afs: Fix rapid cell addition/removal by not using RCU on cells tree

[people/ms/linux.git] / fs / afs / proc.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* /proc interface for AFS
 *
 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/slab.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/sched.h>
#include <linux/uaccess.h>
#include "internal.h"

struct afs_vl_seq_net_private {
	struct seq_net_private		seq;	/* Must be first */
	struct afs_vlserver_list	*vllist;
};

static inline struct afs_net *afs_seq2net(struct seq_file *m)
{
	return afs_net(seq_file_net(m));
}

static inline struct afs_net *afs_seq2net_single(struct seq_file *m)
{
	return afs_net(seq_file_single_net(m));
}

/*
 * Display the list of cells known to the namespace.
 */
static int afs_proc_cells_show(struct seq_file *m, void *v)
{
	struct afs_vlserver_list *vllist;
	struct afs_cell *cell;

	if (v == SEQ_START_TOKEN) {
		/* display header on line 1 */
		seq_puts(m, "USE    TTL SV ST NAME\n");
		return 0;
	}

	cell = list_entry(v, struct afs_cell, proc_link);
	vllist = rcu_dereference(cell->vl_servers);

	/* display one cell per line on subsequent lines */
	seq_printf(m, "%3u %6lld %2u %2u %s\n",
		   atomic_read(&cell->usage),
		   cell->dns_expiry - ktime_get_real_seconds(),
		   vllist->nr_servers,
		   cell->state,
		   cell->name);
	return 0;
}

static void *afs_proc_cells_start(struct seq_file *m, loff_t *_pos)
	__acquires(rcu)
{
	rcu_read_lock();
	return seq_hlist_start_head_rcu(&afs_seq2net(m)->proc_cells, *_pos);
}

static void *afs_proc_cells_next(struct seq_file *m, void *v, loff_t *pos)
{
	return seq_hlist_next_rcu(v, &afs_seq2net(m)->proc_cells, pos);
}

static void afs_proc_cells_stop(struct seq_file *m, void *v)
	__releases(rcu)
{
	rcu_read_unlock();
}

static const struct seq_operations afs_proc_cells_ops = {
	.start	= afs_proc_cells_start,
	.next	= afs_proc_cells_next,
	.stop	= afs_proc_cells_stop,
	.show	= afs_proc_cells_show,
};

/*
 * handle writes to /proc/fs/afs/cells
 * - to add cells: echo "add <cellname> <IP>[:<IP>][:<IP>]"
 */
static int afs_proc_cells_write(struct file *file, char *buf, size_t size)
{
	struct seq_file *m = file->private_data;
	struct afs_net *net = afs_seq2net(m);
	char *name, *args;
	int ret;

	/* trim to first NL */
	name = memchr(buf, '\n', size);
	if (name)
		*name = 0;

	/* split into command, name and argslist */
	name = strchr(buf, ' ');
	if (!name)
		goto inval;
	do {
		*name++ = 0;
	} while(*name == ' ');
	if (!*name)
		goto inval;

	args = strchr(name, ' ');
	if (args) {
		do {
			*args++ = 0;
		} while(*args == ' ');
		if (!*args)
			goto inval;
	}

	/* determine command to perform */
	_debug("cmd=%s name=%s args=%s", buf, name, args);

	if (strcmp(buf, "add") == 0) {
		struct afs_cell *cell;

		cell = afs_lookup_cell(net, name, strlen(name), args, true);
		if (IS_ERR(cell)) {
			ret = PTR_ERR(cell);
			goto done;
		}

		if (test_and_set_bit(AFS_CELL_FL_NO_GC, &cell->flags))
			afs_put_cell(net, cell);
	} else {
		goto inval;
	}

	ret = 0;

done:
	_leave(" = %d", ret);
	return ret;

inval:
	ret = -EINVAL;
	printk("kAFS: Invalid Command on /proc/fs/afs/cells file\n");
	goto done;
}

/*
 * Display the name of the current workstation cell.
 */
static int afs_proc_rootcell_show(struct seq_file *m, void *v)
{
	struct afs_cell *cell;
	struct afs_net *net;

	net = afs_seq2net_single(m);
	if (rcu_access_pointer(net->ws_cell)) {
		rcu_read_lock();
		cell = rcu_dereference(net->ws_cell);
		if (cell)
			seq_printf(m, "%s\n", cell->name);
		rcu_read_unlock();
	}
	return 0;
}

