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linux/fs/ext2/namei.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

444 lines
9.9 KiB
C
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// SPDX-License-Identifier: GPL-2.0
/*
* linux/fs/ext2/namei.c
*
* Rewrite to pagecache. Almost all code had been changed, so blame me
* if the things go wrong. Please, send bug reports to
* viro@parcelfarce.linux.theplanet.co.uk
*
* Stuff here is basically a glue between the VFS and generic UNIXish
* filesystem that keeps everything in pagecache. All knowledge of the
* directory layout is in fs/ext2/dir.c - it turned out to be easily separatable
* and it's easier to debug that way. In principle we might want to
* generalize that a bit and turn it into a library. Or not.
*
* The only non-static object here is ext2_dir_inode_operations.
*
* TODO: get rid of kmap() use, add readahead.
*
* Copyright (C) 1992, 1993, 1994, 1995
* Remy Card (card@masi.ibp.fr)
* Laboratoire MASI - Institut Blaise Pascal
* Universite Pierre et Marie Curie (Paris VI)
*
* from
*
* linux/fs/minix/namei.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* Big-endian to little-endian byte-swapping/bitmaps by
* David S. Miller (davem@caip.rutgers.edu), 1995
*/
#include <linux/pagemap.h>
#include <linux/quotaops.h>
#include "ext2.h"
#include "xattr.h"
#include "acl.h"
static inline int ext2_add_nondir(struct dentry *dentry, struct inode *inode)
{
int err = ext2_add_link(dentry, inode);
if (!err) {
d_instantiate_new(dentry, inode);
return 0;
}
inode_dec_link_count(inode);
discard_new_inode(inode);
return err;
}
/*
* Methods themselves.
*/
static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry, unsigned int flags)
{
struct inode * inode;
ino_t ino;
int res;
if (dentry->d_name.len > EXT2_NAME_LEN)
return ERR_PTR(-ENAMETOOLONG);
res = ext2_inode_by_name(dir, &dentry->d_name, &ino);
if (res) {
if (res != -ENOENT)
return ERR_PTR(res);
inode = NULL;
} else {
inode = ext2_iget(dir->i_sb, ino);
if (inode == ERR_PTR(-ESTALE)) {
ext2_error(dir->i_sb, __func__,
"deleted inode referenced: %lu",
(unsigned long) ino);
return ERR_PTR(-EIO);
}
}
return d_splice_alias(inode, dentry);
}
struct dentry *ext2_get_parent(struct dentry *child)
{
ino_t ino;
int res;
res = ext2_inode_by_name(d_inode(child), &dotdot_name, &ino);
if (res)
return ERR_PTR(res);
return d_obtain_alias(ext2_iget(child->d_sb, ino));
}
/*
* By the time this is called, we already have created
* the directory cache entry for the new file, but it
* is so far negative - it has no inode.
*
* If the create succeeds, we fill in the inode information
* with d_instantiate().
