fs/afs/dynroot.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* AFS dynamic root handling
  *
  * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  */

 #include <linux/fs.h>
 #include <linux/namei.h>
 #include <linux/dns_resolver.h>
 #include "internal.h"

 /*
  * Probe to see if a cell may exist.  This prevents positive dentries from
  * being created unnecessarily.
  */
 static int afs_probe_cell_name(struct dentry *dentry)
 {
 	struct afs_cell *cell;
 	struct afs_net *net = afs_d2net(dentry);
 	const char *name = dentry->d_name.name;
 	size_t len = dentry->d_name.len;
 	int ret;

 	/* Names prefixed with a dot are R/W mounts. */
 	if (name[0] == '.') {
 		if (len == 1)
 			return -EINVAL;
 		name++;
 		len--;
 	}

 	cell = afs_lookup_cell_rcu(net, name, len);
 	if (!IS_ERR(cell)) {
 		afs_put_cell(net, cell);
 		return 0;
 	}

 	ret = dns_query(net->net, "afsdb", name, len, "srv=1",
 			NULL, NULL, false);
 	if (ret == -ENODATA)
 		ret = -EDESTADDRREQ;
 	return ret;
 }

 /*
  * Try to auto mount the mountpoint with pseudo directory, if the autocell
  * operation is setted.
  */
 struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir)
 {
 	struct afs_vnode *vnode = AFS_FS_I(dir);
 	struct inode *inode;
 	int ret = -ENOENT;

 	_enter("%p{%pd}, {%llx:%llu}",
 	       dentry, dentry, vnode->fid.vid, vnode->fid.vnode);

 	if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
 		goto out;

 	ret = afs_probe_cell_name(dentry);
 	if (ret < 0)
 		goto out;

 	inode = afs_iget_pseudo_dir(dir->i_sb, false);
 	if (IS_ERR(inode)) {
 		ret = PTR_ERR(inode);
 		goto out;
 	}

 	_leave("= %p", inode);
 	return inode;

 out:
 	_leave("= %d", ret);
 	return ret == -ENOENT ? NULL : ERR_PTR(ret);
 }

 /*
  * Look up @cell in a dynroot directory.  This is a substitution for the
  * local cell name for the net namespace.
  */
 static struct dentry *afs_lookup_atcell(struct dentry *dentry)
 {
 	struct afs_cell *cell;
 	struct afs_net *net = afs_d2net(dentry);
 	struct dentry *ret;
 	unsigned int seq = 0;
 	char *name;
 	int len;

 	if (!net->ws_cell)
 		return ERR_PTR(-ENOENT);

 	ret = ERR_PTR(-ENOMEM);
 	name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
 	if (!name)
 		goto out_p;

 	rcu_read_lock();
 	do {
 		read_seqbegin_or_lock(&net->cells_lock, &seq);
 		cell = rcu_dereference_raw(net->ws_cell);
 		if (cell) {
 			len = cell->name_len;
 			memcpy(name, cell->name, len + 1);
 		}
 	} while (need_seqretry(&net->cells_lock, seq));
 	done_seqretry(&net->cells_lock, seq);
 	rcu_read_unlock();

 	ret = ERR_PTR(-ENOENT);
 	if (!cell)
 		goto out_n;

 	ret = lookup_one_len(name, dentry->d_parent, len);

 	/* We don't want to d_add() the @cell dentry here as we don't want to
 	 * the cached dentry to hide changes to the local cell name.
 	 */

 out_n:
 	kfree(name);
 out_p:
 	return ret;
 }

 /*
  * Look up an entry in a dynroot directory.
  */
 static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
 					 unsigned int flags)
 {
 	_enter("%pd", dentry);

 	ASSERTCMP(d_inode(dentry), ==, NULL);

 	if (flags & LOOKUP_CREATE)
 		return ERR_PTR(-EOPNOTSUPP);

 	if (dentry->d_name.len >= AFSNAMEMAX) {
 		_leave(" = -ENAMETOOLONG");
 		return ERR_PTR(-ENAMETOOLONG);
 	}

 	if (dentry->d_name.len == 5 &&
 	    memcmp(dentry->d_name.name, "@cell", 5) == 0)
 		return afs_lookup_atcell(dentry);

 	return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
 }

 const struct inode_operations afs_dynroot_inode_operations = {
 	.lookup		= afs_dynroot_lookup,
 };

