mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-04-06 00:16:18 +00:00
Code Issues Packages Projects Releases Wiki Activity
linux/fs/fat/namei_msdos.c
NeilBrown 88d5baf690
Change inode_operations.mkdir to return struct dentry * 
Some filesystems, such as NFS, cifs, ceph, and fuse, do not have
complete control of sequencing on the actual filesystem (e.g.  on a
different server) and may find that the inode created for a mkdir
request already exists in the icache and dcache by the time the mkdir
request returns.  For example, if the filesystem is mounted twice the
directory could be visible on the other mount before it is on the
original mount, and a pair of name_to_handle_at(), open_by_handle_at()
calls could instantiate the directory inode with an IS_ROOT() dentry
before the first mkdir returns.

This means that the dentry passed to ->mkdir() may not be the one that
is associated with the inode after the ->mkdir() completes.  Some
callers need to interact with the inode after the ->mkdir completes and
they currently need to perform a lookup in the (rare) case that the
dentry is no longer hashed.

This lookup-after-mkdir requires that the directory remains locked to
avoid races.  Planned future patches to lock the dentry rather than the
directory will mean that this lookup cannot be performed atomically with
the mkdir.

To remove this barrier, this patch changes ->mkdir to return the
resulting dentry if it is different from the one passed in.
Possible returns are:
  NULL - the directory was created and no other dentry was used
  ERR_PTR() - an error occurred
  non-NULL - this other dentry was spliced in

This patch only changes file-systems to return "ERR_PTR(err)" instead of
"err" or equivalent transformations.  Subsequent patches will make
further changes to some file-systems to return a correct dentry.

Not all filesystems reliably result in a positive hashed dentry:

- NFS, cifs, hostfs will sometimes need to perform a lookup of
  the name to get inode information.  Races could result in this
  returning something different. Note that this lookup is
  non-atomic which is what we are trying to avoid.  Placing the
  lookup in filesystem code means it only happens when the filesystem
  has no other option.
- kernfs and tracefs leave the dentry negative and the ->revalidate
  operation ensures that lookup will be called to correctly populate
  the dentry.  This could be fixed but I don't think it is important
  to any of the users of vfs_mkdir() which look at the dentry.

The recommendation to use
    d_drop();d_splice_alias()
is ugly but fits with current practice.  A planned future patch will
change this.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20250227013949.536172-2-neilb@suse.de
Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-02-27 20:00:17 +01:00

