linux/fs/bad_inode.c
Christian Brauner cac2f8b8d8
fs: rename current get acl method
The current way of setting and getting posix acls through the generic
xattr interface is error prone and type unsafe. The vfs needs to
interpret and fixup posix acls before storing or reporting it to
userspace. Various hacks exist to make this work. The code is hard to
understand and difficult to maintain in it's current form. Instead of
making this work by hacking posix acls through xattr handlers we are
building a dedicated posix acl api around the get and set inode
operations. This removes a lot of hackiness and makes the codepaths
easier to maintain. A lot of background can be found in [1].

The current inode operation for getting posix acls takes an inode
argument but various filesystems (e.g., 9p, cifs, overlayfs) need access
to the dentry. In contrast to the ->set_acl() inode operation we cannot
simply extend ->get_acl() to take a dentry argument. The ->get_acl()
inode operation is called from:

acl_permission_check()
-> check_acl()
   -> get_acl()

which is part of generic_permission() which in turn is part of
inode_permission(). Both generic_permission() and inode_permission() are
called in the ->permission() handler of various filesystems (e.g.,
overlayfs). So simply passing a dentry argument to ->get_acl() would
amount to also having to pass a dentry argument to ->permission(). We
should avoid this unnecessary change.

So instead of extending the existing inode operation rename it from
->get_acl() to ->get_inode_acl() and add a ->get_acl() method later that
passes a dentry argument and which filesystems that need access to the
dentry can implement instead of ->get_inode_acl(). Filesystems like cifs
which allow setting and getting posix acls but not using them for
permission checking during lookup can simply not implement
->get_inode_acl().

This is intended to be a non-functional change.

Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1]
Suggested-by/Inspired-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-10-20 10:13:27 +02:00