 /*
  * Dirs in the dynamic root don't need revalidation.
  */
 static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
 {
 	return 1;
 }

 /*
  * Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
  * sleep)
  * - called from dput() when d_count is going to 0.
  * - return 1 to request dentry be unhashed, 0 otherwise
  */
 static int afs_dynroot_d_delete(const struct dentry *dentry)
 {
 	return d_really_is_positive(dentry);
 }

 const struct dentry_operations afs_dynroot_dentry_operations = {
 	.d_revalidate	= afs_dynroot_d_revalidate,
 	.d_delete	= afs_dynroot_d_delete,
 	.d_release	= afs_d_release,
 	.d_automount	= afs_d_automount,
 };

 /*
  * Create a manually added cell mount directory.
  * - The caller must hold net->proc_cells_lock
  */
 int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
 {
 	struct super_block *sb = net->dynroot_sb;
 	struct dentry *root, *subdir;
 	int ret;

 	if (!sb || atomic_read(&sb->s_active) == 0)
 		return 0;

 	/* Let the ->lookup op do the creation */
 	root = sb->s_root;
 	inode_lock(root->d_inode);
 	subdir = lookup_one_len(cell->name, root, cell->name_len);
 	if (IS_ERR(subdir)) {
 		ret = PTR_ERR(subdir);
 		goto unlock;
 	}

 	/* Note that we're retaining an extra ref on the dentry */
 	subdir->d_fsdata = (void *)1UL;
 	ret = 0;
 unlock:
 	inode_unlock(root->d_inode);
 	return ret;
 }

 /*
  * Remove a manually added cell mount directory.
  * - The caller must hold net->proc_cells_lock
  */
 void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
 {
 	struct super_block *sb = net->dynroot_sb;
 	struct dentry *root, *subdir;

 	if (!sb || atomic_read(&sb->s_active) == 0)
 		return;

 	root = sb->s_root;
 	inode_lock(root->d_inode);

 	/* Don't want to trigger a lookup call, which will re-add the cell */
 	subdir = try_lookup_one_len(cell->name, root, cell->name_len);
 	if (IS_ERR_OR_NULL(subdir)) {
 		_debug("lookup %ld", PTR_ERR(subdir));
 		goto no_dentry;
 	}

 	_debug("rmdir %pd %u", subdir, d_count(subdir));

 	if (subdir->d_fsdata) {
 		_debug("unpin %u", d_count(subdir));
 		subdir->d_fsdata = NULL;
 		dput(subdir);
 	}
 	dput(subdir);
 no_dentry:
 	inode_unlock(root->d_inode);
 	_leave("");
 }

 /*
  * Populate a newly created dynamic root with cell names.
  */
 int afs_dynroot_populate(struct super_block *sb)
 {
 	struct afs_cell *cell;
 	struct afs_net *net = afs_sb2net(sb);
 	int ret;

 	mutex_lock(&net->proc_cells_lock);

 	net->dynroot_sb = sb;
 	hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
 		ret = afs_dynroot_mkdir(net, cell);
 		if (ret < 0)
 			goto error;
 	}

 	ret = 0;
 out:
 	mutex_unlock(&net->proc_cells_lock);
 	return ret;

 error:
 	net->dynroot_sb = NULL;
 	goto out;
 }

 /*
  * When a dynamic root that's in the process of being destroyed, depopulate it
  * of pinned directories.
  */
 void afs_dynroot_depopulate(struct super_block *sb)
 {
 	struct afs_net *net = afs_sb2net(sb);
 	struct dentry *root = sb->s_root, *subdir, *tmp;

 	/* Prevent more subdirs from being created */
 	mutex_lock(&net->proc_cells_lock);
 	if (net->dynroot_sb == sb)
 		net->dynroot_sb = NULL;
 	mutex_unlock(&net->proc_cells_lock);

 	inode_lock(root->d_inode);

 	/* Remove all the pins for dirs created for manually added cells */
 	list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
 		if (subdir->d_fsdata) {
 			subdir->d_fsdata = NULL;
 			dput(subdir);
 		}
 	}

 	inode_unlock(root->d_inode);
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* AFS dynamic root handling
	*
	* Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*/

