[2/4] cifs: fix use-after-free bug in refresh_cache_worker()

diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
index 013a4bd65280..651759192280 100644
--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -61,8 +61,6 @@  struct cifs_sb_info {
 	/* only used when CIFS_MOUNT_USE_PREFIX_PATH is set */
 	char *prepath;
 
-	/* randomly generated 128-bit number for indexing dfs mount groups in referral cache */
-	uuid_t dfs_mount_id;
 	/*
 	 * Indicate whether serverino option was turned off later
 	 * (cifs_autodisable_serverino) in order to match new mounts.
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index a6f3e03e5790..9da301d18491 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1233,6 +1233,7 @@  struct cifs_tcon {
 	/* BB add field for back pointer to sb struct(s)? */
 #ifdef CONFIG_CIFS_DFS_UPCALL
 	struct list_head ulist; /* cache update list */
+	struct list_head dfs_ses_list;
 #endif
 	struct delayed_work	query_interfaces; /* query interfaces workqueue job */
 };
@@ -1749,8 +1750,8 @@  struct cifs_mount_ctx {
 	struct TCP_Server_Info *server;
 	struct cifs_ses *ses;
 	struct cifs_tcon *tcon;
-	uuid_t mount_id;
 	char *origin_fullpath, *leaf_fullpath;
+	struct list_head dfs_ses_list;
 };
 
 static inline void free_dfs_info_param(struct dfs_info3_param *param)
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 5038dcd045b9..a356c8c2fae0 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3408,7 +3408,8 @@  int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx)
 	bool isdfs;
 	int rc;
 
-	uuid_gen(&mnt_ctx.mount_id);
+	INIT_LIST_HEAD(&mnt_ctx.dfs_ses_list);
+
 	rc = dfs_mount_share(&mnt_ctx, &isdfs);
 	if (rc)
 		goto error;
@@ -3428,7 +3429,6 @@  int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx)
 	kfree(cifs_sb->prepath);
 	cifs_sb->prepath = ctx->prepath;
 	ctx->prepath = NULL;
-	uuid_copy(&cifs_sb->dfs_mount_id, &mnt_ctx.mount_id);
 
 out:
 	cifs_try_adding_channels(cifs_sb, mnt_ctx.ses);
@@ -3440,7 +3440,7 @@  int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx)
 	return rc;
 
 error:
-	dfs_cache_put_refsrv_sessions(&mnt_ctx.mount_id);
+	dfs_put_root_smb_sessions(&mnt_ctx.dfs_ses_list);
 	kfree(mnt_ctx.origin_fullpath);
 	kfree(mnt_ctx.leaf_fullpath);
 	cifs_mount_put_conns(&mnt_ctx);
@@ -3638,9 +3638,6 @@  cifs_umount(struct cifs_sb_info *cifs_sb)
 	spin_unlock(&cifs_sb->tlink_tree_lock);
 
 	kfree(cifs_sb->prepath);
-#ifdef CONFIG_CIFS_DFS_UPCALL
-	dfs_cache_put_refsrv_sessions(&cifs_sb->dfs_mount_id);
-#endif
 	call_rcu(&cifs_sb->rcu, delayed_free);
 }
 
diff --git a/fs/cifs/dfs.c b/fs/cifs/dfs.c
index eb35259b48fa..fc86de9ebea7 100644
--- a/fs/cifs/dfs.c
+++ b/fs/cifs/dfs.c
@@ -99,18 +99,27 @@  static int get_session(struct cifs_mount_ctx *mnt_ctx, const char *full_path)
 	return rc;
 }
 
-static void set_root_ses(struct cifs_mount_ctx *mnt_ctx)
+static int get_root_smb_session(struct cifs_mount_ctx *mnt_ctx)
 {
 	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+	struct dfs_root_ses *root_ses;
 	struct cifs_ses *ses = mnt_ctx->ses;
 
 	if (ses) {
+		root_ses = kmalloc(sizeof(*root_ses), GFP_KERNEL);
+		if (!root_ses)
+			return -ENOMEM;
+
+		INIT_LIST_HEAD(&root_ses->list);
+
 		spin_lock(&cifs_tcp_ses_lock);
 		ses->ses_count++;
 		spin_unlock(&cifs_tcp_ses_lock);
-		dfs_cache_add_refsrv_session(&mnt_ctx->mount_id, ses);
+		root_ses->ses = ses;
+		list_add_tail(&root_ses->list, &mnt_ctx->dfs_ses_list);
 	}
-	ctx->dfs_root_ses = mnt_ctx->ses;
+	ctx->dfs_root_ses = ses;
+	return 0;
 }
 
 static int get_dfs_conn(struct cifs_mount_ctx *mnt_ctx, const char *ref_path, const char *full_path,
@@ -118,7 +127,8 @@  static int get_dfs_conn(struct cifs_mount_ctx *mnt_ctx, const char *ref_path, co
 {
 	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 	struct dfs_info3_param ref = {};
-	int rc;
+	bool is_refsrv = false;
+	int rc, rc2;
 
 	rc = dfs_cache_get_tgt_referral(ref_path + 1, tit, &ref);
 	if (rc)
@@ -133,8 +143,7 @@  static int get_dfs_conn(struct cifs_mount_ctx *mnt_ctx, const char *ref_path, co
 	if (rc)
 		goto out;
 
-	if (ref.flags & DFSREF_REFERRAL_SERVER)
-		set_root_ses(mnt_ctx);
+	is_refsrv = !!(ref.flags & DFSREF_REFERRAL_SERVER);
 
 	rc = -EREMOTE;
 	if (ref.flags & DFSREF_STORAGE_SERVER) {
@@ -143,13 +152,17 @@  static int get_dfs_conn(struct cifs_mount_ctx *mnt_ctx, const char *ref_path, co
 			goto out;
 
