linux/fs/overlayfs/inode.c

426 lines
8.7 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/xattr.h>
#include "overlayfs.h"
static int ovl_copy_up_last(struct dentry *dentry, struct iattr *attr,
bool no_data)
{
int err;
struct dentry *parent;
struct kstat stat;
struct path lowerpath;
parent = dget_parent(dentry);
err = ovl_copy_up(parent);
if (err)
goto out_dput_parent;
ovl_path_lower(dentry, &lowerpath);
err = vfs_getattr(&lowerpath, &stat);
if (err)
goto out_dput_parent;
if (no_data)
stat.size = 0;
err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat, attr);
out_dput_parent:
dput(parent);
return err;
}
int ovl_setattr(struct dentry *dentry, struct iattr *attr)
{
int err;
struct dentry *upperdentry;
err = ovl_want_write(dentry);
if (err)
goto out;
upperdentry = ovl_dentry_upper(dentry);
if (upperdentry) {
mutex_lock(&upperdentry->d_inode->i_mutex);
err = notify_change(upperdentry, attr, NULL);
mutex_unlock(&upperdentry->d_inode->i_mutex);
} else {
err = ovl_copy_up_last(dentry, attr, false);
}
ovl_drop_write(dentry);
out:
return err;
}
static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
struct kstat *stat)
{
struct path realpath;
ovl_path_real(dentry, &realpath);
return vfs_getattr(&realpath, stat);
}
int ovl_permission(struct inode *inode, int mask)
{
struct ovl_entry *oe;
struct dentry *alias = NULL;
struct inode *realinode;
struct dentry *realdentry;
bool is_upper;
int err;
if (S_ISDIR(inode->i_mode)) {
oe = inode->i_private;
} else if (mask & MAY_NOT_BLOCK) {
return -ECHILD;
} else {
/*
* For non-directories find an alias and get the info
* from there.
*/
alias = d_find_any_alias(inode);
if (WARN_ON(!alias))
return -ENOENT;
oe = alias->d_fsdata;
}
realdentry = ovl_entry_real(oe, &is_upper);
/* Careful in RCU walk mode */
realinode = ACCESS_ONCE(realdentry->d_inode);
if (!realinode) {
WARN_ON(!(mask & MAY_NOT_BLOCK));
err = -ENOENT;
goto out_dput;
}
if (mask & MAY_WRITE) {
umode_t mode = realinode->i_mode;
/*
* Writes will always be redirected to upper layer, so
* ignore lower layer being read-only.
*
* If the overlay itself is read-only then proceed
* with the permission check, don't return EROFS.
* This will only happen if this is the lower layer of
* another overlayfs.
*
* If upper fs becomes read-only after the overlay was
* constructed return EROFS to prevent modification of
* upper layer.
*/
err = -EROFS;
if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
goto out_dput;
}
err = __inode_permission(realinode, mask);
out_dput:
dput(alias);
return err;
}
struct ovl_link_data {
struct dentry *realdentry;
void *cookie;
};
static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
{
void *ret;
struct dentry *realdentry;
struct inode *realinode;
realdentry = ovl_dentry_real(dentry);
realinode = realdentry->d_inode;
if (WARN_ON(!realinode->i_op->follow_link))
return ERR_PTR(-EPERM);
ret = realinode->i_op->follow_link(realdentry, nd);
if (IS_ERR(ret))
return ret;
if (realinode->i_op->put_link) {
struct ovl_link_data *data;
data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
if (!data) {
realinode->i_op->put_link(realdentry, nd, ret);
return ERR_PTR(-ENOMEM);
}
data->realdentry = realdentry;
data->cookie = ret;
return data;
} else {
return NULL;
}
}
static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)
{
struct inode *realinode;
struct ovl_link_data *data = c;
if (!data)
return;
realinode = data->realdentry->d_inode;
realinode->i_op->put_link(data->realdentry, nd, data->cookie);
kfree(data);
}
static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
{
struct path realpath;
struct inode *realinode;
ovl_path_real(dentry, &realpath);
realinode = realpath.dentry->d_inode;
if (!realinode->i_op->readlink)
return -EINVAL;
touch_atime(&realpath);
return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
}
