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linux-stable-mirror/fs/hfsplus/dir.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

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// SPDX-License-Identifier: GPL-2.0
/*
* linux/fs/hfsplus/dir.c
*
* Copyright (C) 2001
* Brad Boyer (flar@allandria.com)
* (C) 2003 Ardis Technologies <roman@ardistech.com>
*
* Handling of directories
*/
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/nls.h>
#include "hfsplus_fs.h"
#include "hfsplus_raw.h"
#include "xattr.h"
static inline void hfsplus_instantiate(struct dentry *dentry,
struct inode *inode, u32 cnid)
{
dentry->d_fsdata = (void *)(unsigned long)cnid;
d_instantiate(dentry, inode);
}
/* Find the entry inside dir named dentry->d_name */
static struct dentry *hfsplus_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
struct inode *inode = NULL;
struct hfs_find_data fd;
struct super_block *sb;
hfsplus_cat_entry entry;
int err;
u32 cnid, linkid = 0;
u16 type;
sb = dir->i_sb;
dentry->d_fsdata = NULL;
err = hfs_find_init(HFSPLUS_SB(sb)->cat_tree, &fd);
if (err)
return ERR_PTR(err);
err = hfsplus_cat_build_key(sb, fd.search_key, dir->i_ino,
&dentry->d_name);
if (unlikely(err < 0))
goto fail;
again:
err = hfs_brec_read(&fd, &entry, sizeof(entry));
if (err) {
if (err == -ENOENT) {
hfs_find_exit(&fd);
/* No such entry */
inode = NULL;
goto out;
}
goto fail;
}
type = be16_to_cpu(entry.type);
if (type == HFSPLUS_FOLDER) {
if (fd.entrylength < sizeof(struct hfsplus_cat_folder)) {
err = -EIO;
goto fail;
}
cnid = be32_to_cpu(entry.folder.id);
dentry->d_fsdata = (void *)(unsigned long)cnid;
} else if (type == HFSPLUS_FILE) {
if (fd.entrylength < sizeof(struct hfsplus_cat_file)) {
err = -EIO;
goto fail;
}
cnid = be32_to_cpu(entry.file.id);
if (entry.file.user_info.fdType ==
cpu_to_be32(HFSP_HARDLINK_TYPE) &&
entry.file.user_info.fdCreator ==
cpu_to_be32(HFSP_HFSPLUS_CREATOR) &&
HFSPLUS_SB(sb)->hidden_dir &&
(entry.file.create_date ==
HFSPLUS_I(HFSPLUS_SB(sb)->hidden_dir)->
create_date ||
entry.file.create_date ==
HFSPLUS_I(d_inode(sb->s_root))->
create_date)) {
struct qstr str;
char name[32];
if (dentry->d_fsdata) {
/*
* We found a link pointing to another link,
* so ignore it and treat it as regular file.
*/
cnid = (unsigned long)dentry->d_fsdata;
linkid = 0;
} else {
dentry->d_fsdata = (void *)(unsigned long)cnid;
linkid =
be32_to_cpu(entry.file.permissions.dev);
str.len = sprintf(name, "iNode%d", linkid);
str.name = name;
err = hfsplus_cat_build_key(sb, fd.search_key,
HFSPLUS_SB(sb)->hidden_dir->i_ino,
&str);
if (unlikely(err < 0))
goto fail;
goto again;
}
} else if (!dentry->d_fsdata)
dentry->d_fsdata = (void *)(unsigned long)cnid;
} else {
pr_err("invalid catalog entry type in lookup\n");
err = -EIO;
goto fail;
}
hfs_find_exit(&fd);
inode = hfsplus_iget(dir->i_sb, cnid);
if (IS_ERR(inode))
return ERR_CAST(inode);
if (S_ISREG(inode->i_mode))
HFSPLUS_I(inode)->linkid = linkid;
out:
return d_splice_alias(inode, dentry);
fail:
hfs_find_exit(&fd);
return ERR_PTR(err);
}
static int hfsplus_readdir(struct file *file, struct dir_context *ctx)
{
struct inode *inode = file_inode(file);
