path: root/fs/cifs/dfs_cache.c

// SPDX-License-Identifier: GPL-2.0
/*
 * DFS referral cache routines
 *
 * Copyright (c) 2018-2019 Paulo Alcantara <palcantara@suse.de>
 */

#include <linux/jhash.h>
#include <linux/ktime.h>
#include <linux/slab.h>
#include <linux/proc_fs.h>
#include <linux/nls.h>
#include <linux/workqueue.h>
#include "cifsglob.h"
#include "smb2pdu.h"
#include "smb2proto.h"
#include "cifsproto.h"
#include "cifs_debug.h"
#include "cifs_unicode.h"
#include "smb2glob.h"

#include "dfs_cache.h"

#define CACHE_HTABLE_SIZE 32
#define CACHE_MAX_ENTRIES 64

#define IS_INTERLINK_SET(v) ((v) & (DFSREF_REFERRAL_SERVER | \
				    DFSREF_STORAGE_SERVER))

struct cache_dfs_tgt {
	char *name;
	struct list_head list;
};

struct cache_entry {
	struct hlist_node hlist;
	const char *path;
	int ttl;
	int srvtype;
	int flags;
	struct timespec64 etime;
	int path_consumed;
	int numtgts;
	struct list_head tlist;
	struct cache_dfs_tgt *tgthint;
};

struct vol_info {
	char *fullpath;
	spinlock_t smb_vol_lock;
	struct smb_vol smb_vol;
	char *mntdata;
	struct list_head list;
	struct list_head rlist;
	struct kref refcnt;
};

static struct kmem_cache *cache_slab __read_mostly;
static struct workqueue_struct *dfscache_wq __read_mostly;

static int cache_ttl;
static DEFINE_SPINLOCK(cache_ttl_lock);

static struct nls_table *cache_nlsc;

/*
 * Number of entries in the cache
 */
static atomic_t cache_count;

static struct hlist_head cache_htable[CACHE_HTABLE_SIZE];
static DECLARE_RWSEM(htable_rw_lock);

static LIST_HEAD(vol_list);
static DEFINE_SPINLOCK(vol_list_lock);

static void refresh_cache_worker(struct work_struct *work);

static DECLARE_DELAYED_WORK(refresh_task, refresh_cache_worker);

static int get_normalized_path(const char *path, char **npath)
{
	if (!path || strlen(path) < 3 || (*path != '\\' && *path != '/'))
		return -EINVAL;

	if (*path == '\\') {
		*npath = (char *)path;
	} else {
		*npath = kstrndup(path, strlen(path), GFP_KERNEL);
		if (!*npath)
			return -ENOMEM;
		convert_delimiter(*npath, '\\');
	}
	return 0;
}

static inline void free_normalized_path(const char *path, char *npath)
{
	if (path != npath)
		kfree(npath);
}

static inline bool cache_entry_expired(const struct cache_entry *ce)
{
	struct timespec64 ts;

	ktime_get_coarse_real_ts64(&ts);
	return timespec64_compare(&ts, &ce->etime) >= 0;
}

static inline void free_tgts(struct cache_entry *ce)
{
	struct cache_dfs_tgt *t, *n;

	list_for_each_entry_safe(t, n, &ce->tlist, list) {
		list_del(&t->list);
		kfree(t->name);
		kfree(t);
	}
}

static inline void flush_cache_ent(struct cache_entry *ce)
{
	hlist_del_init(&ce->hlist);
	kfree(ce->path);
	free_tgts(ce);
	atomic_dec(&cache_count);
	kmem_cache_free(cache_slab, ce);
}

static void flush_cache_ents(void)
{
	int i;

	for (i = 0; i < CACHE_HTABLE_SIZE; i++) {
		struct hlist_head *l = &cache_htable[i];
		struct hlist_node *n;
		struct cache_entry *ce;

		hlist_for_each_entry_safe(ce, n, l, hlist) {
			if (!hlist_unhashed(&ce->hlist))
				flush_cache_ent(ce);
		}
	}
}

