ksmbd: fix out of bounds read in smb2_sess_setup

ksmbd does not consider the case of that smb2 session setup is
in compound request. If this is the second payload of the compound,
OOB read issue occurs while processing the first payload in
the smb2_sess_setup().

Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-21355
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/server/smb2pdu.c

@@ -1322,9 +1322,8 @@ static int decode_negotiation_token(struct ksmbd_conn *conn,
 
 static int ntlm_negotiate(struct ksmbd_work *work,
 			  struct negotiate_message *negblob,
-			  size_t negblob_len)
+			  size_t negblob_len, struct smb2_sess_setup_rsp *rsp)
 {
-	struct smb2_sess_setup_rsp *rsp = smb2_get_msg(work->response_buf);
 	struct challenge_message *chgblob;
 	unsigned char *spnego_blob = NULL;
 	u16 spnego_blob_len;
@@ -1429,10 +1428,10 @@ static struct ksmbd_user *session_user(struct ksmbd_conn *conn,
 	return user;
 }
 
-static int ntlm_authenticate(struct ksmbd_work *work)
+static int ntlm_authenticate(struct ksmbd_work *work,
+			     struct smb2_sess_setup_req *req,
+			     struct smb2_sess_setup_rsp *rsp)
 {
-	struct smb2_sess_setup_req *req = smb2_get_msg(work->request_buf);
-	struct smb2_sess_setup_rsp *rsp = smb2_get_msg(work->response_buf);
 	struct ksmbd_conn *conn = work->conn;
 	struct ksmbd_session *sess = work->sess;
 	struct channel *chann = NULL;
@@ -1566,10 +1565,10 @@ static int ntlm_authenticate(struct ksmbd_work *work)
 }
 
 #ifdef CONFIG_SMB_SERVER_KERBEROS5
-static int krb5_authenticate(struct ksmbd_work *work)
+static int krb5_authenticate(struct ksmbd_work *work,
+			     struct smb2_sess_setup_req *req,
+			     struct smb2_sess_setup_rsp *rsp)
 {
-	struct smb2_sess_setup_req *req = smb2_get_msg(work->request_buf);
-	struct smb2_sess_setup_rsp *rsp = smb2_get_msg(work->response_buf);
 	struct ksmbd_conn *conn = work->conn;
 	struct ksmbd_session *sess = work->sess;
 	char *in_blob, *out_blob;
@@ -1647,7 +1646,9 @@ static int krb5_authenticate(struct ksmbd_work *work)
 	return 0;
 }
 #else
-static int krb5_authenticate(struct ksmbd_work *work)
+static int krb5_authenticate(struct ksmbd_work *work,
+			     struct smb2_sess_setup_req *req,
+			     struct smb2_sess_setup_rsp *rsp)
 {
 	return -EOPNOTSUPP;
 }
@@ -1656,8 +1657,8 @@ static int krb5_authenticate(struct ksmbd_work *work)
 int smb2_sess_setup(struct ksmbd_work *work)
 {
 	struct ksmbd_conn *conn = work->conn;
-	struct smb2_sess_setup_req *req = smb2_get_msg(work->request_buf);
-	struct smb2_sess_setup_rsp *rsp = smb2_get_msg(work->response_buf);
+	struct smb2_sess_setup_req *req;
+	struct smb2_sess_setup_rsp *rsp;
 	struct ksmbd_session *sess;
 	struct negotiate_message *negblob;
 	unsigned int negblob_len, negblob_off;
@@ -1665,6 +1666,8 @@ int smb2_sess_setup(struct ksmbd_work *work)
 
 	ksmbd_debug(SMB, "Received request for session setup\n");
 
+	WORK_BUFFERS(work, req, rsp);
+
 	rsp->StructureSize = cpu_to_le16(9);
 	rsp->SessionFlags = 0;
 	rsp->SecurityBufferOffset = cpu_to_le16(72);
@@ -1786,7 +1789,7 @@ int smb2_sess_setup(struct ksmbd_work *work)
 
 		if (conn->preferred_auth_mech &
 				(KSMBD_AUTH_KRB5 | KSMBD_AUTH_MSKRB5)) {
-			rc = krb5_authenticate(work);
+			rc = krb5_authenticate(work, req, rsp);
 			if (rc) {
 				rc = -EINVAL;
 				goto out_err;
@@ -1800,7 +1803,7 @@ int smb2_sess_setup(struct ksmbd_work *work)
 			sess->Preauth_HashValue = NULL;
 		} else if (conn->preferred_auth_mech == KSMBD_AUTH_NTLMSSP) {
 			if (negblob->MessageType == NtLmNegotiate) {
-				rc = ntlm_negotiate(work, negblob, negblob_len);
+				rc = ntlm_negotiate(work, negblob, negblob_len, rsp);
 				if (rc)
 					goto out_err;
 				rsp->hdr.Status =
@@ -1813,7 +1816,7 @@ int smb2_sess_setup(struct ksmbd_work *work)
 						le16_to_cpu(rsp->SecurityBufferLength) - 1);
 
 			} else if (negblob->MessageType == NtLmAuthenticate) {
-				rc = ntlm_authenticate(work);
+				rc = ntlm_authenticate(work, req, rsp);
 				if (rc)
 					goto out_err;