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![Christian Brauner](/assets/img/avatar_default.png)
Convert to struct mnt_idmap.
Last cycle we merged the necessary infrastructure in
256c8aed2b
("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.
Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.
Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
586 lines
15 KiB
C
586 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) Neil Brown 2002
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* Copyright (C) Christoph Hellwig 2007
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*
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* This file contains the code mapping from inodes to NFS file handles,
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* and for mapping back from file handles to dentries.
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*
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* For details on why we do all the strange and hairy things in here
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* take a look at Documentation/filesystems/nfs/exporting.rst.
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*/
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#include <linux/exportfs.h>
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/module.h>
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#include <linux/mount.h>
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#include <linux/namei.h>
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#include <linux/sched.h>
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#include <linux/cred.h>
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#define dprintk(fmt, args...) pr_debug(fmt, ##args)
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static int get_name(const struct path *path, char *name, struct dentry *child);
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static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir,
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char *name, struct dentry *child)
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{
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const struct export_operations *nop = dir->d_sb->s_export_op;
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struct path path = {.mnt = mnt, .dentry = dir};
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if (nop->get_name)
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return nop->get_name(dir, name, child);
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else
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return get_name(&path, name, child);
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}
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/*
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* Check if the dentry or any of it's aliases is acceptable.
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*/
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static struct dentry *
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find_acceptable_alias(struct dentry *result,
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int (*acceptable)(void *context, struct dentry *dentry),
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void *context)
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{
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struct dentry *dentry, *toput = NULL;
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struct inode *inode;
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if (acceptable(context, result))
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return result;
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inode = result->d_inode;
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spin_lock(&inode->i_lock);
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hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
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dget(dentry);
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spin_unlock(&inode->i_lock);
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if (toput)
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dput(toput);
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if (dentry != result && acceptable(context, dentry)) {
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dput(result);
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return dentry;
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}
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spin_lock(&inode->i_lock);
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toput = dentry;
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}
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spin_unlock(&inode->i_lock);
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if (toput)
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dput(toput);
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return NULL;
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}
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static bool dentry_connected(struct dentry *dentry)
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{
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dget(dentry);
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while (dentry->d_flags & DCACHE_DISCONNECTED) {
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struct dentry *parent = dget_parent(dentry);
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dput(dentry);
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if (dentry == parent) {
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dput(parent);
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return false;
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}
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dentry = parent;
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}
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dput(dentry);
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return true;
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}
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static void clear_disconnected(struct dentry *dentry)
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{
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dget(dentry);
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while (dentry->d_flags & DCACHE_DISCONNECTED) {
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struct dentry *parent = dget_parent(dentry);
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WARN_ON_ONCE(IS_ROOT(dentry));
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spin_lock(&dentry->d_lock);
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dentry->d_flags &= ~DCACHE_DISCONNECTED;
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spin_unlock(&dentry->d_lock);
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dput(dentry);
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dentry = parent;
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}
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dput(dentry);
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}
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/*
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* Reconnect a directory dentry with its parent.
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*
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* This can return a dentry, or NULL, or an error.
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*
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* In the first case the returned dentry is the parent of the given
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* dentry, and may itself need to be reconnected to its parent.
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*
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* In the NULL case, a concurrent VFS operation has either renamed or
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* removed this directory. The concurrent operation has reconnected our
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* dentry, so we no longer need to.
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*/
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static struct dentry *reconnect_one(struct vfsmount *mnt,
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struct dentry *dentry, char *nbuf)
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{
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struct dentry *parent;
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struct dentry *tmp;
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int err;
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parent = ERR_PTR(-EACCES);
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inode_lock(dentry->d_inode);
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if (mnt->mnt_sb->s_export_op->get_parent)
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parent = mnt->mnt_sb->s_export_op->get_parent(dentry);
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inode_unlock(dentry->d_inode);
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if (IS_ERR(parent)) {
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dprintk("get_parent of %lu failed, err %ld\n",
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dentry->d_inode->i_ino, PTR_ERR(parent));
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return parent;
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}
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dprintk("%s: find name of %lu in %lu\n", __func__,
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dentry->d_inode->i_ino, parent->d_inode->i_ino);
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err = exportfs_get_name(mnt, parent, nbuf, dentry);
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if (err == -ENOENT)
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goto out_reconnected;
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if (err)
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goto out_err;
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dprintk("%s: found name: %s\n", __func__, nbuf);
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tmp = lookup_one_unlocked(mnt_idmap(mnt), nbuf, parent, strlen(nbuf));
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if (IS_ERR(tmp)) {
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dprintk("lookup failed: %ld\n", PTR_ERR(tmp));
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err = PTR_ERR(tmp);
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goto out_err;
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}
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if (tmp != dentry) {
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/*
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* Somebody has renamed it since exportfs_get_name();
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* great, since it could've only been renamed if it
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* got looked up and thus connected, and it would
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* remain connected afterwards. We are done.