/*
 * Set the current workstation cell and optionally supply its list of volume
 * location servers.
 *
 *	echo "cell.name:192.168.231.14" >/proc/fs/afs/rootcell
 */
static int afs_proc_rootcell_write(struct file *file, char *buf, size_t size)
{
	struct seq_file *m = file->private_data;
	struct afs_net *net = afs_seq2net_single(m);
	char *s;
	int ret;

	ret = -EINVAL;
	if (buf[0] == '.')
		goto out;
	if (memchr(buf, '/', size))
		goto out;

	/* trim to first NL */
	s = memchr(buf, '\n', size);
	if (s)
		*s = 0;

	/* determine command to perform */
	_debug("rootcell=%s", buf);

	ret = afs_cell_init(net, buf);

out:
	_leave(" = %d", ret);
	return ret;
}

static const char afs_vol_types[3][3] = {
	[AFSVL_RWVOL]	= "RW",
	[AFSVL_ROVOL]	= "RO",
	[AFSVL_BACKVOL]	= "BK",
};

/*
 * Display the list of volumes known to a cell.
 */
static int afs_proc_cell_volumes_show(struct seq_file *m, void *v)
{
	struct afs_volume *vol = hlist_entry(v, struct afs_volume, proc_link);

	/* Display header on line 1 */
	if (v == SEQ_START_TOKEN) {
		seq_puts(m, "USE VID      TY NAME\n");
		return 0;
	}

	seq_printf(m, "%3d %08llx %s %s\n",
		   atomic_read(&vol->usage), vol->vid,
		   afs_vol_types[vol->type],
		   vol->name);

	return 0;
}

static void *afs_proc_cell_volumes_start(struct seq_file *m, loff_t *_pos)
	__acquires(cell->proc_lock)
{
	struct afs_cell *cell = PDE_DATA(file_inode(m->file));

	rcu_read_lock();
	return seq_hlist_start_head_rcu(&cell->proc_volumes, *_pos);
}

static void *afs_proc_cell_volumes_next(struct seq_file *m, void *v,
					loff_t *_pos)
{
	struct afs_cell *cell = PDE_DATA(file_inode(m->file));

	return seq_hlist_next_rcu(v, &cell->proc_volumes, _pos);
}

static void afs_proc_cell_volumes_stop(struct seq_file *m, void *v)
	__releases(cell->proc_lock)
{
	rcu_read_unlock();
}

static const struct seq_operations afs_proc_cell_volumes_ops = {
	.start	= afs_proc_cell_volumes_start,
	.next	= afs_proc_cell_volumes_next,
	.stop	= afs_proc_cell_volumes_stop,
	.show	= afs_proc_cell_volumes_show,
};

static const char *const dns_record_sources[NR__dns_record_source + 1] = {
	[DNS_RECORD_UNAVAILABLE]	= "unav",
	[DNS_RECORD_FROM_CONFIG]	= "cfg",
	[DNS_RECORD_FROM_DNS_A]		= "A",
	[DNS_RECORD_FROM_DNS_AFSDB]	= "AFSDB",
	[DNS_RECORD_FROM_DNS_SRV]	= "SRV",
	[DNS_RECORD_FROM_NSS]		= "nss",
	[NR__dns_record_source]		= "[weird]"
};

static const char *const dns_lookup_statuses[NR__dns_lookup_status + 1] = {
	[DNS_LOOKUP_NOT_DONE]		= "no-lookup",
	[DNS_LOOKUP_GOOD]		= "good",
	[DNS_LOOKUP_GOOD_WITH_BAD]	= "good/bad",
	[DNS_LOOKUP_BAD]		= "bad",
	[DNS_LOOKUP_GOT_NOT_FOUND]	= "not-found",
	[DNS_LOOKUP_GOT_LOCAL_FAILURE]	= "local-failure",
	[DNS_LOOKUP_GOT_TEMP_FAILURE]	= "temp-failure",
	[DNS_LOOKUP_GOT_NS_FAILURE]	= "ns-failure",
	[NR__dns_lookup_status]		= "[weird]"
};