714 lines
17 KiB
C
Raw Permalink Blame History

// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/fs/msdos/namei.c
*
* Written 1992,1993 by Werner Almesberger
* Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
* Rewritten for constant inumbers 1999 by Al Viro
*/
#include <linux/module.h>
#include <linux/iversion.h>
#include "fat.h"
/* Characters that are undesirable in an MS-DOS file name */
static unsigned char bad_chars[] = "*?<>|\"";
static unsigned char bad_if_strict[] = "+=,; ";
/***** Formats an MS-DOS file name. Rejects invalid names. */
static int msdos_format_name(const unsigned char *name, int len,
unsigned char *res, struct fat_mount_options *opts)
/*
* name is the proposed name, len is its length, res is
* the resulting name, opts->name_check is either (r)elaxed,
* (n)ormal or (s)trict, opts->dotsOK allows dots at the
* beginning of name (for hidden files)
*/
{
unsigned char *walk;
unsigned char c;
int space;
if (name[0] == '.') { /* dotfile because . and .. already done */
if (opts->dotsOK) {
/* Get rid of dot - test for it elsewhere */
name++;
len--;
} else
return -EINVAL;
}
/*
* disallow names that _really_ start with a dot
*/
space = 1;
c = 0;
for (walk = res; len && walk - res < 8; walk++) {
c = *name++;
len--;
if (opts->name_check != 'r' && strchr(bad_chars, c))
return -EINVAL;
if (opts->name_check == 's' && strchr(bad_if_strict, c))
return -EINVAL;
if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
return -EINVAL;
if (c < ' ' || c == ':' || c == '\\')
return -EINVAL;
/*
* 0xE5 is legal as a first character, but we must substitute
* 0x05 because 0xE5 marks deleted files. Yes, DOS really
* does this.
* It seems that Microsoft hacked DOS to support non-US
* characters after the 0xE5 character was already in use to
* mark deleted files.
*/
if ((res == walk) && (c == 0xE5))
c = 0x05;
if (c == '.')
break;
space = (c == ' ');
*walk = (!opts->nocase && c >= 'a' && c <= 'z') ? c - 32 : c;
}
if (space)
return -EINVAL;
if (opts->name_check == 's' && len && c != '.') {
c = *name++;
len--;
if (c != '.')
return -EINVAL;
}
while (c != '.' && len--)
c = *name++;
if (c == '.') {
while (walk - res < 8)
*walk++ = ' ';
while (len > 0 && walk - res < MSDOS_NAME) {
c = *name++;
len--;
if (opts->name_check != 'r' && strchr(bad_chars, c))
return -EINVAL;
if (opts->name_check == 's' &&
strchr(bad_if_strict, c))
return -EINVAL;
if (c < ' ' || c == ':' || c == '\\')
return -EINVAL;
if (c == '.') {
if (opts->name_check == 's')
return -EINVAL;
break;
}
if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
return -EINVAL;
space = c == ' ';
if (!opts->nocase && c >= 'a' && c <= 'z')
*walk++ = c - 32;
else
*walk++ = c;
}
if (space)
return -EINVAL;
if (opts->name_check == 's' && len)
return -EINVAL;
}
while (walk - res < MSDOS_NAME)
*walk++ = ' ';
return 0;
}
/***** Locates a directory entry. Uses unformatted name. */
static int msdos_find(struct inode *dir, const unsigned char *name, int len,
struct fat_slot_info *sinfo)
{
struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
unsigned char msdos_name[MSDOS_NAME];
int err;
err = msdos_format_name(name, len, msdos_name, &sbi->options);
if (err)
return -ENOENT;
err = fat_scan(dir, msdos_name, sinfo);
if (!err && sbi->options.dotsOK) {
if (name[0] == '.') {
if (!(sinfo->de->attr & ATTR_HIDDEN))
err = -ENOENT;
} else {
if (sinfo->de->attr & ATTR_HIDDEN)
err = -ENOENT;
}
if (err)
brelse(sinfo->bh);
}
return err;
}
/*
* Compute the hash for the msdos name corresponding to the dentry.
* Note: if the name is invalid, we leave the hash code unchanged so
* that the existing dentry can be used. The msdos fs routines will
* return ENOENT or EINVAL as appropriate.
*/
static int msdos_hash(const struct dentry *dentry, struct qstr *qstr)
{
struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
unsigned char msdos_name[MSDOS_NAME];
int error;
error = msdos_format_name(qstr->name, qstr->len, msdos_name, options);
if (!error)
qstr->hash = full_name_hash(dentry, msdos_name, MSDOS_NAME);
return 0;
}
/*
* Compare two msdos names. If either of the names are invalid,
* we fall back to doing the standard name comparison.
*/
static int msdos_cmp(const struct dentry *dentry,