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*/
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dput(tmp);
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goto out_reconnected;
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}
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dput(tmp);
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if (IS_ROOT(dentry)) {
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err = -ESTALE;
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goto out_err;
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}
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return parent;
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out_err:
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dput(parent);
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return ERR_PTR(err);
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out_reconnected:
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dput(parent);
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/*
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* Someone must have renamed our entry into another parent, in
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* which case it has been reconnected by the rename.
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*
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* Or someone removed it entirely, in which case filehandle
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* lookup will succeed but the directory is now IS_DEAD and
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* subsequent operations on it will fail.
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*
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* Alternatively, maybe there was no race at all, and the
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* filesystem is just corrupt and gave us a parent that doesn't
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* actually contain any entry pointing to this inode. So,
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* double check that this worked and return -ESTALE if not:
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*/
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if (!dentry_connected(dentry))
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return ERR_PTR(-ESTALE);
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return NULL;
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}
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/*
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* Make sure target_dir is fully connected to the dentry tree.
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*
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* On successful return, DCACHE_DISCONNECTED will be cleared on
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* target_dir, and target_dir->d_parent->...->d_parent will reach the
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* root of the filesystem.
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*
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* Whenever DCACHE_DISCONNECTED is unset, target_dir is fully connected.
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* But the converse is not true: target_dir may have DCACHE_DISCONNECTED
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* set but already be connected. In that case we'll verify the
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* connection to root and then clear the flag.
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*
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* Note that target_dir could be removed by a concurrent operation. In
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* that case reconnect_path may still succeed with target_dir fully
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* connected, but further operations using the filehandle will fail when
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* necessary (due to S_DEAD being set on the directory).
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*/
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static int
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reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
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{
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struct dentry *dentry, *parent;
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dentry = dget(target_dir);
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while (dentry->d_flags & DCACHE_DISCONNECTED) {
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BUG_ON(dentry == mnt->mnt_sb->s_root);
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if (IS_ROOT(dentry))
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parent = reconnect_one(mnt, dentry, nbuf);
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else
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parent = dget_parent(dentry);
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if (!parent)
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break;
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dput(dentry);
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if (IS_ERR(parent))
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return PTR_ERR(parent);
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dentry = parent;
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}
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dput(dentry);
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clear_disconnected(target_dir);
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return 0;
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}
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struct getdents_callback {
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struct dir_context ctx;
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char *name; /* name that was found. It already points to a
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buffer NAME_MAX+1 is size */
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u64 ino; /* the inum we are looking for */
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int found; /* inode matched? */
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int sequence; /* sequence counter */
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};
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/*
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* A rather strange filldir function to capture
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* the name matching the specified inode number.
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*/
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static bool filldir_one(struct dir_context *ctx, const char *name, int len,
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loff_t pos, u64 ino, unsigned int d_type)
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{
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struct getdents_callback *buf =
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container_of(ctx, struct getdents_callback, ctx);
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buf->sequence++;
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if (buf->ino == ino && len <= NAME_MAX) {
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memcpy(buf->name, name, len);
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buf->name[len] = '\0';
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buf->found = 1;
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return false; // no more
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}
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return true;
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}
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/**
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* get_name - default export_operations->get_name function
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* @path: the directory in which to find a name
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* @name: a pointer to a %NAME_MAX+1 char buffer to store the name
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* @child: the dentry for the child directory.
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*
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* calls readdir on the parent until it finds an entry with
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* the same inode number as the child, and returns that.