 		/* some servers may not advertise referral capability under ref.flags */
-		if (!(ref.flags & DFSREF_REFERRAL_SERVER) &&
-		    is_tcon_dfs(mnt_ctx->tcon))
-			set_root_ses(mnt_ctx);
+		is_refsrv |= is_tcon_dfs(mnt_ctx->tcon);
 
 		rc = cifs_is_path_remote(mnt_ctx);
 	}
 
+	if (rc == -EREMOTE && is_refsrv) {
+		rc2 = get_root_smb_session(mnt_ctx);
+		if (rc2)
+			rc = rc2;
+	}
+
 out:
 	free_dfs_info_param(&ref);
 	return rc;
@@ -162,6 +175,7 @@  static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
 	char *ref_path = NULL, *full_path = NULL;
 	struct dfs_cache_tgt_iterator *tit;
 	struct TCP_Server_Info *server;
+	struct cifs_tcon *tcon;
 	char *origin_fullpath = NULL;
 	int num_links = 0;
 	int rc;
@@ -231,12 +245,22 @@  static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
 
 	if (!rc) {
 		server = mnt_ctx->server;
+		tcon = mnt_ctx->tcon;
 
 		mutex_lock(&server->refpath_lock);
-		server->origin_fullpath = origin_fullpath;
-		server->current_fullpath = server->leaf_fullpath;
+		if (!server->origin_fullpath) {
+			server->origin_fullpath = origin_fullpath;
+			server->current_fullpath = server->leaf_fullpath;
+			origin_fullpath = NULL;
+		}
 		mutex_unlock(&server->refpath_lock);
-		origin_fullpath = NULL;
+
+		if (list_empty(&tcon->dfs_ses_list)) {
+			list_replace_init(&mnt_ctx->dfs_ses_list,
+					  &tcon->dfs_ses_list);
+		} else {
+			dfs_put_root_smb_sessions(&mnt_ctx->dfs_ses_list);
+		}
 	}
 
 out:
@@ -277,7 +301,9 @@  int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs)
 	}
 
 	*isdfs = true;
-	set_root_ses(mnt_ctx);
+	rc = get_root_smb_session(mnt_ctx);
+	if (rc)
+		return rc;
 
 	return __dfs_mount_share(mnt_ctx);
 }
diff --git a/fs/cifs/dfs.h b/fs/cifs/dfs.h
index baf16df55d7e..13f26e01f7b9 100644
--- a/fs/cifs/dfs.h
+++ b/fs/cifs/dfs.h
@@ -10,6 +10,11 @@ 
 #include "fs_context.h"
 #include "cifs_unicode.h"
 
+struct dfs_root_ses {
+	struct list_head list;
+	struct cifs_ses *ses;
+};
+
 int dfs_parse_target_referral(const char *full_path, const struct dfs_info3_param *ref,
 			      struct smb3_fs_context *ctx);
 int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs);
@@ -44,4 +49,15 @@  static inline char *dfs_get_automount_devname(struct dentry *dentry, void *page)
 							true);
 }
 
+static inline void dfs_put_root_smb_sessions(struct list_head *head)
+{
+	struct dfs_root_ses *root, *tmp;
+
+	list_for_each_entry_safe(root, tmp, head, list) {
+		list_del_init(&root->list);
+		cifs_put_smb_ses(root->ses);
+		kfree(root);
+	}
+}
+
 #endif /* _CIFS_DFS_H */
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 @@  int dfs_cache_get_tgt_referral(const char *path, const struct dfs_cache_tgt_iter
 	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).
diff --git a/fs/cifs/dfs_cache.h b/fs/cifs/dfs_cache.h
index be3b5a44cf82..e0d39393035a 100644
--- a/fs/cifs/dfs_cache.h
+++ b/fs/cifs/dfs_cache.h
@@ -40,8 +40,6 @@  int dfs_cache_get_tgt_referral(const char *path, const struct dfs_cache_tgt_iter
 			       struct dfs_info3_param *ref);
 int dfs_cache_get_tgt_share(char *path, const struct dfs_cache_tgt_iterator *it, char **share,
 			    char **prefix);
-void dfs_cache_put_refsrv_sessions(const uuid_t *mount_id);
-void dfs_cache_add_refsrv_session(const uuid_t *mount_id, struct cifs_ses *ses);
 char *dfs_cache_canonical_path(const char *path, const struct nls_table *cp, int remap);
 int dfs_cache_remount_fs(struct cifs_sb_info *cifs_sb);
 
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index a0d286ee723d..6f9c78650528 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -22,6 +22,7 @@ 
 #ifdef CONFIG_CIFS_DFS_UPCALL
 #include "dns_resolve.h"
 #include "dfs_cache.h"
+#include "dfs.h"
 #endif
 #include "fs_context.h"
 #include "cached_dir.h"
@@ -134,6 +135,9 @@  tconInfoAlloc(void)
 	spin_lock_init(&ret_buf->stat_lock);
 	atomic_set(&ret_buf->num_local_opens, 0);
 	atomic_set(&ret_buf->num_remote_opens, 0);
+#ifdef CONFIG_CIFS_DFS_UPCALL
+	INIT_LIST_HEAD(&ret_buf->dfs_ses_list);
+#endif
 
 	return ret_buf;
 }
@@ -149,6 +153,9 @@  tconInfoFree(struct cifs_tcon *tcon)
 	atomic_dec(&tconInfoAllocCount);
 	kfree(tcon->nativeFileSystem);
 	kfree_sensitive(tcon->password);
+#ifdef CONFIG_CIFS_DFS_UPCALL
+	dfs_put_root_smb_sessions(&tcon->dfs_ses_list);
+#endif
 	kfree(tcon);
 }