unsigned int len, const char *str, const struct qstr *name)
{
struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
unsigned char a_msdos_name[MSDOS_NAME], b_msdos_name[MSDOS_NAME];
int error;
error = msdos_format_name(name->name, name->len, a_msdos_name, options);
if (error)
goto old_compare;
error = msdos_format_name(str, len, b_msdos_name, options);
if (error)
goto old_compare;
error = memcmp(a_msdos_name, b_msdos_name, MSDOS_NAME);
out:
return error;
old_compare:
error = 1;
if (name->len == len)
error = memcmp(name->name, str, len);
goto out;
}
static const struct dentry_operations msdos_dentry_operations = {
.d_hash = msdos_hash,
.d_compare = msdos_cmp,
};
/*
* AV. Wrappers for FAT sb operations. Is it wise?
*/
/***** Get inode using directory and name */
static struct dentry *msdos_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
struct super_block *sb = dir->i_sb;
struct fat_slot_info sinfo;
struct inode *inode;
int err;
mutex_lock(&MSDOS_SB(sb)->s_lock);
err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
switch (err) {
case -ENOENT:
inode = NULL;
break;
case 0:
inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
brelse(sinfo.bh);
break;
default:
inode = ERR_PTR(err);
}
mutex_unlock(&MSDOS_SB(sb)->s_lock);
return d_splice_alias(inode, dentry);
}
/***** Creates a directory entry (name is already formatted). */
static int msdos_add_entry(struct inode *dir, const unsigned char *name,
int is_dir, int is_hid, int cluster,
struct timespec64 *ts, struct fat_slot_info *sinfo)
{
struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
struct msdos_dir_entry de;
__le16 time, date;
int err;
memcpy(de.name, name, MSDOS_NAME);
de.attr = is_dir ? ATTR_DIR : ATTR_ARCH;
if (is_hid)
de.attr |= ATTR_HIDDEN;
de.lcase = 0;
fat_time_unix2fat(sbi, ts, &time, &date, NULL);
de.cdate = de.adate = 0;
de.ctime = 0;
de.ctime_cs = 0;
de.time = time;
de.date = date;
fat_set_start(&de, cluster);
de.size = 0;
err = fat_add_entries(dir, &de, 1, sinfo);
if (err)
return err;
fat_truncate_time(dir, ts, S_CTIME|S_MTIME);
if (IS_DIRSYNC(dir))
(void)fat_sync_inode(dir);
else
mark_inode_dirty(dir);
return 0;
}
/***** Create a file */
static int msdos_create(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, umode_t mode, bool excl)
{
struct super_block *sb = dir->i_sb;
struct inode *inode = NULL;
struct fat_slot_info sinfo;
struct timespec64 ts;
unsigned char msdos_name[MSDOS_NAME];
int err, is_hid;
mutex_lock(&MSDOS_SB(sb)->s_lock);
err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
msdos_name, &MSDOS_SB(sb)->options);
if (err)
goto out;
is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
/* Have to do it due to foo vs. .foo conflicts */
if (!fat_scan(dir, msdos_name, &sinfo)) {
brelse(sinfo.bh);
err = -EINVAL;
goto out;
}
ts = current_time(dir);
err = msdos_add_entry(dir, msdos_name, 0, is_hid, 0, &ts, &sinfo);
if (err)
goto out;
inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
brelse(sinfo.bh);
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
goto out;
}
fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
/* timestamp is already written, so mark_inode_dirty() is unneeded. */
d_instantiate(dentry, inode);
out:
mutex_unlock(&MSDOS_SB(sb)->s_lock);
if (!err)
err = fat_flush_inodes(sb, dir, inode);
return err;
}
/***** Remove a directory */
static int msdos_rmdir(struct inode *dir, struct dentry *dentry)
{
struct super_block *sb = dir->i_sb;
struct inode *inode = d_inode(dentry);
struct fat_slot_info sinfo;
int err;
mutex_lock(&MSDOS_SB(sb)->s_lock);
err = fat_dir_empty(inode);
if (err)
goto out;
err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
if (err)
goto out;
err = fat_remove_entries(dir, &sinfo); /* and releases bh */
if (err)
goto out;
drop_nlink(dir);
clear_nlink(inode);
fat_truncate_time(inode, NULL, S_CTIME);
fat_detach(inode);
out:
mutex_unlock(&MSDOS_SB(sb)->s_lock);
if (!err)
err = fat_flush_inodes(sb, dir, inode);
return err;
}
/***** Make a directory */
static struct dentry *msdos_mkdir(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, umode_t mode)
{
struct super_block *sb = dir->i_sb;
struct fat_slot_info sinfo;
struct inode *inode;
