cifs: fix use-after-free bug in refresh_cache_worker()

The UAF bug occurred because we were putting DFS root sessions in
cifs_umount() while DFS cache refresher was being executed.

Make DFS root sessions have same lifetime as DFS tcons so we can avoid
the use-after-free bug is DFS cache refresher and other places that
require IPCs to get new DFS referrals on.  Also, get rid of mount
group handling in DFS cache as we no longer need it.

This fixes below use-after-free bug catched by KASAN

[ 379.946955] BUG: KASAN: use-after-free in __refresh_tcon.isra.0+0x10b/0xc10 [cifs]
[ 379.947642] Read of size 8 at addr ffff888018f57030 by task kworker/u4:3/56
[ 379.948096]
[ 379.948208] CPU: 0 PID: 56 Comm: kworker/u4:3 Not tainted 6.2.0-rc7-lku #23
[ 379.948661] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
rel-1.16.0-0-gd239552-rebuilt.opensuse.org 04/01/2014
[ 379.949368] Workqueue: cifs-dfscache refresh_cache_worker [cifs]
[ 379.949942] Call Trace:
[ 379.950113] <TASK>
[ 379.950260] dump_stack_lvl+0x50/0x67
[ 379.950510] print_report+0x16a/0x48e
[ 379.950759] ? __virt_addr_valid+0xd8/0x160
[ 379.951040] ? __phys_addr+0x41/0x80
[ 379.951285] kasan_report+0xdb/0x110
[ 379.951533] ? __refresh_tcon.isra.0+0x10b/0xc10 [cifs]
[ 379.952056] ? __refresh_tcon.isra.0+0x10b/0xc10 [cifs]
[ 379.952585] __refresh_tcon.isra.0+0x10b/0xc10 [cifs]
[ 379.953096] ? __pfx___refresh_tcon.isra.0+0x10/0x10 [cifs]
[ 379.953637] ? __pfx___mutex_lock+0x10/0x10
[ 379.953915] ? lock_release+0xb6/0x720
[ 379.954167] ? __pfx_lock_acquire+0x10/0x10
[ 379.954443] ? refresh_cache_worker+0x34e/0x6d0 [cifs]
[ 379.954960] ? __pfx_wb_workfn+0x10/0x10
[ 379.955239] refresh_cache_worker+0x4ad/0x6d0 [cifs]
[ 379.955755] ? __pfx_refresh_cache_worker+0x10/0x10 [cifs]
[ 379.956323] ? __pfx_lock_acquired+0x10/0x10
[ 379.956615] ? read_word_at_a_time+0xe/0x20
[ 379.956898] ? lockdep_hardirqs_on_prepare+0x12/0x220
[ 379.957235] process_one_work+0x535/0x990
[ 379.957509] ? __pfx_process_one_work+0x10/0x10
[ 379.957812] ? lock_acquired+0xb7/0x5f0
[ 379.958069] ? __list_add_valid+0x37/0xd0
[ 379.958341] ? __list_add_valid+0x37/0xd0
[ 379.958611] worker_thread+0x8e/0x630
[ 379.958861] ? __pfx_worker_thread+0x10/0x10
[ 379.959148] kthread+0x17d/0x1b0
[ 379.959369] ? __pfx_kthread+0x10/0x10
[ 379.959630] ret_from_fork+0x2c/0x50
[ 379.959879] </TASK>

Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Cc: stable@vger.kernel.org # 6.2
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 0 insertions, 140 deletions

diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
index ac86bd0ebd63..1c59811bfa73 100644
--- a/fs/cifs/dfs_cache.c
+++ b/fs/cifs/dfs_cache.c
@@ -49,17 +49,6 @@ struct cache_entry {
 	struct cache_dfs_tgt *tgthint;
 };
 
-/* List of referral server sessions per dfs mount */
-struct mount_group {
-	struct list_head list;
-	uuid_t id;
-	struct cifs_ses *sessions[CACHE_MAX_ENTRIES];
-	int num_sessions;
-	spinlock_t lock;
-	struct list_head refresh_list;
-	struct kref refcount;
-};
-
 static struct kmem_cache *cache_slab __read_mostly;
 static struct workqueue_struct *dfscache_wq __read_mostly;
 
@@ -76,85 +65,10 @@ static atomic_t cache_count;
 static struct hlist_head cache_htable[CACHE_HTABLE_SIZE];
 static DECLARE_RWSEM(htable_rw_lock);
 
-static LIST_HEAD(mount_group_list);
-static DEFINE_MUTEX(mount_group_list_lock);
-
 static void refresh_cache_worker(struct work_struct *work);
 
 static DECLARE_DELAYED_WORK(refresh_task, refresh_cache_worker);
 