/*
 * Display the list of Volume Location servers we're using for a cell.
 */
static int afs_proc_cell_vlservers_show(struct seq_file *m, void *v)
{
	const struct afs_vl_seq_net_private *priv = m->private;
	const struct afs_vlserver_list *vllist = priv->vllist;
	const struct afs_vlserver_entry *entry;
	const struct afs_vlserver *vlserver;
	const struct afs_addr_list *alist;
	int i;

	if (v == SEQ_START_TOKEN) {
		seq_printf(m, "# source %s, status %s\n",
			   dns_record_sources[vllist ? vllist->source : 0],
			   dns_lookup_statuses[vllist ? vllist->status : 0]);
		return 0;
	}

	entry = v;
	vlserver = entry->server;
	alist = rcu_dereference(vlserver->addresses);

	seq_printf(m, "%s [p=%hu w=%hu s=%s,%s]:\n",
		   vlserver->name, entry->priority, entry->weight,
		   dns_record_sources[alist ? alist->source : entry->source],
		   dns_lookup_statuses[alist ? alist->status : entry->status]);
	if (alist) {
		for (i = 0; i < alist->nr_addrs; i++)
			seq_printf(m, " %c %pISpc\n",
				   alist->preferred == i ? '>' : '-',
				   &alist->addrs[i].transport);
	}
	seq_printf(m, " info: fl=%lx rtt=%d\n", vlserver->flags, vlserver->rtt);
	seq_printf(m, " probe: fl=%x e=%d ac=%d out=%d\n",
		   vlserver->probe.flags, vlserver->probe.error,
		   vlserver->probe.abort_code,
		   atomic_read(&vlserver->probe_outstanding));
	return 0;
}

static void *afs_proc_cell_vlservers_start(struct seq_file *m, loff_t *_pos)
	__acquires(rcu)
{
	struct afs_vl_seq_net_private *priv = m->private;
	struct afs_vlserver_list *vllist;
	struct afs_cell *cell = PDE_DATA(file_inode(m->file));
	loff_t pos = *_pos;

	rcu_read_lock();

	vllist = rcu_dereference(cell->vl_servers);
	priv->vllist = vllist;

	if (pos < 0)
		*_pos = pos = 0;
	if (pos == 0)
		return SEQ_START_TOKEN;

	if (pos - 1 >= vllist->nr_servers)
		return NULL;

	return &vllist->servers[pos - 1];
}

static void *afs_proc_cell_vlservers_next(struct seq_file *m, void *v,
					  loff_t *_pos)
{
	struct afs_vl_seq_net_private *priv = m->private;
	struct afs_vlserver_list *vllist = priv->vllist;
	loff_t pos;

	pos = *_pos;
	pos++;
	*_pos = pos;
	if (!vllist || pos - 1 >= vllist->nr_servers)
		return NULL;

	return &vllist->servers[pos - 1];
}

static void afs_proc_cell_vlservers_stop(struct seq_file *m, void *v)
	__releases(rcu)
{
	rcu_read_unlock();
}

static const struct seq_operations afs_proc_cell_vlservers_ops = {
	.start	= afs_proc_cell_vlservers_start,
	.next	= afs_proc_cell_vlservers_next,
	.stop	= afs_proc_cell_vlservers_stop,
	.show	= afs_proc_cell_vlservers_show,
};

/*
 * Display the list of fileservers we're using within a namespace.
 */
static int afs_proc_servers_show(struct seq_file *m, void *v)
{
	struct afs_server *server;
	struct afs_addr_list *alist;
	int i;

	if (v == SEQ_START_TOKEN) {
		seq_puts(m, "UUID                                 REF ACT\n");
		return 0;
	}

	server = list_entry(v, struct afs_server, proc_link);
	alist = rcu_dereference(server->addresses);
	seq_printf(m, "%pU %3d %3d\n",
		   &server->uuid,
		   atomic_read(&server->ref),
		   atomic_read(&server->active));
	seq_printf(m, "  - info: fl=%lx rtt=%u brk=%x\n",
		   server->flags, server->rtt, server->cb_s_break);
	seq_printf(m, "  - probe: last=%d out=%d\n",
		   (int)(jiffies - server->probed_at) / HZ,
		   atomic_read(&server->probe_outstanding));
	seq_printf(m, "  - ALIST v=%u rsp=%lx f=%lx\n",
		   alist->version, alist->responded, alist->failed);
	for (i = 0; i < alist->nr_addrs; i++)
		seq_printf(m, "    [%x] %pISpc%s\n",
			   i, &alist->addrs[i].transport,
			   alist->preferred == i ? "*" : "");
	return 0;
}

static void *afs_proc_servers_start(struct seq_file *m, loff_t *_pos)
	__acquires(rcu)
{
	rcu_read_lock();
	return seq_hlist_start_head_rcu(&afs_seq2net(m)->fs_proc, *_pos);
}

static void *afs_proc_servers_next(struct seq_file *m, void *v, loff_t *_pos)
{
	return seq_hlist_next_rcu(v, &afs_seq2net(m)->fs_proc, _pos);
}

static void afs_proc_servers_stop(struct seq_file *m, void *v)
	__releases(rcu)
{
	rcu_read_unlock();
}

static const struct seq_operations afs_proc_servers_ops = {
	.start	= afs_proc_servers_start,
	.next	= afs_proc_servers_next,
	.stop	= afs_proc_servers_stop,
	.show	= afs_proc_servers_show,
};