unsigned char msdos_name[MSDOS_NAME];
struct timespec64 ts;
int err, is_hid, cluster;
mutex_lock(&MSDOS_SB(sb)->s_lock);
err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
msdos_name, &MSDOS_SB(sb)->options);
if (err)
goto out;
is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
/* foo vs .foo situation */
if (!fat_scan(dir, msdos_name, &sinfo)) {
brelse(sinfo.bh);
err = -EINVAL;
goto out;
}
ts = current_time(dir);
cluster = fat_alloc_new_dir(dir, &ts);
if (cluster < 0) {
err = cluster;
goto out;
}
err = msdos_add_entry(dir, msdos_name, 1, is_hid, cluster, &ts, &sinfo);
if (err)
goto out_free;
inc_nlink(dir);
inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
brelse(sinfo.bh);
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
/* the directory was completed, just return a error */
goto out;
}
set_nlink(inode, 2);
fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
/* timestamp is already written, so mark_inode_dirty() is unneeded. */
d_instantiate(dentry, inode);
mutex_unlock(&MSDOS_SB(sb)->s_lock);
fat_flush_inodes(sb, dir, inode);
return NULL;
out_free:
fat_free_clusters(dir, cluster);
out:
mutex_unlock(&MSDOS_SB(sb)->s_lock);
return ERR_PTR(err);
}
/***** Unlink a file */
static int msdos_unlink(struct inode *dir, struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
struct super_block *sb = inode->i_sb;
struct fat_slot_info sinfo;
int err;
mutex_lock(&MSDOS_SB(sb)->s_lock);
err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
if (err)
goto out;
err = fat_remove_entries(dir, &sinfo); /* and releases bh */
if (err)
goto out;
clear_nlink(inode);
fat_truncate_time(inode, NULL, S_CTIME);
fat_detach(inode);
out:
mutex_unlock(&MSDOS_SB(sb)->s_lock);
if (!err)
err = fat_flush_inodes(sb, dir, inode);
return err;
}
static int do_msdos_rename(struct inode *old_dir, unsigned char *old_name,
struct dentry *old_dentry,
struct inode *new_dir, unsigned char *new_name,
struct dentry *new_dentry, int is_hid)
{
struct buffer_head *dotdot_bh;
struct msdos_dir_entry *dotdot_de;
struct inode *old_inode, *new_inode;
struct fat_slot_info old_sinfo, sinfo;
struct timespec64 ts;
loff_t new_i_pos;
int err, old_attrs, is_dir, update_dotdot, corrupt = 0;
old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
old_inode = d_inode(old_dentry);
new_inode = d_inode(new_dentry);
err = fat_scan(old_dir, old_name, &old_sinfo);
if (err) {
err = -EIO;
goto out;
}
is_dir = S_ISDIR(old_inode->i_mode);
update_dotdot = (is_dir && old_dir != new_dir);
if (update_dotdot) {
if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de)) {
err = -EIO;
goto out;
}
}
old_attrs = MSDOS_I(old_inode)->i_attrs;
err = fat_scan(new_dir, new_name, &sinfo);
if (!err) {
if (!new_inode) {
/* "foo" -> ".foo" case. just change the ATTR_HIDDEN */
if (sinfo.de != old_sinfo.de) {
err = -EINVAL;
goto out;
}
if (is_hid)
MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
else
MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
if (IS_DIRSYNC(old_dir)) {
err = fat_sync_inode(old_inode);
if (err) {
MSDOS_I(old_inode)->i_attrs = old_attrs;
goto out;
}
} else
mark_inode_dirty(old_inode);
inode_inc_iversion(old_dir);
fat_truncate_time(old_dir, NULL, S_CTIME|S_MTIME);
if (IS_DIRSYNC(old_dir))
(void)fat_sync_inode(old_dir);
else
mark_inode_dirty(old_dir);
goto out;
}
}
ts = current_time(old_inode);
if (new_inode) {
if (err)
goto out;
if (is_dir) {
err = fat_dir_empty(new_inode);
if (err)
goto out;
}
new_i_pos = MSDOS_I(new_inode)->i_pos;
fat_detach(new_inode);
} else {
err = msdos_add_entry(new_dir, new_name, is_dir, is_hid, 0,
&ts, &sinfo);
if (err)
goto out;
new_i_pos = sinfo.i_pos;
}
inode_inc_iversion(new_dir);
fat_detach(old_inode);
fat_attach(old_inode, new_i_pos);
if (is_hid)
MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
else
MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
if (IS_DIRSYNC(new_dir)) {
err = fat_sync_inode(old_inode);
if (err)
goto error_inode;
} else
mark_inode_dirty(old_inode);
if (update_dotdot) {
fat_set_start(dotdot_de, MSDOS_I(new_dir)->i_logstart);
mark_buffer_dirty_inode(dotdot_bh, old_inode);
if (IS_DIRSYNC(new_dir)) {
err = sync_dirty_buffer(dotdot_bh);
if (err)
goto error_dotdot;
}