253 lines
5.8 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* linux/fs/bad_inode.c
*
* Copyright (C) 1997, Stephen Tweedie
*
* Provide stub functions for unreadable inodes
*
* Fabian Frederick : August 2003 - All file operations assigned to EIO
*/
#include <linux/fs.h>
#include <linux/export.h>
#include <linux/stat.h>
#include <linux/time.h>
#include <linux/namei.h>
#include <linux/poll.h>
#include <linux/fiemap.h>
static int bad_file_open(struct inode *inode, struct file *filp)
{
return -EIO;
}
static const struct file_operations bad_file_ops =
{
.open = bad_file_open,
};
static int bad_inode_create(struct user_namespace *mnt_userns,
struct inode *dir, struct dentry *dentry,
umode_t mode, bool excl)
{
return -EIO;
}
static struct dentry *bad_inode_lookup(struct inode *dir,
struct dentry *dentry, unsigned int flags)
{
return ERR_PTR(-EIO);
}
static int bad_inode_link (struct dentry *old_dentry, struct inode *dir,
struct dentry *dentry)
{
return -EIO;
}
static int bad_inode_unlink(struct inode *dir, struct dentry *dentry)
{
return -EIO;
}
static int bad_inode_symlink(struct user_namespace *mnt_userns,
struct inode *dir, struct dentry *dentry,
const char *symname)
{
return -EIO;
}
static int bad_inode_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
struct dentry *dentry, umode_t mode)
{
return -EIO;
}
static int bad_inode_rmdir (struct inode *dir, struct dentry *dentry)
{
return -EIO;
}
static int bad_inode_mknod(struct user_namespace *mnt_userns, struct inode *dir,
struct dentry *dentry, umode_t mode, dev_t rdev)
{
return -EIO;
}
static int bad_inode_rename2(struct user_namespace *mnt_userns,
struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry,
unsigned int flags)
{
return -EIO;
}
static int bad_inode_readlink(struct dentry *dentry, char __user *buffer,
int buflen)
{
return -EIO;
}
static int bad_inode_permission(struct user_namespace *mnt_userns,
struct inode *inode, int mask)
{
return -EIO;
}
static int bad_inode_getattr(struct user_namespace *mnt_userns,
const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int query_flags)
{
return -EIO;
}
static int bad_inode_setattr(struct user_namespace *mnt_userns,
struct dentry *direntry, struct iattr *attrs)
{
return -EIO;
}
static ssize_t bad_inode_listxattr(struct dentry *dentry, char *buffer,
size_t buffer_size)
{
return -EIO;
}
static const char *bad_inode_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
return ERR_PTR(-EIO);
}
static struct posix_acl *bad_inode_get_acl(struct inode *inode, int type, bool rcu)
{
return ERR_PTR(-EIO);
}
static int bad_inode_fiemap(struct inode *inode,
struct fiemap_extent_info *fieinfo, u64 start,
u64 len)
{
return -EIO;
}
static int bad_inode_update_time(struct inode *inode, struct timespec64 *time,
int flags)
{
return -EIO;
}
static int bad_inode_atomic_open(struct inode *inode, struct dentry *dentry,
struct file *file, unsigned int open_flag,
umode_t create_mode)
{
return -EIO;
}
static int bad_inode_tmpfile(struct user_namespace *mnt_userns,
struct inode *inode, struct file *file,
umode_t mode)
{
return -EIO;
}
static int bad_inode_set_acl(struct user_namespace *mnt_userns,
struct dentry *dentry, struct posix_acl *acl,
int type)
{
return -EIO;
}
static const struct inode_operations bad_inode_ops =
{
.create = bad_inode_create,
.lookup = bad_inode_lookup,
.link = bad_inode_link,
.unlink = bad_inode_unlink,
.symlink = bad_inode_symlink,
.mkdir = bad_inode_mkdir,
.rmdir = bad_inode_rmdir,
.mknod = bad_inode_mknod,
.rename = bad_inode_rename2,
.readlink = bad_inode_readlink,
.permission = bad_inode_permission,
.getattr = bad_inode_getattr,
.setattr = bad_inode_setattr,
.listxattr = bad_inode_listxattr,
.get_link = bad_inode_get_link,
.get_inode_acl = bad_inode_get_acl,
.fiemap = bad_inode_fiemap,
.update_time = bad_inode_update_time,
.atomic_open = bad_inode_atomic_open,
.tmpfile = bad_inode_tmpfile,
.set_acl = bad_inode_set_acl,
};
/*
* When a filesystem is unable to read an inode due to an I/O error in
* its read_inode() function, it can call make_bad_inode() to return a
* set of stubs which will return EIO errors as required.
*
* We only need to do limited initialisation: all other fields are
* preinitialised to zero automatically.
*/
/**
* make_bad_inode - mark an inode bad due to an I/O error
* @inode: Inode to mark bad
*
* When an inode cannot be read due to a media or remote network
* failure this function makes the inode "bad" and causes I/O operations
* on it to fail from this point on.
*/
void make_bad_inode(struct inode *inode)
{
remove_inode_hash(inode);
inode->i_mode = S_IFREG;
inode->i_atime = inode->i_mtime = inode->i_ctime =
current_time(inode);
inode->i_op = &bad_inode_ops;
inode->i_opflags &= ~IOP_XATTR;
inode->i_fop = &bad_file_ops;
}
EXPORT_SYMBOL(make_bad_inode);
/*
* This tests whether an inode has been flagged as bad. The test uses
* &bad_inode_ops to cover the case of invalidated inodes as well as
* those created by make_bad_inode() above.
*/
/**
* is_bad_inode - is an inode errored
* @inode: inode to test
*
* Returns true if the inode in question has been marked as bad.
*/
bool is_bad_inode(struct inode *inode)
{
return (inode->i_op == &bad_inode_ops);
}
EXPORT_SYMBOL(is_bad_inode);
/**
* iget_failed - Mark an under-construction inode as dead and release it
* @inode: The inode to discard
*
* Mark an under-construction inode as dead and release it.
*/
void iget_failed(struct inode *inode)
{
make_bad_inode(inode);
unlock_new_inode(inode);
iput(inode);
}
EXPORT_SYMBOL(iget_failed);