_get_upper(sb, ofs, &layers[0], &upperpath);
if (err)
goto out_err;
upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
if (!ovl_should_sync(ofs)) {
ofs->errseq = errseq_sample(&upper_sb->s_wb_err);
if (errseq_check(&upper_sb->s_wb_err, ofs->errseq)) {
err = -EIO;
pr_err("Cannot mount volatile when upperdir has an unseen error. Sync upperdir fs to clear state.\n");
goto out_err;
}
}
err = ovl_get_workdir(sb, ofs, &upperpath);
if (err)
goto out_err;
if (!ofs->workdir)
sb->s_flags |= SB_RDONLY;
sb->s_stack_depth = upper_sb->s_stack_depth;
sb->s_time_gran = upper_sb->s_time_gran;
}
oe = ovl_get_lowerstack(sb, splitlower, numlower, ofs, layers);
err = PTR_ERR(oe);
if (IS_ERR(oe))
goto out_err;
/* If the upper fs is nonexistent, we mark overlayfs r/o too */
if (!ovl_upper_mnt(ofs))
sb->s_flags |= SB_RDONLY;
if (!ofs->config.uuid && ofs->numfs > 1) {
pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=on.\n");
ofs->config.uuid = true;
}
if (!ovl_force_readonly(ofs) && ofs->config.index) {
err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
if (err)
goto out_free_oe;
/* Force r/o mount with no index dir */
if (!ofs->indexdir)
sb->s_flags |= SB_RDONLY;
}
err = ovl_check_overlapping_layers(sb, ofs);
if (err)
goto out_free_oe;
/* Show index=off in /proc/mounts for forced r/o mount */
if (!ofs->indexdir) {
ofs->config.index = false;
if (ovl_upper_mnt(ofs) && ofs->config.nfs_export) {
pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n");
ofs->config.nfs_export = false;
}
}
if (ofs->config.metacopy && ofs->config.nfs_export) {
pr_warn("NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
ofs->config.nfs_export = false;
}
if (ofs->config.nfs_export)
sb->s_export_op = &ovl_export_operations;
/* 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_xattr = ofs->config.userxattr ? ovl_user_xattr_handlers :
ovl_trusted_xattr_handlers;
sb->s_fs_info = ofs;
sb->s_flags |= SB_POSIXACL;
sb->s_iflags |= SB_I_SKIP_SYNC;
err = -ENOMEM;
root_dentry = ovl_get_root(sb, upperpath.dentry, oe);
if (!root_dentry)
goto out_free_oe;
mntput(upperpath.mnt);
kfree(splitlower);
sb->s_root = root_dentry;
return 0;
out_free_oe:
ovl_entry_stack_free(oe);
kfree(oe);
out_err:
kfree(splitlower);
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",
.fs_flags = FS_USERNS_MOUNT,
.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 = ovl_aio_request_cache_init();
if (!err) {
err = register_filesystem(&ovl_fs_type);
if (!err)
return 0;
ovl_aio_request_cache_destroy();
}
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);
ovl_aio_request_cache_destroy();
}
module_init(ovl_init);
module_exit(ovl_exit);