/*
 * Display the list of strings that may be substituted for the @sys pathname
 * macro.
 */
static int afs_proc_sysname_show(struct seq_file *m, void *v)
{
	struct afs_net *net = afs_seq2net(m);
	struct afs_sysnames *sysnames = net->sysnames;
	unsigned int i = (unsigned long)v - 1;

	if (i < sysnames->nr)
		seq_printf(m, "%s\n", sysnames->subs[i]);
	return 0;
}

static void *afs_proc_sysname_start(struct seq_file *m, loff_t *pos)
	__acquires(&net->sysnames_lock)
{
	struct afs_net *net = afs_seq2net(m);
	struct afs_sysnames *names;

	read_lock(&net->sysnames_lock);

	names = net->sysnames;
	if (*pos >= names->nr)
		return NULL;
	return (void *)(unsigned long)(*pos + 1);
}

static void *afs_proc_sysname_next(struct seq_file *m, void *v, loff_t *pos)
{
	struct afs_net *net = afs_seq2net(m);
	struct afs_sysnames *names = net->sysnames;

	*pos += 1;
	if (*pos >= names->nr)
		return NULL;
	return (void *)(unsigned long)(*pos + 1);
}

static void afs_proc_sysname_stop(struct seq_file *m, void *v)
	__releases(&net->sysnames_lock)
{
	struct afs_net *net = afs_seq2net(m);

	read_unlock(&net->sysnames_lock);
}

static const struct seq_operations afs_proc_sysname_ops = {
	.start	= afs_proc_sysname_start,
	.next	= afs_proc_sysname_next,
	.stop	= afs_proc_sysname_stop,
	.show	= afs_proc_sysname_show,
};

/*
 * Allow the @sys substitution to be configured.
 */
static int afs_proc_sysname_write(struct file *file, char *buf, size_t size)
{
	struct afs_sysnames *sysnames, *kill;
	struct seq_file *m = file->private_data;
	struct afs_net *net = afs_seq2net(m);
	char *s, *p, *sub;
	int ret, len;

	sysnames = kzalloc(sizeof(*sysnames), GFP_KERNEL);
	if (!sysnames)
		return -ENOMEM;
	refcount_set(&sysnames->usage, 1);
	kill = sysnames;

	p = buf;
	while ((s = strsep(&p, " \t\n"))) {
		len = strlen(s);
		if (len == 0)
			continue;
		ret = -ENAMETOOLONG;
		if (len >= AFSNAMEMAX)
			goto error;

		if (len >= 4 &&
		    s[len - 4] == '@' &&
		    s[len - 3] == 's' &&
		    s[len - 2] == 'y' &&
		    s[len - 1] == 's')
			/* Protect against recursion */
			goto invalid;

		if (s[0] == '.' &&
		    (len < 2 || (len == 2 && s[1] == '.')))
			goto invalid;

		if (memchr(s, '/', len))
			goto invalid;

		ret = -EFBIG;
		if (sysnames->nr >= AFS_NR_SYSNAME)
			goto out;

		if (strcmp(s, afs_init_sysname) == 0) {
			sub = (char *)afs_init_sysname;
		} else {
			ret = -ENOMEM;
			sub = kmemdup(s, len + 1, GFP_KERNEL);
			if (!sub)
				goto out;
		}

		sysnames->subs[sysnames->nr] = sub;
		sysnames->nr++;
	}

	if (sysnames->nr == 0) {
		sysnames->subs[0] = sysnames->blank;
		sysnames->nr++;
	}

	write_lock(&net->sysnames_lock);
	kill = net->sysnames;
	net->sysnames = sysnames;
	write_unlock(&net->sysnames_lock);
	ret = 0;
out:
	afs_put_sysnames(kill);
	return ret;

invalid:
	ret = -EINVAL;
error:
	goto out;
}

void afs_put_sysnames(struct afs_sysnames *sysnames)
{
	int i;

	if (sysnames && refcount_dec_and_test(&sysnames->usage)) {
		for (i = 0; i < sysnames->nr; i++)
			if (sysnames->subs[i] != afs_init_sysname &&
			    sysnames->subs[i] != sysnames->blank)
				kfree(sysnames->subs[i]);
		kfree(sysnames);
	}
}

