[PATCH 6.1 02/76] ksmbd: fix racy issue from session lookup and expire

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Namjae Jeon <linkinjeon@kernel.org>

commit b95629435b84b9ecc0c765995204a4d8a913ed52 upstream.

Increment the session reference count within the lock for lookup to avoid
racy issue with session expire.

Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-25737
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/smb/server/auth.c              |    2 ++
 fs/smb/server/mgmt/user_session.c |    6 +++++-
 fs/smb/server/server.c            |    4 ++--
 fs/smb/server/smb2pdu.c           |   27 ++++++++++++++-------------
 4 files changed, 23 insertions(+), 16 deletions(-)

--- a/fs/smb/server/auth.c
+++ b/fs/smb/server/auth.c
@@ -1010,6 +1010,8 @@ static int ksmbd_get_encryption_key(stru
 
 	ses_enc_key = enc ? sess->smb3encryptionkey :
 		sess->smb3decryptionkey;
+	if (enc)
+		ksmbd_user_session_get(sess);
 	memcpy(key, ses_enc_key, SMB3_ENC_DEC_KEY_SIZE);
 
 	return 0;
--- a/fs/smb/server/mgmt/user_session.c
+++ b/fs/smb/server/mgmt/user_session.c
@@ -262,8 +262,10 @@ struct ksmbd_session *ksmbd_session_look
 
 	down_read(&conn->session_lock);
 	sess = xa_load(&conn->sessions, id);
-	if (sess)
+	if (sess) {
 		sess->last_active = jiffies;
+		ksmbd_user_session_get(sess);
+	}
 	up_read(&conn->session_lock);
 	return sess;
 }
@@ -274,6 +276,8 @@ struct ksmbd_session *ksmbd_session_look
 
 	down_read(&sessions_table_lock);
 	sess = __session_lookup(id);
+	if (sess)
+		ksmbd_user_session_get(sess);
 	up_read(&sessions_table_lock);
 
 	return sess;
--- a/fs/smb/server/server.c
+++ b/fs/smb/server/server.c
@@ -241,14 +241,14 @@ send:
 	if (work->tcon)
 		ksmbd_tree_connect_put(work->tcon);
 	smb3_preauth_hash_rsp(work);
-	if (work->sess)
-		ksmbd_user_session_put(work->sess);
 	if (work->sess && work->sess->enc && work->encrypted &&
 	    conn->ops->encrypt_resp) {
 		rc = conn->ops->encrypt_resp(work);
 		if (rc < 0)
 			conn->ops->set_rsp_status(work, STATUS_DATA_ERROR);
 	}
+	if (work->sess)
+		ksmbd_user_session_put(work->sess);
 
 	ksmbd_conn_write(work);
 }
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -66,8 +66,10 @@ static inline bool check_session_id(stru
 		return false;
 
 	sess = ksmbd_session_lookup_all(conn, id);
-	if (sess)
+	if (sess) {
+		ksmbd_user_session_put(sess);
 		return true;
+	}
 	pr_err("Invalid user session id: %llu\n", id);
 	return false;
 }
@@ -604,10 +606,8 @@ int smb2_check_user_session(struct ksmbd
 
 	/* Check for validity of user session */
 	work->sess = ksmbd_session_lookup_all(conn, sess_id);
-	if (work->sess) {
-		ksmbd_user_session_get(work->sess);
+	if (work->sess)
 		return 1;
-	}
 	ksmbd_debug(SMB, "Invalid user session, Uid %llu\n", sess_id);
 	return -ENOENT;
 }
@@ -1720,29 +1720,35 @@ int smb2_sess_setup(struct ksmbd_work *w
 
 		if (conn->dialect != sess->dialect) {
 			rc = -EINVAL;
+			ksmbd_user_session_put(sess);
 			goto out_err;
 		}
 
 		if (!(req->hdr.Flags & SMB2_FLAGS_SIGNED)) {
 			rc = -EINVAL;
+			ksmbd_user_session_put(sess);
 			goto out_err;
 		}
 
 		if (strncmp(conn->ClientGUID, sess->ClientGUID,
 			    SMB2_CLIENT_GUID_SIZE)) {
 			rc = -ENOENT;
+			ksmbd_user_session_put(sess);
 			goto out_err;
 		}
 
 		if (sess->state == SMB2_SESSION_IN_PROGRESS) {
 			rc = -EACCES;
+			ksmbd_user_session_put(sess);
 			goto out_err;
 		}
 
 		if (sess->state == SMB2_SESSION_EXPIRED) {
 			rc = -EFAULT;
+			ksmbd_user_session_put(sess);
 			goto out_err;
 		}
+		ksmbd_user_session_put(sess);
 
 		if (ksmbd_conn_need_reconnect(conn)) {
 			rc = -EFAULT;
@@ -1750,7 +1756,8 @@ int smb2_sess_setup(struct ksmbd_work *w
 			goto out_err;
 		}
 
-		if (ksmbd_session_lookup(conn, sess_id)) {
+		sess = ksmbd_session_lookup(conn, sess_id);
+		if (!sess) {
 			rc = -EACCES;
 			goto out_err;
 		}
@@ -1761,7 +1768,6 @@ int smb2_sess_setup(struct ksmbd_work *w
 		}
 
 		conn->binding = true;
-		ksmbd_user_session_get(sess);
 	} else if ((conn->dialect < SMB30_PROT_ID ||
 		    server_conf.flags & KSMBD_GLOBAL_FLAG_SMB3_MULTICHANNEL) &&
 		   (req->Flags & SMB2_SESSION_REQ_FLAG_BINDING)) {
@@ -1788,7 +1794,6 @@ int smb2_sess_setup(struct ksmbd_work *w
 		}
 
 		conn->binding = false;
-		ksmbd_user_session_get(sess);
 	}
 	work->sess = sess;
 
@@ -2207,9 +2212,9 @@ err_out:
 int smb2_session_logoff(struct ksmbd_work *work)
 {
 	struct ksmbd_conn *conn = work->conn;
+	struct ksmbd_session *sess = work->sess;
 	struct smb2_logoff_req *req;
 	struct smb2_logoff_rsp *rsp;
-	struct ksmbd_session *sess;
 	u64 sess_id;
 	int err;
 
@@ -2231,11 +2236,6 @@ int smb2_session_logoff(struct ksmbd_wor
 	ksmbd_close_session_fds(work);
 	ksmbd_conn_wait_idle(conn, sess_id);
 
-	/*
-	 * Re-lookup session to validate if session is deleted
-	 * while waiting request complete
-	 */
-	sess = ksmbd_session_lookup_all(conn, sess_id);
 	if (ksmbd_tree_conn_session_logoff(sess)) {
 		ksmbd_debug(SMB, "Invalid tid %d\n", req->hdr.Id.SyncId.TreeId);
 		rsp->hdr.Status = STATUS_NETWORK_NAME_DELETED;
@@ -8682,6 +8682,7 @@ int smb3_decrypt_req(struct ksmbd_work *
 		       le64_to_cpu(tr_hdr->SessionId));
 		return -ECONNABORTED;
 	}
+	ksmbd_user_session_put(sess);
 
 	iov[0].iov_base = buf;
 	iov[0].iov_len = sizeof(struct smb2_transform_hdr) + 4;