	#include <linux/fs.h>
	#include <linux/namei.h>
	#include <linux/dns_resolver.h>
	#include "internal.h"

	/*
	* Probe to see if a cell may exist. This prevents positive dentries from
	* being created unnecessarily.
	*/
	static int afs_probe_cell_name(struct dentry *dentry)
	{
	struct afs_cell *cell;
	struct afs_net *net = afs_d2net(dentry);
	const char *name = dentry->d_name.name;
	size_t len = dentry->d_name.len;
	int ret;

	/* Names prefixed with a dot are R/W mounts. */
	if (name[0] == '.') {
	if (len == 1)
	return -EINVAL;
	name++;
	len--;
	}

	cell = afs_lookup_cell_rcu(net, name, len);
	if (!IS_ERR(cell)) {
	afs_put_cell(net, cell);
	return 0;
	}

	ret = dns_query(net->net, "afsdb", name, len, "srv=1",
	NULL, NULL, false);
	if (ret == -ENODATA)
	ret = -EDESTADDRREQ;
	return ret;
	}

	/*
	* Try to auto mount the mountpoint with pseudo directory, if the autocell
	* operation is setted.
	*/
	struct inode afs_try_auto_mntpt(struct dentry dentry, struct inode *dir)
	{
	struct afs_vnode *vnode = AFS_FS_I(dir);
	struct inode *inode;
	int ret = -ENOENT;

	_enter("%p{%pd}, {%llx:%llu}",
	dentry, dentry, vnode->fid.vid, vnode->fid.vnode);

	if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
	goto out;

	ret = afs_probe_cell_name(dentry);
	if (ret < 0)
	goto out;

	inode = afs_iget_pseudo_dir(dir->i_sb, false);
	if (IS_ERR(inode)) {
	ret = PTR_ERR(inode);
	goto out;
	}

	_leave("= %p", inode);
	return inode;

	out:
	_leave("= %d", ret);
	return ret == -ENOENT ? NULL : ERR_PTR(ret);
	}

	/*
	* Look up @cell in a dynroot directory. This is a substitution for the
	* local cell name for the net namespace.
	*/
	static struct dentry afs_lookup_atcell(struct dentry dentry)
	{
	struct afs_cell *cell;
	struct afs_net *net = afs_d2net(dentry);
	struct dentry *ret;
	unsigned int seq = 0;
	char *name;
	int len;

	if (!net->ws_cell)
	return ERR_PTR(-ENOENT);

	ret = ERR_PTR(-ENOMEM);
	name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
	if (!name)
	goto out_p;

	rcu_read_lock();
	do {
	read_seqbegin_or_lock(&net->cells_lock, &seq);
	cell = rcu_dereference_raw(net->ws_cell);
	if (cell) {
	len = cell->name_len;
	memcpy(name, cell->name, len + 1);
	}
	} while (need_seqretry(&net->cells_lock, seq));
	done_seqretry(&net->cells_lock, seq);
	rcu_read_unlock();

	ret = ERR_PTR(-ENOENT);
	if (!cell)
	goto out_n;

	ret = lookup_one_len(name, dentry->d_parent, len);

	/* We don't want to d_add() the @cell dentry here as we don't want to
	* the cached dentry to hide changes to the local cell name.
	*/

	out_n:
	kfree(name);
	out_p:
	return ret;
	}

	/*
	* Look up an entry in a dynroot directory.
	*/
	static struct dentry afs_dynroot_lookup(struct inode dir, struct dentry *dentry,
	unsigned int flags)
	{
	_enter("%pd", dentry);

	ASSERTCMP(d_inode(dentry), ==, NULL);

	if (flags & LOOKUP_CREATE)
	return ERR_PTR(-EOPNOTSUPP);

	if (dentry->d_name.len >= AFSNAMEMAX) {
	_leave(" = -ENAMETOOLONG");
	return ERR_PTR(-ENAMETOOLONG);
	}

	if (dentry->d_name.len == 5 &&
	memcmp(dentry->d_name.name, "@cell", 5) == 0)
	return afs_lookup_atcell(dentry);

	return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
	}

	const struct inode_operations afs_dynroot_inode_operations = {
	.lookup = afs_dynroot_lookup,
	};

