client MUST ignore EncryptionKeyLength if CAP_EXTENDED_SECURITY is set

commit f291095f upstream.

[MS-SMB] 2.2.4.5.2.1 states:

"ChallengeLength (1 byte): When the CAP_EXTENDED_SECURITY bit is set,
 the server MUST set this value to zero and clients MUST ignore this
 value."
Signed-off-by: Noel Power <noel.power@suse.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

fs/cifs/cifssmb.c

@@ -629,9 +629,8 @@ CIFSSMBNegotiate(const unsigned int xid, struct cifs_ses *ses)
 		server->negflavor = CIFS_NEGFLAVOR_UNENCAP;
 		memcpy(ses->server->cryptkey, pSMBr->u.EncryptionKey,
 		       CIFS_CRYPTO_KEY_SIZE);
-	} else if ((pSMBr->hdr.Flags2 & SMBFLG2_EXT_SEC ||
-			server->capabilities & CAP_EXTENDED_SECURITY) &&
-				(pSMBr->EncryptionKeyLength == 0)) {
+	} else if (pSMBr->hdr.Flags2 & SMBFLG2_EXT_SEC ||
+			server->capabilities & CAP_EXTENDED_SECURITY) {
 		server->negflavor = CIFS_NEGFLAVOR_EXTENDED;
 		rc = decode_ext_sec_blob(ses, pSMBr);
 	} else if (server->sec_mode & SECMODE_PW_ENCRYPT) {