-static void __mount_group_release(struct mount_group *mg)
-{
-	int i;
-
-	for (i = 0; i < mg->num_sessions; i++)
-		cifs_put_smb_ses(mg->sessions[i]);
-	kfree(mg);
-}
-
-static void mount_group_release(struct kref *kref)
-{
-	struct mount_group *mg = container_of(kref, struct mount_group, refcount);
-
-	mutex_lock(&mount_group_list_lock);
-	list_del(&mg->list);
-	mutex_unlock(&mount_group_list_lock);
-	__mount_group_release(mg);
-}
-
-static struct mount_group *find_mount_group_locked(const uuid_t *id)
-{
-	struct mount_group *mg;
-
-	list_for_each_entry(mg, &mount_group_list, list) {
-		if (uuid_equal(&mg->id, id))
-			return mg;
-	}
-	return ERR_PTR(-ENOENT);
-}
-
-static struct mount_group *__get_mount_group_locked(const uuid_t *id)
-{
-	struct mount_group *mg;
-
-	mg = find_mount_group_locked(id);
-	if (!IS_ERR(mg))
-		return mg;
-
-	mg = kmalloc(sizeof(*mg), GFP_KERNEL);
-	if (!mg)
-		return ERR_PTR(-ENOMEM);
-	kref_init(&mg->refcount);
-	uuid_copy(&mg->id, id);
-	mg->num_sessions = 0;
-	spin_lock_init(&mg->lock);
-	list_add(&mg->list, &mount_group_list);
-	return mg;
-}
-
-static struct mount_group *get_mount_group(const uuid_t *id)
-{
-	struct mount_group *mg;
-
-	mutex_lock(&mount_group_list_lock);
-	mg = __get_mount_group_locked(id);
-	if (!IS_ERR(mg))
-		kref_get(&mg->refcount);
-	mutex_unlock(&mount_group_list_lock);
-
-	return mg;
-}
-
-static void free_mount_group_list(void)
-{
-	struct mount_group *mg, *tmp_mg;
-
-	list_for_each_entry_safe(mg, tmp_mg, &mount_group_list, list) {
-		list_del_init(&mg->list);
-		__mount_group_release(mg);
-	}
-}
-
 /**
  * dfs_cache_canonical_path - get a canonical DFS path
  *
@@ -704,7 +618,6 @@ void dfs_cache_destroy(void)
 {
 	cancel_delayed_work_sync(&refresh_task);
 	unload_nls(cache_cp);
-	free_mount_group_list();
 	flush_cache_ents();
 	kmem_cache_destroy(cache_slab);
 	destroy_workqueue(dfscache_wq);
@@ -1111,54 +1024,6 @@ out_unlock:
 	return rc;
 }
 
-/**
- * dfs_cache_add_refsrv_session - add SMB session of referral server
- *
- * @mount_id: mount group uuid to lookup.
- * @ses: reference counted SMB session of referral server.
- */
-void dfs_cache_add_refsrv_session(const uuid_t *mount_id, struct cifs_ses *ses)
-{
-	struct mount_group *mg;
-
-	if (WARN_ON_ONCE(!mount_id || uuid_is_null(mount_id) || !ses))
-		return;
-
-	mg = get_mount_group(mount_id);
-	if (WARN_ON_ONCE(IS_ERR(mg)))
-		return;
-
-	spin_lock(&mg->lock);
-	if (mg->num_sessions < ARRAY_SIZE(mg->sessions))
-		mg->sessions[mg->num_sessions++] = ses;
-	spin_unlock(&mg->lock);
-	kref_put(&mg->refcount, mount_group_release);
-}
-
-/**
- * dfs_cache_put_refsrv_sessions - put all referral server sessions
- *
- * Put all SMB sessions from the given mount group id.
- *
- * @mount_id: mount group uuid to lookup.
- */
-void dfs_cache_put_refsrv_sessions(const uuid_t *mount_id)
-{
-	struct mount_group *mg;
-
-	if (!mount_id || uuid_is_null(mount_id))
-		return;
-
-	mutex_lock(&mount_group_list_lock);
-	mg = find_mount_group_locked(mount_id);
-	if (IS_ERR(mg)) {
-		mutex_unlock(&mount_group_list_lock);
-		return;
-	}
-	mutex_unlock(&mount_group_list_lock);
-	kref_put(&mg->refcount, mount_group_release);
-}
-
 /* Extract share from DFS target and return a pointer to prefix path or NULL */
 static const char *parse_target_share(const char *target, char **share)
 {
@@ -1384,11 +1249,6 @@ int dfs_cache_remount_fs(struct cifs_sb_info *cifs_sb)
 		cifs_dbg(FYI, "%s: not a dfs mount\n", __func__);
 		return 0;
 	}
-
-	if (uuid_is_null(&cifs_sb->dfs_mount_id)) {
-		cifs_dbg(FYI, "%s: no dfs mount group id\n", __func__);
-		return -EINVAL;
-	}
 	/*
 	 * After reconnecting to a different server, unique ids won't match anymore, so we disable
 	 * serverino. This prevents dentry revalidation to think the dentry are stale (ESTALE).