/*
 * dfs cache /proc file
 */
static int dfscache_proc_show(struct seq_file *m, void *v)
{
	int i;
	struct cache_entry *ce;
	struct cache_dfs_tgt *t;

	seq_puts(m, "DFS cache\n---------\n");

	down_read(&htable_rw_lock);
	for (i = 0; i < CACHE_HTABLE_SIZE; i++) {
		struct hlist_head *l = &cache_htable[i];

		hlist_for_each_entry(ce, l, hlist) {
			if (hlist_unhashed(&ce->hlist))
				continue;

			seq_printf(m,
				   "cache entry: path=%s,type=%s,ttl=%d,etime=%ld,"
				   "interlink=%s,path_consumed=%d,expired=%s\n",
				   ce->path,
				   ce->srvtype == DFS_TYPE_ROOT ? "root" : "link",
				   ce->ttl, ce->etime.tv_nsec,
				   IS_INTERLINK_SET(ce->flags) ? "yes" : "no",
				   ce->path_consumed,
				   cache_entry_expired(ce) ? "yes" : "no");

			list_for_each_entry(t, &ce->tlist, list) {
				seq_printf(m, "  %s%s\n",
					   t->name,
					   ce->tgthint == t ? " (target hint)" : "");
			}
		}
	}
	up_read(&htable_rw_lock);

	return 0;
}

static ssize_t dfscache_proc_write(struct file *file, const char __user *buffer,
				   size_t count, loff_t *ppos)
{
	char c;
	int rc;

	rc = get_user(c, buffer);
	if (rc)
		return rc;

	if (c != '0')
		return -EINVAL;

	cifs_dbg(FYI, "clearing dfs cache\n");

	down_write(&htable_rw_lock);
	flush_cache_ents();
	up_write(&htable_rw_lock);

	return count;
}

static int dfscache_proc_open(struct inode *inode, struct file *file)
{
	return single_open(file, dfscache_proc_show, NULL);
}

const struct proc_ops dfscache_proc_ops = {
	.proc_open	= dfscache_proc_open,
	.proc_read	= seq_read,
	.proc_lseek	= seq_lseek,
	.proc_release	= single_release,
	.proc_write	= dfscache_proc_write,
};

#ifdef CONFIG_CIFS_DEBUG2
static inline void dump_tgts(const struct cache_entry *ce)
{
	struct cache_dfs_tgt *t;

	cifs_dbg(FYI, "target list:\n");
	list_for_each_entry(t, &ce->tlist, list) {
		cifs_dbg(FYI, "  %s%s\n", t->name,
			 ce->tgthint == t ? " (target hint)" : "");
	}
}

static inline void dump_ce(const struct cache_entry *ce)
{
	cifs_dbg(FYI, "cache entry: path=%s,type=%s,ttl=%d,etime=%ld,interlink=%s,path_consumed=%d,expired=%s\n",
		 ce->path,
		 ce->srvtype == DFS_TYPE_ROOT ? "root" : "link", ce->ttl,
		 ce->etime.tv_nsec,
		 IS_INTERLINK_SET(ce->flags) ? "yes" : "no",
		 ce->path_consumed,
		 cache_entry_expired(ce) ? "yes" : "no");
	dump_tgts(ce);
}

static inline void dump_refs(const struct dfs_info3_param *refs, int numrefs)
{
	int i;

	cifs_dbg(FYI, "DFS referrals returned by the server:\n");
	for (i = 0; i < numrefs; i++) {
		const struct dfs_info3_param *ref = &refs[i];

		cifs_dbg(FYI,
			 "\n"
			 "flags:         0x%x\n"
			 "path_consumed: %d\n"
			 "server_type:   0x%x\n"
			 "ref_flag:      0x%x\n"