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*/
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static int get_name(const struct path *path, char *name, struct dentry *child)
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{
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const struct cred *cred = current_cred();
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struct inode *dir = path->dentry->d_inode;
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int error;
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struct file *file;
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struct kstat stat;
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struct path child_path = {
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.mnt = path->mnt,
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.dentry = child,
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};
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struct getdents_callback buffer = {
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.ctx.actor = filldir_one,
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.name = name,
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};
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error = -ENOTDIR;
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if (!dir || !S_ISDIR(dir->i_mode))
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goto out;
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error = -EINVAL;
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if (!dir->i_fop)
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goto out;
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/*
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* inode->i_ino is unsigned long, kstat->ino is u64, so the
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* former would be insufficient on 32-bit hosts when the
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* filesystem supports 64-bit inode numbers. So we need to
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* actually call ->getattr, not just read i_ino:
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*/
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error = vfs_getattr_nosec(&child_path, &stat,
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STATX_INO, AT_STATX_SYNC_AS_STAT);
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if (error)
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return error;
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buffer.ino = stat.ino;
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/*
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* Open the directory ...
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*/
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file = dentry_open(path, O_RDONLY, cred);
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error = PTR_ERR(file);
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if (IS_ERR(file))
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goto out;
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error = -EINVAL;
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if (!file->f_op->iterate && !file->f_op->iterate_shared)
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goto out_close;
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buffer.sequence = 0;
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while (1) {
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int old_seq = buffer.sequence;
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error = iterate_dir(file, &buffer.ctx);
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if (buffer.found) {
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error = 0;
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break;
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}
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if (error < 0)
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break;
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error = -ENOENT;
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if (old_seq == buffer.sequence)
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break;
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}
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out_close:
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fput(file);
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out:
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return error;
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}
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/**
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* export_encode_fh - default export_operations->encode_fh function
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* @inode: the object to encode
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* @fid: where to store the file handle fragment
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* @max_len: maximum length to store there
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* @parent: parent directory inode, if wanted
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*
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* This default encode_fh function assumes that the 32 inode number
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* is suitable for locating an inode, and that the generation number
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* can be used to check that it is still valid. It places them in the
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* filehandle fragment where export_decode_fh expects to find them.
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*/
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static int export_encode_fh(struct inode *inode, struct fid *fid,
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int *max_len, struct inode *parent)
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{
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int len = *max_len;
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int type = FILEID_INO32_GEN;
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if (parent && (len < 4)) {
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*max_len = 4;
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return FILEID_INVALID;
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} else if (len < 2) {
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*max_len = 2;
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return FILEID_INVALID;
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}
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len = 2;
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fid->i32.ino = inode->i_ino;
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fid->i32.gen = inode->i_generation;
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if (parent) {
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fid->i32.parent_ino = parent->i_ino;
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fid->i32.parent_gen = parent->i_generation;
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len = 4;
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type = FILEID_INO32_GEN_PARENT;
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}
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*max_len = len;
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return type;
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}
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int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
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int *max_len, struct inode *parent)
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{
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const struct export_operations *nop = inode->i_sb->s_export_op;
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if (nop && nop->encode_fh)
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return nop->encode_fh(inode, fid->raw, max_len, parent);
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return export_encode_fh(inode, fid, max_len, parent);
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}
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EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh);
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int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
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int connectable)
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{
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int error;
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struct dentry *p = NULL;
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struct inode *inode = dentry->d_inode, *parent = NULL;
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if (connectable && !S_ISDIR(inode->i_mode)) {
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p = dget_parent(dentry);
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/*
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* note that while p might've ceased to be our parent already,
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* it's still pinned by and still positive.
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*/
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parent = p->d_inode;
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}
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error = exportfs_encode_inode_fh(inode, fid, max_len, parent);
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dput(p);
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return error;
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}
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EXPORT_SYMBOL_GPL(exportfs_encode_fh);
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struct dentry *
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exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
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int fileid_type,
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int (*acceptable)(void *, struct dentry *),
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void *context)
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{
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const struct export_operations *nop = mnt->mnt_sb->s_export_op;
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struct dentry *result, *alias;
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char nbuf[NAME_MAX+1];
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int err;
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/*
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* Try to get any dentry for the given file handle from the filesystem.
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*/
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if (!nop || !nop->fh_to_dentry)
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return ERR_PTR(-ESTALE);
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result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
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if (IS_ERR_OR_NULL(result))
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return result;
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/*
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* If no acceptance criteria was specified by caller, a disconnected
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* dentry is also accepatable. Callers may use this mode to query if
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* file handle is stale or to get a reference to an inode without
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* risking the high overhead caused by directory reconnect.