static bool ovl_is_private_xattr(const char *name)
{
return strncmp(name, "trusted.overlay.", 14) == 0;
}
int ovl_setxattr(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags)
{
int err;
struct dentry *upperdentry;
err = ovl_want_write(dentry);
if (err)
goto out;
err = -EPERM;
if (ovl_is_private_xattr(name))
goto out_drop_write;
err = ovl_copy_up(dentry);
if (err)
goto out_drop_write;
upperdentry = ovl_dentry_upper(dentry);
err = vfs_setxattr(upperdentry, name, value, size, flags);
out_drop_write:
ovl_drop_write(dentry);
out:
return err;
}
ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
void *value, size_t size)
{
if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
ovl_is_private_xattr(name))
return -ENODATA;
return vfs_getxattr(ovl_dentry_real(dentry), name, value, size);
}
ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
{
ssize_t res;
int off;
res = vfs_listxattr(ovl_dentry_real(dentry), list, size);
if (res <= 0 || size == 0)
return res;
if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE)
return res;
/* filter out private xattrs */
for (off = 0; off < res;) {
char *s = list + off;
size_t slen = strlen(s) + 1;
BUG_ON(off + slen > res);
if (ovl_is_private_xattr(s)) {
res -= slen;
memmove(s, s + slen, res - off);
} else {
off += slen;
}
}
return res;
}
int ovl_removexattr(struct dentry *dentry, const char *name)
{
int err;
struct path realpath;
enum ovl_path_type type;
err = ovl_want_write(dentry);
if (err)
goto out;
if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
ovl_is_private_xattr(name))
goto out_drop_write;
type = ovl_path_real(dentry, &realpath);
if (type == OVL_PATH_LOWER) {
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;
ovl_path_upper(dentry, &realpath);
}
err = vfs_removexattr(realpath.dentry, name);
out_drop_write:
ovl_drop_write(dentry);
out:
return err;
}
static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
struct dentry *realdentry)
{
if (type != OVL_PATH_LOWER)
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;
}
static int ovl_dentry_open(struct dentry *dentry, struct file *file,
const struct cred *cred)
{
int err;
struct path realpath;
enum ovl_path_type type;
bool want_write = false;
type = ovl_path_real(dentry, &realpath);
if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) {
want_write = true;
err = ovl_want_write(dentry);
if (err)
goto out;
if (file->f_flags & O_TRUNC)
err = ovl_copy_up_last(dentry, NULL, true);
else
err = ovl_copy_up(dentry);
if (err)
goto out_drop_write;
ovl_path_upper(dentry, &realpath);
}
err = vfs_open(&realpath, file, cred);
out_drop_write:
if (want_write)
ovl_drop_write(dentry);
out:
return err;
}
static const struct inode_operations ovl_file_inode_operations = {
.setattr = ovl_setattr,
.permission = ovl_permission,
.getattr = ovl_getattr,
.setxattr = ovl_setxattr,
.getxattr = ovl_getxattr,
.listxattr = ovl_listxattr,
.removexattr = ovl_removexattr,
.dentry_open = ovl_dentry_open,
};
static const struct inode_operations ovl_symlink_inode_operations = {
.setattr = ovl_setattr,
.follow_link = ovl_follow_link,
.put_link = ovl_put_link,
.readlink = ovl_readlink,
.getattr = ovl_getattr,
.setxattr = ovl_setxattr,
.getxattr = ovl_getxattr,
.listxattr = ovl_listxattr,
.removexattr = ovl_removexattr,
};
struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
struct ovl_entry *oe)
{
struct inode *inode;
inode = new_inode(sb);
if (!inode)
return NULL;
mode &= S_IFMT;
inode->i_ino = get_next_ino();
inode->i_mode = mode;
inode->i_flags |= S_NOATIME | S_NOCMTIME;
switch (mode) {
case S_IFDIR:
inode->i_private = oe;
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;
case S_IFREG:
case S_IFSOCK:
case S_IFBLK:
case S_IFCHR:
case S_IFIFO:
inode->i_op = &ovl_file_inode_operations;
break;
default:
WARN(1, "illegal file type: %i\n", mode);
iput(inode);
inode = NULL;
}
return inode;
}