drop_nlink(old_dir);
if (!new_inode)
inc_nlink(new_dir);
}
err = fat_remove_entries(old_dir, &old_sinfo); /* and releases bh */
old_sinfo.bh = NULL;
if (err)
goto error_dotdot;
inode_inc_iversion(old_dir);
fat_truncate_time(old_dir, &ts, S_CTIME|S_MTIME);
if (IS_DIRSYNC(old_dir))
(void)fat_sync_inode(old_dir);
else
mark_inode_dirty(old_dir);
if (new_inode) {
drop_nlink(new_inode);
if (is_dir)
drop_nlink(new_inode);
fat_truncate_time(new_inode, &ts, S_CTIME);
}
out:
brelse(sinfo.bh);
brelse(dotdot_bh);
brelse(old_sinfo.bh);
return err;
error_dotdot:
/* data cluster is shared, serious corruption */
corrupt = 1;
if (update_dotdot) {
fat_set_start(dotdot_de, MSDOS_I(old_dir)->i_logstart);
mark_buffer_dirty_inode(dotdot_bh, old_inode);
corrupt |= sync_dirty_buffer(dotdot_bh);
}
error_inode:
fat_detach(old_inode);
fat_attach(old_inode, old_sinfo.i_pos);
MSDOS_I(old_inode)->i_attrs = old_attrs;
if (new_inode) {
fat_attach(new_inode, new_i_pos);
if (corrupt)
corrupt |= fat_sync_inode(new_inode);
} else {
/*
* If new entry was not sharing the data cluster, it
* shouldn't be serious corruption.
*/
int err2 = fat_remove_entries(new_dir, &sinfo);
if (corrupt)
corrupt |= err2;
sinfo.bh = NULL;
}
if (corrupt < 0) {
fat_fs_error(new_dir->i_sb,
"%s: Filesystem corrupted (i_pos %lld)",
__func__, sinfo.i_pos);
}
goto out;
}
/***** Rename, a wrapper for rename_same_dir & rename_diff_dir */
static int msdos_rename(struct mnt_idmap *idmap,
struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry,
unsigned int flags)
{
struct super_block *sb = old_dir->i_sb;
unsigned char old_msdos_name[MSDOS_NAME], new_msdos_name[MSDOS_NAME];
int err, is_hid;
if (flags & ~RENAME_NOREPLACE)
return -EINVAL;
mutex_lock(&MSDOS_SB(sb)->s_lock);
err = msdos_format_name(old_dentry->d_name.name,
old_dentry->d_name.len, old_msdos_name,
&MSDOS_SB(old_dir->i_sb)->options);
if (err)
goto out;
err = msdos_format_name(new_dentry->d_name.name,
new_dentry->d_name.len, new_msdos_name,
&MSDOS_SB(new_dir->i_sb)->options);
if (err)
goto out;
is_hid =
(new_dentry->d_name.name[0] == '.') && (new_msdos_name[0] != '.');
err = do_msdos_rename(old_dir, old_msdos_name, old_dentry,
new_dir, new_msdos_name, new_dentry, is_hid);
out:
mutex_unlock(&MSDOS_SB(sb)->s_lock);
if (!err)
err = fat_flush_inodes(sb, old_dir, new_dir);
return err;
}
static const struct inode_operations msdos_dir_inode_operations = {
.create = msdos_create,
.lookup = msdos_lookup,
.unlink = msdos_unlink,
.mkdir = msdos_mkdir,
.rmdir = msdos_rmdir,
.rename = msdos_rename,
.setattr = fat_setattr,
.getattr = fat_getattr,
.update_time = fat_update_time,
};
static void setup(struct super_block *sb)
{
MSDOS_SB(sb)->dir_ops = &msdos_dir_inode_operations;
sb->s_d_op = &msdos_dentry_operations;
sb->s_flags |= SB_NOATIME;
}
static int msdos_fill_super(struct super_block *sb, struct fs_context *fc)
{
return fat_fill_super(sb, fc, setup);
}
static int msdos_get_tree(struct fs_context *fc)
{
return get_tree_bdev(fc, msdos_fill_super);
}
static int msdos_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
return fat_parse_param(fc, param, false);
}
static const struct fs_context_operations msdos_context_ops = {
.parse_param = msdos_parse_param,
.get_tree = msdos_get_tree,
.reconfigure = fat_reconfigure,
.free = fat_free_fc,
};
static int msdos_init_fs_context(struct fs_context *fc)
{
int err;
/* Initialize with is_vfat == false */
err = fat_init_fs_context(fc, false);
if (err)
return err;
fc->ops = &msdos_context_ops;
return 0;
}
static struct file_system_type msdos_fs_type = {
.owner = THIS_MODULE,
.name = "msdos",
.kill_sb = kill_block_super,
.fs_flags = FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
.init_fs_context = msdos_init_fs_context,
.parameters = fat_param_spec,
};
MODULE_ALIAS_FS("msdos");
static int __init init_msdos_fs(void)
{
return register_filesystem(&msdos_fs_type);
}
static void __exit exit_msdos_fs(void)
{
unregister_filesystem(&msdos_fs_type);
}
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Werner Almesberger");
MODULE_DESCRIPTION("MS-DOS filesystem support");
module_init(init_msdos_fs)
module_exit(exit_msdos_fs)
Reference in New Issue View Git Blame Copy Permalink