struct super_block *sb = inode->i_sb;
int len, err;
char *strbuf;
hfsplus_cat_entry entry;
struct hfs_find_data fd;
struct hfsplus_readdir_data *rd;
u16 type;
if (file->f_pos >= inode->i_size)
return 0;
err = hfs_find_init(HFSPLUS_SB(sb)->cat_tree, &fd);
if (err)
return err;
strbuf = kmalloc(NLS_MAX_CHARSET_SIZE * HFSPLUS_MAX_STRLEN + 1, GFP_KERNEL);
if (!strbuf) {
err = -ENOMEM;
goto out;
}
hfsplus_cat_build_key_with_cnid(sb, fd.search_key, inode->i_ino);
err = hfs_brec_find(&fd, hfs_find_rec_by_key);
if (err)
goto out;
if (ctx->pos == 0) {
/* This is completely artificial... */
if (!dir_emit_dot(file, ctx))
goto out;
ctx->pos = 1;
}
if (ctx->pos == 1) {
if (fd.entrylength > sizeof(entry) || fd.entrylength < 0) {
err = -EIO;
goto out;
}
hfs_bnode_read(fd.bnode, &entry, fd.entryoffset,
fd.entrylength);
if (be16_to_cpu(entry.type) != HFSPLUS_FOLDER_THREAD) {
pr_err("bad catalog folder thread\n");
err = -EIO;
goto out;
}
if (fd.entrylength < HFSPLUS_MIN_THREAD_SZ) {
pr_err("truncated catalog thread\n");
err = -EIO;
goto out;
}
if (!dir_emit(ctx, "..", 2,
be32_to_cpu(entry.thread.parentID), DT_DIR))
goto out;
ctx->pos = 2;
}
if (ctx->pos >= inode->i_size)
goto out;
err = hfs_brec_goto(&fd, ctx->pos - 1);
if (err)
goto out;
for (;;) {
if (be32_to_cpu(fd.key->cat.parent) != inode->i_ino) {
pr_err("walked past end of dir\n");
err = -EIO;
goto out;
}
if (fd.entrylength > sizeof(entry) || fd.entrylength < 0) {
err = -EIO;
goto out;
}
hfs_bnode_read(fd.bnode, &entry, fd.entryoffset,
fd.entrylength);
type = be16_to_cpu(entry.type);
len = NLS_MAX_CHARSET_SIZE * HFSPLUS_MAX_STRLEN;
err = hfsplus_uni2asc(sb, &fd.key->cat.name, strbuf, &len);
if (err)
goto out;
if (type == HFSPLUS_FOLDER) {
if (fd.entrylength <
sizeof(struct hfsplus_cat_folder)) {
pr_err("small dir entry\n");
err = -EIO;
goto out;
}
if (HFSPLUS_SB(sb)->hidden_dir &&
HFSPLUS_SB(sb)->hidden_dir->i_ino ==
be32_to_cpu(entry.folder.id))
goto next;
if (!dir_emit(ctx, strbuf, len,
be32_to_cpu(entry.folder.id), DT_DIR))
break;
} else if (type == HFSPLUS_FILE) {
u16 mode;
unsigned type = DT_UNKNOWN;
if (fd.entrylength < sizeof(struct hfsplus_cat_file)) {
pr_err("small file entry\n");
err = -EIO;
goto out;
}
mode = be16_to_cpu(entry.file.permissions.mode);
if (S_ISREG(mode))
type = DT_REG;
else if (S_ISLNK(mode))
type = DT_LNK;
else if (S_ISFIFO(mode))
type = DT_FIFO;
else if (S_ISCHR(mode))
type = DT_CHR;
else if (S_ISBLK(mode))
type = DT_BLK;
else if (S_ISSOCK(mode))
type = DT_SOCK;
if (!dir_emit(ctx, strbuf, len,
be32_to_cpu(entry.file.id), type))
break;
} else {
pr_err("bad catalog entry type\n");
err = -EIO;
goto out;
}
next:
ctx->pos++;
if (ctx->pos >= inode->i_size)
goto out;
err = hfs_brec_goto(&fd, 1);
if (err)
goto out;
}
rd = file->private_data;
if (!rd) {
rd = kmalloc(sizeof(struct hfsplus_readdir_data), GFP_KERNEL);
if (!rd) {
err = -ENOMEM;
goto out;
}
file->private_data = rd;
rd->file = file;
spin_lock(&HFSPLUS_I(inode)->open_dir_lock);
list_add(&rd->list, &HFSPLUS_I(inode)->open_dir_list);
spin_unlock(&HFSPLUS_I(inode)->open_dir_lock);
}
/*
* Can be done after the list insertion; exclusion with
* hfsplus_delete_cat() is provided by directory lock.
