[linux.git] / fs / afs / dynroot.c

// 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 ([email protected])
 */

#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 (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);
}
Commit	Line	Data
b4d0d230	1	// SPDX-License-Identifier: GPL-2.0-or-later
0da0b7fd	2	/* AFS dynamic root handling
66c7e1d3 DH	3	*
	4	* Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
	5	* Written by David Howells ([email protected])
66c7e1d3 DH	6	*/
	7
	8	#include <linux/fs.h>
	9	#include <linux/namei.h>
	10	#include <linux/dns_resolver.h>
	11	#include "internal.h"
	12
66c7e1d3 DH	13	/*
	14	* Probe to see if a cell may exist. This prevents positive dentries from
	15	* being created unnecessarily.
	16	*/
	17	static int afs_probe_cell_name(struct dentry *dentry)
	18	{
	19	struct afs_cell *cell;
a58946c1	20	struct afs_net *net = afs_d2net(dentry);
66c7e1d3 DH	21	const char *name = dentry->d_name.name;
	22	size_t len = dentry->d_name.len;
	23	int ret;
	24
	25	/* Names prefixed with a dot are R/W mounts. */
	26	if (name[0] == '.') {
	27	if (len == 1)
	28	return -EINVAL;
	29	name++;
	30	len--;
	31	}
	32
a58946c1	33	cell = afs_lookup_cell_rcu(net, name, len);
66c7e1d3	34	if (!IS_ERR(cell)) {
a58946c1	35	afs_put_cell(net, cell);
66c7e1d3 DH	36	return 0;
	37	}
	38
a58946c1 DH	39	ret = dns_query(net->net, "afsdb", name, len, "srv=1",
a58946c1 DH	40	NULL, NULL, false);
66c7e1d3 DH	41	if (ret == -ENODATA)
	42	ret = -EDESTADDRREQ;
	43	return ret;
	44	}
	45
	46	/*
	47	* Try to auto mount the mountpoint with pseudo directory, if the autocell
	48	* operation is setted.
	49	*/
	50	struct inode afs_try_auto_mntpt(struct dentry dentry, struct inode *dir)
	51	{
	52	struct afs_vnode *vnode = AFS_FS_I(dir);
	53	struct inode *inode;
	54	int ret = -ENOENT;
	55
3b6492df	56	_enter("%p{%pd}, {%llx:%llu}",
66c7e1d3 DH	57	dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
	58
	59	if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
	60	goto out;
	61
	62	ret = afs_probe_cell_name(dentry);
	63	if (ret < 0)
	64	goto out;
	65
	66	inode = afs_iget_pseudo_dir(dir->i_sb, false);
	67	if (IS_ERR(inode)) {
	68	ret = PTR_ERR(inode);
	69	goto out;
	70	}
	71
	72	_leave("= %p", inode);
	73	return inode;
	74
	75	out:
	76	_leave("= %d", ret);
1401a0fc	77	return ret == -ENOENT ? NULL : ERR_PTR(ret);
66c7e1d3 DH	78	}
	79
	80	/*
	81	* Look up @cell in a dynroot directory. This is a substitution for the
	82	* local cell name for the net namespace.
	83	*/
	84	static struct dentry afs_lookup_atcell(struct dentry dentry)
	85	{
	86	struct afs_cell *cell;
	87	struct afs_net *net = afs_d2net(dentry);
	88	struct dentry *ret;
	89	unsigned int seq = 0;
	90	char *name;
	91	int len;
	92
	93	if (!net->ws_cell)
	94	return ERR_PTR(-ENOENT);
	95
	96	ret = ERR_PTR(-ENOMEM);
	97	name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
	98	if (!name)
	99	goto out_p;
	100
	101	rcu_read_lock();
	102	do {
	103	read_seqbegin_or_lock(&net->cells_lock, &seq);
	104	cell = rcu_dereference_raw(net->ws_cell);
	105	if (cell) {
	106	len = cell->name_len;
	107	memcpy(name, cell->name, len + 1);
	108	}
	109	} while (need_seqretry(&net->cells_lock, seq));
	110	done_seqretry(&net->cells_lock, seq);
	111	rcu_read_unlock();
	112
	113	ret = ERR_PTR(-ENOENT);
	114	if (!cell)
	115	goto out_n;
	116
	117	ret = lookup_one_len(name, dentry->d_parent, len);
	118
	119	/* We don't want to d_add() the @cell dentry here as we don't want to
	120	* the cached dentry to hide changes to the local cell name.
	121	*/
	122
	123	out_n:
	124	kfree(name);
	125	out_p:
	126	return ret;
	127	}
	128
	129	/*
	130	* Look up an entry in a dynroot directory.
	131	*/
	132	static struct dentry afs_dynroot_lookup(struct inode dir, struct dentry *dentry,
	133	unsigned int flags)
	134	{
66c7e1d3 DH	135	_enter("%pd", dentry);
	136
	137	ASSERTCMP(d_inode(dentry), ==, NULL);
	138
	139	if (dentry->d_name.len >= AFSNAMEMAX) {
	140	_leave(" = -ENAMETOOLONG");
	141	return ERR_PTR(-ENAMETOOLONG);
	142	}
	143
	144	if (dentry->d_name.len == 5 &&
	145	memcmp(dentry->d_name.name, "@cell", 5) == 0)
	146	return afs_lookup_atcell(dentry);
	147
1401a0fc	148	return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
66c7e1d3 DH	149	}
	150
	151	const struct inode_operations afs_dynroot_inode_operations = {
	152	.lookup = afs_dynroot_lookup,
	153	};
	154
	155	/*
	156	* Dirs in the dynamic root don't need revalidation.