/*
 * Display general per-net namespace statistics
 */
static int afs_proc_stats_show(struct seq_file *m, void *v)
{
	struct afs_net *net = afs_seq2net_single(m);

	seq_puts(m, "kAFS statistics\n");

	seq_printf(m, "dir-mgmt: look=%u reval=%u inval=%u relpg=%u\n",
		   atomic_read(&net->n_lookup),
		   atomic_read(&net->n_reval),
		   atomic_read(&net->n_inval),
		   atomic_read(&net->n_relpg));

	seq_printf(m, "dir-data: rdpg=%u\n",
		   atomic_read(&net->n_read_dir));

	seq_printf(m, "dir-edit: cr=%u rm=%u\n",
		   atomic_read(&net->n_dir_cr),
		   atomic_read(&net->n_dir_rm));

	seq_printf(m, "file-rd : n=%u nb=%lu\n",
		   atomic_read(&net->n_fetches),
		   atomic_long_read(&net->n_fetch_bytes));
	seq_printf(m, "file-wr : n=%u nb=%lu\n",
		   atomic_read(&net->n_stores),
		   atomic_long_read(&net->n_store_bytes));
	return 0;
}

/*
 * initialise /proc/fs/afs/<cell>/
 */
int afs_proc_cell_setup(struct afs_cell *cell)
{
	struct proc_dir_entry *dir;
	struct afs_net *net = cell->net;

	_enter("%p{%s},%p", cell, cell->name, net->proc_afs);

	dir = proc_net_mkdir(net->net, cell->name, net->proc_afs);
	if (!dir)
		goto error_dir;

	if (!proc_create_net_data("vlservers", 0444, dir,
				  &afs_proc_cell_vlservers_ops,
				  sizeof(struct afs_vl_seq_net_private),
				  cell) ||
	    !proc_create_net_data("volumes", 0444, dir,
				  &afs_proc_cell_volumes_ops,
				  sizeof(struct seq_net_private),
				  cell))
		goto error_tree;

	_leave(" = 0");
	return 0;

error_tree:
	remove_proc_subtree(cell->name, net->proc_afs);
error_dir:
	_leave(" = -ENOMEM");
	return -ENOMEM;
}

/*
 * remove /proc/fs/afs/<cell>/
 */
void afs_proc_cell_remove(struct afs_cell *cell)
{
	struct afs_net *net = cell->net;

	_enter("");
	remove_proc_subtree(cell->name, net->proc_afs);
	_leave("");
}

/*
 * initialise the /proc/fs/afs/ directory
 */
int afs_proc_init(struct afs_net *net)
{
	struct proc_dir_entry *p;

	_enter("");

	p = proc_net_mkdir(net->net, "afs", net->net->proc_net);
	if (!p)
		goto error_dir;

	if (!proc_create_net_data_write("cells", 0644, p,
					&afs_proc_cells_ops,
					afs_proc_cells_write,
					sizeof(struct seq_net_private),
					NULL) ||
	    !proc_create_net_single_write("rootcell", 0644, p,
					  afs_proc_rootcell_show,
					  afs_proc_rootcell_write,
					  NULL) ||
	    !proc_create_net("servers", 0444, p, &afs_proc_servers_ops,
			     sizeof(struct seq_net_private)) ||
	    !proc_create_net_single("stats", 0444, p, afs_proc_stats_show, NULL) ||
	    !proc_create_net_data_write("sysname", 0644, p,
					&afs_proc_sysname_ops,
					afs_proc_sysname_write,
					sizeof(struct seq_net_private),
					NULL))
		goto error_tree;

	net->proc_afs = p;
	_leave(" = 0");
	return 0;

error_tree:
	proc_remove(p);
error_dir:
	_leave(" = -ENOMEM");
	return -ENOMEM;
}

/*
 * clean up the /proc/fs/afs/ directory
 */
void afs_proc_cleanup(struct afs_net *net)
{
	proc_remove(net->proc_afs);
	net->proc_afs = NULL;
}