ksmbd: fix Preauh_HashValue race condition

commit 44a3059 upstream.

If client send multiple session setup requests to ksmbd,
Preauh_HashValue race condition could happen.
There is no need to free sess->Preauh_HashValue at session setup phase.
It can be freed together with session at connection termination phase.

Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-27661
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>

Author: namjaejeon

fs/smb/server/smb2pdu.c

@@ -1847,8 +1847,6 @@ int smb2_sess_setup(struct ksmbd_work *work)
 				ksmbd_conn_set_good(conn);
 				sess->state = SMB2_SESSION_VALID;
 			}
-			kfree(sess->Preauth_HashValue);
-			sess->Preauth_HashValue = NULL;
 		} else if (conn->preferred_auth_mech == KSMBD_AUTH_NTLMSSP) {
 			if (negblob->MessageType == NtLmNegotiate) {
 				rc = ntlm_negotiate(work, negblob, negblob_len, rsp);
@@ -1875,8 +1873,6 @@ int smb2_sess_setup(struct ksmbd_work *work)
 						kfree(preauth_sess);
 					}
 				}
-				kfree(sess->Preauth_HashValue);
-				sess->Preauth_HashValue = NULL;
 			} else {
 				pr_info_ratelimited("Unknown NTLMSSP message type : 0x%x\n",
 						le32_to_cpu(negblob->MessageType));