*/
static int ext2_create (struct user_namespace * mnt_userns,
struct inode * dir, struct dentry * dentry,
umode_t mode, bool excl)
{
struct inode *inode;
int err;
err = dquot_initialize(dir);
if (err)
return err;
inode = ext2_new_inode(dir, mode, &dentry->d_name);
if (IS_ERR(inode))
return PTR_ERR(inode);
ext2_set_file_ops(inode);
mark_inode_dirty(inode);
return ext2_add_nondir(dentry, inode);
}
static int ext2_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
struct file *file, umode_t mode)
{
struct inode *inode = ext2_new_inode(dir, mode, NULL);
if (IS_ERR(inode))
return PTR_ERR(inode);
ext2_set_file_ops(inode);
mark_inode_dirty(inode);
d_tmpfile(file, inode);
unlock_new_inode(inode);
return finish_open_simple(file, 0);
}
static int ext2_mknod (struct user_namespace * mnt_userns, struct inode * dir,
struct dentry *dentry, umode_t mode, dev_t rdev)
{
struct inode * inode;
int err;
err = dquot_initialize(dir);
if (err)
return err;
inode = ext2_new_inode (dir, mode, &dentry->d_name);
err = PTR_ERR(inode);
if (!IS_ERR(inode)) {
init_special_inode(inode, inode->i_mode, rdev);
inode->i_op = &ext2_special_inode_operations;
mark_inode_dirty(inode);
err = ext2_add_nondir(dentry, inode);
}
return err;
}
static int ext2_symlink (struct user_namespace * mnt_userns, struct inode * dir,
struct dentry * dentry, const char * symname)
{
struct super_block * sb = dir->i_sb;
int err = -ENAMETOOLONG;
unsigned l = strlen(symname)+1;
struct inode * inode;
if (l > sb->s_blocksize)
goto out;
err = dquot_initialize(dir);
if (err)
goto out;
inode = ext2_new_inode (dir, S_IFLNK | S_IRWXUGO, &dentry->d_name);
err = PTR_ERR(inode);
if (IS_ERR(inode))
goto out;
if (l > sizeof (EXT2_I(inode)->i_data)) {
/* slow symlink */
inode->i_op = &ext2_symlink_inode_operations;
inode_nohighmem(inode);
inode->i_mapping->a_ops = &ext2_aops;
err = page_symlink(inode, symname, l);
if (err)
goto out_fail;
} else {
/* fast symlink */
inode->i_op = &ext2_fast_symlink_inode_operations;
inode->i_link = (char*)EXT2_I(inode)->i_data;
memcpy(inode->i_link, symname, l);
inode->i_size = l-1;
}
mark_inode_dirty(inode);
err = ext2_add_nondir(dentry, inode);
out:
return err;
out_fail:
inode_dec_link_count(inode);
discard_new_inode(inode);
goto out;
}
static int ext2_link (struct dentry * old_dentry, struct inode * dir,
struct dentry *dentry)
{
struct inode *inode = d_inode(old_dentry);
int err;
err = dquot_initialize(dir);
if (err)
return err;
inode->i_ctime = current_time(inode);
inode_inc_link_count(inode);
ihold(inode);
err = ext2_add_link(dentry, inode);
if (!err) {
d_instantiate(dentry, inode);
return 0;
}
inode_dec_link_count(inode);
iput(inode);
return err;
}
static int ext2_mkdir(struct user_namespace * mnt_userns,
struct inode * dir, struct dentry * dentry, umode_t mode)
{
struct inode * inode;
int err;
err = dquot_initialize(dir);
if (err)
return err;
inode_inc_link_count(dir);
inode = ext2_new_inode(dir, S_IFDIR | mode, &dentry->d_name);
err = PTR_ERR(inode);
if (IS_ERR(inode))
goto out_dir;
inode->i_op = &ext2_dir_inode_operations;
inode->i_fop = &ext2_dir_operations;
inode->i_mapping->a_ops = &ext2_aops;
inode_inc_link_count(inode);
err = ext2_make_empty(inode, dir);
if (err)
goto out_fail;
err = ext2_add_link(dentry, inode);
if (err)
goto out_fail;
d_instantiate_new(dentry, inode);
out:
return err;
out_fail:
inode_dec_link_count(inode);
inode_dec_link_count(inode);
discard_new_inode(inode);
out_dir:
inode_dec_link_count(dir);
goto out;
}
static int ext2_unlink(struct inode * dir, struct dentry *dentry)
{
struct inode * inode = d_inode(dentry);
