Merge tag 'v6.15-rc4-ksmbd-server-fixes' of git://git.samba.org/ksmbd

Pull smb server fixes from Steve French:

 - Fix three potential use after frees: in session logoff, in krb5 auth,
   and in RPC open

 - Fix missing rc check in session setup authentication

* tag 'v6.15-rc4-ksmbd-server-fixes' of git://git.samba.org/ksmbd:
  ksmbd: fix use-after-free in session logoff
  ksmbd: fix use-after-free in kerberos authentication
  ksmbd: fix use-after-free in ksmbd_session_rpc_open
  smb: server: smb2pdu: check return value of xa_store()

fs/smb/server/auth.c

@@ -550,7 +550,19 @@ int ksmbd_krb5_authenticate(struct ksmbd_session *sess, char *in_blob,
 		retval = -ENOMEM;
 		goto out;
 	}
-	sess->user = user;
+
+	if (!sess->user) {
+		/* First successful authentication */
+		sess->user = user;
+	} else {
+		if (!ksmbd_compare_user(sess->user, user)) {
+			ksmbd_debug(AUTH, "different user tried to reuse session\n");
+			retval = -EPERM;
+			ksmbd_free_user(user);
+			goto out;
+		}
+		ksmbd_free_user(user);
+	}
 
 	memcpy(sess->sess_key, resp->payload, resp->session_key_len);
 	memcpy(out_blob, resp->payload + resp->session_key_len,

fs/smb/server/mgmt/user_session.c

@@ -59,10 +59,12 @@ static void ksmbd_session_rpc_clear_list(struct ksmbd_session *sess)
 	struct ksmbd_session_rpc *entry;
 	long index;
 
+	down_write(&sess->rpc_lock);
 	xa_for_each(&sess->rpc_handle_list, index, entry) {
 		xa_erase(&sess->rpc_handle_list, index);
 		__session_rpc_close(sess, entry);
 	}
+	up_write(&sess->rpc_lock);
 
 	xa_destroy(&sess->rpc_handle_list);
 }
@@ -92,7 +94,7 @@ int ksmbd_session_rpc_open(struct ksmbd_session *sess, char *rpc_name)
 {
 	struct ksmbd_session_rpc *entry, *old;
 	struct ksmbd_rpc_command *resp;
-	int method;
+	int method, id;
 
 	method = __rpc_method(rpc_name);
 	if (!method)
@@ -102,26 +104,29 @@ int ksmbd_session_rpc_open(struct ksmbd_session *sess, char *rpc_name)
 	if (!entry)
 		return -ENOMEM;
 
+	down_read(&sess->rpc_lock);
 	entry->method = method;
-	entry->id = ksmbd_ipc_id_alloc();
-	if (entry->id < 0)
+	entry->id = id = ksmbd_ipc_id_alloc();
+	if (id < 0)
 		goto free_entry;
-	old = xa_store(&sess->rpc_handle_list, entry->id, entry, KSMBD_DEFAULT_GFP);
+	old = xa_store(&sess->rpc_handle_list, id, entry, KSMBD_DEFAULT_GFP);
 	if (xa_is_err(old))
 		goto free_id;
 
-	resp = ksmbd_rpc_open(sess, entry->id);
+	resp = ksmbd_rpc_open(sess, id);
 	if (!resp)
 		goto erase_xa;
 
+	up_read(&sess->rpc_lock);
 	kvfree(resp);
-	return entry->id;
+	return id;
 erase_xa:
 	xa_erase(&sess->rpc_handle_list, entry->id);
 free_id:
 	ksmbd_rpc_id_free(entry->id);
 free_entry:
 	kfree(entry);
+	up_read(&sess->rpc_lock);
 	return -EINVAL;
 }
 
@@ -129,9 +134,11 @@ void ksmbd_session_rpc_close(struct ksmbd_session *sess, int id)
 {
 	struct ksmbd_session_rpc *entry;
 
+	down_write(&sess->rpc_lock);
 	entry = xa_erase(&sess->rpc_handle_list, id);
 	if (entry)
 		__session_rpc_close(sess, entry);
+	up_write(&sess->rpc_lock);
 }
 
 int ksmbd_session_rpc_method(struct ksmbd_session *sess, int id)
@@ -439,6 +446,7 @@ static struct ksmbd_session *__session_create(int protocol)
 	sess->sequence_number = 1;
 	rwlock_init(&sess->tree_conns_lock);
 	atomic_set(&sess->refcnt, 2);
+	init_rwsem(&sess->rpc_lock);
 
 	ret = __init_smb2_session(sess);
 	if (ret)

fs/smb/server/mgmt/user_session.h

@@ -63,6 +63,7 @@ struct ksmbd_session {
 	rwlock_t			tree_conns_lock;
 
 	atomic_t			refcnt;
+	struct rw_semaphore		rpc_lock;
 };
 
 static inline int test_session_flag(struct ksmbd_session *sess, int bit)

fs/smb/server/smb2pdu.c

@@ -1445,7 +1445,7 @@ static int ntlm_authenticate(struct ksmbd_work *work,
 {
 	struct ksmbd_conn *conn = work->conn;
 	struct ksmbd_session *sess = work->sess;
-	struct channel *chann = NULL;
+	struct channel *chann = NULL, *old;
 	struct ksmbd_user *user;
 	u64 prev_id;
 	int sz, rc;
@@ -1557,7 +1557,12 @@ binding_session:
 				return -ENOMEM;
 
 			chann->conn = conn;
-			xa_store(&sess->ksmbd_chann_list, (long)conn, chann, KSMBD_DEFAULT_GFP);
+			old = xa_store(&sess->ksmbd_chann_list, (long)conn, chann,
+					KSMBD_DEFAULT_GFP);
+			if (xa_is_err(old)) {
+				kfree(chann);
+				return xa_err(old);
+			}
 		}
 	}
 
@@ -1602,11 +1607,6 @@ static int krb5_authenticate(struct ksmbd_work *work,
 	if (prev_sess_id && prev_sess_id != sess->id)
 		destroy_previous_session(conn, sess->user, prev_sess_id);
 
-	if (sess->state == SMB2_SESSION_VALID) {
-		ksmbd_free_user(sess->user);
-		sess->user = NULL;
-	}
-
 	retval = ksmbd_krb5_authenticate(sess, in_blob, in_len,
 					 out_blob, &out_len);
 	if (retval) {
@@ -2249,10 +2249,6 @@ int smb2_session_logoff(struct ksmbd_work *work)
 	sess->state = SMB2_SESSION_EXPIRED;
 	up_write(&conn->session_lock);
 
-	if (sess->user) {
-		ksmbd_free_user(sess->user);
-		sess->user = NULL;
-	}
 	ksmbd_all_conn_set_status(sess_id, KSMBD_SESS_NEED_SETUP);
 
 	rsp->StructureSize = cpu_to_le16(4);