linux/fs/overlayfs/inode.c

480 lines
12 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 <linux/fs.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include "overlayfs.h"
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);
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;
/*
* 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.
*
* We also 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 (ovl_same_sb(dentry->d_sb)) {
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;
WARN_ON_ONCE(stat->dev != lowerstat.dev);
/*
* Lower hardlinks are 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.
*/
if (is_dir || lowerstat.nlink == 1)
stat->ino = lowerstat.ino;
}
stat->dev = dentry->d_sb->s_dev;
} else if (is_dir) {
/*
* 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.
*
* 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.
*/
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;
out:
revert_creds(old_cred);
return err;
}
int ovl_permission(struct inode *inode, int mask)
{
bool is_upper;
struct inode *realinode = ovl_inode_real(inode, &is_upper);
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 (!is_upper && !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, const char *name, const void *value,
size_t size, int flags)
{
int err;
struct path realpath;
enum ovl_path_type type = ovl_path_real(dentry, &realpath);
const struct cred *old_cred;
err = ovl_want_write(dentry);
if (err)
goto out;
if (!value && !OVL_TYPE_UPPER(type)) {
err = vfs_getxattr(realpath.dentry, name, NULL, 0);
if (err < 0)
goto out_drop_write;
}
err = ovl_copy_up(dentry);
if (err)
goto out_drop_write;
if (!OVL_TYPE_UPPER(type))
ovl_path_upper(dentry, &realpath);
old_cred = ovl_override_creds(dentry->d_sb);
if (value)
err = vfs_setxattr(realpath.dentry, name, value, size, flags);
else {
WARN_ON(flags != XATTR_REPLACE);
err = vfs_removexattr(realpath.dentry, name);
}
revert_creds(old_cred);
out_drop_write:
ovl_drop_write(dentry);
out:
return err;
}
int ovl_xattr_get(struct dentry *dentry, const char *name,
void *value, size_t size)
{
struct dentry *realdentry = ovl_dentry_real(dentry);
ssize_t res;
const struct cred *old_cred;
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, NULL);
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(int flags, enum ovl_path_type type,
struct dentry *realdentry)
{
if (OVL_TYPE_UPPER(type))
return false;
if (special_file(realdentry->d_inode->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;
struct path realpath;
enum ovl_path_type type;
type = ovl_path_real(dentry, &realpath);
if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
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];
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]);
#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;
}
}
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 ovl_inode_real(inode, NULL) == data;
}
static int ovl_inode_set(struct inode *inode, void *data)
{
inode->i_private = (void *) (((unsigned long) data) | OVL_ISUPPER_MASK);
return 0;
}
struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode)
{
struct inode *inode;
inode = iget5_locked(sb, (unsigned long) realinode,
ovl_inode_test, ovl_inode_set, realinode);
if (inode && inode->i_state & I_NEW) {
ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
set_nlink(inode, realinode->i_nlink);
unlock_new_inode(inode);
}
return inode;
}