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*/
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if (!acceptable)
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return result;
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if (d_is_dir(result)) {
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/*
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* This request is for a directory.
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*
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* On the positive side there is only one dentry for each
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* directory inode. On the negative side this implies that we
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* to ensure our dentry is connected all the way up to the
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* filesystem root.
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*/
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if (result->d_flags & DCACHE_DISCONNECTED) {
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err = reconnect_path(mnt, result, nbuf);
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if (err)
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goto err_result;
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}
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if (!acceptable(context, result)) {
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err = -EACCES;
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goto err_result;
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}
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return result;
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} else {
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/*
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* It's not a directory. Life is a little more complicated.
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*/
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struct dentry *target_dir, *nresult;
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/*
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* See if either the dentry we just got from the filesystem
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* or any alias for it is acceptable. This is always true
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* if this filesystem is exported without the subtreecheck
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* option. If the filesystem is exported with the subtree
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* check option there's a fair chance we need to look at
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* the parent directory in the file handle and make sure
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* it's connected to the filesystem root.
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*/
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alias = find_acceptable_alias(result, acceptable, context);
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if (alias)
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return alias;
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/*
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* Try to extract a dentry for the parent directory from the
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* file handle. If this fails we'll have to give up.
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*/
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err = -ESTALE;
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if (!nop->fh_to_parent)
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goto err_result;
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target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
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fh_len, fileid_type);
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if (!target_dir)
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goto err_result;
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err = PTR_ERR(target_dir);
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if (IS_ERR(target_dir))
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goto err_result;
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/*
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* And as usual we need to make sure the parent directory is
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* connected to the filesystem root. The VFS really doesn't
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* like disconnected directories..
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*/
|
|
err = reconnect_path(mnt, target_dir, nbuf);
|
|
if (err) {
|
|
dput(target_dir);
|
|
goto err_result;
|
|
}
|
|
|
|
/*
|
|
* Now that we've got both a well-connected parent and a
|
|
* dentry for the inode we're after, make sure that our
|
|
* inode is actually connected to the parent.
|
|
*/
|
|
err = exportfs_get_name(mnt, target_dir, nbuf, result);
|
|
if (err) {
|
|
dput(target_dir);
|
|
goto err_result;
|
|
}
|
|
|
|
inode_lock(target_dir->d_inode);
|
|
nresult = lookup_one(mnt_idmap(mnt), nbuf,
|
|
target_dir, strlen(nbuf));
|
|
if (!IS_ERR(nresult)) {
|
|
if (unlikely(nresult->d_inode != result->d_inode)) {
|
|
dput(nresult);
|
|
nresult = ERR_PTR(-ESTALE);
|
|
}
|
|
}
|
|
inode_unlock(target_dir->d_inode);
|
|
/*
|
|
* At this point we are done with the parent, but it's pinned
|
|
* by the child dentry anyway.
|
|
*/
|
|
dput(target_dir);
|
|
|
|
if (IS_ERR(nresult)) {
|
|
err = PTR_ERR(nresult);
|
|
goto err_result;
|
|
}
|
|
dput(result);
|
|
result = nresult;
|
|
|
|
/*
|
|
* And finally make sure the dentry is actually acceptable
|
|
* to NFSD.
|
|
*/
|
|
alias = find_acceptable_alias(result, acceptable, context);
|
|
if (!alias) {
|
|
err = -EACCES;
|
|
goto err_result;
|
|
}
|
|
|
|
return alias;
|
|
}
|
|
|
|
err_result:
|
|
dput(result);
|
|
return ERR_PTR(err);
|
|
}
|
|
EXPORT_SYMBOL_GPL(exportfs_decode_fh_raw);
|
|
|
|
struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
|
|
int fh_len, int fileid_type,
|
|
int (*acceptable)(void *, struct dentry *),
|
|
void *context)
|
|
{
|
|
struct dentry *ret;
|
|
|
|
ret = exportfs_decode_fh_raw(mnt, fid, fh_len, fileid_type,
|
|
acceptable, context);
|
|
if (IS_ERR_OR_NULL(ret)) {
|
|
if (ret == ERR_PTR(-ENOMEM))
|
|
return ret;
|
|
return ERR_PTR(-ESTALE);
|
|
}
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(exportfs_decode_fh);
|
|
|
|
MODULE_LICENSE("GPL");
|