Commit 53ff5cf8 authored by Namjae Jeon's avatar Namjae Jeon Committed by Steve French
Browse files

ksmbd: fix race condition between session lookup and expire 



 Thread A                        +  Thread B
 ksmbd_session_lookup            |  smb2_sess_setup
   sess = xa_load                |
                                 |
                                 |    xa_erase(&conn->sessions, sess->id);
                                 |
                                 |    ksmbd_session_destroy(sess) --> kfree(sess)
                                 |
   // UAF!                       |
   sess->last_active = jiffies   |
                                 +

This patch add rwsem to fix race condition between ksmbd_session_lookup
and ksmbd_expire_session.

Reported-by: default avatarluosili <rootlab@huawei.com>
Signed-off-by: default avatarNamjae Jeon <linkinjeon@kernel.org>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 8a749fd1

fs/smb/server/connection.c

+2 −0
Original line number Diff line number Diff line
@@ -84,6 +84,8 @@ struct ksmbd_conn *ksmbd_conn_alloc(void) 
	spin_lock_init(&conn->llist_lock);

	INIT_LIST_HEAD(&conn->lock_list);



	init_rwsem(&conn->session_lock);



	down_write(&conn_list_lock);

	list_add(&conn->conns_list, &conn_list);

	up_write(&conn_list_lock);

fs/smb/server/connection.h

+1 −0
Original line number Diff line number Diff line
@@ -50,6 +50,7 @@ struct ksmbd_conn { 
	struct nls_table		*local_nls;

	struct unicode_map		*um;

	struct list_head		conns_list;

	struct rw_semaphore		session_lock;

	/* smb session 1 per user */

	struct xarray			sessions;

	unsigned long			last_active;

fs/smb/server/mgmt/user_session.c

+7 −3
Original line number Diff line number Diff line
@@ -174,7 +174,7 @@ static void ksmbd_expire_session(struct ksmbd_conn *conn) 
	unsigned long id;

	struct ksmbd_session *sess;



	down_write(&sessions_table_lock);

	down_write(&conn->session_lock);

	xa_for_each(&conn->sessions, id, sess) {

		if (sess->state != SMB2_SESSION_VALID ||

		    time_after(jiffies,
@@ -185,7 +185,7 @@ static void ksmbd_expire_session(struct ksmbd_conn *conn) 
			continue;

		}

	}

	up_write(&sessions_table_lock);

	up_write(&conn->session_lock);

}



int ksmbd_session_register(struct ksmbd_conn *conn,
@@ -227,7 +227,9 @@ void ksmbd_sessions_deregister(struct ksmbd_conn *conn) 
			}

		}

	}

	up_write(&sessions_table_lock);



	down_write(&conn->session_lock);

	xa_for_each(&conn->sessions, id, sess) {

		unsigned long chann_id;

		struct channel *chann;
@@ -244,7 +246,7 @@ void ksmbd_sessions_deregister(struct ksmbd_conn *conn) 
			ksmbd_session_destroy(sess);

		}

	}

	up_write(&sessions_table_lock);

	up_write(&conn->session_lock);

}



struct ksmbd_session *ksmbd_session_lookup(struct ksmbd_conn *conn,
@@ -252,9 +254,11 @@ struct ksmbd_session *ksmbd_session_lookup(struct ksmbd_conn *conn, 
{

	struct ksmbd_session *sess;



	down_read(&conn->session_lock);

	sess = xa_load(&conn->sessions, id);

	if (sess)

		sess->last_active = jiffies;

	up_read(&conn->session_lock);

	return sess;

}