*/
memcpy(&rd->key, fd.key, sizeof(struct hfsplus_cat_key));
out:
kfree(strbuf);
hfs_find_exit(&fd);
return err;
}
static int hfsplus_dir_release(struct inode *inode, struct file *file)
{
struct hfsplus_readdir_data *rd = file->private_data;
if (rd) {
spin_lock(&HFSPLUS_I(inode)->open_dir_lock);
list_del(&rd->list);
spin_unlock(&HFSPLUS_I(inode)->open_dir_lock);
kfree(rd);
}
return 0;
}
static int hfsplus_link(struct dentry *src_dentry, struct inode *dst_dir,
struct dentry *dst_dentry)
{
struct hfsplus_sb_info *sbi = HFSPLUS_SB(dst_dir->i_sb);
struct inode *inode = d_inode(src_dentry);
struct inode *src_dir = d_inode(src_dentry->d_parent);
struct qstr str;
char name[32];
u32 cnid, id;
int res;
if (HFSPLUS_IS_RSRC(inode))
return -EPERM;
if (!S_ISREG(inode->i_mode))
return -EPERM;
mutex_lock(&sbi->vh_mutex);
if (inode->i_ino == (u32)(unsigned long)src_dentry->d_fsdata) {
for (;;) {
get_random_bytes(&id, sizeof(cnid));
id &= 0x3fffffff;
str.name = name;
str.len = sprintf(name, "iNode%d", id);
res = hfsplus_rename_cat(inode->i_ino,
src_dir, &src_dentry->d_name,
sbi->hidden_dir, &str);
if (!res)
break;
if (res != -EEXIST)
goto out;
}
HFSPLUS_I(inode)->linkid = id;
cnid = sbi->next_cnid++;
src_dentry->d_fsdata = (void *)(unsigned long)cnid;
res = hfsplus_create_cat(cnid, src_dir,
&src_dentry->d_name, inode);
if (res)
/* panic? */
goto out;
sbi->file_count++;
}
cnid = sbi->next_cnid++;
res = hfsplus_create_cat(cnid, dst_dir, &dst_dentry->d_name, inode);
if (res)
goto out;
inc_nlink(inode);
hfsplus_instantiate(dst_dentry, inode, cnid);
ihold(inode);
inode_set_ctime_current(inode);
mark_inode_dirty(inode);
sbi->file_count++;
hfsplus_mark_mdb_dirty(dst_dir->i_sb);
out:
mutex_unlock(&sbi->vh_mutex);
return res;
}
static int hfsplus_unlink(struct inode *dir, struct dentry *dentry)
{
struct hfsplus_sb_info *sbi = HFSPLUS_SB(dir->i_sb);
struct inode *inode = d_inode(dentry);
struct qstr str;
char name[32];
u32 cnid;
int res;
if (HFSPLUS_IS_RSRC(inode))
return -EPERM;
mutex_lock(&sbi->vh_mutex);
cnid = (u32)(unsigned long)dentry->d_fsdata;
if (inode->i_ino == cnid &&
atomic_read(&HFSPLUS_I(inode)->opencnt)) {
str.name = name;
str.len = sprintf(name, "temp%lu", inode->i_ino);
res = hfsplus_rename_cat(inode->i_ino,
dir, &dentry->d_name,
sbi->hidden_dir, &str);
if (!res) {
inode->i_flags |= S_DEAD;
drop_nlink(inode);
}
goto out;
}
res = hfsplus_delete_cat(cnid, dir, &dentry->d_name);
if (res)
goto out;
if (inode->i_nlink > 0)
drop_nlink(inode);
if (inode->i_ino == cnid)
clear_nlink(inode);
if (!inode->i_nlink) {
if (inode->i_ino != cnid) {
sbi->file_count--;
if (!atomic_read(&HFSPLUS_I(inode)->opencnt)) {
res = hfsplus_delete_cat(inode->i_ino,
sbi->hidden_dir,
NULL);
if (!res)
hfsplus_delete_inode(inode);
} else
inode->i_flags |= S_DEAD;
} else
hfsplus_delete_inode(inode);
} else
sbi->file_count--;
inode_set_ctime_current(inode);
mark_inode_dirty(inode);
out:
mutex_unlock(&sbi->vh_mutex);
return res;
}
static int hfsplus_rmdir(struct inode *dir, struct dentry *dentry)
{
struct hfsplus_sb_info *sbi = HFSPLUS_SB(dir->i_sb);
struct inode *inode = d_inode(dentry);
int res;
if (inode->i_size != 2)
return -ENOTEMPTY;
mutex_lock(&sbi->vh_mutex);
res = hfsplus_delete_cat(inode->i_ino, dir, &dentry->d_name);
if (res)
goto out;
clear_nlink(inode);
inode_set_ctime_current(inode);
hfsplus_delete_inode(inode);
mark_inode_dirty(inode);
out:
mutex_unlock(&sbi->vh_mutex);
return res;
}
static int hfsplus_symlink(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, const char *symname)
{