	/*
	* Dirs in the dynamic root don't need revalidation.
	*/
	static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
	{
	return 1;
	}

	/*
	* Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
	* sleep)
	* - called from dput() when d_count is going to 0.
	* - return 1 to request dentry be unhashed, 0 otherwise
	*/
	static int afs_dynroot_d_delete(const struct dentry *dentry)
	{
	return d_really_is_positive(dentry);
	}

	const struct dentry_operations afs_dynroot_dentry_operations = {
	.d_revalidate = afs_dynroot_d_revalidate,
	.d_delete = afs_dynroot_d_delete,
	.d_release = afs_d_release,
	.d_automount = afs_d_automount,
	};

	/*
	* Create a manually added cell mount directory.
	* - The caller must hold net->proc_cells_lock
	*/
	int afs_dynroot_mkdir(struct afs_net net, struct afs_cell cell)
	{
	struct super_block *sb = net->dynroot_sb;
	struct dentry root, subdir;
	int ret;

	if (!sb \|\| atomic_read(&sb->s_active) == 0)
	return 0;

	/* Let the ->lookup op do the creation */
	root = sb->s_root;
	inode_lock(root->d_inode);
	subdir = lookup_one_len(cell->name, root, cell->name_len);
	if (IS_ERR(subdir)) {
	ret = PTR_ERR(subdir);
	goto unlock;
	}

	/* Note that we're retaining an extra ref on the dentry */
	subdir->d_fsdata = (void *)1UL;
	ret = 0;
	unlock:
	inode_unlock(root->d_inode);
	return ret;
	}

	/*
	* Remove a manually added cell mount directory.
	* - The caller must hold net->proc_cells_lock
	*/
	void afs_dynroot_rmdir(struct afs_net net, struct afs_cell cell)
	{
	struct super_block *sb = net->dynroot_sb;
	struct dentry root, subdir;

	if (!sb \|\| atomic_read(&sb->s_active) == 0)
	return;

	root = sb->s_root;
	inode_lock(root->d_inode);

	/* Don't want to trigger a lookup call, which will re-add the cell */
	subdir = try_lookup_one_len(cell->name, root, cell->name_len);
	if (IS_ERR_OR_NULL(subdir)) {
	_debug("lookup %ld", PTR_ERR(subdir));
	goto no_dentry;
	}

	_debug("rmdir %pd %u", subdir, d_count(subdir));

	if (subdir->d_fsdata) {
	_debug("unpin %u", d_count(subdir));
	subdir->d_fsdata = NULL;
	dput(subdir);
	}
	dput(subdir);
	no_dentry:
	inode_unlock(root->d_inode);
	_leave("");
	}

	/*
	* Populate a newly created dynamic root with cell names.
	*/
	int afs_dynroot_populate(struct super_block *sb)
	{
	struct afs_cell *cell;
	struct afs_net *net = afs_sb2net(sb);
	int ret;

	mutex_lock(&net->proc_cells_lock);

	net->dynroot_sb = sb;
	hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
	ret = afs_dynroot_mkdir(net, cell);
	if (ret < 0)
	goto error;
	}

	ret = 0;
	out:
	mutex_unlock(&net->proc_cells_lock);
	return ret;

	error:
	net->dynroot_sb = NULL;
	goto out;
	}

	/*
	* When a dynamic root that's in the process of being destroyed, depopulate it
	* of pinned directories.
	*/
	void afs_dynroot_depopulate(struct super_block *sb)
	{
	struct afs_net *net = afs_sb2net(sb);
	struct dentry root = sb->s_root, subdir, *tmp;

	/* Prevent more subdirs from being created */
	mutex_lock(&net->proc_cells_lock);
	if (net->dynroot_sb == sb)
	net->dynroot_sb = NULL;
	mutex_unlock(&net->proc_cells_lock);

	inode_lock(root->d_inode);

	/* Remove all the pins for dirs created for manually added cells */
	list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
	if (subdir->d_fsdata) {
	subdir->d_fsdata = NULL;
	dput(subdir);
	}
	}

	inode_unlock(root->d_inode);
	}