struct ext2_dir_entry_2 * de;
struct page * page;
void *page_addr;
int err;
err = dquot_initialize(dir);
if (err)
goto out;
de = ext2_find_entry(dir, &dentry->d_name, &page, &page_addr);
if (IS_ERR(de)) {
err = PTR_ERR(de);
goto out;
}
err = ext2_delete_entry (de, page, page_addr);
ext2_put_page(page, page_addr);
if (err)
goto out;
inode->i_ctime = dir->i_ctime;
inode_dec_link_count(inode);
err = 0;
out:
return err;
}
static int ext2_rmdir (struct inode * dir, struct dentry *dentry)
{
struct inode * inode = d_inode(dentry);
int err = -ENOTEMPTY;
if (ext2_empty_dir(inode)) {
err = ext2_unlink(dir, dentry);
if (!err) {
inode->i_size = 0;
inode_dec_link_count(inode);
inode_dec_link_count(dir);
}
}
return err;
}
static int ext2_rename (struct user_namespace * mnt_userns,
struct inode * old_dir, struct dentry * old_dentry,
struct inode * new_dir, struct dentry * new_dentry,
unsigned int flags)
{
struct inode * old_inode = d_inode(old_dentry);
struct inode * new_inode = d_inode(new_dentry);
struct page * dir_page = NULL;
void *dir_page_addr;
struct ext2_dir_entry_2 * dir_de = NULL;
struct page * old_page;
void *old_page_addr;
struct ext2_dir_entry_2 * old_de;
int err;
if (flags & ~RENAME_NOREPLACE)
return -EINVAL;
err = dquot_initialize(old_dir);
if (err)
goto out;
err = dquot_initialize(new_dir);
if (err)
goto out;
old_de = ext2_find_entry(old_dir, &old_dentry->d_name, &old_page,
&old_page_addr);
if (IS_ERR(old_de)) {
err = PTR_ERR(old_de);
goto out;
}
if (S_ISDIR(old_inode->i_mode)) {
err = -EIO;
dir_de = ext2_dotdot(old_inode, &dir_page, &dir_page_addr);
if (!dir_de)
goto out_old;
}
if (new_inode) {
void *page_addr;
struct page *new_page;
struct ext2_dir_entry_2 *new_de;
err = -ENOTEMPTY;
if (dir_de && !ext2_empty_dir (new_inode))
goto out_dir;
new_de = ext2_find_entry(new_dir, &new_dentry->d_name,
&new_page, &page_addr);
if (IS_ERR(new_de)) {
err = PTR_ERR(new_de);
goto out_dir;
}
ext2_set_link(new_dir, new_de, new_page, page_addr, old_inode, 1);
ext2_put_page(new_page, page_addr);
new_inode->i_ctime = current_time(new_inode);
if (dir_de)
drop_nlink(new_inode);
inode_dec_link_count(new_inode);
} else {
err = ext2_add_link(new_dentry, old_inode);
if (err)
goto out_dir;
if (dir_de)
inode_inc_link_count(new_dir);
}
/*
* Like most other Unix systems, set the ctime for inodes on a
* rename.
*/
old_inode->i_ctime = current_time(old_inode);
mark_inode_dirty(old_inode);
ext2_delete_entry(old_de, old_page, old_page_addr);
if (dir_de) {
if (old_dir != new_dir)
ext2_set_link(old_inode, dir_de, dir_page,
dir_page_addr, new_dir, 0);
ext2_put_page(dir_page, dir_page_addr);
inode_dec_link_count(old_dir);
}
ext2_put_page(old_page, old_page_addr);
return 0;
out_dir:
if (dir_de)
ext2_put_page(dir_page, dir_page_addr);
out_old:
ext2_put_page(old_page, old_page_addr);
out:
return err;
}
const struct inode_operations ext2_dir_inode_operations = {
.create = ext2_create,
.lookup = ext2_lookup,
.link = ext2_link,
.unlink = ext2_unlink,
.symlink = ext2_symlink,
.mkdir = ext2_mkdir,
.rmdir = ext2_rmdir,
.mknod = ext2_mknod,
.rename = ext2_rename,
.listxattr = ext2_listxattr,
.getattr = ext2_getattr,
.setattr = ext2_setattr,
.get_inode_acl = ext2_get_acl,
.set_acl = ext2_set_acl,
.tmpfile = ext2_tmpfile,
.fileattr_get = ext2_fileattr_get,
.fileattr_set = ext2_fileattr_set,
};
const struct inode_operations ext2_special_inode_operations = {
.listxattr = ext2_listxattr,
.getattr = ext2_getattr,
.setattr = ext2_setattr,
.get_inode_acl = ext2_get_acl,
.set_acl = ext2_set_acl,
};
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