struct hfsplus_sb_info *sbi = HFSPLUS_SB(dir->i_sb);
struct inode *inode;
int res = -ENOMEM;
mutex_lock(&sbi->vh_mutex);
inode = hfsplus_new_inode(dir->i_sb, dir, S_IFLNK | S_IRWXUGO);
if (!inode)
goto out;
res = page_symlink(inode, symname, strlen(symname) + 1);
if (res)
goto out_err;
res = hfsplus_create_cat(inode->i_ino, dir, &dentry->d_name, inode);
if (res)
goto out_err;
res = hfsplus_init_security(inode, dir, &dentry->d_name);
if (res == -EOPNOTSUPP)
res = 0; /* Operation is not supported. */
else if (res) {
/* Try to delete anyway without error analysis. */
hfsplus_delete_cat(inode->i_ino, dir, &dentry->d_name);
goto out_err;
}
hfsplus_instantiate(dentry, inode, inode->i_ino);
mark_inode_dirty(inode);
goto out;
out_err:
clear_nlink(inode);
hfsplus_delete_inode(inode);
iput(inode);
out:
mutex_unlock(&sbi->vh_mutex);
return res;
}
static int hfsplus_mknod(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, umode_t mode, dev_t rdev)
{
struct hfsplus_sb_info *sbi = HFSPLUS_SB(dir->i_sb);
struct inode *inode;
int res = -ENOMEM;
mutex_lock(&sbi->vh_mutex);
inode = hfsplus_new_inode(dir->i_sb, dir, mode);
if (!inode)
goto out;
if (S_ISBLK(mode) || S_ISCHR(mode) || S_ISFIFO(mode) || S_ISSOCK(mode))
init_special_inode(inode, mode, rdev);
res = hfsplus_create_cat(inode->i_ino, dir, &dentry->d_name, inode);
if (res)
goto failed_mknod;
res = hfsplus_init_security(inode, dir, &dentry->d_name);
if (res == -EOPNOTSUPP)
res = 0; /* Operation is not supported. */
else if (res) {
/* Try to delete anyway without error analysis. */
hfsplus_delete_cat(inode->i_ino, dir, &dentry->d_name);
goto failed_mknod;
}
hfsplus_instantiate(dentry, inode, inode->i_ino);
mark_inode_dirty(inode);
goto out;
failed_mknod:
clear_nlink(inode);
hfsplus_delete_inode(inode);
iput(inode);
out:
mutex_unlock(&sbi->vh_mutex);
return res;
}
static int hfsplus_create(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, umode_t mode, bool excl)
{
return hfsplus_mknod(&nop_mnt_idmap, dir, dentry, mode, 0);
}
static struct dentry *hfsplus_mkdir(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, umode_t mode)
{
return ERR_PTR(hfsplus_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFDIR, 0));
}
static int hfsplus_rename(struct mnt_idmap *idmap,
struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry,
unsigned int flags)
{
int res;
if (flags & ~RENAME_NOREPLACE)
return -EINVAL;
/* Unlink destination if it already exists */
if (d_really_is_positive(new_dentry)) {
if (d_is_dir(new_dentry))
res = hfsplus_rmdir(new_dir, new_dentry);
else
res = hfsplus_unlink(new_dir, new_dentry);
if (res)
return res;
}
res = hfsplus_rename_cat((u32)(unsigned long)old_dentry->d_fsdata,
old_dir, &old_dentry->d_name,
new_dir, &new_dentry->d_name);
if (!res)
new_dentry->d_fsdata = old_dentry->d_fsdata;
return res;
}
const struct inode_operations hfsplus_dir_inode_operations = {
.lookup = hfsplus_lookup,
.create = hfsplus_create,
.link = hfsplus_link,
.unlink = hfsplus_unlink,
.mkdir = hfsplus_mkdir,
.rmdir = hfsplus_rmdir,
.symlink = hfsplus_symlink,
.mknod = hfsplus_mknod,
.rename = hfsplus_rename,
.getattr = hfsplus_getattr,
.listxattr = hfsplus_listxattr,
.fileattr_get = hfsplus_fileattr_get,
.fileattr_set = hfsplus_fileattr_set,
};
const struct file_operations hfsplus_dir_operations = {
.fsync = hfsplus_file_fsync,
.read = generic_read_dir,
.iterate_shared = hfsplus_readdir,
.unlocked_ioctl = hfsplus_ioctl,
.llseek = generic_file_llseek,
.release = hfsplus_dir_release,
};
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