	157	*/
	158	static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
	159	{
	160	return 1;
	161	}
	162
	163	/*
	164	* Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
	165	* sleep)
	166	* - called from dput() when d_count is going to 0.
	167	* - return 1 to request dentry be unhashed, 0 otherwise
	168	*/
	169	static int afs_dynroot_d_delete(const struct dentry *dentry)
	170	{
	171	return d_really_is_positive(dentry);
	172	}
	173
	174	const struct dentry_operations afs_dynroot_dentry_operations = {
	175	.d_revalidate = afs_dynroot_d_revalidate,
	176	.d_delete = afs_dynroot_d_delete,
	177	.d_release = afs_d_release,
	178	.d_automount = afs_d_automount,
	179	};
0da0b7fd DH	180
	181	/*
	182	* Create a manually added cell mount directory.
	183	* - The caller must hold net->proc_cells_lock
	184	*/
	185	int afs_dynroot_mkdir(struct afs_net net, struct afs_cell cell)
	186	{
	187	struct super_block *sb = net->dynroot_sb;
	188	struct dentry root, subdir;
	189	int ret;
	190
	191	if (!sb \|\| atomic_read(&sb->s_active) == 0)
	192	return 0;
	193
	194	/* Let the ->lookup op do the creation */
	195	root = sb->s_root;
	196	inode_lock(root->d_inode);
	197	subdir = lookup_one_len(cell->name, root, cell->name_len);
	198	if (IS_ERR(subdir)) {
	199	ret = PTR_ERR(subdir);
	200	goto unlock;
	201	}
	202
	203	/* Note that we're retaining an extra ref on the dentry */
	204	subdir->d_fsdata = (void *)1UL;
	205	ret = 0;
	206	unlock:
	207	inode_unlock(root->d_inode);
	208	return ret;
	209	}
	210
	211	/*
	212	* Remove a manually added cell mount directory.
	213	* - The caller must hold net->proc_cells_lock
	214	*/
	215	void afs_dynroot_rmdir(struct afs_net net, struct afs_cell cell)
	216	{
	217	struct super_block *sb = net->dynroot_sb;
	218	struct dentry root, subdir;
	219
	220	if (!sb \|\| atomic_read(&sb->s_active) == 0)
	221	return;
	222
	223	root = sb->s_root;
	224	inode_lock(root->d_inode);
	225
	226	/* Don't want to trigger a lookup call, which will re-add the cell */
	227	subdir = try_lookup_one_len(cell->name, root, cell->name_len);
	228	if (IS_ERR_OR_NULL(subdir)) {
	229	_debug("lookup %ld", PTR_ERR(subdir));
	230	goto no_dentry;
	231	}
	232
	233	_debug("rmdir %pd %u", subdir, d_count(subdir));
	234
	235	if (subdir->d_fsdata) {
	236	_debug("unpin %u", d_count(subdir));
	237	subdir->d_fsdata = NULL;
	238	dput(subdir);
	239	}
	240	dput(subdir);
	241	no_dentry:
	242	inode_unlock(root->d_inode);
	243	_leave("");
244	}
245
246	/*
247	* Populate a newly created dynamic root with cell names.
248	*/
249	int afs_dynroot_populate(struct super_block *sb)
250	{
251	struct afs_cell *cell;
252	struct afs_net *net = afs_sb2net(sb);
253	int ret;
254
3b05e528	255	mutex_lock(&net->proc_cells_lock);
0da0b7fd DH	256
0da0b7fd DH	257	net->dynroot_sb = sb;
6b3944e4	258	hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
0da0b7fd DH	259	ret = afs_dynroot_mkdir(net, cell);
	260	if (ret < 0)
	261	goto error;
	262	}
	263
	264	ret = 0;
	265	out:
	266	mutex_unlock(&net->proc_cells_lock);
	267	return ret;
	268
	269	error:
	270	net->dynroot_sb = NULL;
	271	goto out;
	272	}
	273
	274	/*
	275	* When a dynamic root that's in the process of being destroyed, depopulate it
	276	* of pinned directories.
	277	*/
	278	void afs_dynroot_depopulate(struct super_block *sb)
	279	{
	280	struct afs_net *net = afs_sb2net(sb);
	281	struct dentry root = sb->s_root, subdir, *tmp;
	282
	283	/* Prevent more subdirs from being created */
	284	mutex_lock(&net->proc_cells_lock);
	285	if (net->dynroot_sb == sb)
	286	net->dynroot_sb = NULL;
	287	mutex_unlock(&net->proc_cells_lock);
	288
	289	inode_lock(root->d_inode);
	290
	291	/* Remove all the pins for dirs created for manually added cells */
	292	list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
	293	if (subdir->d_fsdata) {
	294	subdir->d_fsdata = NULL;
	295	dput(subdir);
	296	}
	297	}
	298
	299	inode_unlock(root->d_inode);
	300	}